Inhibition of autophagy potentiates the cytotoxicity of the irreversible FGFR1-4 inhibitor FIIN-2 on lung adenocarcinoma.

For patients with platinum-resistant lung adenocarcinoma (LUAD), the exploration of new effective drug candidates is urgently needed. Fibroblast growth factor receptors (FGFRs) have been identified as promising targets for LUAD therapy. The purpose of this study was to determine the exact role of the irreversible FGFR1-4 inhibitor FIIN-2 in LUAD and to clarify its underlying molecular mechanisms. Our results demonstrated that FIIN-2 significantly inhibited the proliferation, colony formation, and migration of A549 and A549/DDP cells but induced the mitochondria-mediated apoptosis of these cells. Meanwhile, FIIN-2 increased the autophagy flux of A549 and A549/DDP cells by inhibiting the mammalian target of rapamycin (mTOR) and further activating the class III PI3K complex pathway. More importantly, in vivo and in vitro experiments showed that autophagy inhibitors could enhance the cytotoxicity of FIIN-2 on A549 and A549/DDP cells, confirming that FIIN-2 induced protective autophagy. These findings indicated that FIIN-2 is a potential drug candidate for LUAD treatment, and its use in combination with autophagy inhibitors might be an efficient treatment strategy, especially for patients with cisplatin resistance.