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Cited by 606Lung Cancer Treatments and MutationsHER2/EGFR in Cancer ResearchCancer Genomics and Diagnostics

The Allelic Context of the C797S Mutation Acquired upon Treatment with Third-Generation EGFR Inhibitors Impacts Sensitivity to Subsequent Treatment Strategies

Open access
Niederst, Matthew J., Hu, Haichuan, Mulvey, Hillary E., Lockerman, Elizabeth L., Garcia, Angel R., Piotrowska, Zofia, Sequist, Lecia V., Engelman, Jeffrey A.·2015·Clinical Cancer Research
DOI 10.1158/1078-0432.ccr-15-0560PMC PMC4587765

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Abstract

Purpose: A secondary EGFR mutation, T790M, is the most common resistance mechanism in EGFR-mutant adenocarcinomas that have progressed on erlotinib. Third-generation EGFR inhibitors capable of inhibiting mutant EGFR with T790M produce responses in nearly two thirds of patients. However, acquired resistance mechanisms in patients treated with these drugs are yet to be described. Experimental Design: To study acquired resistance to third-generation EGFR inhibitors, T790M-positive cells derived from an erlotinib-resistant cancer were made resistant to a third-generation TKI and then characterized using cell and molecular analyses. Results: Cells resistant to a third-generation TKI acquired an additional EGFR mutation, C797S, which prevented suppression of EGFR. Our results demonstrate that the allelic context in which C797S was acquired may predict responsiveness to alternative treatments. If the C797S and T790M mutations are in trans, cells will be resistant to third-generation EGFR TKIs, but will be sensitive to a combination of first- and third-generation TKIs. If the mutations are in cis, no EGFR TKIs alone or in combination can suppress activity. If C797S develops in cells wild-type for T790 (when third-generation TKIs are administered in the first-line setting), the cells are resistant to third-generation TKIs, but retain sensitivity to first-generation TKIs. Conclusions: Mutation of C797S in EGFR is a novel mechanism of acquired resistance to third-generation TKIs. The context in which the C797S develops with respect to the other EGFR alleles affects the efficacy of subsequent treatments. Clin Cancer Res; 21(17); 3924–33. ©2015 AACR. See related commentary by Ayeni et al., p. 3818

Verified 2026-10-06 · 1 reference not checked yet

Integrity signals

Registry

Crossref · 10.1158/1078-0432.ccr-15-0560

Cites

41 of 42 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 16 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    MGH121 Res #1 cells acquired a C797S point mutation in EGFR that was absent from parental MGH121 cells.

    “Sequencing of the kinase domain of EGFR revealed a single point mutation resulting in a cysteine to serine change at position 797 (C797S). This mutation was present in the MGH121 Res # 1 cells, but not the MGH121 parental cells (Figure 1D).”
    Quote in the paperSubstantial claim
  • Findingown data

    Expression of C797S mutant EGFR in PC9 cells significantly increased the afatinib IC50 compared with parental PC9 cells.

    “expression of mutant EGFR with C797S in PC9 cells results in a significant increase in the IC50 of afatinib compared to parental PC9 cells.”
    Quote in the paperSubstantial claim
  • Findingown data

    The afatinib concentration required to suppress growth of PC9 Exon 19 deletion/C797S cells was markedly higher than for PC9 parental cells.

    “Of note, the concentration of afatinib required to suppress the growth of cells expressing the Exon 19 Del/C797S construct was markedly higher than the PC9 parental cells (Figure 4B)”
    Quote in the paperSubstantial claim
  • Findingown data

    None of the tested EGFR TKIs suppressed EGFR signaling in MGH121 Res #1 cells.

    “In contrast, none of the EGFR TKIs suppressed EGFR signaling in MGH121 Res # 1 cells.”
    Quote in the paperSubstantial claim
  • Findingown data

    At 1 μM, afatinib inhibited mutant EGFR with C797S in the absence of T790M.

    “Our data reveal that at a concentration of 1μM, afatinib can inhibit mutant EGFR with C797S in the absence of T790M.”
    Quote in the paperSubstantial claim
  • May combine two claims. 21
  • The quote only partly states this claim. 2
  • Classified as probably not a substantial claim. 6

  • May combine two claims.

    Findingown data

    The MGH121 cell line, derived from an erlotinib-resistant EGFR-mutant tumor with T790M, was resistant to gefitinib but highly sensitive to WZ4002.

    “This cell line, MGH121, was resistant to the first generation EGFR TKI gefitinib, consistent with the presence of the T790M resistance mutation, but was highly sensitive to the third generation TKI WZ4002 (Figure 1A).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In MGH121 Res #1 cells, WZ4002 treatment did not suppress EGFR phosphorylation or downstream signaling.

    “WZ4002 treatment failed to suppress EGFR phosphorylation and downstream signaling in these cells (Figure 1C).”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data

    MGH121 Res #1 cells, generated by chronic exposure to increasing WZ4002 concentrations, became highly resistant to WZ4002.

    “The resulting resistant model, MGH121 Res # 1, was highly resistant to WZ4002 (Figure 1A, B)”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In parental MGH121 cells, gefitinib did not suppress EGFR phosphorylation or downstream ERK and S6, while afatinib, WZ4002, CO-1686, and AZD-9291 did.

    “In the MGH121 parental cells, gefitinib failed to suppress EGFR phosphorylation and downstream pathway components ERK and S6, whereas afatinib, WZ4002, CO-1686 and AZD-9291 were all able to do so (Figure 2B).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Parental MGH121 cells were sensitive to afatinib, CO-1686, and AZD-9291, whereas MGH121 Res #1 cells were resistant to these inhibitors.

    “Indeed, MGH121 parental cells are also sensitive to the second generation inhibitor afatinib and other third generation inhibitors CO-1686 and AZD-9291 (Figure 2A left). These inhibitors similarly bind covalently to C797 of EGFR (22, 23, 35) and are ineffective at suppressing the growth of MGH121 Res # 1 cells (Figure 2A right)”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In MGH121 parental cells, the trans configuration induced resistance to third-generation TKI, but gefitinib plus WZ4002 inhibited EGFR signaling and cell growth; this combination was not effective in the cis configuration.

    “We observed results consistent with those from the previous over-expression experiment: The trans setting induced resistance to third generation TKI, but the combination of gefitinib and WZ4002 inhibited EGFR signaling (Figure 3C) and cell growth (Figure 3D). However, this combination was not effective when all the mutations were in cis.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    When Exon 19 deletion/T790M and Exon 19 deletion/C797S were co-expressed to model trans, gefitinib or WZ4002 alone each partially suppressed EGFR phosphorylation, and the combination completely inhibited it.

    “When Exon 19 del/T790M and Exon 19 del/C797S were co-expressed in the same cells to model the trans scenario, treatment with either gefitinib or WZ4002 alone each partially suppressed EGFR phosphorylation, consistent with each drug suppressing a fraction of the EGFR protein expressed in the cells. The combination of gefitinib and WZ4002, however, completely inhibited EGFR phosphorylation (Figure 3”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In 293T cells, EGFR with Exon 19 deletion/T790M was inhibited by second- and third-generation TKIs, whereas EGFR with Exon 19 deletion/T790M/C797S was not suppressed by any tested inhibitor.

    “In this system, EGFR Exon 19 del/T790M phosphorylation was effectively inhibited by second and third generation TKIs, while phosphorylation of EGFR Exon 19 Del/T790M/C797S was not suppressed by any of the inhibitors tested (Figure 2C).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    For EGFR Exon 19 deletion/T790M, gefitinib did not inhibit EGFR phosphorylation, whereas afatinib and WZ4002 suppressed it.

    “As expected for Exon 19 del/T790M, the first generation TKI gefitinib did not inhibit EGFR phosphorylation while afatinib and WZ4002 suppressed it (Figure 3B, lanes 1-4).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    MGH121 parental cells stably expressing EGFR Exon 19 deletion/T790M/C797S were resistant to afatinib and WZ4002 for EGFR phosphorylation and downstream signaling, and their growth was resistant to all generations of EGFR TKIs.

    “Neither afatinib nor WZ4002 were able to block EGFR phosphorylation or the downstream signaling in these cells (Figure 2D). Accordingly, the growth of these cells was resistant to all generations of EGFR TKIs (Figure 2E).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    PC9 cells expressing EGFR Exon 19 deletion/C797S were resistant to WZ4002 but sensitive to gefitinib and afatinib.

    “PC9 Exon 19 Del/C797S cells were indeed resistant to WZ4002, but sensitive to gefitinib and afatinib (Figure 4 A, B).”
    Quote in the paperSubstantial claim

  • May combine two claims. The quote only partly states this claim.

    Findingown data

    MGH121 Res #1 cells had increased EGFR gene copy number compared with parental MGH121 cells, and the C797S mutant allele was specifically amplified.

    “MGH121 Res # 1 have over 9 fold more EGFR gDNA compared to normal control DNA, equal to roughly 18 copies of EGFR and consistent with amplification versus the MGH121 parental cells.”
    • Also stated in: § Results · plain
      “variant allele frequency analysis revealed that the C797S mutant allele was specifically amplified in the MGH121 Res # 1, as the majority of EGFR alleles harbor this mutation (Supplemental Figure 1B).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In MGH121 Res #1 cells, T790M and C797S were in cis: C797S coexisted with T790M on 85% of exon 20 alleles (n=101), 15% had neither mutation, and no alleles had only T790M or only C797S (n=18).

    “This analysis revealed that the T790M and C797S were in cis in MGH121 Res # 1 cells, as the C797S mutation coexisted with T790M on 85% of alleles (n = 101). The other 15% of alleles had no mutations in exon 20. Thus, there were no exon 20 alleles harboring only T790M or C797S (n = 18, Figure 3A).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Cells made resistant to a third-generation TKI acquired C797S, which prevented EGFR suppression.

    “Cells resistant to a third generation TKI acquired an additional EGFR mutation, C797S, which prevented suppression of EGFR.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    T790M is the most common acquired resistance mechanism in EGFR-mutant adenocarcinomas that progress on erlotinib, occurring in more than half of resistant biopsies.

    “A secondary epidermal growth factor receptor (EGFR) mutation, T790M, is the most common resistance mechanism in EGFR mutant adenocarcinomas that have progressed on erlotinib.”
    • Also stated in: § Introduction · plain
      “T790M is the most common resistance mechanism in these cancers and is observed in over 50% of resistant biopsies (12, 14).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [12] Yu, 2013, Analysis of tumor specimens at the time of acquired resistance to EGFR-TKI therapy in 155 patients with EGFR-mutant lung cancers, Clin Cancer Res source

      Not checked in the free run.

    • cites [14] Sequist, 2011, Genotypic and histological evolution of lung cancers acquiring resistance to EGFR inhibitors, Sci Transl Med source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Covalent interaction with C797 is important for the activity of the pan-HER inhibitor CI-1033, and a C797A mutant can confer resistance to HKI-272.

    “The covalent interaction with C797 has also been demonstrated to be important to the activity of the pan-HER inhibitor CI-1033 (38, 39) and exogenous expression of a C797A mutant can confer resistance to another second generation inhibitor, HKI-272 (36).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [38] Godin-Heymann, 2008, The T790M “gatekeeper” mutation in EGFR mediates resistance to low concentrations of an irreversible EGFR inhibitor, Mol Cancer Ther source

      Not checked in the free run.

    • cites [39] Lee, 2013, Noncovalent wild-type-sparing inhibitors of EGFR T790M, Cancer Discov source

      Not checked in the free run.

    • cites [36] Lovly, 2014, Rationale for co-targeting IGF-1R and ALK in ALK fusion-positive lung cancer, Nat Med source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    The allelic configuration of T790M and C797S (cis versus trans) affects drug response and has clinical implications.

    “These experiments demonstrate an important difference in drug response if the T790M and C797S mutations occur on the same or on different alleles, a result that has clinical implications.”
    • Also stated in: § Discussion · hedged
      “For T790M positive, erlotinib-resistant NSCLCs that develop a C797S mutation following treatment with a third generation TKI, the configuration of the T790M and C797S mutations affect how the cells could respond to therapy.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    C797 lies opposite T790 in the ATP-binding pocket, forms a covalent bond with all third-generation EGFR TKIs, and is required for these inhibitors to suppress EGFR.

    “C797 is located opposite T790 in the ATP binding pocket and forms a covalent bond with all third-generation TKIs and is necessary for the inhibitor to suppress EGFR (21).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [21] Zhou, 2009, Novel mutant-selective EGFR kinase inhibitors against EGFR T790M, Nature source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    Experiments involving 293FT cells were completed within 6 months of purchase and the cells did not undergo further testing.

    “Experiments involving the 293FT cells were completed within 6 months of purchasing from Invitrogen and did not undergo any further testing.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    When C797S and T790M are in trans, cells are resistant to third-generation EGFR TKIs but sensitive to combined first- and third-generation TKIs.

    “If the C797S and T790M mutations are in trans, cells will be resistant to third generation EGFR TKIs, but will be sensitive to a combination of first and third generation TKIs.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    PC9 cells were verified by STR analysis within 6 months to 1 year of experimentation.

    “PC9 cells were verified by STR analysis within 6 months to 1 year of experimentation.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    When C797S develops in T790-wild-type cells, such as after first-line third-generation TKI treatment, the cells are resistant to third-generation TKIs but retain sensitivity to first-generation TKIs.

    “If C797S develops in cells wild type for T790 (when third generation TKIs are administered in the first line setting), the cells are resistant to third generation TKIs, but retain sensitivity to first generation TKIs.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: PC9 cells are sensitive to all classes of EGFR inhibitors.

  • May combine two claims.

    Interpretationown data

    Combining first- and third-generation EGFR TKIs in the first-line setting may be particularly effective because neither T790M nor C797S alone would be sufficient to cause resistance to the combination.

    “Importantly, these results suggest that combining first and third generation TKIs in the first line setting may be particularly powerful since neither a T790M nor a C797S mutation alone would be sufficient to drive resistance to this combination.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    T790M causes a similar reduction in second-generation inhibitor activity against EGFR.

    “Of note, a similar reduction in activity of second generation inhibitors towards EGFR is caused by T790M (36, 40).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [36] Lovly, 2014, Rationale for co-targeting IGF-1R and ALK in ALK fusion-positive lung cancer, Nat Med source

      Not checked in the free run.

    • cites [40] Avizienyte, 2008, Comparison of the EGFR resistance mutation profiles generated by EGFR-targeted tyrosine kinase inhibitors and the impact of drug combinations, Biochem J source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    The MGH121 cell line was sequenced to confirm that it matched the patient effusion sample.

    “Once completed the cell line was sequenced to confirm that it matched the patient effusion sample.”
    Quote in the paperNot a substantial claim
25 of 25

  • The paper relies on this without support.

    Acquired resistance mechanisms in patients treated with third-generation EGFR inhibitors have not yet been described.

    “However, acquired resistance mechanisms in patients treated with these drugs are yet to be described.”

  • The paper relies on this without support.

    PC9 cells are sensitive to all classes of EGFR inhibitors.

    “PC9, which is sensitive to all classes of EGFR inhibitors.”
2 of 2

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • In a study analysing cell-free DNA of 15 patients with resistance to AZD9291 by next-generation sequencing, distinct EGFR genotypes before and after AZD9291 treatment were defined: acquired C797S together with a T790M mutation (40%), T790M mutation without a C797S mutation (33%) and loss of the T790M mutation without a C797S mutation (27%).

    “In a study analysing cell-free DNA of 15 patients with resistance to AZD9291 by next-generation sequencing (NGS), distinct EGFR genotypes before and after AZD9291 treatment were defined: acquired C797S together with a T790M mutation (40%), T790M mutation without a C797S mutation (33%) and loss of the T790M mutation without a C797S mutation (27%).33”

    From Mechanisms of resistance to EGFR-targeted drugs: lung cancer (2016) · cites this paper as [33]

  • In these models, tumour growth is still dependent on EGFR signalling and under the strong selective pressure of EGFR-TKIs, the tumour developed secondary and tertiary mutations in the EGFR gene (T790M and C797S, respectively).

    “In these models, the tumour growth is still dependent on EGFR signalling and under the strong selective pressure of EGFR-TKIs, the tumour developed secondary and tertiary mutations in the EGFR gene (T790M and C797S, respectively).33”

    From Mechanisms of resistance to EGFR-targeted drugs: lung cancer (2016) · cites this paper as [33]

  • C797S mutation appeared sensitive to first-generation TKIs, and C797S+T790M in trans can be treated with a combination of first- and third-generation TKIs.

    “Furthermore, C797S mutation appeared to be sensitive to 1G‐TKI, and even C797S+T790M in trans can be treated with a combination of 1G and 3G‐TKI.41”

    From Not all epidermal growth factor receptor mutations in lung cancer are created equal: Perspectives for individualized treatment strategy (2016) · cites this paper as [41]

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Related

Authors
Niederst, M. J., Hu, H., Mulvey, H. E., Lockerman, E. L., Garcia, A. R., Piotrowska, Z., Sequist, L. V., & Engelman, J. A.
Affiliations
Harvard University (US)
Corresponding author
Engelman, Jeffrey A.
ORCID
Venue
Clinical Cancer Research
Publisher
American Association for Cancer Research (AACR)
Published
2015-08-31
Volume
21
Issue
17
Pages
3924-3933
ISSN
  • 1078-0432 (ISSN-L)
  • 1557-3265
DOI
10.1158/1078-0432.ccr-15-0560
PMC
PMC4587765
OpenAlex
W1908940658
Cited by
583
References
42
Citations by year
2026: 33 · 2025: 47 · 2024: 47 · 2023: 50 · 2022: 49 · 2021: 57 · 2020: 66 · 2019: 53 · 2018: 65 · 2017: 57 · 2016: 49 · 2015: 10
FWCI
48.25
Type
journal article
Language
en
Open access
Locations
  • Clinical Cancer Research (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (acceptedVersion)
Funders
National Cancer Institute (R01CA137008)
Topics
  • Health Sciences › Medicine › Pulmonary and Respiratory Medicine › Lung Cancer Treatments and Mutations
  • Health Sciences › Medicine › Oncology › HER2/EGFR in Cancer Research
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cancer Research › Cancer Genomics and Diagnostics
Keywords
C797S mutation, T790M mutation, acquired drug resistance, third-generation EGFR tyrosine kinase inhibitors, erlotinib resistance, EGFR-mutant lung adenocarcinoma, predictive biomarkers
MeSH terms
Alleles, Antineoplastic Agents, Cell Survival, Codon, Humans, Mutation, Gene Expression, Drug Resistance, Neoplasm, Amino Acid Substitution, Cell Line, Tumor, Protein Kinase Inhibitors, ErbB Receptors

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