BV6, an IAP Antagonist, Activates Apoptosis and Enhances Radiosensitization of Non-small Cell Lung Carcinoma In Vitro

Abstract

Introduction Defects in the apoptosis pathway limit the effectiveness of radiation in non-small cell lung cancer (NSCLC) therapy. BV6 is an antagonist of cIAP1 and XIAP, members of the inhibitors of apoptosis (IAP) family. We investigated the potential of BV6 to sensitize NSCLC cell lines to radiation. Methods HCC193 and H460 lung cancer cell lines were treated with BV6 to investigate the effects of drug administration on cell proliferation, apoptosis, inhibition of XIAP and cIAP1, and radiosensitivity. Subsequent immunoblotting and Hoechst staining were utilized to determine the role of apoptosis in radiosensitization. Finally, the pathway of apoptosis was characterized by western blot analysis for cleaved caspase-8 and cleaved caspase-9, and ELISA assays for TNF-α. Results HCC193 was found to be more sensitive than H460 to BV6-induced apoptosis in a concentration-dependent and time-dependent manner. BV6 significantly sensitized both cell lines to radiation (HCC193—DER=1.38, p<0.05 at 1μM BV6; H460—DER=1.42, p<0.05 at 5μM BV6), but a higher concentration of and longer incubation time with BV6 was necessary for H460 cells. The BV6-induced radiosensitization of HCC193 favored the extrinsic pathway of apoptosis, while that of H460 favored the intrinsic pathway. Conclusions BV6, an IAP antagonist, significantly enhanced the radiosensitization of HCC193 and H460 cells in vitro. More research is warranted to test the mechanism of action of BV6, and to assess its potential in vivo and in the clinical setting.

Targeting inhibitor of apoptosis proteins by Smac mimetic elicits cell death in poor prognostic subgroups of chronic lymphocytic leukemia

“…31,48,49 Our findings showing that BV6 cooperates together with Obatoclax to induce cell death in CLL cells, but not together with ABT-263 may be related to the differential activity profiles of these BH3 mimetics, as Obatoclax antagonizes BCL-2, BCL-xL, BCL-W and MCL-1, whereas ABT-263 targets BCL-2, BCL-xL and BCL-W, but not MCL-1. 50 Single-agent cytotoxicity of Smac mimetic compounds has been reported for CLL, 40 multiple myeloma or 2, 12, 17, 39) were treated for indicated times with 10 mM BV6, 1 mM Staurosporine and 20 mM zVAD.fmk alone or in combination.…”

“…Mean and SEM of 17 individual CLL samples measured in duplicate or triplicate (samples no. 2,6,8,12,15,17,18,19,24,28,33,36,39,41,43,48,50) 2,6,8,12,15,17,18,19,24,28,33,36,39,41,43,48,50) are shown; *p < 0.05. several solid tumors, 16,35,36,[51][52][53] while another study showed that CLL cells remain resistant against Smac mimetics in the context of CD40 ligand stimulation. 39 Compared with CLL cells, BV6 showed little cytotoxicity against non-malignant B-cells, a finding also reported by other investigators in CLL.…”

“…Mean and SEM of 18 individual CLL samples measured in duplicate or triplicate (samples no. 2,6,8,15,17,18,19,21,24,28,33,36,39,40,41,43,48,50) are shown; **p < 0.001; *p < 0.05; (right) Graph illustrates specific cell death upon treatment with 10 mM Fludarabine or BV6 of genomic subgroups including norm/13q-, IGVH non-mutated, tp53 mutated and 17p deletion. (e and f) BV6-sensitive primary CLL cells were co-treated with 10 mM BV6 and 1,000 ng/ml CD40 ligand (e) or stimulated with BV6 in normal or conditioned medium at indicated concentrations (f) for 48 hr.…”

The SMAC mimetic BV6 induces cell death and sensitizes different cell lines to TNF-α and TRAIL-induced apoptosis

“…23,24 One of the recently developed SMAC mimetics is BV6, which binds to BIR domains of IAPs leading to their ubiquitination, followed by proteosomal degradation and inhibition of XIAP-mediated inhibition of caspases. 25,26 In the present study, we sought to explore the cytotoxic effects of BV6 in numerous human cancer cells. Besides, we studied the sensitizing potential of BV6 on TNF-a and TRAILinduced apoptosis as a novel strategy for combinational antitumor therapy.…”

AT-406, an IAP Inhibitor, Activates Apoptosis and Induces Radiosensitization of Normoxic and Hypoxic Cervical Cancer Cells

“…The cIAP1 expression, rather than XIAP expression, evidently increased in Hela cells after AT-406 treatment. Other studies also found that IAP antagonists induced rapid cIAP1 degradation, which is a key early event in IAP antagonist-induced apoptosis in sensitive cancer cells (28,29). This phenomenon may be associated with the function of the RING-finger of cIAP1 as an active E3 center.…”