Aging, Cellular Senescence, and Cancer

The disruptive effects of senescent fibroblasts in those cultures were due primarily to their secretion of MMPs, which are prominent SASP components.

“the effects of the senescent fibroblasts were due primarily to their secretion of matrix metalloproteinases (MMPs), which are prominent SASP components (32, 94).”

• cites [32] sourceDisputed

  In “SASPs Induce Epithelial–Mesenchyme Transitions and Invasiveness” (page unavailable), the paper reports that senescent fibroblast secretions promoted invasion, but identifies IL-6 and IL-8—not MMPs—as the SASP factors contributing substantially to that effect. Our copy does not identify MMPs as prominent SASP components or as the primary cause of these effects. (LLM, conf=0.82)

  Checked by a reasoning model — may be wrong.

  Experimental — accuracy not yet measured
• cites [94] sourcePartly supported

  The Results section, “Members of MMP and Other Gene Clusters Comprise the Conserved SASP” (page not provided), identifies secreted MMPs as SASP components. The paper does not show that MMPs were primarily responsible for the disruptive effects in the cited cultures; its Discussion instead attributes much of the growth-stimulatory activity to CXCL-1. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

The SASP includes proteins that can help senescent cells evade immune recognition and clearance.

“Finally, the SASP also includes proteins that can help senescent cells evade immune recognition and clearance (92, 93).”

• cites [92] sourcePartly supported

  In “The Senescence-Associated Secretory Phenotype Affects Leukocyte Infiltration and Tumor Immunology” (page unavailable), the paper says molecules overexpressed by senescent fibroblasts can lead to an inadequate immune response near those cells. It does not say that these proteins help senescent cells themselves evade immune recognition or clearance; the discussion concerns immune responses in the tumor environment. (LLM, conf=0.85)

  Experimental — accuracy not yet measured
• cites [93] sourceDisputed

  The “Multiple roles of the SASP” section says the SASP might signal the immune system to clear senescent cells. It also describes SASP-associated cytokines and enzymes promoting clearance in mouse models. The cited paper thus makes the contrary point, rather than identifying proteins that help senescent cells evade recognition or clearance. Page numbers were not available in our copy. (LLM, conf=0.84)

  Checked by a reasoning model — may be wrong.

  Experimental — accuracy not yet measured

The proliferative arrest of mouse cells cultured in ambient oxygen (~20%) has only some features of the senescence response induced under more physiological oxygen concentrations.

“This finding may be complicated by the fact that the proliferative arrest of mouse cells cultured in ambient oxygen concentrations (approximately 20%), which is substantially higher than the oxygen concentrations to which cells are exposed in vivo, has only some features of the senescence response that is induced under more physiological oxygen concentrations (38, 94).”

• cites [38] sourceDisputed

  The paper reports that mouse embryonic fibroblasts arrested and showed a senescent morphology in 20% oxygen. But in its discussion of growth at physiological 3% oxygen (Fig. 2a; page unavailable), it says the cells grew with little evidence of replicative senescence, rather than undergoing the contrasting senescence response described in the claim. It notes an exception for DNA-repair-deficient Balb/c cells, whose eventual senescence at 3% oxygen had a phenotype similar to that of cells grown at 20%. (LLM, conf=0.86)

  Checked by a reasoning model — may be wrong.

  Experimental — accuracy not yet measured
• cites [94] sourceSupported

The permanence of senescence arrest supports that senescence evolved partly to suppress cancer.

“The permanence of the senescence growth arrest enforces the idea that the senescence response evolved at least in part to suppress the development of cancer (9).”

• cites [9] sourceSupported

Molecular manipulations such as sequential inactivation of tumor suppressor genes can make senescent cells proliferate.

“However, molecular biological manipulations, for example, the sequential inactivation of certain tumor suppressor genes, can cause senescent cells to proliferate (10).”

• cites [10] sourceSupported

Many cytotoxic chemotherapies are severe DNA-damaging agents that can induce senescence in tumor and normal cells.

“Many types of cytotoxic chemotherapies are severe DNA-damaging agents that can induce senescence in both tumor cells and surrounding normal cells (31–34).”

• cites [31] sourcePartly supported

  The Results and Discussion (page not available) show that doxorubicin, a DNA-damaging anticancer drug, induced senescence in surviving colon carcinoma cells. The introduction (page not available) also says DNA damage can trigger senescence in normal cells and that various anticancer agents can induce senescence-like arrest in tumor cells. It does not establish that cytotoxic chemotherapies induce senescence in surrounding normal cells. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites [32] sourcePartly supported

  In “Chemotherapy-Induced SASPs Occur In Vivo,” the paper reports that the DNA-damaging chemotherapy mitoxantrone induced senescence in epithelial cell lines and normal fibroblasts in culture, and examines treated tumor cells in vivo. It does not establish that many types of chemotherapy induce senescence in normal cells surrounding tumors. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites [33] sourceNot checked — no full text of the source
• cites [34] sourcePartly supported

  The Introduction (page not supplied) says most conventional agents damage cellular components, often DNA, and that drug-induced damage can initiate senescence. The Discussion reports chemotherapy-induced senescence in a murine lymphoma model. Our copy does not establish that these agents cause severe DNA damage or induce senescence in surrounding normal cells. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

There is substantial overlap among SASPs, with proinflammatory cytokines being the most highly conserved feature across many cell types and senescence-inducing stimuli.

“Nevertheless, there is substantial overlap among SASPs; proinflammatory cytokines are the most highly conserved feature, cutting across many different cell types and senescence-inducing stimuli (33, 42, 96, 99, 100, 112–114).”

• cites [33] sourceNot checked — no full text of the source
• cites [42] sourcePartly supported

  The passages labeled Abstract report IL-6 and IL-8 secretion in several fibroblast models and under multiple DNA-damaging conditions. They do not compare SASPs to establish that proinflammatory cytokines are their most highly conserved feature; the paper also reports that p16-induced senescence without DNA damage did not initiate a cytokine response. Page numbers are unavailable in our copy. (LLM, conf=0.87)

  Experimental — accuracy not yet measured
• cites [96] sourceNot checked — no full text of the source
• cites [99] sourcePartly supported

  The Results report proinflammatory cytokines among factors secreted during oncogene-induced senescence, and the Discussion describes CXCR2-binding chemokines as upregulated during both replicative and oncogene-induced senescence. The paper does not establish substantial overlap among SASPs across many cell types or show that proinflammatory cytokines are their most highly conserved feature. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites [100] sourcePartly supported

  The Results report that IL-6, IL-1α, IL-1β, and IL-8 were upregulated during oncogene-induced senescence in human fibroblasts and melanocytes. The Discussion also identifies cytokines and chemokines as prominent in that setting. The paper does not establish substantial overlap among SASPs across many senescence-inducing stimuli or show that proinflammatory cytokines are their most highly conserved feature. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites [112] sourceNot checked — no full text of the source
• cites [113] sourceNot checked — no full text of the source
• cites [114] sourceNot checked — no full text of the source

The SASP is primarily a property of cells that senesce due to or accompanied by genomic damage or epigenomic perturbation.

“The SASP is primarily a property of cells that senesce owing to, or accompanied by, genomic damage or epigenomic perturbation.”

• cites [115] sourcePartly supported

  The discussion (p. 7) says chronic DNA-damage signaling is required for a SASP and concludes that the SASP is a consequence of severe DNA damage rather than growth arrest alone. This supports the genomic-damage part of the claim, but the passages do not address epigenomic perturbation as a cause of the SASP. (LLM, conf=0.85)

  Experimental — accuracy not yet measured
• cites [32] sourcePartly supported

  The Results (Figure 1D) show that DNA damage sufficient to cause senescence induced a SASP, while a lower radiation dose did not. The Discussion likewise describes the SASP as a response to severe or irreparable damage. These passages support the genomic-damage part of the claim, but our copy does not establish epigenomic perturbation as another basis for the SASP. (LLM, conf=0.87)

  Experimental — accuracy not yet measured
• cites [33] sourceNot checked — no full text of the source
• cites [42] sourcePartly supported

  In the supplied copy’s Abstract (page not specified), persistent DNA damage correlates with secretion of inflammatory SASP factors, while p16-induced senescence without DNA damage does not initiate that cytokine response. The paper says DNA-damage signalling drives only a subset of SASP factors; it does not establish the claim for the SASP as a whole or address epigenomic perturbation. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites [67] sourcePartly supported

  The Introduction and Results link SASP activation to DNA-damage signaling and show that HDAC inhibition can induce SASP factors without detectable DNA breaks. But the Introduction and Discussion also state that cells unable to senesce can express SASP factors, so the paper does not establish that the SASP is primarily a property of cells that senesce under those conditions. Page numbers are unavailable in our copy. (LLM, conf=0.85)

  Experimental — accuracy not yet measured
• cites [94] sourcePartly supported

  The Results section, “Effect of O2 on DNA Damage and Genomic Instability” (page not available), reports that the SASP correlates with persistent DNA-damage foci in mouse cells, as in human cells. The paper does not establish epigenomic perturbation as a basis for the SASP, and its findings in the cells studied do not establish the claim’s broader “primarily a property” characterization. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites [96] sourceNot checked — no full text of the source
• cites [99] sourcePartly supported

  The Discussion (page unavailable) reports increased secretion of CXCR2-binding chemokines during replicative and especially oncogene-induced senescence, and says the DNA-damage response is central to both. It does not establish that the SASP is primarily limited to cells with genomic damage, or link it to epigenomic perturbation. (LLM, conf=0.82)

  Experimental — accuracy not yet measured
• cites [100] sourcePartly supported

  The paper’s Summary links oncogene-induced senescence to an inflammatory transcriptome and secretion of IL-6. The Introduction discusses DNA-damage signaling in oncogene-induced senescence, and the passage headed “IL-6 Depletion Correlates with Reduced Formation of SAHF” reports chromatin changes. These passages do not establish that the SASP is primarily a property of cells senescing with genomic damage or epigenomic perturbation across senescence types. (LLM, conf=0.82)

  Experimental — accuracy not yet measured
• cites [112] sourceNot checked — no full text of the source

Chronic inflammation is a cause or an important contributor to virtually every major age-related disease, both degenerative and hyperplastic.

“Chronic inflammation, of course, is a cause of—or an important contributor to—virtually every major age-related disease, both degenerative and hyperplastic (109–111).”

• cites [109] sourcePartly supported

  The Introduction calls chronic inflammation a major underlying condition of many age-related diseases, including degenerative conditions and cancer. The Conclusion likewise describes it as a primary factor underlying numerous age-related diseases. Neither passage supports the stronger claim that it contributes to virtually every major age-related disease. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites [110] sourceNot checked — no full text of the source
• cites [111] sourcePartly supported

  The Introduction and Conclusions and Prospective sections (page unavailable) describe chronic inflammation as a contributor to cancer risk and tumor development. They do not support the broader claim about virtually every major age-related disease, including degenerative diseases. (LLM, conf=0.87)

  Experimental — accuracy not yet measured

Many components of the senescence-associated secretory phenotype promote inflammation, either directly or indirectly.

“many SASP components directly or indirectly promote inflammation (59, 92, 93, 107, 108).”

• cites [59] sourceNot checked — no full text of the source
• cites [92] sourceSupported
  Experimental — accuracy not yet measured
• cites [93] sourceSupported
• cites [107] sourceSupported
  Experimental — accuracy not yet measured
• cites [108] sourceSupported
  Experimental — accuracy not yet measured

Many cells senesce after severe DNA damage regardless of genomic location.

“Many cells undergo senescence in response to severely damaged DNA, regardless of the genomic location (27) (Figure 1).”

• cites [27] sourceSupported

Other DNA lesions, such as those from oxidative stress, may also drive senescence.

“Other DNA lesions—such as those caused by oxidative stress—may also drive cells into senescence (35–38).”

• cites [35] sourcePartly supported

  The paper’s opening summary (p. 1) identifies oxidative stress as a senescence-inducing condition, and the Discussion (p. 10) describes a pathway by which reactive oxygen species lead to senescence. It does not establish that DNA lesions caused by oxidative stress drive that process; it describes a p38 MAPK–lamin B1 pathway instead. (LLM, conf=0.85)

  Experimental — accuracy not yet measured
• cites [36] sourceNot checked — no full text of the source
• cites [37] sourceSupported
• cites [38] sourceSupported

The secretion of these inflammatory proteins by senescent cells is predicted to cause chronic inflammation locally and possibly systemically.

“The secretion of these and similar proteins by senescent cells is predicted to cause chronic inflammation, at least locally and possibly systemically (91–93, 107).”

• cites [91] Campisi J, 2011, Semin. Cancer Biol. sourceSupported
• cites [92] sourcePartly supported

  The sections on soluble signaling factors and leukocyte recruitment describe senescent cells releasing proinflammatory proteins that affect nearby cells and may sustain local immune-cell recruitment. The passages do not address whether this secretion causes systemic inflammation, so the systemic part of the prediction is not supported by our copy. Page numbers were not available. (LLM, conf=0.82)

  Experimental — accuracy not yet measured
• cites [93] sourceSupported
• cites [107] sourceSupported
  Experimental — accuracy not yet measured

DDR proteins stimulate the SASP only after persistent DDR signaling has been established.

“Of particular importance, these DDR proteins stimulate the SASP only after persistent DDR signaling has been established.”

• cites [32] sourcePartly supported

  In the Discussion, the paper says preliminary data suggest that some DDR components help establish and maintain the SASP. Results associated with Figure 1D show that a robust SASP develops 4–7 days after senescence-causing irradiation, rather than immediately after DNA damage. The paper does not establish that DDR proteins stimulate the SASP only after persistent DDR signaling has been established. (LLM, conf=0.85)

  Experimental — accuracy not yet measured
• cites [42] sourcePartly supported

  The paper’s discussion of its model (page unavailable) says persistent DDR signaling initiates the cytokine response after several days through ATM, NBS1 and CHK2. But its analysis of SASP factors says DDR signaling regulates only a subset, including IL-6 and IL-8, not the SASP as a whole. (LLM, conf=0.85)

  Experimental — accuracy not yet measured

Senescent cells were seen with increased frequency in normal and premature aging skin.

“As a final example, senescent cells were seen with increased frequency in normal and premature aging skin (78, 82, 84, 121).”

• cites [78] sourceNot checked — no full text of the source
• cites [82] sourceNot checked — no full text of the source
• cites [84] sourceNot checked — no full text of the source
• cites [121] sourceSupported

In three-dimensional cultures modeling breast epithelial differentiation, senescent fibroblasts disrupted alveolar and branching morphogenesis and milk protein production.

“In three-dimensional cultures that model the functional and morphological differentiation of breast epithelial cells, for example, the presence of senescent fibroblasts disrupted alveolar and branching morphogenesis, as well as milk protein production (118, 119);”

• cites [118] sourceNot checked — no full text of the source
• cites [119] sourcePartly supported

  The Results report that, in three-dimensional MCF-10A cocultures, senescence-like fibroblasts disrupted branching ductal morphogenesis. They do not report disrupted milk protein production; the resulting cysts retained polarized epithelial cells and hollow lumens. The paper therefore supports the branching finding, but not the full claim about alveolar differentiation and milk production. (LLM, conf=0.90)

  Experimental — accuracy not yet measured

The SASP is positively regulated by the transcription factors NF-κB and C/EBP-β.

“The SASP is also positively regulated by the transcription factors nuclear factor κB (NF-κB) (57, 67, 99) and C/EBP-β (100) (Figure 2).”

• cites [57] sourceNot checked — no full text of the source
• cites [67] sourcePartly supported

  The Discussion states that NF-κB and C/EBPβ are required for expression of some SASP factors, supporting their positive regulatory roles. But the Results show that NF-κB is required for IL6 and IL8 upregulation, not OPN upregulation, so the unqualified statement overgeneralizes their regulation of the SASP. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites [99] sourceSupported
• cites [100] sourceSupported

In most cases, senescent cells have been shown or hypothesized to drive degenerative changes largely through secreted proteins, i.e., the SASP.

“In most cases, senescent cells have been shown or hypothesized to drive degenerative changes largely through secreted proteins—that is, through the SASP (91).”

• cites [91] Campisi J, 2011, Semin. Cancer Biol. sourceSupported

Normal cells that senesce solely from ectopic overexpression of p21 or p16INK4a do not express a SASP, despite undergoing senescence growth arrest and showing other senescent characteristics.

“Thus, normal cells that senesce owing simply to the ectopic overexpression of p21 or p16INK4a do not express a SASP, despite undergoing a senescence growth arrest and displaying several other characteristics of senescent cells (115).”

• cites [115] sourceSupported

Cells that senesce due to DNA damage, dysfunctional telomeres, epigenomic disruption, mitogenic signals, oxidative stress, and other stimuli develop a SASP of varying qualities and robustness.

“In contrast, cells that senesce owing to DNA damage, dysfunctional telomeres, epigenomic disruption, mitogenic signals, oxidative stress, and other senescence-inducing stimuli develop a SASP of varying qualities and robustness (32, 33, 42, 67, 94, 96, 99, 100, 112–114).”

• cites [32] sourcePartly supported

  The Results report that senescence-causing DNA damage induces a SASP, and the discussion reports a more robust SASP with oncogenic RAS. The paper also describes quantitative and qualitative variation among SASPs. Our copy does not establish SASP development specifically after dysfunctional telomeres, epigenomic disruption, or oxidative stress; the cited passages provide no page numbers. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites [33] sourceNot checked — no full text of the source
• cites [42] sourcePartly supported

  The paper reports SASP-associated cytokine secretion after persistent DNA damage, dysfunctional telomeres, and oncogenic RAS expression (sections on replicative senescence and oncogene-induced senescence; page numbers unavailable). It also shows that secretion varies with the stimulus: p16-induced senescence without DNA damage produced little IL-6. Our copy does not establish SASP development after epigenomic disruption or oxidative stress, so it does not support the full list of stimuli. (LLM, conf=0.88)

  Experimental — accuracy not yet measured
• cites [67] sourcePartly supported

  The Introduction links persistent DNA-damage signaling to some SASP factors, and the Results section on HDAC inhibition reports SASP activation after chromatin-modifying treatment. The Introduction also mentions telomere-driven and oncogene-induced senescence, but does not establish that those stimuli, or oxidative stress, produce a SASP. The paper does not establish the claimed variation in SASP quality and robustness across the listed stimuli. Page numbers were not available in our copy. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites [94] sourcePartly supported

  The Results section reports that irradiated mouse cells developed a SASP whose robustness depended on oxygen conditions, supporting the claim that SASPs can vary. But it also reports that mouse cells senescing under oxidative culture conditions did not develop a SASP. The paper does not establish SASP development for every listed stimulus, including epigenomic disruption and mitogenic signals. (LLM, conf=0.88)

  Experimental — accuracy not yet measured
• cites [96] sourceNot checked — no full text of the source
• cites [99] sourcePartly supported

  The Introduction identifies DNA damage, telomere-related senescence, oncogenic signals, and oxidative stress as senescence triggers. The Discussion says senescent cells produce increased quantities of various secreted proteins, and the Results document secretion during oncogene-induced senescence. These passages do not establish that every listed trigger, including epigenomic disruption, produces a SASP or that its qualities and robustness vary by trigger; page numbers are unavailable in our copy. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites [100] sourcePartly supported

  The Results (page unavailable in our copy) show that oncogenic signaling upregulated inflammatory cytokines in senescent fibroblasts and melanocytes, supporting the mitogenic-signaling part of the claim. The paper does not establish that senescence caused by the other listed stimuli produces a SASP, or compare the quality and robustness of SASPs across those stimuli. (LLM, conf=0.88)

  Experimental — accuracy not yet measured
• cites [112] sourceNot checked — no full text of the source
• cites [113] sourceNot checked — no full text of the source

DNA-SCARS and TIF contain activated DDR proteins that ensure persistent DDR signaling needed for both the senescence growth arrest and the SASP.

“These nuclear structures contain the activated DDR proteins that ensure the persistent DDR signaling (43) that is needed for both the senescence growth arrest and the SASP (32, 42, 43).”

• cites [32] sourcePartly supported

  In the discussion of p53 and the SASP (page unavailable), the paper says preliminary, unpublished data suggest that some DDR components help establish and maintain the SASP. It also says p53 imposes senescence growth arrest after genotoxic stress, but does not establish that persistent DDR signaling is necessary for both arrest and the SASP. The nuclear-structure portion of the citing sentence is attached to a different citation. (LLM, conf=0.85)

  Experimental — accuracy not yet measured
• cites [42] sourcePartly supported

  The indexed main text (page not supplied) reports that persistent DNA damage foci contain activated ATM and are associated with sustained DDR signaling; its model links that signaling to senescence growth arrest and inflammatory cytokine secretion. But the paper calls these structures persistent DNA damage foci, rather than specifically establishing the claim for both DNA-SCARS and TIF, and it says DDR signaling regulates only a subset of SASP factors, not the entire SASP. (LLM, conf=0.87)

  Experimental — accuracy not yet measured
• cites [43] sourceSupported

In senescent cells, an early response to senescence-inducing stimuli is increased expression of IL-1α.

“In senescent cells, an early response to senescence-inducing stimuli is increased expression of IL-1α (116, 117).”

• cites [116] sourcePartly supported

  The Results section on IL-1α signaling reports high levels of membrane-bound IL-1α in senescent cells, and the Discussion links IL-1α to inflammatory signaling. Neither passage establishes that IL-1α expression increases early after senescence-inducing stimuli; the paper’s timing results concern the SASP and miR-146a/b, not IL-1α. Page numbers are unavailable in our copy. (LLM, conf=0.82)

  Experimental — accuracy not yet measured
• cites [117] sourceNot checked — no full text of the source

DNA-SCARS and TIF are particularly important for the effects of the DDR on the SASP.

“DNA-SCARS and TIF are particularly important for the effects of the DDR on the SASP.”

• cites [43] sourceSupported

p53 negatively regulates or restrains the SASP.

“In contrast to positive regulation by the DDR, p53 negatively regulates or, more accurately, restrains the SASP (32, 42) (Figure 2).”

• cites [32] sourceSupported
• cites [42] sourceSupported

This study provided the first direct evidence that senescent cells can, at least in a premature aging mouse model, drive degenerative age-related pathology.

“This study provided the first direct evidence that senescent cells can, at least in a premature aging mouse model, drive degenerative age-related pathology.”

• cites [128] sourceSupported

• AssumptionThe authors state this as an assumption: Cells that express p16INK4a are senescent.

In senescence induced by certain oncogenes, IL-6 and IL-8 help sustain the senescence growth arrest.

“In the case of senescence induced by certain oncogenes, these cytokines help sustain the senescence growth arrest (discussed below) (99, 100) (Figure 2).”

• cites [99] sourcePartly supported

  The Results report that knocking down IL-8 or neutralizing it with antibodies alleviated oncogene-induced senescence in IMR-90 cells, supporting a role for IL-8 in reinforcing growth arrest. The cited paper does not establish the same role for IL-6; its experiments here concern IL-8 and other CXCR2 ligands, particularly GROα. (LLM, conf=0.88)

  Experimental — accuracy not yet measured
• cites [100] sourceSupported

Many but not all SASP components are positively regulated by the DDR proteins ATM, NBS1, and CHK2.

“Many, but not all, SASP components are positively regulated by the DDR proteins ATM, NBS1 (Nijmegen breakage syndrome 1), and CHK2 (checkpoint kinase 2) (42, 67).”

• cites [42] sourcePartly supported

  The paper’s passage on SASP factors (section labelled Abstract; page unavailable) reports that ATM depletion reduced 7 of 16 measured factors, while 9 were unchanged. Its passage on NBS1 and CHK2 shows that depleting either suppressed IL-6 secretion, but does not establish that either regulates many SASP components. (LLM, conf=0.88)

  Experimental — accuracy not yet measured
• cites [67] sourceSupported

p53 inactivation in cells that do not express p16INK4a causes cells to resume proliferation while the SASP remains active.

“Furthermore, p53 inactivation in cells that do not express p16INK4a, which renders the senescence growth arrest irreversible (10), causes cells to resume proliferation, but the SASP remains active (32, 42).”

• cites [32] sourcePartly supported

  In the discussion of p53 and the SASP (page not available in our copy), the paper says that cells with low p16INK4a levels resume proliferation after p53 inactivation but do not lose the SASP. It does not say these cells do not express p16INK4a at all; the experimental passage describes reduced or low expression. (LLM, conf=0.87)

  Experimental — accuracy not yet measured
• cites [42] sourcePartly supported

  The passage on p53 inactivation in senescent HCA2 cells (section labeled Abstract; page unavailable) reports that growth arrest reversed while IL-6 secretion persisted and increased. It describes the cells as expressing low levels of p16INK4a, however, not as having no p16INK4a expression. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

In normal senescent cells that express a SASP, inactivation of p53 causes a striking hyperincrease in secretion of several SASP factors, primarily due to increased mRNA abundance.

“In normal senescent cells that express a SASP, inactivation of p53—for example, by RNA interference or expression of dominant negative proteins—causes a striking hyperincrease in the secretion of several SASP factors, due primarily to an increase in mRNA abundance (32).”

• cites [32] sourcePartly supported

  In Results (‘Cell-Nonautonomous Tumor-Suppressive Function of p53’; Fig. 6), the paper reports that p53 inactivation by a suppressor peptide or shRNA markedly increases secretion of a subset of SASP proteins. Results (Fig. 1E–F) and the Discussion say many SASP factors are up-regulated at the mRNA level, but do not establish that increased mRNA abundance is the primary cause of the additional secretion after p53 inactivation. Page numbers are not provided in our copy. (LLM, conf=0.85)

  Experimental — accuracy not yet measured

IL-1α binds its plasma membrane receptor IL1R, initiating a signaling cascade that activates NF-κB.

“This plasma membrane–associated cytokine binds its plasma membrane–associated receptor (IL1R), which in turn initiates a signaling cascade that ultimately activates NF-κB (116, 117).”

• cites [116] sourceSupported
• cites [117] sourceNot checked — no full text of the source

NF-κB induces transcription of genes encoding inflammatory mediators such as IL-6 and IL-8.

“NF-κB, in turn, induces the transcription of genes encoding inflammatory mediators such as IL-6 and IL-8 (32, 94, 99, 100).”

• cites [32] sourcePartly supported

  The SASP-components passage identifies IL-6 and IL-8 as inflammatory cytokines, and the passage on senescent cells reports increased IL-6 and IL-8 protein levels. Neither passage, nor the additional passages retrieved, says that NF-κB induces transcription of their genes. Section labels and page numbers were not supplied for these passages. (LLM, conf=0.82)

  Experimental — accuracy not yet measured
• cites [94] sourcePartly supported

  The Results section on CXCL-1 identifies IL-6 and IL-8 as highly secreted human senescence-associated factors, and the section on mRNA and intracellular protein levels reports increased IL-6 mRNA in senescent mouse cells at 3% oxygen (page numbers unavailable). Neither passage establishes that NF-κB induces transcription of IL-6 or IL-8; searches for NF-κB and NF-kappaB did not locate that mechanism in our copy. (LLM, conf=0.83)

  Experimental — accuracy not yet measured
• cites [99] sourcePartly supported

  The Results (page unavailable) report that depleting the NF-κB component RelA reduced IL-8 production and that RelA bound the IL-8 promoter, suggesting direct regulation. The cited paper does not establish that NF-κB induces IL-6 transcription; its relevant findings concern IL-8 and other CXCR2 ligands. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites [100] sourcePartly supported

  The section “C/EBPβ Is a Critical Regulator of IL-6 in OIS” (page unavailable) identifies IL6 and IL8 as inflammatory genes regulated by C/EBPβ. The “IL-8 Plays a Role in OIS” passage also reports C/EBPβ recruitment to both promoters. Searches for NF-κB and its regulation of IL6 and IL8 found no passage supporting the claim that NF-κB induces their transcription. (LLM, conf=0.82)

  Experimental — accuracy not yet measured

Senescent endothelial and smooth muscle cells have been implicated in the genesis or promotion of age-related cardiovascular disease.

“In addition, senescent endothelial and smooth muscle cells have been implicated in the genesis or promotion of age-related cardiovascular disease (126, 127).”

• cites [126] sourceNot checked — no full text of the source
• cites [127] sourceSupported

The idea that senescent cells can drive age-related pathology recently received substantial support from a transgenic mouse model in which senescent cells could be eliminated by administering a drug.

“The idea that senescent cells can drive age-related pathology recently received substantial support from a transgenic mouse model in which senescent cells could be eliminated by administering a drug (128).”

• cites [128] sourceSupported

• AssumptionThe authors state this as an assumption: Cells that express p16INK4a are senescent.

Senescent cells, particularly those that senesce in response to DNA-damaging radiation or chemotherapeutic agents, secrete factors that can protect neighboring tumor cells from being killed by those same chemotherapeutic agents.

“Even more ironic is the finding that senescent cells, particularly those that senesce in response to DNA-damaging radiation or chemotherapeutic agents, secrete factors that can protect neighboring tumor cells from being killed by those same chemotherapeutic agents (133, 134).”

• cites [133] sourcePartly supported

  The Results section (‘Therapy induces damage responses in tumor microenvironments’; page unavailable) reports that chemotherapy or radiation increased extracellular WNT16B from prostate fibroblasts. ‘Paracrine WNT16B attenuates the effect of cytotoxic therapy’ reports improved tumor-cell survival and reduced apoptosis during mitoxantrone treatment. The Discussion links the damage-response secretome to a senescence phenotype, but the cited experiments do not establish that the protective fibroblasts had themselves become senescent. (LLM, conf=0.83)

  Experimental — accuracy not yet measured
• cites [134] sourcePartly supported

  The Results and Discussion (page not provided) show that endothelial cells exposed to doxorubicin release factors that protect nearby lymphoma cells from chemotherapy. But the protective release occurs before senescence; the Discussion says the later senescence-associated secretory response cannot effectively alter the initial treatment response. The paper therefore does not establish that already-senescent cells provide the protection described. (LLM, conf=0.89)

  Experimental — accuracy not yet measured

GROα, a SASP component induced by oncogenic RAS, promotes senescence of normal human ovarian fibroblasts.

“Likewise, GROα, a potent mitogen that is a SASP component and is induced by oncogenic RAS, promotes the senescence of normal human ovarian fibroblasts (95).”

• cites [95] sourcePartly supported

  The Results report that Gro-1 treatment induced senescence markers in two normal ovarian stromal fibroblast lines, and the paper states that RAS activates Gro-1. It also describes Gro-1 as a mitogen. Our copy does not identify Gro-1 as a SASP component, so that part of the attributed description is unsupported. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

In the cases of IL-6 and IL-8, these SASP components appear to act by instituting a self-sustaining intracellular signaling loop that ultimately activates NF-κB and C/EBP-β.

“In the cases of IL-6 and IL-8, these SASP components appear to act by instituting a self-sustaining intracellular signaling loop that ultimately activates the NF-κB and C/EBP-β transcription factors (99, 100).”

• cites [99] sourcePartly supported

  The Results report that IL-8 reinforces senescence and that NF-κB and C/EBPβ regulate IL-8 production. The Discussion suggests CXCR2 ligands may act through intracellular or autocrine receptor activation, but the paper does not establish a self-sustaining loop in which IL-8 activates those transcription factors; the passages also do not address IL-6 in that mechanism. Pages are not available in our copy. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites [100] sourcePartly supported

  In the passage on IL-6 and C/EBPβ (labelled Abstract in our copy; page unavailable), the authors propose a positive feedback loop that sustains C/EBPβ activity. The 'IL-8 Plays a Role in OIS' passage describes IL-8 as dependent on IL-6 and regulated by C/EBPβ, but does not establish that IL-8 drives the loop. The passages do not support the claimed activation of NF-κB or describe the loop as intracellular. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

Senescent fibroblasts induce EMT in premalignant epithelial cells and nonaggressive cancer epithelial cells in part through secretion of IL-6 and IL-8.

“Senescent fibroblasts induce an epithelial-to-mesenchymal transition in premalignant epithelial cells and nonaggressive cancer epithelial cells in part through the secretion of IL-6 and IL-8 (32, 102, 118).”

• cites [32] sourcePartly supported

  In “SASPs Induce Epithelial–Mesenchyme Transitions and Invasiveness” (page unavailable), the paper reports that senescent fibroblast secretions induced EMT in two nonaggressive breast cancer cell lines. It also reports invasion by premalignant MCF-10A cells and finds that blocking IL-6 and IL-8 reduced invasion, but it does not directly show EMT in the premalignant cells. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites [102] sourcePartly supported

  The sections “Effects of the SASP on Cell Migration and Invasion” and “Effects of the SASP on Epithelial Cell Proliferation and Differentiation” report EMT in nonaggressive breast cancer cells and attribute EMT-like changes in mammary epithelial cells partly to IL-6 and IL-8. For premalignant epithelial cells, the paper describes stimulated growth or progression, not an IL-6/IL-8-mediated EMT. Page numbers are not available in our copy. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites [118] sourceNot checked — no full text of the source

One such malignant phenotype is the epithelial-to-mesenchymal transition.

“One such phenotype is the epithelial-to-mesenchymal transition (102) (Figure 2).”

• cites [102] sourceSupported

Genomic damage, a common cause of cellular senescence, induces expression of membrane-bound ligands for the major natural killer cell receptor NKG2D.

“In addition, genomic damage—a common cause of cellular senescence—induces expression of the membrane-bound ligands for the major natural killer cell receptor NKG2D (140).”

• cites [140] sourceSupported

At least some SASP components can be chemosensitizing.

“In contrast, at least some SASP components can be chemosensitizing.”

• cites [135] sourceSupported

Global suppression of the SASP through NF-κB inhibition promoted resistance to chemotherapy in a mouse lymphoma model.

“For example, global suppression of the SASP (through NF-κB inhibition) promoted resistance to chemotherapy in a mouse lymphoma model (135).”

• cites [135] sourceSupported

Aging tissues show a steady accumulation of cells that harbor DNA damage foci, similar to foci found in senescent cells.

“Indeed, aging tissues show a steady accumulation of cells that harbor DNA damage foci, similar to the foci that are found in senescent cells (29, 30, 144).”

• cites [29] sourceNot checked — no full text of the source
• cites [30] sourceNot checked — no full text of the source
• cites [144] sourceSupported

Among the cells that participate in clearance of senescent cells are natural killer cells, macrophages, and T cells.

“Among the cells that participate in the clearance of senescent cells are natural killer cells, macrophages, and T cells (131, 135, 139).”

• cites [131] sourceNot checked — no full text of the source
• cites [135] sourcePartly supported

  The NF-κB controls the SASP section reports that natural killer cells target senescent cells, and the figure caption describes their recognition and killing of those cells. The paper does not identify macrophages or T cells as clearing senescent cells; its mention of macrophages concerns apoptotic cells in lymph nodes. Page numbers are unavailable in our copy. (LLM, conf=0.88)

  Experimental — accuracy not yet measured
• cites [139] sourcePartly supported

  The Discussion says natural killer (NK) cells clear senescent activated stellate cells, and the Results show that altering NK-cell activity affects their clearance. The Results also place macrophages near cells with senescence markers and mention T cells as potential participants in NK-influenced killing, but do not establish that macrophages or T cells participate in clearing the senescent cells studied here. The indexed passages provide section labels but no page numbers. (LLM, conf=0.87)

  Experimental — accuracy not yet measured

In mouse cells, the SASP factor PAI-1 reinforces replicative senescence.

“In mouse cells, the SASP factor PAI-1 (plasminogen activator inhibitor 1) reinforces replicative senescence (137).”

• cites [137] sourceSupported

There is little doubt that the senescence growth arrest suppresses the development of cancer.

“There is little doubt that the senescence growth arrest suppresses the development of cancer (8, 48, 136).”

• cites [8] sourceNot checked — no full text of the source
• cites [48] sourceNot checked — no full text of the source
• cites [136] sourceSupported

Senescent cells, presumably via SASP-derived factors, can stimulate infiltration of leukocytes, which produce reactive toxic moieties that can cause DNA damage.

“Senescent cells, presumably by virtue of SASP-derived factors, can stimulate the infiltration of leukocytes (93, 131, 132), which produce reactive toxic moieties that can cause DNA damage.”

• cites [93] sourceSupported
• cites [131] sourceNot checked — no full text of the source
• cites [132] sourceSupported

These chemoprotective SASP factors include WNT16B, IL-6, and TIMP-1.

“These chemoprotective SASP factors include WNT16B, IL-6, and TIMP-1 (tissue inhibitor of metalloproteinases-1).”

• cites [133] sourcePartly supported

  The Results section ('Paracrine WNT16B attenuates the effect of cytotoxic therapy'; page unavailable) shows that WNT16B-containing conditioned medium reduced chemotherapy-induced cytotoxicity. The Discussion (page unavailable) links the damage-response secretory program to SASP and mentions IL-6, but describes IL-6 as reinforcing senescence and immune responses, not as chemoprotective. The copy does not establish TIMP-1 as a chemoprotective SASP factor (searched: TIMP-1, TIMP1, tissue inhibitor of metalloproteinases). (LLM, conf=0.87)

  Experimental — accuracy not yet measured
• cites [134] sourcePartly supported

  The Introduction and Results identify IL-6 and TIMP-1 as factors that protect lymphoma cells from chemotherapy, but our copy does not identify WNT16B as one of them. The Discussion also distinguishes the acute chemoprotective response from the later senescence-associated secretory phenotype (SASP), stating that SASP occurs too late to alter the initial treatment response. No page numbers are available in our copy. (LLM, conf=0.88)

  Experimental — accuracy not yet measured

Other SASP factors implicated in stimulating tumor cell growth are amphiregulin and the GROs.

“Other SASP factors implicated in stimulating tumor cell growth are amphiregulin and the GROs (94–96), but there are a plethora of other candidates.”

• cites [94] sourcePartly supported

  The Results section, “CXCL-1 (GRO-α/KC) Is a Major Conserved Factor That Stimulates Epithelial Cell Growth” (page unavailable), identifies GRO-α/KC as a SASP factor that stimulates growth of premalignant and malignant epithelial cells. Our copy does not identify amphiregulin as a growth-stimulating SASP factor; it also directly tests GRO-α/KC rather than establishing the effect for GROs generally. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites [95] sourcePartly supported

  The Results show that Gro-1 promotes ovarian tumor growth and that Gro-1-induced senescent fibroblasts enhance tumor formation. But the paper studies Gro-1 specifically, not the GRO family as a whole, and describes Gro-1 secretion by transformed epithelial cells rather than establishing it as a factor secreted by senescent cells. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites [96] sourceNot checked — no full text of the source

Given the proinflammatory nature of the SASP, senescent cells can attract immune cells, including destructive leukocytes of the innate and adaptive immune systems.

“Given the proinflammatory nature of the SASP, it is not surprising that senescent cells can attract immune cells, including destructive leukocytes of the innate and adaptive immune systems (131, 132, 135).”

• cites [131] sourceNot checked — no full text of the source
• cites [132] sourcePartly supported

  The Abstract reports that senescent liver tumours produced inflammatory signals that attract immune cells and were infiltrated by neutrophils, macrophages and natural killer cells. It supports attraction and destructive activity by innate immune cells, but not by adaptive immune cells: the main experiments used mice lacking functional B and T cells. (LLM, conf=0.90)

  Experimental — accuracy not yet measured
• cites [135] sourcePartly supported

  The introductory passage (page unavailable) says SASP factors attract immune cells that can eliminate senescent cells. The NF-κB controls the SASP section reports targeting by natural killer cells, and the drug-induced senescence section reports immune-cell infiltration, especially NK cells. Our copy does not establish attraction of destructive leukocytes from both the innate and adaptive immune systems. (LLM, conf=0.85)

  Experimental — accuracy not yet measured

In human cells, IL-6, IL-8, and IGFBP7 reinforce the senescence growth arrest caused by oncogenic RAS and BRAF.

“In human cells, IL-6, IL-8, and IGFBP7 (insulin-like growth factor–binding protein 7) reinforce the senescence growth arrest caused by the oncogenic forms of RAS and BRAF (99, 100, 114).”

• cites [99] sourcePartly supported

  The Results report that reducing or neutralizing IL-8 alleviated oncogene-induced senescence in human IMR-90 cells, supporting IL-8’s role in reinforcing the arrest. The paper does not establish the same role for IL-6; its Discussion mentions IGFBP7 and BRAF in connection with another study rather than as a finding of this study. Thus this source supports part, but not all, of the combined claim. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites [100] sourcePartly supported

  The Results ('IL-6 Inhibits Proliferation in the Context of Oncogenic Stress'; page unavailable) report that IL-6 augmented growth arrest under oncogenic stress, including in a BRAF-mutant setting. The section 'IL-8 Plays a Role in OIS' reports that IL-8 knockdown allowed cells to bypass senescence. Our copy does not establish the claimed role for IGFBP7, so it supports only part of the sentence. (LLM, conf=0.88)

  Experimental — accuracy not yet measured
• cites [114] sourceNot checked — no full text of the source

SASP factors can stimulate malignant phenotypes in culture.

“In addition to stimulating tumor growth in mice, SASP factors can stimulate malignant phenotypes in culture.”

• cites [102] sourceSupported

There is a striking, well-documented age-related decline in the adaptive immune system, particularly in the ability to mount functional T cell-mediated responses.

“There is a striking, well-documented age-related decline in the adaptive immune system, particularly in the ability to mount functional T cell–mediated responses (141).”

• cites [141] sourceSupported

This decline is largely responsible for the heightened susceptibility to infection in the elderly.

“This decline is largely responsible for the heightened susceptibility to infection in the elderly.”

• cites [141] sourceSupported

These results provide a causal explanation for earlier findings showing that presence of senescent hepatic stellate cells correlates with increased inflammation but reduced fibrosis.

“These results provide a causal explanation for earlier findings showing that the presence of senescent hepatic stellate cells correlates with increased inflammation but reduced fibrosis (148).”

• cites [148] sourcePartly supported

  The Results and Discussion report that senescent hepatic stellate cells in culture have a more inflammatory, less fibrogenic phenotype. They do not show that the presence of these cells in the liver correlates with increased inflammation and reduced fibrosis; the Discussion describes its comparison of human livers as preliminary gene-expression evidence, not that correlation. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

In that skin wound model, the senescence response was induced by a signaling cascade initiated by binding of CCN1 to its integrin receptor on target cells.

“In this case, the senescence response was induced by a signaling cascade that was initiated by the binding of CCN1, a matricellular protein, to its receptor, an integrin, on the surface of the target cells (149).”

• cites [149] sourceSupported

When chronically present, senescent cells may promote phenotypes associated with skin aging.

“However, when chronically present, they may promote phenotypes associated with skin aging (121).”

• cites [121] sourceSupported

In skin, senescent cells clearly promote optimal wound healing.

“In the skin, for example, senescent cells clearly promote optimal wound healing (149).”

• cites [149] sourcePartly supported

  The Results section reports that CCN1-induced senescent fibroblasts restrict excessive collagen deposition in healing mouse skin wounds, supporting a beneficial role. But it also reports that wounds with markedly fewer senescent cells closed somewhat faster, so the paper supports reduced fibrosis rather than an unqualified claim that senescent cells promote optimal wound healing overall. Page numbers are unavailable in our copy. (LLM, conf=0.84)

  Experimental — accuracy not yet measured

Recent findings have uncovered an additional beneficial effect of the senescence response and accompanying SASP: the ability to promote optimal repair of damaged tissue.

“Recent findings have uncovered an additional beneficial effect of the senescence response and accompanying SASP: the ability to promote optimal repair of damaged tissue (59, 91, 145–147).”

• cites [59] sourceNot checked — no full text of the source
• cites [91] Campisi J, 2011, Semin. Cancer Biol. sourceSupported
• cites [145] sourceSupported
• cites [146] sourcePartly supported

  The section “p53 and PAI-1 Regulate Senescence via Secreted Factors” (p. 4) suggests that secreted factors from senescent fibroblasts may help nearby epithelial cells proliferate and close a wound. But “Conclusions and outlook” (p. 5) says their effect on epithelial cells remains to be investigated. The paper therefore supports a possible role in wound repair, not an established ability of senescence and its accompanying secretions to promote optimal tissue repair. (LLM, conf=0.88)

  Experimental — accuracy not yet measured
• cites [147] sourceSupported

In a mouse model of acute liver injury, the injury induced senescence of hepatic stellate cells, which were eventually cleared by the immune system, principally by natural killer cells.

“In a mouse model of acute liver injury, the injury induced the senescence of hepatic stellate cells, which were eventually cleared by the immune system (principally by natural killer cells) (139).”

• cites [139] sourcePartly supported

  The Results section reports that senescent activated hepatic stellate cells were cleared from mouse livers, principally through natural killer cell activity. But the Introduction and Experimental Procedures describe repeated CCl4 treatment to induce fibrosis—a model of chronic liver damage, not a model of acute liver injury. Page numbers are unavailable in our copy. (LLM, conf=0.90)

  Experimental — accuracy not yet measured

In a mouse model of skin wounding, the injury induced cellular senescence, most likely in resident fibroblasts.

“Likewise, in a mouse model of skin wounding, the injury again induced cellular senescence, most likely in resident fibroblasts.”

• cites [149] sourcePartly supported

  The Results section reports that senescent cells accumulated in healing mouse wounds and identifies them as myofibroblasts; fibroblasts isolated from the wounds also showed senescence. It does not establish that those fibroblasts were resident cells rather than cells of another origin. No page number is available in our copy. (LLM, conf=0.82)

  Experimental — accuracy not yet measured

When acute liver injury was performed on mice deficient in the p53/p21 and p16INK4a/pRB pathways-mice deficient in undergoing a senescence response-healing was accompanied by a marked increase in fibrosis.

“When the injury was performed on mice that were deficient in the p53/p21 and p16INK4a/pRB pathways—that is, mice deficient in undergoing a senescence response—healing was accompanied by a marked increase in fibrosis (139).”

• cites [139] sourcePartly supported

  The Results section (“Fibrosis progression is restricted by an intact senescence machinery”; page unavailable) reports that mice lacking both p53 and INK4a/ARF had impaired senescence and more than 50% greater fibrotic area than wild-type mice. But the experiment used repeated CCl4 treatment, which the paper describes as chronic liver damage, not acute injury. The Results section on fibrosis reversion also reports more lesions remaining in the double mutants after treatment stopped, rather than an increase arising during healing from an acute injury. (LLM, conf=0.90)

  Experimental — accuracy not yet measured

Wounds in these mutant CCN1 mice healed with significantly more fibrosis.

“Importantly, wounds in these mice healed with significantly more fibrosis (149).”

• cites [149] sourceSupported

In mice engineered to express a mutant CCN1 protein defective in integrin binding and inducing senescence, wounds were deficient in senescent cells and SASP gene expression.

“In mice engineered to express a mutant CCN1 protein that is defective in integrin binding and hence in inducing senescence, the wounds were deficient in senescent cells and SASP gene expression.”

• cites [149] sourceSupported

Senescence arrest is stringent.

“Regardless, the senescence arrest is stringent.”

The senescence response may arise from antagonistically pleiotropic gene action.

“Thus, the senescence response may be the result of antagonistically pleiotropic gene action.”

Cancer's age-related incidence pattern is similar to other aging diseases.

“In this regard, cancer is no different from the other diseases of aging, despite very different manifestations.”

Selection cannot remove genes that help early life but harm late life.

“That is, natural selection cannot eliminate genes that promote early-life survival but incongruously also promote late-life debility (2), a concept termed antagonistic pleiotropy.”

• cites [2] sourceNot checked — no full text of the source

Many aging pathologies have been linked directly or indirectly to senescence.

“Nonetheless, a surprisingly large number of aging pathologies have been linked, directly or indirectly, to the senescence response.”

Senescence arrest is established and maintained by at least two major tumor suppressor pathways, p53/p21 and p16INK4a/pRB.

“It is established and maintained by at least two major tumor suppressor pathways—the p53/p21 and p16INK4a/pRB pathways—and is now recognized as a formidable barrier to malignant tumorigenesis.”

Evolutionary theory says aging results from weakening natural selection with age.

“Evolutionary theory holds that aging is a consequence of the declining force of natural selection with age (1).”

• cites [1] Rose MR, 1991 sourceNot checked — no full text of the source

No known physiological stimulus can make senescent cells re-enter the cell cycle.

“The senescence arrest is considered irreversible because no known physiological stimuli can stimulate senescent cells to reenter the cell cycle.”

In most species, aging causes degenerative diseases marked by loss of tissue or cellular function.

“For most species, aging promotes a host of degenerative pathologies that are characterized by debilitating losses of tissue or cellular function.”

Mounting evidence indicates cellular senescence links several aging pathologies, both degenerative and hyperplastic.

“There is mounting evidence that at least one process—a stress response termed cellular senescence—links multiple pathologies of aging, both degenerative and hyperplastic.”

Antagonistic pleiotropy is central to understanding aging and its link to cancer.

“As discussed below, antagonistic pleiotropy is key to understanding many aspects of aging, especially the relationship between aging and cancer.”

• cites [2] sourceNot checked — no full text of the source

Cells senesce in response to many potentially oncogenic stimuli or their sequelae.

“Consistent with this view, cells undergo senescence in response to a host of potentially oncogenic stimuli or their sequelae.”

Few old survivors remain for selection to remove late-acting harmful alleles.

“Consequently, there are generally few old survivors on which natural selection can act to eliminate alleles or genes that have late-acting deleterious effects.”

• cites [1] Rose MR, 1991 sourceNot checked — no full text of the source

Age-related pathologies generally increase with roughly exponential kinetics starting near mid-life.

“Although species vary in their susceptibilities to specific age-related pathologies, collectively, age-related pathologies generally rise with approximately exponential kinetics beginning at approximately the mid-point of the species-specific life span (e.g., 50–60 years of age for humans) (3, 4).”

• cites [3] 3. Alliance Aging Res. 2009. The Silver Book. Chronic Disease and Medical Innovation in an Aging Nation. http://www.silverbook.org/Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites [4] 4. Natl. Cent. Health Stat. 2007. Health, United States, 2007. Hayattsville, MD: US Gov. Print. Off. 567 pp.Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Malignant cells must gain new aberrant functions to become a lethal tumor.

“In contrast to the loss of function that characterizes degenerating cells and tissues, malignant (cancerous) cells must acquire new (albeit aberrant) functions that allow them to develop into a lethal tumor.”

Recent evidence supports that senescence also promotes degenerative and hyperplastic diseases, probably by causing chronic inflammation.

“However, recent evidence strengthens the idea that it also drives both degenerative and hyper-plastic pathologies, most likely by promoting chronic inflammation.”

Cancer incidence rises with nearly exponential kinetics beginning around mid-life in susceptible species.

“Cancer, like the age-related degenerative diseases, increases in incidence with nearly exponential kinetics beginning at approximately the mid-point of the life span (in species that are susceptible to this disease) (3, 6, 7).”

• cites [3] 3. Alliance Aging Res. 2009. The Silver Book. Chronic Disease and Medical Innovation in an Aging Nation. http://www.silverbook.org/Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites [6] sourceNot checked — no full text of the source
• cites [7] sourceNot checked — no full text of the source

In organisms with renewable tissues, aging involves increased hyperplasias, most seriously cancers.

“In organisms with renewable tissues, aging is also marked by an increase in hyperplasias, the most serious of which are cancers.”

The degenerative and hyperplastic diseases of aging are at least partly connected through cellular senescence.

“This review discusses the idea that, despite seemingly opposite characteristics, the degenerative and hyperplastic pathologies of aging are at least partly linked by a common biological phenomenon: a cellular stress response known as cellular senescence.”

Functional telomeres prevent DNA repair machinery from treating chromosome ends as double-strand breaks.

“Functional telomeres prevent DNA repair machineries from recognizing chromosome ends as DNA double-strand breaks (DSBs), to which cells rapidly respond and attempt repair.”

Repeated division without telomerase eventually makes one or more telomeres critically short and dysfunctional.

“Thus, repeated cell division in the absence of telomerase eventually causes one or more telomeres to become critically short and dysfunctional.”

Paracrine activities of senescent cells can be beneficial or harmful depending on physiological context.

“As discussed below, the paracrine activities of senescent cells can be either beneficial or deleterious, depending on the physiological context.”

Telomere shortening does not occur in cells expressing telomerase.

“Telomere shortening does not occur in cells that express telomerase, the reverse transcriptase that can replenish the repetitive telomeric DNA de novo (15, 16).”

• cites [15] sourceNot checked — no full text of the source
• cites [16] sourceNot checked — no full text of the source

The DNA damage response arrests division mainly via p53, preventing genomic instability.

“The DDR, in turn, arrests cell division primarily through activities of the p53 tumor suppressor, thereby preventing genomic instability.”

Senescent cells show widespread changes in chromatin organization and gene expression.

“In addition to arrested growth, senescent cells show widespread changes in chromatin organization and gene expression.”

The link between the Hayflick limit and aging was conjectural and tenuous for many years, largely because senescent cells appeared degenerated but remained viable and metabolically active.

“The link between the Hayflick limit and aging was, for many years, conjectural and tenuous—largely on the basis that replicatively senescent cells appeared to be degenerated, although they remained viable and metabolically active.”

Hayflick and colleague showed normal human fibroblasts do not proliferate indefinitely in culture.

“Cellular senescence was first formally described approximately five decades ago when Hayflick and colleague (11, 12) showed that normal human cells (in this case fibroblasts) did not proliferate indefinitely in culture.”

• cites [11] sourceNot checked — no full text of the source
• cites [12] sourceNot checked — no full text of the source

The mechanism behind the finite replicative lifespan of normal cells is now understood.

“The mechanism behind the finite replicative life span of normal cells is now understood.”

Telomere dysfunction is one of many oncogenic stimuli that can cause senescence.

“Telomere dysfunction is one of many potentially oncogenic stimuli that can elicit a senescence response (Figure 1).”

In mice, many adult cells are telomerase positive.

“In mice, for example, many cells in the adult animal are telomerase positive.”

Even 50 years ago, most cancer cells were known to lack a finite replicative lifespan.

“Even 50 years ago, it was evident that most cancer cells do not have a finite replicative life span (11).”

• cites [11] sourceNot checked — no full text of the source

DNA double-strand breaks are especially potent senescence inducers.

“DNA DSBs, such as those induced by ionizing radiation, topoisomerase inhibitors, and other agents, are especially potent senescence inducers (28–30).”

• cites [28] sourceNot checked — no full text of the source
• cites [29] sourceNot checked — no full text of the source
• cites [30] sourceNot checked — no full text of the source

Telomeres shorten with each cell division.

“Thus, telomeres, the DNA-protein structures that cap the ends of linear chromosomes, shorten with each cell division (14).”

• cites [14] sourceNot checked — no full text of the source

SASP has powerful paracrine activities, suggesting senescence is not only a cancer prevention mechanism.

“The SASP has powerful paracrine activities, the nature of which suggests that the senescence response is not solely a mechanism for preventing cancer.”

The numbers and types of telomerase-expressing cells vary widely among species.

“The numbers and types of telomerase-expressing cells vary widely among species (17–19).”

• cites [17] sourceNot checked — no full text of the source
• cites [18] sourceNot checked — no full text of the source
• cites [19] sourceNot checked — no full text of the source

In humans, telomerase-positive cells are rare.

“In humans, however, such cells are rare.”

Coinjection of senescent, but not nonsenescent, fibroblasts significantly stimulated proliferation of mouse and human epithelial tumor cells in immunocompromised mice.

“Coinjection of senescent, but not nonsenescent, fibroblasts significantly stimulated the proliferation of mouse and human epithelial tumor cells in immunocompromised mice (97, 129, 130).”

• cites [97] sourceNot checked — no full text of the source
• cites [129] sourceNot checked — no full text of the source
• cites [130] sourceNot checked — no full text of the source

Indirect evidence suggests that astrocyte senescence and its associated SASP can promote age-related neurodegeneration giving rise to cognitive impairment, Alzheimer's disease, and Parkinson's disease.

“For example, indirect evidence suggests that the senescence and associated SASP of astrocytes can promote the age-related neurodegeneration that gives rise to cognitive impairment, as well as to Alzheimer’s and Parkinson’s diseases (122, 123).”

• cites [122] sourceNot checked — no full text of the source
• cites [123] sourceNot checked — no full text of the source

Senescent pulmonary artery smooth muscle cells stimulated proliferation and migration of neighboring smooth muscle cells, in part via secretion of IL-6, IL-8, and other factors including extracellular matrix proteins.

“Likewise, senescent pulmonary artery smooth muscle cells stimulated the proliferation and migration of neighboring smooth muscle cells, in part due to their secretion of IL-6, IL-8, and other factors (including extracellular matrix proteins) (120).”

• cites [120] sourceNot checked — no full text of the source

Senescent cells and the SASP can fuel overt age-related disease.

“Senescent cells and the SASP can also fuel overt age-related disease.”

Senescent cells can disrupt normal tissue structures that are essential for normal tissue function.

“Senescent cells can disrupt normal tissue structures, which are essential for normal tissue function.”

There is mounting evidence that senescent cells can also drive hyperplastic pathology.

“There is mounting evidence that, in addition to driving degenerative pathology, senescent cells can also drive hyperplastic pathology.”

There is mounting evidence that senescent cells can contribute to both degenerative and hyperplastic age-related pathology.

“There is mounting evidence that senescent cells can contribute to both of these types of age-related pathology.”

Senescent cells have been implicated in many age-associated degenerative phenotypes, both normal and pathological.

“Senescent cells have been implicated in many age-associated degenerative phenotypes, both normal and pathological.”

At least some SASP factors, including IL-6, IL-8, IGFBP7, and GROα, help establish the oncogene-induced senescence response.

“Thus, at least some SASP factors (in these examples, IL-6, IL-8, IGFBP7, and GROα) help establish the oncogene-induced senescence response.”

Together, these findings support the idea that, at least for some factors and under some circumstances, the SASP helps maintain the tumor suppressive growth arrest of senescent cells.

“Together, these findings support the idea that, at least for some factors and under some circumstances, the SASP helps maintain the tumor suppressive growth arrest of senescent cells.”

Certain SASP components can act in an autocrine fashion to buttress the senescence growth arrest.

“Indeed, certain SASP components can apparently act in an autocrine fashion to buttress such growth arrest.”

In these cases, SASP components appear to help establish the senescence growth arrest rather than maintain the arrest once it is fully established.

“In these cases, the SASP components appear to help establish the senescence growth arrest, rather than maintain the arrest once it is fully established.”

Senescent cells may also promote cancer initiation.

“Senescent cells may also promote cancer initiation.”

Another function appears to be stimulation of a local immune reaction to eliminate oncogene-expressing cells, both those that underwent oncogene-induced senescence and those transformed cells that bypassed or escaped senescence.

“Another function appears to be the stimulation of a local immune reaction to eliminate oncogene-expressing cells, both those cells that have undergone oncogene-induced senescence and those oncogene-transformed cells that have bypassed or escaped senescence (131).”

• cites [131] sourceNot checked — no full text of the source

Senescent cells, in part by virtue of the SASP, appear to be programmed to mobilize the immune system to ensure their eventual elimination.

“Thus, senescent cells, in part by virtue of the SASP, appear to be programmed to mobilize the immune system to ensure their eventual elimination.”

This stimulation is due in part to soluble factors produced by senescent cells.

“This stimulation is due in part to soluble factors produced by senescent cells (129).”

• cites [129] sourceNot checked — no full text of the source

One function of this immune reaction appears to be the killing and eventual clearance of senescent cells.

“One function of this immune reaction appears to be the killing and eventual clearance of senescent cells.”

In the cases of acute liver injury and cutaneous wounds, senescent cells limit the development of fibrosis.

“In the case of acute liver injury and cutaneous wounds, senescent cells limit the development of fibrosis.”

The same is true for the many age-related pathologies in which senescent cells are chronically present.

“The same is true for the plethora of age-related pathologies in which senescent cells are chronically present, as discussed above.”

Taken together, these studies suggest that one function of the senescence response and accompanying SASP is to promote optimal wound healing after tissue injury.

“Taken together, these studies suggest that one function of the senescence response and accompanying SASP is to promote optimal wound healing after tissue injury.”

MMPs can cleave cell surface ligands on natural killer target cells and receptors on natural killer cells, preventing NK cells from targeting and killing senescent cells.

“These proteases can cleave both the cell surface ligands on natural killer target cells and the cell surface receptors on natural killer cells, thereby preventing natural killer cells from targeting and killing senescent cells.”

Senescent cells secrete high levels of MMPs.

“For example, as noted above, senescent cells secrete high levels of MMPs.”