Liver cancer, mainly hepatocellular carcinoma (HCC), has become a most deadly malignant disease worldwide. So far, pharmaceutic inhibition of major oncogenic pathways has achieved little therapeutic benefit to liver cancer patients. We believe this is due to under- appreciation of the complexity in mechanisms of hepato-oncogenesis. In recent experiments, we and others have identified paradoxically anti-oncogenic effects of classical oncogenic molecules, such as c-Met, EGFR, ?-catenin, Ikk?, Jnk, and Shp2, in the liver. Ablating these molecules in hepatocytes enhanced HCC induced by chemical carcinogen DEN. To test a theory that loss of the oncogenic molecules generates an oncogenic microenvironment that promotes DEN-induced HCC, we have established another mouse HCC model, by transfection of oncogenic ?-catenin (CAT), c-Met (MET) and PIK3CA (PIK), oncoproteins frequently detected in human HCCs. As expected, MET/CAT-driven HCC was aggravated in ?-catenin-deficient liver, due to tumor-promoting factors induced by ?-catenin removal. In contrast, Shp2 deletion dramatically suppressed HCC driven by MET/CAT or MET/PIK, despite a similar pro-tumorigenic environment in Shp2-deficient liver. Based on these novel unanticipated data, we propose a new hypothesis that although removal of Shp2 or ?-catenin generates cell-extrinsic tumorigenic factors in the hepatic environment, the endogenous Shp2 is indispensable for oncogenic signaling in hepatocytes. To test this hypothesis, we propose three specific aims on this project.
Aim 1 is to determine the cell-intrinsic role of Shp2 in hepato-oncogenic signaling.
Aim 2 is to determine the cell-autonomous effect of ?-catenin in liver tumorigenesis.
Aim 3 is to search and identify cell-extrinsic factors induced by loss of the oncoproteins in hepatocytes. The results are expected to be instrumental for design of novel therapeutic strategies for liver cancer by inhibiting both cell-intrinsic oncogenic signals and the secondary environmental factors.
Liver cancer is now escalated to be a primary cause in cancer-related deaths worldwide, with no effective pharmaceutical or immune therapies available to treat liver cancer patients. The goal of this project is to better understand the complexity in the pathogenic process and therefore help develop novel therapeutic strategies for the deadly malignant disease.