The Translational Characterization of the Role of Wnt/Beta-Catenin/Tcf Signaling in the Generation of Invasive and Chemoresistant Cancer Stem Population in Liver Cancer

Cancer stem cells (CSCs)/tumor-initiating cells have been defined as a subset of tumor cells responsible for initiating and sustaining tumor development. Emerging evidence strongly supports the existence of CSCs in human hepatocellular carcinoma (HCC) exhibiting stem cell properties that contributes to the drug resistance, invasion and metastasis. Wnt/β-Catenin/TCF signaling has been shown to play a central role in the growth of liver cancer. However, Wnt/β-Catenin/TCF has not yet been studied in chemotherapy resistant liver cancer stem cells. We have preliminarily demonstrated that the sorted side population (SP) cells possessed cancer stem cell properties, such as clonogenecity, high expression of drug resistance genes (ABCG2) and expression of surface marker CD133 as well as asymmetric division property for self-renewal. Purified fraction of SP cells from Huh7 cell line exhibited resistance to chemotherapeutic agents such as and doxorubicin and cisplatin Moreover, as compared to non-SP cells, SP cells appeared to be highly invasive and deregulated in Wnt/β-Catenin/TCF signaling pathway. Importantly, Wnt-upregulated Hu7 SP cells exhibited an enhanced tumor initiating and promoting ability in vivo. This has led to our long-term objective to elucidate the role of Wnt/β-Catenin/TCF signaling in liver CSCs as a prerequisite to the development of new therapies. In this proposal, we intend to show that the deregulation of Wnt/β-Catenin/TCF is important for the development and progression of liver CSCs; blockage of the Wnt/β-Catenin/TCF pathway should suppress liver CSCs tumor growth. To test our hypothesis, we will specifically address the following issues. In year I, we will characterize the heterogeneity of liver CSCs using in vitro and in vivo functional assays and investigate the regulatory role of Wnt/β-catenin signaling in the maintenance and growth of liver CSCs using three different human liver cancer cells: Huh7 (HCC), WRL68 (hepatoblastoma) and SK-ChA-1 (cholangiocarcinoma cells). In year II, we aim to functionally determine the consequence of Wnt/β-catenin signaling down-regulation in liver CSCs using siRNA or small molecule antagonists. In year III, the suppression of Wnt/β-Catenin/TCF signaling will be further examined in vivo using non-invasive molecular imaging technique. The findings derived from this proposal may provide essential insights into liver cancer pathogenesis and offer a rational target for the development for clinical interventions.