Abstract 2463: Side population cells have some stem-like properties in hepatocellular carcinoma

Abstract

Abstract Background: There are many problems to be solved in cancer stem cells (CSCs) in digestive organs. Liver cancer stem cells also have a major problem that we have to determine the cancer stem cell markers and clarify the function of CSCs. In this study, we tried to validate CSC markers that are previously reported using side population (SP) cells in hepatocellular carcinoma cell lines. Methods: Side population cells in seven hepatocellular carcinoma (HCC) cell lines (PLC/PRF/5, HuH1, HuH7, HLE, HepG2, HLF, and SK-Hep1) were analyzed using Flow cytometry (FACS AriaII). The differences between SP cells and Non-SP cells in several markers relating to epithelial-mesenchymal transition and in several liver CSC markers were investigated using quantitative RT-PCR. The difference about intracellular signals between them was also studied using Western blot analysis. Using HuH7 cell, the ability of spheroid formation of SP cells and the difference between spheroid forming cells and 2-dimensional cultured cells were investigated. Results: The range of percentage of SP cells was from 0 % to 4.1 %. We sorted SP cells from four HCC cell lines (PLC/PRF/5, HuH1, HuH7, and HLE). There were no remarkable difference of CDH1 and vimentin between SP cells and Non-SP cells. Previously reported liver cancer stem cell markers such as EpCAM, CD90, and CD44 were significantly increased in SP cells. However, the expression of CD133 and Bmi1 in SP cells was unexpectedly decreased or similar to non-SP cells. The ability of spheroid formation of SP cells was significantly higher than that of non-SP cells. Spheroid forming cells showed remarkably higher expression of EpCAM, CD90, and CD44 than 2-dimensional cultured cells. These were considered to be important markers regulating CSCs. The expression of cell cycle marker MIB1 in the SP cells was remarkably decreased compared to that of non-SP cells. This fact supports to the theory that normal or cancer stem cells maintain their cell cycle arrest. SP cells maintained specific signals activated such as sonic hedgehog and MAPK signals. Conclusions: Liver cancer stem cell markers such as EpCAM, CD90, and CD44 were considered to be important for the maintenance of SP cells in hepatocellular carcinoma. The activation of specific intracellular signals was also seen in SP cells. We are now challenging to confirm the importance of those signals using HCC cells extracted from human liver tissues. The current study may be help of understanding the regulation of liver cancer stem cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2463. doi:10.1158/1538-7445.AM2011-2463