Potent antitumor activity of Oct4 and hypoxia dual-regulated oncolytic adenovirus against bladder cancer

Most solid tumors undergo hypoxia, leading to rapid cell division, metastasis and expansion of a cell population with hallmarks of cancer stem cells (CSCs). Tumor-selective replication of oncolytic adenoviruses may be hindered by oxygen deprivation in tumors. It is desirable to develop a potent oncolytic adenovirus, retaining its antitumor activity even in a hypoxic environment. We have previously generated an Oct4-dependent oncolytic adenovirus, namely Ad9OC, driven by nine copies of the Oct4 response element (ORE) for specifically killing Oct4-overexpressing bladder tumors. Here, we developed a novel Oct4 and hypoxia dual-regulated oncolytic adenovirus, designated AdLCY, driven by both hypoxia response element (HRE) and ORE. We showed that hypoxiainducible factor (HIF)-2 alpha and Oct4 were frequently overexpressed in hypoxic bladder cancer cells, and HIF-2 alpha was involved in HRE-dependent and Oct4 transactivation. AdLCY exhibited higher cytolytic activities than Ad9OC against hypoxic bladder cancer cells, while sparing normal cells. AdLCY exerted potent antitumor effects in mice bearing human bladder tumor xenografts and syngeneic bladder tumors. It could target hypoxic CD44- and CD133-positive bladder tumor cells. Therefore, AdLCY may have therapeutic potential for targeting hypoxic bladder tumors and CSCs. As Oct4 is expressed in various cancers, AdLCY may be further explored as a broad-spectrum anticancer agent.