The APE1-mediated IL-6/STAT3 Signaling Pathway Regulates Chemosensitivity To CDDP In Nsclc A549 Cells

Objective: Cisplatin(CDDP)-resistance has an important role in failure of treatment of non-small cell lung cancer(NSCLC). However, the details of the molecular mechanisms are not fully clear. The aim is to investigate whether and how APE1(apurinic/apyrimidinic endonuclease 1) regulates IL-6(interleukin-6)/STAT3(Signal transducer and activator of transcription 3) signaling in chemosensitivity of CDDP in lung cancer A549 cells.Methods:(1) Using SILAC(stable-isotope labeling by amino acids in cell culture)-based proteomic experiments to systematically and quantitatively investigate the effects of CDDP treatment in A549 cells and identify its potential molecular proteins and related signaling pathways.(2) To carry out multifaceted experiments such as cell, gene and inhibitor, to explore the mechanism about APE1–mediated IL-6/STAT3 signaling involved in CDDP chemosensitivity in A549 cells.(3) To assess the antitumor effects of sequential treatment of AT-101, as the inhibitor of APE1 dual functions, combined with CDDP in vitro and in vivo, also to test the molecular mechanism about APE1-mediated IL-6/STAT3 signaling in A549 xenograft nude model using western blot assay.Results:(1) The proteomic data showed that upon A549 treated with CDDP, 3262 proteins were involved in cellular events. Of these protein molecules, 1013 quantitative molecules could be quantitative, with 450-protein expressions increased and 563-protein expressions decreased. Moreover, many pathways was affected by CDDP treatment, including the APE1 protein in base excision repair pathway contributing to chromatin structure, DNA repair and transcription regulation, and IL-6/STAT3 signaling having a pro-survival role.(2) The results demonstrated that IL-6/STAT3 signaling pathway be activated by CDDP treatment. Following treatment of si RNA, or inhibitor AT-101, or exotic redoxed APE1, further proved that the CDDP-chemosensitivity mechanism in A549 cells is about reduced APE1 regulating IL-6/STAT3 signaling.(3) We found that compared with control, AT-101 alone or CDDP alone, the sequential treatment of AT-101 combined with CDDP significantly decreased the A549 cell proliferation, migration abilities and A549-induced HUVEC angiogenesis, thus markedly promoted apoptosis through down-regulating antiapoptotic protein expressions of Bcl-2 and Bcl-x L in vitro and in vivo. Furthermore, the mechanism about APE1-mediated IL-6/STAT3 signaling was alos approved through western blot in A549 xenograt model in vivo.Conclusions: The sequential AT-101 treatment can enhance A549 cells apoptosis to CDDP through inhibition of reduced APE1-mediated IL-6/STAT3 signaling, further down-regulating antiapoptotic protein expressions of Bcl-2 and Bcl-x L. This might be a potential anti-tumor strategy in patients with CDDP chemoresistance.