Abstract PR14: Real-time in-vivo image-guided cell-cycle perturbation to increase tumor chemosensitivity
Authors: Yano Shuya , Tazawa Hiroshi , Kishimoto Hiroyuki , Kagawa Shunsuke , Kadowaki Yoshihiko , Ishido Nobuhiro , Okamoto Takahiro , Urata Yasuo , Takehara Kiyoto , Hoffman Robert M. , Fujiwara Toshiyoshi 
Published: November 2016

Abstract
Tumor heterogeneity has been recognized as a major reason for anticancer drug resistance and therapy failure in solid cancers. Therefore, we simply categorized the tumor heterogeneity as cycling and quiescent cancer cells. A multi-color genetic reporter system has been previously-developed termed fluorescence ubiquitination cell cycle indicator (FUCCI) (Cell 2008; 132:487-98) whereby cycling cells fluorescence yellow/green and quiescent cells fluoresce red. We demonstrated the monitoring of real-time spatiotemporal cell cycle dynamics of cancer cells throughout a live tumor intravitally using a FUCCI system. According to cell cycle distribution, we defined three in vivo tumor models; an early stage nascent tumor consists of proliferating cancer cells, a late-stage established tumor consists on proliferating cancer cells at the surface area and quiescent cancer cells at the center area, and a dormant tumor consists of almost quiescent cancer cells without changing the cell cycle and the size for more than two months. Longitudinal intravital real-time imaging in living mice also demonstrated that cytotoxic agents killed only cycling cancer cells at the surface and, in contrast, had little effect on quiescent cancer cells, which are the vast majority of a late-stage established tumor and a dormant tumor. Moreover, resistant quiescent cancer cells restarted cycling after the cessation of chemotherapy. We have utilized FUCCI in vivo intravital real-time imaging to first determine that the vast majority of cancer cells within a tumor are quiescent in G0/G1 and thereby resistant to drugs used in chemotherapy, since they only target cycling cells. This phenomenon based on the cell cycle mimics clinical courses of drug-resistant solid cancers. Therefore, quiescent cancer cells should be targeted. We then utilized in vivo FUCCI intravital real-time imaging to decoy quiescent cancer cells to cycle to S/G2, by administering telomerase-dependent oncolytic adenovirus OBP-301 or tumor-targeting Salmonella typhimurium A1-R, causing the cells to change from red to yellow/green fluorescence. After cell-cycle decoy determined by FUCCI, cytotoxic chemotherapy was applied and the decoyed tumors became chemosensitive. In order to further increase tumor chemosensitivity we have used FUCCI to develop an image-guided tumor-specific cell-cycle block in S/G2 with administration of recombinant methioninase (rMETase) treatment, thereby increasing the time period of chemosensitivity of cancer cells after cell-cycle decoy. Thus, image-guided cell-cycle perturbation has important potential to design new more effective paradigms for cancer chemotherapy.
This abstract is also being presented as Poster A19.
Citation Format: Shuya Yano, Hiroshi Tazawa, Hiroyuki Kishimoto, Shunsuke Kagawa, Yoshihiko Kadowaki, Nobuhiro Ishido, Takahiro Okamoto, Yasuo Urata, Kiyoto Takehara, Robert M. Hoffman, Toshiyoshi Fujiwara. Real-time in-vivo image-guided cell-cycle perturbation to increase tumor chemosensitivity. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr PR14.