β2SP(ELF) is one of adapter proteins for Smad3/Smad4 complex formation during TGF-β signal transduction. 40% of β2SP+/- mice spontaneously develop hepatocellular carcinoma (HCC) and most cases of human HCC, gastric cancer, and lung cancer demonstrate significant reductions in β2SP expression. In our study, we investigated the possible mechanism for loss of β2SP induced HCC tumorigenesis. Recent studies have highlighted the involvement of cancer stem cells during the formation and progression of various types of cancers, epithelial cells that have undergone EMT (epithelial mesenchymal transition) acquire stem-cell properties during cancer development. Giving the role of TGF-beta signaling in stem cell differentiation and EMT during embryonic development, we hypothesize loss of β2SP results in alteration of liver stem cell that may contribute to the development of HCC in β2SP+/ mice. It has been shown that EpCAM-positive adult liver cells has stem cell property and can differentiate into functional hepatocytes in xenograft model. We found that EpCAM-positive hepatocyte number doubled in β2SP+/ mouse compared to wild type by fluorescence-activated cell sorter (FACS). Furthermore EpCAM level in β2SP+/ mouse liver was three times higher than that in the liver of wild type mouse. To study the mechanism by which Epcam is regulated by β2SP, HCC cells were transfected by β2SP siRNA. Inhibition of β2SP increased the expression of Epcam, and EMT markers vimentin was increased and E-cadherin expression was decreased in PLC/PRF/5 and SNU449 cells, while TGF-β1 and Smad3 rescued the expression of Epcam and E-cadherin, but not vimentin. We also found that suppression of β2SP expression promotes adhesion, migration and cloning formation of PLC/PRF/5 and SNU449 cells. Our data suggests loss of β2SP enhances the stem-like traits and invasiveness of HCC cells.

Citation Format: Xiuling Zhi, Ling Lin, Narayan Shivapurkar, Wilma Jogunoori, Lopa Mishra, Aiwu R He. Loss of β2SP (ELF) enhances the stem-like traits and invasiveness of HCC cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3764. doi:10.1158/1538-7445.AM2013-3764