Abstract 3319: Identification of cervical cancer stem cells by using an imaging system for proteasome activity

Abstract

Abstract Cervical cancer is one of the most common cancers among women worldwide and the fourth most common cause of cancer death in women worldwide (275,100 deaths in 2008). For advanced cervical cancer, concurrent radiotherapy and chemotherapy are commonly administered. However, the 5-year survival rate remains at only ∼60%, indicating the need for significant improvements in clinical outcomes. Recurrence and metastatic potential can be due to a specific radioresistant subpopulation of cells with stem-like characteristics, cancer stem cells (CSCs) which maintain the capacity to regenerate entire tumors. Targeting of the CSCs is a promising avenue to explore to develop new therapies for this devastating cancer. Recently, cancer cells with low proteasome activity have been identified as CSCs in breast cancer, glioma, and pancreatic cancer with a fluorescence marker system for level of proteasome activity. We stably infected two cervical cancer cell lines, HeLa and CaSki, with an expression vector for a fusion protein between the green fluorescent protein, ZsGreen, and the C-terminal degron of murine ornithine decarboxylase to monitor 26S proteasome activity in living cells. we divided these cells into ZsGreen-high (low proteasome activity) and ZsGreen-low (high proteasome activity) groups according to their fluorescence intensity. Sphere forming assay revealed that the self-renewal ability of the ZsGreen-high population was significantly higher than that of the ZsGreen-low population. Tumorigenicity assay confirmed that the ZsGreen-high population exhibited higher tumorigenic potential than the ZsGreen-low population. The radioresistance of the ZsGreen-high population of both HeLa and CaSki cells and the chemoresistance of the ZsGreen-high population of CaSki cells were confirmed by clonogenic survival assay and the MTT assay, respectively. These results indicated that ZsGreen-high populations of both the HeLa and CaSki cell lines possess CSC-like properties and therapeutic resistance. We conclude that established cervical cancer cell lines are heterogeneous with regard to their intrinsic proteasome activity and that they contain CSCs-enriched subpopulations that can be identified by low proteasome activity. Citation Format: Keisuke Tamari, Hideshi Ishii, Kazuhiko Hayashi, Masamitsu Konno, Koichi Kawamoto, Naohiro Nishida, Jun Kozeki, Takahito Fukusumi, Yuichiro Doki, Masaki Mori, Kazuhiko Ogawa. Identification of cervical cancer stem cells by using an imaging system for proteasome activity. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3319. doi:10.1158/1538-7445.AM2015-3319