STAT3 Contributes to the Mitogenic Response of Hepatocytes during Liver Regeneration

In the paper

“Three did not show IL-6 regulation posthepatectomy but were activated by IL-6 injection in the liver (TDAG51, membrane glycoproteingp130, and Erp72, the endoplasmic reticulum stress protein) (4”

What the sources say

• Disputed

  Table 1 (HEPATOLOGY June 2001 section; page not supplied) lists ERp72, gp130, and TDAG51 with differential expression between IL-6-positive and IL-6-deficient livers two hours after hepatectomy. That is contrary to the claim that these three showed no IL-6 regulation posthepatectomy. The table passage does not clearly establish the claimed injection result for all three. (LLM, conf=0.82)

  Checked by a reasoning model — may be wrong.

  cites [4] Li, 2001, Hepatology sourceExperimental — accuracy not yet measured

In the paper

“STAT3 is rapidly induced during liver regeneration in an interleukin 6 (IL-6)-dependent fashion, and IL-6 is required for normal liver regeneration.”

What the sources say

• ?Not checked — no full text of the sourcecites [3] Cressman, 1996, Science source
• Supported

  The Results report that Stat3 expression was induced twofold within two hours of partial hepatectomy. The introductory passage under Abstract reports reduced Stat3 induction in IL-6-deficient livers during regeneration, and the Discussion states that IL-6 activates Stat3 after hepatectomy. The paper also states that IL-6 is necessary for normal liver regeneration. Exact pages for these passages are not specified in our copy. (LLM, conf=0.92)

  cites [4] Li, 2001, Hepatology source

In the paper

“STAT3 is rapidly induced during liver regeneration in an interleukin 6 (IL-6)-dependent fashion, and IL-6 is required for normal liver regeneration.”

What the sources say

• ?Not checked — no full text of the sourcecites [3] Cressman, 1996, Science source
• Supported

  The paper states that IL-6 is essential for normal liver regeneration (opening text following the Abstract). The Discussion also says its findings establish IL-6 as a critical component of the normal regenerative response. (LLM, conf=0.94)

  cites [4] Li, 2001, Hepatology source

In the paper

“IL-6−/− mice have impaired liver regeneration characterized by liver necrosis and failure, a blunted DNA synthetic response in hepatocytes, and reduced gene activation during G1 phase.”

What the sources say

• ?Not checked — no full text of the sourcecites [3] Cressman, 1996, Science source
• Partly supported

  The introductory passage following the Abstract says IL-6-deficient mice have impaired regeneration and liver necrosis after 70% partial hepatectomy. It says they are prone to liver failure, rather than stating that liver failure occurs in all such mice; the claim omits that qualification. (LLM, conf=0.83)

  cites [4] Li, 2001, Hepatology sourceExperimental — accuracy not yet measured

In the paper

“IL-6−/− mice have impaired liver regeneration characterized by liver necrosis and failure, a blunted DNA synthetic response in hepatocytes, and reduced gene activation during G1 phase.”

What the sources say

• ?Not checked — no full text of the sourcecites [3] Cressman, 1996, Science source
• Supported

  The Abstract states that genes involved in G0/G1 transition and G1 progression showed reduced induction in IL-6−/− livers during regeneration. It also reports blunted DNA synthesis, liver necrosis and a risk of liver failure after partial hepatectomy, supporting the full citing sentence. (LLM, conf=0.94)

  cites [4] Li, 2001, Hepatology source

In the paper

“However, because IL-6 also activates other signaling pathways including the mitogen-activated protein kinase (MAPK) pathway during liver regeneration (4”

What the sources say

• Supported

  The Discussion states that MAPK activation is delayed in IL-6-deficient livers and that an IL-6 injection induces MAPK phosphorylation in the liver. It explicitly describes IL-6 activation of the MAPK pathway during liver regeneration as a mechanism complementary to Stat3 signaling. (LLM, conf=0.94)

  cites [4] Li, 2001, Hepatology source

In the paper

“Interleukin-6 (IL-6)1 is known as one of the most important initiators of the regenerative response (3”

What the sources say

• ?Not checked — no full text of the sourcecites [3] Cressman, 1996, Science source
• Supported

  The Discussion describes IL-6 as an early stimulus during liver regeneration and a critical component of the normal regenerative response. It also links IL-6 to initiation of the regenerative process, supporting the paraphrase in the paper’s liver-regeneration context. (LLM, conf=0.88)

  cites [4] Li, 2001, Hepatology source

In the paper

“IL-6−/− mice have impaired liver regeneration characterized by liver necrosis and failure, a blunted DNA synthetic response in hepatocytes, and reduced gene activation during G1 phase.”

What the sources say

• ?Not checked — no full text of the sourcecites [3] Cressman, 1996, Science source
• Supported

  The passage labeled Abstract states that IL-6-deficient mice have blunted DNA synthesis after 70% partial hepatectomy. This directly supports the attributed claim about a blunted DNA synthetic response during liver regeneration. (LLM, conf=0.93)

  cites [4] Li, 2001, Hepatology source

In the paper

“their expression is likely to be directly regulated by STAT3 because their full transactivation requires the STAT binding elements in their promoters (19”

What the sources say

• Partly supported

  The c-fos promoter experiments (section labeled Introduction; page unavailable) show that a SIF-binding element enhances c-sis/PDGF-induced transcription and that nonbinding mutations abolish induction in the tested constructs. The paper does not address junB or identify SIF as STAT3, and these experiments do not establish that STAT binding elements are required for full transactivation of both genes. (LLM, conf=0.87)

  cites [19] Wagner, 1990, EMBO J. sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [27] Coffer, 1995, Oncogene

In the paper

“In IL-6−/− livers, the first peak of MAPK activation is delayed until 12 h compared with 2 h posthepatectomy in IL-6+/+ livers”

What the sources say

• Supported

  The passage accompanying Fig. 6B (Hepatology, June 2001) reports peak p44/p42 MAPK phosphorylation at 2 hours posthepatectomy in IL-6+/+ livers, while activation in IL-6−/− livers was delayed until 12 hours. This matches the cited comparison. (LLM, conf=0.95)

  cites [4] Li, 2001, Hepatology source

In the paper

“Only 1 of 10 STAT3 target genes had not previously been identified as an IL-6 target gene (lymphotoxin receptor).”

In the paper

“Unlike in control livers, STAT1 was activated in STAT3 conditional-mutant livers posthepatectomy.”

In the paper

“However, the degree of overlap between the two gene sets was high.”

In the paper

“STAT3 DNA binding activity was also absent in Alb+ STAT3fl/fllivers.”

In the paper

“STAT3 regulates the expression of some IL-6 target genes during liver regeneration but could not account for all of the gene expression abnormalities observed in IL-6−/− livers.”

In the paper

“There was no significant difference in the serum indexes from the Alb+ compared with the Alb−STAT3fl/fl livers”

In the paper

“We found that DNA synthesis was partially impaired in Alb+ STAT3fl/fl livers but that liver regeneration still occurred in the absence of STAT3.”

In the paper

“We found that DNA synthesis was partially impaired in Alb+ STAT3fl/fl livers but that liver regeneration still occurred in the absence of STAT3.”

In the paper

“We estimated that there was more than 90% deletion of the STAT3 gene.”

In the paper

“The activation of MAPK in Alb+ STAT3fl/fl livers followed the same kinetics as found in control livers.”

In the paper

“Alb+STAT3fl/fl livers had abnormalities in immediate-early gene activation that largely correlated with but were not identical to those seen in IL-6−/− livers.”

In the paper

“G1 phase cyclins including cyclins D1 and E had lower expression levels in Alb+ STAT3fl/fl livers, indicating an abnormal G1 to S phase transition.”

In the paper

“As in IL-6−/− livers, c-fos, and junB expression were significantly reduced in Alb+STAT3fl/fl livers at all time points compared with Alb− STAT3fl/fl livers.”

In the paper

“A smaller number of immediate-early genes were differentially expressed in Alb− STAT3fl/fl liversversus Alb+ STAT3fl/fllivers compared with those differentially expressed in the IL-6+/+ and −/− livers.”

In the paper

“The activation of MAPK in Alb+ STAT3fl/fl livers followed the same kinetics as found in control livers.”

In the paper

“STAT3 mRNA was present in the quiescent Alb−STAT3fl/fl liver but not in Alb+STAT3fl/fl livers.”

In the paper

“After partial hepatectomy, there was virtually no STAT3 RNA or protein induction in Alb+STAT3fl/fl livers.”

In the paper

“STAT3 regulates the expression of some IL-6 target genes during liver regeneration but could not account for all of the gene expression abnormalities observed in IL-6−/− livers.”

In the paper

“After quantification using scanning densitometry, no consistent or significant difference in the level of either the phosphorylated Erk1 or the phosphorylated Erk2 was observed at any time point.”

In the paper

“The most prominent form of the DNA binding complex was the STAT3/STAT3 homodimer.”

In the paper

“In contrast, there was no detectable STAT3 protein in Alb+STAT3fl/fl livers.”

In the paper

“Interestingly, Egr-1, which was down-regulated in IL-6−/− livers 2 h posthepatectomy, was up-regulated in Alb+ STAT3fl/fllivers”

In the paper

“Peak activation of c-myc was delayed in Alb+STAT3fl/fl livers compared with Alb− STAT3fl/fl livers.”

In the paper

“Of the nine IL-6 target genes, six were differentially expressed in the IL-6+/+ and −/− livers posthepatectomy, including c-myc, TNFR2, GADD-45, serine protease inhibitor 2.4, c-fos, and Egr-1.”

In the paper

“Hepatocyte DNA synthesis at 40 h posthepatectomy in Alb+STAT3fl/fl livers was reduced to approximately one-third of the control.”

• Also stated in: § RESULTS · plain

  “There was a 3-fold difference in the number of hepatocytes undergoing DNA synthesis at 40 h posthepatectomy (p < 0.02) and reduced DNA synthesis at other time points (Fig. 3, A andB)”

In the paper

“Peak STAT3 DNA binding occurred at 2 h posthepatectomy in control livers.”

In the paper

“STAT3 was also necessary for the activation of G1 phase cyclins that support DNA synthesis and mitosis.”

In the paper

“In the STAT3 conditional knock-out, we observed that the spectrum of genes in which expression levels are reduced is smaller compared with that seen in the IL-6 knock-out.”

In the paper

“In the absence of STAT3, STAT1 activation was dramatically increased posthepatectomy”

In the paper

“However, the change is not as great as that seen in the IL-6−/− livers (5”

What the sources say

• ?Not checked — no full text of the sourcecites [5] Leu, 2001, Mol. Cell. Biol. source

In the paper

“In Alb−STAT3fl/fl livers, induction of c-Fos was detected as early as 1 h, and there was a peak induction at 2 h posthepatectomy. There was little induction of c-Fos until 4 h posthepatectomy in Alb+ STAT3fl/fllivers.”

In the paper

“This result correlated with the increased STAT1 DNA binding activity in Alb+ STAT3fl/fl livers posthepatectomy.”

In the paper

“In STAT3 conditional-mutant livers,IGFBP-1 expression is reduced at 2 h posthepatectomy by 2-fold based on the result of three different sets of samples.”

In the paper

“These two genes are the most strongly affected immediate-early genes in IL-6−/− livers”

In the paper

“STAT3 was required for the activation of several immediate-early genes at the gene expression level including c-fos and junB.”

In the paper

“DNA synthesis posthepatectomy was partially impaired in the absence of STAT3”

In the paper

“at the peak of S phase, which is approximately 40 h posthepatectomy in mouse livers, the percentage of hepatocytes undergoing DNA synthesis is 5-fold lower in IL-6−/− livers than IL-6+/+ livers”

In the paper

“whereas the difference between the Alb+ and Alb− STAT3fl/fl livers is smaller at about 3-fold.”

In the paper

“In contrast, MAPK activation is normal in Alb+STAT3fl/fl livers during the early time points posthepatectomy”

In the paper

“Normal activation of the MAPK pathway in Alb+STAT3fl/fl livers reinforces the fact that at least part of the effect of IL-6 on hepatocyte proliferation is not mediated by STAT3.”

In the paper

“This is the first in vivo evidence that STAT3 promotes cell cycle progression and cell proliferation by up-regulating immediate-early growth response genes.”

In the paper

“In IL-6−/− livers, abnormalities in the induction and temporal expression of several important immediate-early growth response genes are observed posthepatectomy (3”

What the sources say

• ?Not checked — no full text of the sourcecites [3] Cressman, 1996, Science source

In the paper

“Furthermore, STAT3 activation is absent posthepatectomy in IL-6−/− livers, which supports a possible pro-proliferative role of STAT3 in hepatocytes (3”

What the sources say

• ?Not checked — no full text of the sourcecites [3] Cressman, 1996, Science source

In the paper

“Furthermore, STAT3 activation is absent posthepatectomy in IL-6−/− livers, which supports a possible pro-proliferative role of STAT3 in hepatocytes (3”

What the sources say

• ?Not checked — no full text of the sourcecites [3] Cressman, 1996, Science source

In the paper

“indicating a STAT3-independent activation of Egr-1posthepatectomy.”

In the paper

“Therefore, STAT3 accounts for part of the DNA synthetic response of the hepatocytes during liver regeneration, which cannot be compensated for by induction of STAT1.”

In the paper

“This finding supports the conclusion that STAT3 and MAPK represent two independent IL-6 signaling pathways.”

In the paper

“These results proved that the disruption of STAT3 gene by Cre recombinase in the liver is efficient.”

In the paper

“Supershift assay was used to confirm the composition of the DNA binding complexes in both the Alb− and Alb+ STAT3fl/fl livers (Fig.2 B).”

In the paper

“This study provides the first in vivoevidence that STAT3 promotes cell cycle progression and cell proliferation under physiological growth conditions.”

In the paper

“Also the conditional deletion of STAT3 in the liver demonstrated that STAT3 is essential for the induction of all acute phase response genes downstream of IL-6 (14”

What the sources say

• ?Not checked — no full text of the sourcecites [14] Alonzi, 2001, Mol. Cell. Biol. source

In the paper

“Therefore, STAT3 accounts for part of the DNA synthetic response of the hepatocytes during liver regeneration, which cannot be compensated for by induction of STAT1.”

In the paper

“G1 phase cyclins including cyclins D1 and E had lower expression levels in Alb+ STAT3fl/fl livers, indicating an abnormal G1 to S phase transition.”

In the paper

“However, STAT1 activation was not sufficient to compensate for all STAT3 function because disruption of STAT3 still led to down-regulation of several immediate-early genes, and the level of the reduction was comparable with that seen in the IL-6 knock-outs.”

In the paper

“Its activation is in part regulated by IL-6 via direct interaction between STAT3, AP-1, and HNF-1 transcription factors (5”

What the sources say

• ?Not checked — no full text of the sourcecites [5] Leu, 2001, Mol. Cell. Biol. source

In the paper

“It was demonstrated clearly that activation of the MAPK pathway is a key signal for the G1 phase progression of the proliferating hepatocytes after partial hepatectomy (47”

What the sources say

• ?Not checked — no full text of the sourcecites [47] Talarmin, 1999, Mol. Cell. Biol. source

In the paper

“All of the other STAT knock-outs have relatively mild phenotypes correlated with rather specific defects in response to certain cytokines or growth factors (12”

What the sources say

• ?Not checked — no full text of the sourcecites [12] Takeda, 1997, Proc. Natl. Acad. Sci. U. S. A. source
• ?Not checked — no full text of the sourcecites [34] Kaplan, 1996, Nature source
• ?Not checked — no full text of the sourcecites [35] Liu, 1997, Genes Dev. source
• ?Not checked — no full text of the sourcecites [36] Takeda, 1996, Nature source
• ?Not checked — no full text of the sourcecites [37] Shimoda, 1996, Nature source

In the paper

“suggesting that normally STAT3 may inhibit STAT1 activation during liver regeneration by unknown mechanisms.”

In the paper

“It represents a class of STAT3 target genes for which expression may be rescued partially in the presence of STAT1”

In the paper

“STAT1 is the only STAT in addition to STAT3 that is activated during liver regeneration (17”

What the sources say

• ?Not checked — no full text of the sourcecites [17] Cressman, 1995, Hepatology source

In the paper

“The results obtained from Alb+STAT3fl/fl are important because they represent the first example of a pro-proliferative role of STAT3 under physiological growth conditions in vivo.”

In the paper

“The expression of IGFBP-1 is activated by STAT3 in coordination with AP-1 and HNF-1 transcription factors via an HNF-1 binding site during liver regeneration.”

In the paper

“The study reported here is the first in vivo evidence that STAT3 can directly participate in cell cycle progression.”

In the paper

“suggesting that IL-6 activation of the MAPK pathway is independent of STAT3 activation.”

In the paper

“A certain percentage of IL-6−/− animals die after surgery because of liver necrosis and failure (3”

What the sources say

• ?Not checked — no full text of the sourcecites [3] Cressman, 1996, Science source

In the paper

“it also suggests that the STAT3 effect on hepatocyte DNA synthesis and cell proliferation is not secondary to direct effects on the MAPK pathway.”