Characterization of EGFR T790M, L792F, and C797S Mutations as Mechanisms of Acquired Resistance to Afatinib in Lung Cancer

Abstract

Lung cancers harboring common EGFR mutations respond to EGFR tyrosine kinase inhibitors (TKI). We previously reported that tumors with exon 18 mutations are particularly sensitive to irreversible second-generation (2G) afatinib compared with first-generation TKIs (1G-TKI). However, data on the mechanisms of acquired resistance to afatinib are limited. We established afatinib-resistant cells by transfecting Ba/F3 cells with common or exon 18 (G719A and Del18) mutations and subjecting them to chronic exposure to increasing concentrations of afatinib. Afatinib-resistant clones were separately established through N-ethyl-N-nitrosourea (ENU) mutagenesis and exposure to fixed concentrations of afatinib. Rebiopsy samples from patients whose tumors acquired resistance to afatinib were analyzed. Afatinib-resistant cells with Del19, L858R, or G719A developed T790M, whereas those with Del18 acquired novel L792F mutation. ENU mutagenesis screening established 84 afatinib-resistant clones. All Del19 clones and most of the other clones acquired only T790M. However, C797S occurred in subsets of L858R, G719A, and Del18 clones. In addition, subsets of Del18 clones acquired L792F. C797S-acquired cells were sensitive to 1G erlotinib. L792F demonstrated intermediate resistance between T790M and C797S to both 1G- and 3G-TKIs, whereas L792F was the least resistant to 2G-TKIs, particularly dacomitinib. Chronic exposure of Del18 + L792F cells to dacomitinib induced additional T790M. T790M was detected in one of four clinical samples. In conclusion, L792F and C797S, in addition to the major T790M, can develop in afatinib-resistant cells particularly using a low dose of afatinib, and these minor mutations appear to exhibit sensitivity to dacomitinib and erlotinib, respectively. These secondary mutations should be tested in clinical practice. Mol Cancer Ther; 16(2); 357-64. ©2016 AACRSee related article by Talbert et al., p. 344.

Patient with Three EGFR Mutations – Gradual Development of Resistance to Previous Targeted Treatment

“…Jejich přítomnost je spojena s horší prognózou pa cientů [21] a stejně jako u naší nemocné jsou obvykle spojeny s pohrudničními maligními výpotky [14]. Kazuisticky byla doložena regrese tohoto typu metastáz po erlotinibu, který navíc dle jiné práce dokládal slibnou účinnost po léčbě afatinibem se získanou mutací C797S a delecí na exonu 19 [23,24]. V našem případě tato léčba však benefit nepřinesla, patrně pro současně přítomnou mutaci T790M.…”

ErbB Family Signalling: A Paradigm for Oncogene Addiction and Personalized Oncology

“…The inhibition of specific ErbB proteins with low molecular weight tyrosine kinase inhibitors (TKI) or antibodies was often sufficient to cause cancer cell death [66,67]. On the contrary, certain mutations of ErbB proteins conferred resistance to treatment [48,54,68,69,70,71,72,73]. …”

“…In such cases, the treatments with selective drugs such as gefitinib and erlotinib have shown impressive clinical efficacies [76,77,78,79]. On the other hand, the most important alteration that has been frequently associated with acquired resistance is the point mutation T790M in exon 20 [68,72,73,80]. It occurs first and foremost in advanced tumours that have lost normal regulatory feedback circuits and use mutated EGFR to constitutively drive proliferation and survival [68].…”

“…On the other hand, the most important alteration that has been frequently associated with acquired resistance is the point mutation T790M in exon 20 [68,72,73,80]. It occurs first and foremost in advanced tumours that have lost normal regulatory feedback circuits and use mutated EGFR to constitutively drive proliferation and survival [68]. Effective targeting of T790M mutated EGFR has been a research challenge of the last decade.…”

Prospective exosome‐focused translational research for afatinib study of non‐small cell lung cancer patients expressing EGFR (EXTRA study)

“…With regard to the mechanism of acquired resistance, it remains unclear why a T790M mutation is acquired following treatment with a first‐generation EGFR‐TKI or why C797S and L792F mutations are acquired following treatment with osimertinib, a third‐generation EGFR‐TKI …”