Phenformin inhibits proliferation of acquired gefitinib resistant non‐small‐cell lung cancer(NSCLC) through the reduction of NAD+/NADH ratio

Abstract

Epidermal growth factor receptor(EGFR) tyrosine kinase inhibitors(TKI) including gefitinib and erlotinib are now recommended as a first‐line chemo therapy for NSCLC. Unfortunately majority of NSCLC patients administered with gefitinib showed acquired resistance within 1 yr. To overcome it, second‐ and third‐generation of EGFR inhibitors were developed, but eve0n in the third‐generation of EGFR inhibitors, NSCLCs were found to be resistant and new therapeutic strategies have become necessary.HCC827, a NSCLC cell line were cultured with stepwise escalation of gefitinib over 1 yrs to establish acquired gefitinib resistance HCC827(HCC827‐GR) cells. EGFR exons from 18 to 21(tyrosine kinase domain) in HCC827‐GR were not mutated, and the activities of EGFR tyrosine kinase and its downstream kinases(Akt and Erk) were all downregulated in HCC827‐GR cells compared to HCC827 cells. Because EGFR signaling is critical to the regulation of Warburg effect and oxidative phosphorylation(OXPHOS) in cancer cells, we assessed glucose metabolism in both HCC827 and HCC827‐GR cells. Determination of oxygen consumption rate(OCR) and extracellular acidification rate(ECAR) showed that HCC827‐GR cells mainly use OXPHOS in glucose utilization compared to HCC827 cells. Inhibition of OXPHOS by phenformin, known as a strong complex 1 inhibitor, exhibited significant anti‐proliferative effect in HCC827‐GR cells. Phenformin reduced the NAD+/NADH ratio and decreased cellular aspartate level. Moreover treatment of HCC827‐GR cells with α‐ketobutyrate (AKB) which is an electron acceptor or aspartate significantly reversed inhibition of HCC827‐GR cells proliferation. In conclusion, we propose that phenformin is effective to inhibit cell growth of acquired gefitinib resistant NSCLC and suggest OXPHOS targeting as a potential therapeutic target.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.