The Clinical Application And The Optimization Strategy Of Metformin In Overcoming EGFR-TKI Resistance

BackgroundTyrosine kinase inhibitor(TKI)of the epidermal growth factor receptor(EGFR)significantly improves the prognosis of non small cell lung cancer(NSCLC)patients as compared to treatment with standard chemotherapy,it is currently the first choice for advanced NSCLC patients with EGFR sensitive mutation.Unfortunately,almost all patients initially responding to EGFR-TKI would inevitably progress to a status of acquired resistance.EGFR-TKI resistance has become a bottleneck restricting its clinical application.To explore the combined therapy strategy to overcome drug resistance according to different drug resistance mechanisms,and further enhance the clinical efficacy of targeted therapy,is currently one of the hotspots in the field.More and more studies have confirmed that the classic hypoglycemic agent metformin has anti-cancer effect,the role of metformin in overcoming EGFR-TKI resistance has also attracted increasing attention.However,the effective dose,the efficacy of overcoming EGFR-TKI resistance and the optimization of combination strategy still need further research.In clinical practice aspect,it is found that metformin may decrease lung cancer risks,and improve the effect of chemotherapy in thetreatment of patients with advanced non small cell lung cancer and diabetes.These studies provide a basis for the clinical effect of metformin as auxiliary therapeutic drugs in treating advanced lung cancer.However,Because the heterogeneity of tumor cells,and the complexity of resistance mechanisms of EGFR-TKI,no enough evidences showed that metformin can delay the emergence of EGFR-TKI resistance and improve the clinical prognosis of lung cancer patients taking EGFR-TKI.Therefore,it is necessary to analyze the relevant clinical data,so as to analyze the effect of metformin on improving clinical curative effect,and to explore the potential beneficiaries of metformin treatment.The basal study has confirmed that there is a close relation between pro-apoptosis protein BIM and EGFR-TKIs resistance caused by multiple mechanisms.Pan-histone deacetylase inhibitor(HDACi)represented by vorinostat can overcome resistance induced by with BIM deletion polymorphism,it has also been proved to play an anti-cancer role in many solid tumors.However,this effect is attenuated by the high expression of B-cell lymphoma 2(Bcl-2)family anti-apoptotic proteins in EGFR-TKIs resistant NSCLC cells.Our previous studies showed that merformin could enhance the expression of BIM and inhibit the expression of prosurvival Bcl-2 proteins such as Bcl-2 and Mcl-1 in EGFR-TKIs resistant NSCLC cells,thus enhance EGFR-TKIs sensitivity.So metformin and HDACi may cooperately target BIM signaling pathway and then overcome TKI resistance with super-compound effects.Objective1.We aimed to observe the combined effect of metformin and first-generation TKI on the treatment of NSCLC patients with diabetes mellitus type 2(DM2).2.Metformin in combination with vorinostat might cooperate to activate apoptotic signaling and overcome EGFR-TKI resistance.We intended to investigate the cooperative effect and evaluate possible molecular mechanisms.Methods1.Data of NSCLC patients with DM2 who received treatment in six hospitals in china between January 2006 and January 2014 were reviewed retrospectively.They were divided into two groups: Group A,where the patients(n=44)received EGFR-TKI plus metformin;and Group B,where the patients(n=46)received EGFR-TKI plus hypoglycemic agents other than metformin.Prognostic differences between the two groups were assessed.2.The EGFR-TKI resistant lung cancer cell lines H1975 and PC-9GR were used,to evaluate cell proliferation and cell invasion by MTT assay and Brdu incorporation assay.The effect of metformin combined with vorinostat on reversing TKI resistance were verified.Western blot and siRNA technique were used to detect the expression of apoptotic signaling pathway related proteins and to explore the reversal of TKI resistance by metformin combined with vorinostat.Results1.The median progression-free survival(PFS)and median overall survival(OS)in Group A were significantly longer than those in Group B(19.0 months vs.8.0 months,P= 0.005;32.0 months vs.23.0 months,P=0.002).The objective response rate(ORR)and disease control rate(DCR)in Group A were significantly higher than those in Group B(70.5% vs.45.7%,P= 0.017;97.7% vs.80.4%,P=0.009).Secondary data analysis showed that metformin use significantly prolonged the median PFS in subgroups using either first-line EGFR-TKI or second-line EGFR-TKI.2.The results showed that vorinostat combined with gefitinib augmented BIM expression and increased the sensitivity of EGFR-TKI resistant NSCLC cells to gefitinib,adding metformin simultaneously could obviously inhibit the expression of anti-apoptotic proteins,and further increased expression levels of BIM and BAX,and as a result,further improved the sensitivity of gefitinib both on the NSCLC cells with intrinsic and acquired resistance to EGFR-TKI.In addition,autophagy induced by gefitinib and vorinostat could be significantly suppressed by metformin,which might also contribute to enhance apoptosis and improve sensitivity of gefitinib.Conclusion1.Metformin and EGFR-TKI have a synergistic effect in the treatment of DM2 NSCLC patients harboring EGFR-activating mutations,metformin use is associated with improved survival and delayed onset of acquired resistance to EGFR-TKI.2.These results suggested that the combination of vorinostat and metformin might represent a novel strategy to overcome EGFR-TKI resistance associated with BIM-dependent apoptosis in larger heterogeneous populations.