Distinct Afatinib Resistance Mechanisms Identified in Lung Adenocarcinoma Harboring an EGFR Mutation.

EGFR tyrosine kinase inhibitors (TKI) are associated with significant responses in non-small cell lung cancer (NSCLC) patients harboring EGFR-activating mutations. However, acquired resistance to reversible EGFR-TKIs remains a major obstacle. In particular, although the second-generation irreversible EGFR-TKI afatinib is currently used for treating NSCLC patients, the mechanisms underlying acquired afatinib resistance remain poorly understood. Here, heterogeneous mechanisms of acquired resistance were identified following long-term exposure to increasing doses of afatinib in EGFR-mutant lung adenocarcinoma PC-9 cells. Notably, three resistant cell lines, PC-9AFR1, PC-9AFR2, and PC-9AFR3 (AFR1, AFR2, and AFR3, respectively) employed distinct mechanisms for avoiding EGFR inhibition, with increased EGFR expression being detected in all resistant cell lines. Moreover, an activating EGFR mutation was partially lost in AFR1 and AFR2 cells. AFR1 cells exhibited afatinib resistance as a result of wild-type KRAS amplification and overexpression; however, these cells showed a progressive decrease and eventual loss of the acquired KRAS dependence, as well as resensitization to afatinib, following a drug holiday. Meanwhile, AFR2 cells exhibited increased expression of insulin-like growth factor-binding protein 3 (IGFBP3), which promoted insulin-like growth factor 1 receptor (IGF1R) activity and subsequent AKT phosphorylation, thereby indicating a potential bypass signaling pathway associated with IGFR1. Finally, AFR3 cells harbored the secondary EGFR mutation T790M. Our findings constitute the first report showing acquired wild-type KRAS overexpression and attenuation of afatinib resistance following a drug holiday.Implications: The heterogeneous mechanisms of afatinib resistance should facilitate the development of more effective therapeutic strategies for NSCLC patients. Mol Cancer Res; 15(7); 915-28. ©2017 AACR.

Yamaoka T ，Ohmori T ，Ohba M ，Arata S ，Murata Y ，Kusumoto S ，Ando K ，Ishida H ，Ohnishi T ，Sasaki Y ... -  《-》

Inhibition of IGF1R signaling abrogates resistance to afatinib (BIBW2992) in EGFR T790M mutant lung cancer cells.

Non-small cell lung cancer (NSCLC) patients with an epidermal growth factor receptor (EGFR) mutation have benefited from treatment of reversible EGFR tyrosine kinase inhibitors (TKIs) such as gefitinib and erlotinib. Acquisition of a secondary mutation in EGFR T790M is the most common mechanism of resistance to first generation EGFR TKIs, resulting in therapeutic failure. Afatinib is a second generation of EGFR TKI that showed great efficacy against tumors bearing the EGFR T790M mutation, but it failed to show the improvement on overall survival of lung cancer patients with EGFR mutations possibly because of novel acquired resistance mechanisms. Currently, there are no therapeutic options available for lung cancer patients who develop acquired resistance to afatinib. To identify novel resistance mechanism(s) to afatinib, we developed afatinib resistant cell lines from a parental human-derived NSCLC cell line, H1975, harboring both EGFR L858R and T790M mutations. We found that activation of the insulin-like growth factor 1 receptor (IGF1R) signaling pathway contributes to afatinib resistance in NSCLC cells harboring the T790M mutation. IGF1R knockdown not only significantly sensitizes resistant cells to afatinib, but also induces apoptosis in afatinib resistance cells. In addition, combination treatment with afatinib and linsitinib shows more than additive effects on tumor growth in in vivo H1975 xenograft. Therefore, these finding suggest that IGF1R inhibition or combination of EGFR-IGF1R inhibition strategies would be potential ways to prevent or potentiate the effects of current therapeutic options to lung cancer patients demonstrating resistance to either first or second generation EGFR TKIs.

Lee Y ，Wang Y ，James M ，Jeong JH ，You M ... -  《-》

Acquired Resistance Mechanisms to Combination Met-TKI/EGFR-TKI Exposure in Met-Amplified EGFR-TKI-Resistant Lung Adenocarcinoma Harboring an Activating EGFR Mutation.

Met-amplified EGFR-tyrosine kinase inhibitor (TKI)-resistant non-small cell lung cancer (NSCLC) harboring an activating EGFR mutation is responsive to concurrent EGFR-TKI and Met-TKI treatment in a preclinical model. Here, we determined that Met-amplified gefitinib-resistant cells acquire dual resistance to inhibition of EGFR and Met tyrosine kinase activities. PC-9 lung adenocarcinoma cells harboring 15-bp deletions (Del E746_A750) in EGFR exon 19 were treated with increasing concentrations of the Met-TKI PHA665752 and 1 μmol/L gefitinib for 1 year; three resistant clones were established via Met amplification. The three dual-resistance cell lines (PC-9DR2, PC-9DR4, and PC-9DR6, designated as DR2, DR4, and DR6, respectively) exhibited different mechanisms for evading both EGFR and Met inhibition. None of the clones harbored a secondary mutation of EGFR T790M or a Met mutation. Insulin-like growth factor (IGF)/IGF1 receptor activation in DR2 and DR4 cells acted as a bypass signaling pathway. Met expression was attenuated to a greater extent in DR2 than in PC-9 cells, but was maintained in DR4 cells by overexpression of IGF-binding protein 3. In DR6 cells, Met was further amplified by association with HSP90, which protected Met from degradation and induced SET and MYND domain-containing 3 (SMYD3)-mediated Met transcription. This is the first report describing the acquisition of dual resistance mechanisms in NSCLC harboring an activating EGFR mutation to Met-TKI and EGFR-TKI following previous EGFR-TKI treatment. These results might inform the development of more effective therapeutic strategies for NSCLC treatment. Mol Cancer Ther; 15(12); 3040-54. ©2016 AACR.

Yamaoka T ，Ohmori T ，Ohba M ，Arata S ，Kishino Y ，Murata Y ，Kusumoto S ，Ishida H ，Shirai T ，Hirose T ，Ohnishi T ，Sasaki Y ... -  《-》

Small Molecule T315 Promotes Casitas B-Lineage Lymphoma-Dependent Degradation of Epidermal Growth Factor Receptor via Y1045 Autophosphorylation.

Huang KY ，Kao SH ，Wang WL ，Chen CY ，Hsiao TH ，Salunke SB ，Chen JJ ，Su KY ，Yang SC ，Hong TM ，Chen CS ，Yang PC ... -  《-》

The mechanism of acquired resistance to irreversible EGFR tyrosine kinase inhibitor-afatinib in lung adenocarcinoma patients.

Wu SG ，Liu YN ，Tsai MF ，Chang YL ，Yu CJ ，Yang PC ，Yang JC ，Wen YF ，Shih JY ... -  《Oncotarget》