Cancer Therapy: Preclinical A Genetically Engineered Oncolytic Adenovirus Decoys and Lethally Traps Quiescent Cancer Stem–like Cells in S/G2/M Phases

Purpose:Because chemoradiotherapy selectively targets proliferating cancer cells, quiescent cancer stem– like cells are resistant. Mobilization of the cell cycle in quiescent leukemia stem cells sensitizes them to cell death signals. However, it is unclear that mobilization of the cell cycle can eliminate quiescent cancer stem– like cells in solid cancers. Thus, we explored the use of a genetically-engineered telomerase-specific oncolytic adenovirus, OBP-301, to mobilize the cell cycle and kill quiescent cancer stem–like cells. Experimental Design: We established CD133þ cancer stem–like cells from human gastric cancer MKN45 and MKN7 cells. We investigated the efficacy of OBP-301 against quiescent cancer stem–like cells. We visualized the treatment dynamics of OBP-301 killing of quiescent cancer stem–like cells in dormant tumor spheres and xenografts using a fluorescent ubiquitination cell-cycle indicator (FUCCI). Results: CD133þ gastric cancer cells had stemness properties. OBP-301 efficiently killed CD133þ cancer stem–like cells resistant to chemoradiotherapy. OBP-301 induced cell-cycle mobilization from G0–G1 to S/G2/M phases and subsequent cell death in quiescent CD133 þ cancer stem–like cells by mobilizing cellcycle–related proteins. FUCCI enabled visualization of quiescent CD133þ cancer stem–like cells and proliferating CD133 non–cancer stem–like cells. Three-dimensional visualization of the cell-cycle behavior in tumor spheres showed that CD133þ cancer stem–like cells maintained stemness by remaining in G0–G1 phase. We showed that OBP-301 mobilized quiescent cancer stem–like cells in tumor spheres and xenografts into S/G2/M phases where they lost viability and cancer stem–like cell properties and became chemosensitive. Conclusion: Oncolytic adenoviral infection is an effective mechanism of cancer cell killing in solid cancer and can be a new therapeutic paradigm to eliminate quiescent cancer stem–like cells.Clin Cancer Res; 19(23); 6495–505. 2013 AACR. Introduction Current cytotoxic chemoradiotherapy selectively targets proliferating cancer cells. Quiescent or dormant cancer cells in contrast are often drug-resistant and are a major impediment to cancer therapy (1, 2). Cancer stem–like cells or tumor-initiating cells (3–5) maintain a quiescent or dormant state, which appears to contribute to their resistance to conventional therapies (6–8). Recently, several therapeutic strategies have targeted inhibition of the cancer stem–like cell quiescent state. For example, treatment with arsenic trioxide enhanced the sensitivity of leukemia stem cells (LSC) to cytosine arabinoside through inhibition of LCS quiescence (9). Acute myeloid leukemia stem cells can be induced to enter the cell cycle and apoptosis by treatment with granulocyte colony-stimulating factor (10). However, it is still unclear whether cancer stem–like cells in solid tumors can also be eliminated by inducing them to cycle. Viruses can infect target cells, multiply, cause cell death, and release viral particles. These features enable the use of viruses as anticancer agents that induce specific tumor lysis (11, 12). Adenoviral E1A, in particular, has been shown to exert tumor-suppressive functions, including enhancement of chemoradiotherapy-induced apoptosis via inhibition of the cellular DNA repair machinery (13) Authors' Affiliations: Department of Gastroenterological Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences; Center for innovative clinical medicine, Okayama University Hospital, Okayama; Oncolys BioPharma, Inc., Tokyo, Japan; Department of Surgery, University of California San Diego; and AntiCancer, Inc., San Diego, California Note: Supplementary data for this article are available at Clinical Cancer Research Online (http://clincancerres.aacrjournals.org/). Corresponding Author: Toshiyoshi Fujiwara, Department of Gastroenterological Surgery, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan. Phone: 81-86-235-7255; Fax: 81-86-221-8775; E-mail: [email protected] doi: 10.1158/1078-0432.CCR-13-0742 2013 American Association for Cancer Research. Clinical Cancer Research www.aacrjournals.org 6495 on April 20, 2017. © 2013 American Association for Cancer Research. clincancerres.aacrjournals.org Downloaded from Published OnlineFirst September 30, 2013; DOI: 10.1158/1078-0432.CCR-13-0742