Arginase-1 and P-glycoprotein are downregulated in canine hepatocellular carcinoma.

BACKGROUND Hepatocellular carcinoma is the most common primary hepatic malignancy in humans and dogs. Several differentially expressed molecules have been studied and reported in human hepatocellular carcinoma and non-neoplastic liver lesions. However, studies on the features of canine hepatocellular carcinoma are limited, especially related to the differential characteristics of neoplastic and non-neoplastic lesions. OBJECTIVES The study's objective was 1) to examine and evaluate the expression of arginase-1, P-glycoprotein, and cytokeratin 19 in canine liver tissues and 2) to investigate the differential features of hepatocellular carcinomas, liver tissue with non-neoplastic lesions, and paracancerous liver tissues in dogs. METHODS The expression levels of three markers underwent immunohistochemical analysis in 40 non-neoplastic liver tissues, 32 hepatocellular carcinoma tissues, and 11 paracancerous liver tissues. Scoring of each marker was performed semi-quantitatively. RESULTS Arginase-1 and P-glycoprotein were significantly downregulated in hepatocellular carcinoma, compared with hepatic tissues with non-neoplastic diseases (p < 0.001). Expression levels of arginase-1 and P-glycoprotein were also significantly lower in hepatocellular carcinoma than in paracancerous liver tissues (arginase-1, p = 0.0195; P-glycoprotein, p = 0.047). Few cytokeratin 19-positive hepatocytes were detected and only in one hepatocellular carcinoma and one cirrhotic liver sample. CONCLUSIONS The results of this study suggest that downregulation of arginase-1 and P-glycoprotein is a feature of canine hepatocellular carcinoma; thus, those markers are potential candidates for use in differentiating hepatocellular carcinomas from non-neoplastic liver lesions in dogs.