Abstract
Abstract Cancer stem cells (CSCs) defined by differentiation capacity, self-renewal capacity and tumorigenicity have been identified in many tumors, including cervical cancer. Current studies in the field of cancer stem cell research identify CSCs by several specific biomarkers, such as ALDH1, but it is difficult to monitor cervical CSCs in real-time in vitro and in vivo. Recent research reported the visualization of CSCs in breast cancer and giloma using green fluorescent protein ZsGreen fused to a degron motif ornithine decarboxylase (ODC) which is destructed by the proteasome. According to the research, CSCs are low 26S proteasome activity, while non-CSCs are high. Therefore it is possible to observe CSCs which accumulate fluorescent ZsGreen protein. In this study, we investigated optical imaging of CSCs in human cervical cancer cell lines of CaSki and Hela. We engineered CaSki and HeLa cervical cancer cells expressing ZsGeen-ODC (Zs positive cells) by a retroviral vector. The cancer stemness of their Zs positive cells was assessed by sphere formation assay, and the resistance of cancer stem cells to chemotherapy and radiation therapy was investigated by MTT(3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide)assay and clonogenic survival assay. The low 26S proteasome activity of Zs positive cells was confirmed by Proteasome-Glo™ Cell Based Assay (Promega). Zs positive cells of both CaSki and HeLa showed high ability in sphere formation assay, compared with cancer cells which did not express ZsGreen-ODC (Zs negative cells). In MTT assay, Zs positive cells of CaSki were resistant to cisplatin and paclitaxel, whereas those of HeLa were not resistant as compared with Zs negative cells of HeLa. Our data of clonogenic survival assay suggested that Zs positive cells of both CaSki and HeLa were more resistant to ionizing radiation than Zs negative cells. Thus our results indicated that Zs positive cells of CaSki and Hela had features of CSCs. In conclusion, we could visualize cervical cancer stem-like cells using a fluorescence protein system. Further researches of detecting real-time asymmetric cell division in vitro and analyzing the tumorigenicity of these cells in vivo are necessary to show evidence of cancer stemness and they are now going. In the next step, we will research the relationship between epithelial-mesenchymal transition and the radiation resistance using this real-time tracking system. Citation Format: Kazuhiko Hayashi, Keisuke Tamari, Yoshihiro Kano, Shimpei Nishikawa, Takahito Fukusumi, Masaaki Miyo, Kozo Noguchi, Hisataka Ogawa, Atsushi Hamabe, Masamitsu Konno, Yuji Seo, Hideshi Ishii, Yuichiro Doki, Masaki Mori, Kazuhiko Ogawa. Optical imaging of cancer stem-like cells in cervical cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3028. doi:10.1158/1538-7445.AM2014-3028
Published Version
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