Abstract
The non-oxidative pentose phosphate pathway is known involved in tumorigenesis. Yet the role of ribose-5-phosphate isomerase A (RPIA) in human hepatocellular carcinoma (HCC) is not well understood. Previously, we have discovered that RPIA regulates hepatocarcinogenesis via PP2A and ERK signaling in vitro using cell culture. We also demonstrated that RPIA regulates tumor growth in nude mice xenotransplant RPIA overexpressed cells. It sheds new light on RPIA as a potential biomarker and target for liver cancer therapy. However, the RPIA transgenic animal HCC model is still missing. Zebrafish has become an excellent model for cancer study and drug discovery. Hence, we have generated RPIA transgenic fish using liver specific promoter drive human RPIA in zebrafish and examine the hepatocarcinogenesis at different stage. Using F2 of Tg (fabp10a: RPIA) transgenic fish, we collected the liver specimens from five different stage, 3, 5, 7, 9 and 11 months respectively, and analyzed the expression of lipogenic factor, lipogenic enzyme, fibrosis markers and cell cycle related genes using QPCR. The lipogenic factor and enzyme were up-regulated at 5 months, and using HE stain and Oil Red stain, and the liver has become fatty liver. At 7 months, we discovered the increasing expression of fibrosis markers, and using Sirius red staining, we found the hepatocyte has fibrosis. At 9 and 11 months, the cell cycle/proliferation markers were up-regulated; via HE staining we found the 9 to 11 months old fish showed hyperplasia and hepatocellular carcinoma. These results revealed that RPIA overexpression in zebrafish could promote liver cancer progression. RPIA has been known to activate ERK signaling in liver cancer cell lines, and β-catenin pathway in colorectal cancer cell lines. We have examined the p-ERK and β-catenin by immunostaining, and found both p-ERK and β-catenin were activated at 9 and 11 months, and PCNA proliferation markers are also activated at this stage. In the future, we would like to use the RPIA transgenic fish liver cancer model to screen for therapeutic means for preventing RPIA mediated HCC formation.