Role of Survivin in EGFR Inhibitor–Induced Apoptosis in Non–Small Cell Lung Cancers Positive for EGFR Mutations

Abstract

The molecular mechanism by which epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKI) induce apoptosis in non-small cell-lung cancer (NSCLC) cells that are positive for activating mutations of the EGFR remains unclear. In this study, we report the effects of the EGFR-TKI gefitinib on expression of the antiapoptotic protein survivin that have functional consequences in EGFR mutation-positive NSCLC cells. Immunoblot analysis revealed that gefitinib downregulated survivin expression, likely through inhibition of the PI3K-AKT signaling pathway, in NSCLC cells positive for EGFR mutation. Stable overexpression of survivin attenuated gefitinib-induced apoptosis and also inhibited the antitumor effect of gefitinib in human tumor xenografts. Furthermore, the combination of survivin overexpression with inhibition of the gefitinib-induced upregulation of the proapoptotic protein BIM attenuated gefitinib-induced apoptosis to a greater extent than either approach alone. Our results indicate that downregulation of survivin plays a pivotal role in gefitinibinduced apoptosis in EGFR mutation-positive NSCLC cells. Furthermore, they suggest that simultaneous interruption of the PI3K-AKT-survivin and MEK-ERK-BIM signaling pathways is responsible for EGFR-TKIinduced apoptotic death in these cells.

Antitumor Action of the MET Tyrosine Kinase Inhibitor Crizotinib (PF-02341066) in Gastric Cancer Positive for MET Amplification

“…Furthermore, depletion of BIM by RNAi resulted in inhibition of crizotinib-induced apoptosis in gastric cancer cells with MET amplification, indicating that upregulation of BIM contributes to the induction of apoptosis by the MET-TKI in such cells. These findings are consistent with those of previous studies of lung cancer cells with EGFR mutations and breast cancer cells with HER2 amplification (13)(14)(15)(16)(17). However, our observations revealed that depletion of BIM did not completely abolish crizotinib-induced apoptosis, suggesting that another apoptotic regulator might contribute to MET-TKIinduced apoptotic cell death.…”

“…However, depletion of STAT3 by RNAi had no substantial effect on expression of XIAP and c-IAP1 in such cells (data not shown). Previous studies have shown that XIAP and c-IAP1 were not substantially affected by EGFR-TKIs in EGFR mutationpositive non-small cell lung cancer cells or by HER2-targeting agents in breast cancer cells positive for HER2 amplification (16,17). Given that inhibition of MET results in downregulation of XIAP and c-IAP1 in MET amplification-positive gastric cancer cells, the mechanism by which the expression of such proteins is regulated likely differs between MET and other receptor tyrosine kinases including EGFR and HER2.…”

“…We found that a PI3K inhibitor or RNAimediated depletion of AKT reduced the abundance of survivin, indicating that the expression of survivin is regulated by PI3K-AKT signaling in MET amplification-positive gastric cancer cells. Previous studies have shown that the expression of survivin is dependent on PI3K-AKT signaling that operates downstream of receptor tyrosine kinases and is essential for cell survival in EGFR mutation-positive non-small cell lung cancer cells as well as in breast cancer cells positive for HER2 amplification (16,17). These results suggest that downregulation of survivin via inhibition of the MET-PI3K-AKT pathway likely also contributes to the induction of apoptosis by crizotinib in MET amplification-positive gastric cancer cells.…”

“…Induction of the proapoptotic BH3-only protein BIM has been found to be important for TKI-induced apoptosis in EGF receptor (EGFR) gene mutation-positive lung cancer and HER2 amplification-positive breast cancer (13)(14)(15)(16)(17). To investigate whether the upregulation of BIM is related to the induction of apoptosis by crizotinib, we transfected MET amplification-positive gastric cancer cells with siRNAs specific for BIM mRNAs.…”

Molecular pathology of lung cancer: key to personalized medicine

“…183 The EGFR pathway has a central role in a subset of adenocarcinomas through converging signals for cell proliferation, motility, and other cancer cell behaviors. 5,184 However, the mechanisms underlying tumor resistance to EGFR-targeted therapy are still not completely known. Genetic alterations frequently occur during lung cancer progression owing to genomic instability.…”