Anterior gradient-2 is overexpressed by fibrolamellar carcinomas
Anterior gradient-2 expression is critical in normal embryonic development. Aberrant expression of anterior gradient-2 in adult tissues has been linked to breast, prostate, esophageal, and pancreatic carcinoma. To define the role of anterior gradient-2 in primary hepatocellular neoplasms, we used tissue microarrays and examined protein expression in typical hepatocellular carcinomas (n = 44), fibrolamellar carcinomas (n = 12), and hepatic adenomas (n = 9). In nonneoplastic liver tissues, anterior gradient-2 was expressed in the septal-sized bile ducts and weakly in zone 3 hepatocytes in 11 (18%) of 61 cases. In tumors, anterior gradient-2 was overexpressed by only 1 (2%) of 44 hepatocellular carcinomas. In contrast, 6 (75%) of 8 fibrolamellar and 3 (75%) of 4 metastatic fibrolamellar carcinomas were positive. All 9 hepatic adenomas were negative. Further analysis of mRNA in fibrolamellar carcinomas identified 2 novel splice variants, but expression levels were very low. Sequencing of the anterior gradient-2 gene in fibrolamellar carcinomas identified several polymorphisms (refSNP Ids: rs6842, rs8071, rs1051905) but no mutations. In conclusion, anterior gradient-2 is overexpressed in the majority of fibrolamellar carcinomas but is only rarely overexpressed in hepatocellular carcinomas.