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Case Reports
. 2014 Jun 4;13:141.
doi: 10.1186/1476-4598-13-141.

Colon Cancer-Derived Oncogenic EGFR G724S Mutant Identified by Whole Genome Sequence Analysis Is Dependent on Asymmetric Dimerization and Sensitive to Cetuximab

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Free PMC article
Case Reports

Colon Cancer-Derived Oncogenic EGFR G724S Mutant Identified by Whole Genome Sequence Analysis Is Dependent on Asymmetric Dimerization and Sensitive to Cetuximab

Jeonghee Cho et al. Mol Cancer. .
Free PMC article

Abstract

Background: Inhibition of the activated epidermal growth factor receptor (EGFR) with either enzymatic kinase inhibitors or anti-EGFR antibodies such as cetuximab, is an effective modality of treatment for multiple human cancers. Enzymatic EGFR inhibitors are effective for lung adenocarcinomas with somatic kinase domain EGFR mutations while, paradoxically, anti-EGFR antibodies are more effective in colon and head and neck cancers where EGFR mutations occur less frequently. In colorectal cancer, anti-EGFR antibodies are routinely used as second-line therapy of KRAS wild-type tumors. However, detailed mechanisms and genomic predictors for pharmacological response to these antibodies in colon cancer remain unclear.

Findings: We describe a case of colorectal adenocarcinoma, which was found to harbor a kinase domain mutation, G724S, in EGFR through whole genome sequencing. We show that G724S mutant EGFR is oncogenic and that it differs from classic lung cancer derived EGFR mutants in that it is cetuximab responsive in vitro, yet relatively insensitive to small molecule kinase inhibitors. Through biochemical and cellular pharmacologic studies, we have determined that cells harboring the colon cancer-derived G719S and G724S mutants are responsive to cetuximab therapy in vitro and found that the requirement for asymmetric dimerization of these mutant EGFR to promote cellular transformation may explain their greater inhibition by cetuximab than small-molecule kinase inhibitors.

Conclusion: The colon-cancer derived G719S and G724S mutants are oncogenic and sensitive in vitro to cetuximab. These data suggest that patients with these mutations may benefit from the use of anti-EGFR antibodies as part of the first-line therapy.

Figures

Figure 1
Figure 1
Identification of a somatic EGFR mutation in colorectal adenocarcinoma via whole genome sequencing. (A) Depiction of the somatic structural rearrangements in this colorectal cancer genome by a Circos plot. The chromosomes are depicted along the circle with somatic rearrangements depicted in purple (interchromosomal) and green (intrachromosomal), including a deletion at the APC tumor suppressor locus. (B) Depiction of numbers of candidate mutations and non-synonymous alterations in coding genes, and mutations in known cancer genes, TP53 and EGFR. (C) Schematic of somatic EGFR mutations found in glioblastoma (green lettering), lung adenocarcinoma (blue lettering) and colorectal adenocarcinoma (red lettering), with insertions and deletions above the domain structure, and substitution mutations below the domain structure indicated by red dots.
Figure 2
Figure 2
Pharmacological effects of cetuximab against oncogenic G719S and G724S mutants in vitro and in vivo. (A) Cetuximab suppresses the growth of Ba/F3 cells dependent upon the G719S and G724S mutants, but not control cells. Ba/F3 cells transformed with the indicated EGFR mutants were treated with cetuximab at the concentrations indicated and assayed for viability after 72 hours of drug treatment. The results are indicated as mean +/- SD of sextuplicate wells and are representative of three independent experiments (B and C) Cetuximab is effective against SW48 (EGFR G719S mutant)-induced tumors but not HCT8 (KRAS G13D mutant) induced-tumors in xenografted mice. BALB/c-nu/nu mice (6–8 weeks of age) were injected subcutaneously to the flank with 0.5 ~ 1x107 SW48 or HCT8 cells in 150 ~ 200 μl of PBS. Tumor sizes were measured two times a week using a Vernier caliper and tumor volumes were calculated according to the formula of (short diameter)2 x (long diameter)/2. When tumor volume reached around 100 ~ 150 mm3, mice were randomized into each group. After confirming that mean tumor volumes were not statistically different between two groups, mice were administered either with PBS or cetuximab (1 mg/mouse) intra-peritoneally twice a week.
Figure 3
Figure 3
Dimerization disruption has effects on the transforming activity of G719S and G724S EGFR proteins. (A and B) G719S and G724S mutants are dependent on asymmetric dimerization for their transforming potential. NIH-3T3 cells expressing the indicated EGFR mutants with or without receiver-impairing (L704N) or/and activator-impairing (I941R) mutations were assayed for anchorage-independent growth in soft agar. The bar graph depicts the relative number of colonies in the dimerization-defective mutants normalized to the number of colonies formed by cells expressing the respective parental mutants (n = 3, mean + SD). (C and D) Ligand-induced and constitutive tyrosine-phosphorylation is abrogated on dimerization-impaired compound mutants of cetuximab-sensitive EGFR mutants. Whole cell lysates from the same cells analyzed in Figure  3A and B expressing G719S (C), and G724S (D) mutants with or/and without dimerization-impairing mutations (L704N or I941R) in the absence or presence of EGF treatment for 15 minutes (25 ng/ml) were subjected to immunoblotting with antibodies against phospho-tyrosine (4G10) and EGFR.

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References

    1. Hynes NE, Lane HA. ERBB receptors and cancer: the complexity of targeted inhibitors. Nat Rev Cancer. 2005;5:341–354. doi: 10.1038/nrc1609. - DOI - PubMed
    1. Chan SK, Gullick WJ, Hill ME. Mutations of the epidermal growth factor receptor in non-small cell lung cancer – search and destroy. Eur J Cancer. 2006;42:17–23. doi: 10.1016/j.ejca.2005.07.031. - DOI - PubMed
    1. Lynch TJ, Bell DW, Sordella R, Gurubhagavatula S, Okimoto RA, Brannigan BW, Harris PL, Haserlat SM, Supko JG, Haluska FG, Louis DN, Christiani DC, Settleman J, Haber DA. Activating mutations in the epidermal growth factor receptor underlying responsiveness of non-small-cell lung cancer to gefitinib. N Engl J Med. 2004;350:2129–2139. doi: 10.1056/NEJMoa040938. - DOI - PubMed
    1. Pao W, Miller V, Zakowski M, Doherty J, Politi K, Sarkaria I, Singh B, Heelan R, Rusch V, Fulton L, Mardis E, Kupfer D, Wilson R, Kris M, Varmus H. EGF receptor gene mutations are common in lung cancers from "never smokers" and are associated with sensitivity of tumors to gefitinib and erlotinib. Proc Natl Acad Sci U S A. 2004;101:13306–13311. doi: 10.1073/pnas.0405220101. - DOI - PMC - PubMed
    1. Paez JG, Janne PA, Lee JC, Tracy S, Greulich H, Gabriel S, Herman P, Kaye FJ, Lindeman N, Boggon TJ, Naoki K, Sasaki H, Fujii Y, Eck MJ, Sellers WR, Johnson BE, Meyerson M. EGFR mutations in lung cancer: correlation with clinical response to gefitinib therapy. Science. 2004;304:1497–1500. doi: 10.1126/science.1099314. - DOI - PubMed

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