Purpose: The EGF receptor tyrosine kinase inhibitors (EGFR-TKI) have become a standard therapy in patients with EGFR-activating mutations. Unfortunately, acquired resistance eventually limits the clinical effects and application of EGFR-TKIs. Studies have shown that suppression of epithelial-mesenchymal transition (EMT) and the interleukin (IL)-6/STAT3 pathway may abrogate this acquired mechanism of drug resistance of TKIs. This study aims to investigate the effect of metformin on sensitizing EGFR-TKI-resistant human lung cancer cells in vitro and in vivo through inhibition of IL-6 signaling and EMT reversal.Experimental Design: The effect of metformin on reversing TKI resistance was examined in vitro and in vivo using MTT, BrdUrd incorporation assay, invasion assay, flow cytometry analysis, immunostaining, Western blot analysis, and xenograft implantation.Results: In this study, metformin, a widely used antidiabetic agent, effectively increased the sensitivity of TKI-resistant lung cancer cells to erlotinib or gefitinib. Metformin reversed EMT and decreased IL-6 signaling activation in TKI-resistant cells, while adding IL-6 to those cells bypassed the anti-TKI-resistance effect of metformin. Furthermore, overexpression or addition of IL-6 to TKI-sensitive cells induced TKI resistance, which could be overcome by metformin. Finally, metformin-based combinatorial therapy effectively blocked tumor growth in xenografts with TKI-resistant cancer cells, which was associated with decreased IL-6 secretion and expression, EMT reversal, and decreased IL-6-signaling activation in vivo.Conclusion: Metformin, generally considered nontoxic and remarkably inexpensive, might be used in combination with TKIs in patients with non-small cell lung cancer, harboring EGFR mutations to overcome TKI resistance and prolong survival.

BackgroundIn the AVAGAST study, fluoropyrimidine and cisplatin plus bevacizumab did not significantly improve overall survival (OS) versus fluoropyrimidine and cisplatin plus placebo in patients with advanced gastric cancer. Geographic differences in efficacy were observed in AVAGAST, but the study only included 12 Chinese patients. AVATAR, a study similar in design to AVAGAST, was a randomized, double-blind, phase III study conducted in Chinese patients with advanced gastric cancer.MethodsPatients more than 18 years of age with gastric adenocarcinoma were randomized 1:1 to capecitabine–cisplatin plus either bevacizumab or placebo. The primary endpoint was OS; secondary endpoints included progression-free survival (PFS) and safety.ResultsIn total, 202 patients were included (placebo n = 102; bevacizumab n = 100). Baseline characteristics were well balanced. The primary analysis result did not show a difference in OS for the bevacizumab arm compared to the placebo arm [hazard ratio, 1.11 (95 % CI, 0.79–1.56); P = 0.5567]. Median PFS was also similar in both arms. Bevacizumab plus capecitabine–cisplatin was well tolerated. Grade 3–5 adverse events (AEs) occurred in 60 % of bevacizumab-treated and 68 % of placebo-treated patients, respectively. Grade 3–5 AEs of special interest with bevacizumab occurred in 8 % of bevacizumab-treated patients and 15 % of placebo-treated patients, mainly grade 3–5 hemorrhage (bevacizumab 4 %, placebo 12 %).ConclusionsAddition of bevacizumab to capecitabine–cisplatin in Chinese patients with advanced gastric cancer did not improve outcomes in AVATAR. There was no difference in OS between the two arms and PFS was similar in both arms. Safety findings were as previously experienced with bevacizumab, including AVAGAST; no new safety signals were reported.

Dually targeted mitochondrial proteins usually possess an unconventional mitochondrial targeting sequence (MTS), which makes them difficult to predict by current bioinformatics approaches. Human apurinic/apyrimidinic endonuclease (APE1) plays a central role in the cellular response to oxidative stress. It is a dually targeted protein preferentially residing in the nucleus with conditional distribution in the mitochondria. However, the mitochondrial translocation mechanism of APE1 is not well characterized because it harbors an unconventional MTS that is difficult to predict by bioinformatics analysis. Two experimental approaches were combined in this study to identify the MTS of APE1. First, the interactions between the peptides from APE1 and the three purified translocase receptors of the outer mitochondrial membrane (Tom) were evaluated using a peptide array screen. Consequently, the intracellular distribution of green fluorescent protein-tagged, truncated, or mutated APE1 proteins was traced by tag detection. The results demonstrated that the only MTS of APE1 is harbored within residues 289 -318 in the C terminus, which is normally masked by the intact N-terminal structure. As a dually targeted mitochondrial protein, APE1 possesses a special distribution pattern of different subcellular targeting signals, the identification of which sheds light on future prediction of MTSs.Human APE1 (apurinic/apyrimidinic endonuclease) is an important multifunctional protein that plays a central role in the cellular response to oxidative stress. The two major activities of APE1 are DNA repair and redox regulation of transcriptional factors. On one hand, APE1 functions as a critical ratelimiting enzyme in DNA base excision repair and accounts for nearly all of the AP site incision activities in cell extracts (1). On the other hand, APE1 also exerts unique redox activity to regulate the DNA binding affinity of certain transcriptional factors by controlling the redox status of their DNA-binding domain (2). Inhibition of the redox function of APE1 blocks murine endothelial cell growth and angiogenesis and also blocks the growth of human tumor cell lines (3). The biological importance of APE1 is highlighted by the finding that APE1 knockout mice exhibit an embryonic lethal phenotype (4). Although APE1 has long been labeled as a nuclear protein, a growing body of evidence has shown that the subcellular distribution of APE1 can be cytoplasmic in some cell types with high metabolic or proliferative rates, with predominant localization in the mitochondria and the endoplasmic reticulum (5-7). Recent mitochondrial proteomic studies have further confirmed the existence of APE1 in the mitochondria (8). Considering the importance of the mitochondria in cellular response to oxidative stress, the roles of APE1 in the mitochondria have been extensively investigated.

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