Combination of a third generation bisphosphonate and replication-competent adenoviruses augments the cytotoxicity on mesothelioma. Issue 1 (December 2016) - Jiang, Yuanyuan
Abstract Background Approximately 80 % of mesothelioma specimens have the wild-typep53 gene, whereas they contain homozygous deletions in the INK4A/ARF locus that encodesp14 ARF and the16 INK4A genes. Consequently, the majority of mesothelioma is defective of the p53 pathways. We examined whether zoledronic acid (ZOL), a third generation bisphosphonate, and adenoviruses with a deletion of theE1B-55kD gene (Ad-delE1B55), which augments p53 levels in the infected tumors, could produce combinatory anti-tumor effects on human mesothelioma cells bearing the wild-typep53 gene. Methods Cytotoxicity of ZOL and Ad-delE1B55 was assessed with a WST assay. Cell cycle changes were tested with flow cytometry. Expression levels of relevant molecules were examined with western blot analysis to investigate a possible mechanism of cytotoxicity. Furthermore, the expressions of Ad receptors on target cells and infectivity were estimated with flow cytometry. Viral replication was assayed with the tissue culture infection dose method. Results A combinatory use of ZOL and Ad-delE1B55 suppressed cell growth and increased sub-G1 or S-phase populations compared with a single agent, depending on cells tested. The combinatory treatment up-regulated p53 levels and subsequently enhanced the cleavage of caspase-3, 8, 9 and poly (ADP-ribose) polymerase, but expression of molecules involved in autophagy pathways were inconsistent. ZOL-treated cells also increased Ad infectivity with a dose-dependent manner and augmented Ad replication although the expression levels of integrin molecules, one of the Ad receptors, were down-regulated. Conclusions These findings indicated that ZOL and Ad-delE1B55 achieved combinatory anti-tumor effects through augmented apoptotic pathways or increased viral replication.