Altered expression of AT-rich interactive domain 1A in hepatocellular carcinoma

AT-rich interactive domain 1A (ARID1A) is a subunit of the Switch/Sucrose non-fermentable (SWI/SNF) chromatin remodeling complex. Recently, genome-wide whole exome sequencing revealed frequent mutations of ARID1A in hepatocellular carcinoma, but clinicopathological significance of ARID1A alteration has not been clarified yet. In this study, expression of ARID1A was investigated immunohistochemically in 290 cases of hepatocellular carcinomas. In the evaluation of tissue microarrays, cases of ARID1A alteration (63 total cases, 21.7%) consisted of 11 (3.8%) cases showing loss of expression and 52 (17.9%) with weak expression. Alteration of ARID1A was correlated with larger tumor size (P=0.034) and well or moderate differentiation of tumor histology (P=0.035). There was no significant correlation with age, sex, cirrhosis, TNM stage, tumor size, number of tumors, vascular invasion, patient survival, HBV infection, HCV infection, heavy use of alcohol, nor diabetes mellitus. EBER in situ hybridization was negative in all 11 cases with loss of ARID1A. Altered expression of ARID1A was inversely correlated with nuclear expression of p53 (P=0.018) or beta-catenin (P=0.025). There was some heterogeneity of ARID1A alteration within each case, and immunohistochemistry of the whole sections demonstrated that four of 11 cases with loss of ARID1A in TMA analysis showed localized positive area within the tumor. Alteration of ARID1A may accelerate tumor growth in a subset of hepatocellular carcinoma, and this pathway may be distinct from p53 and beta-catenin pathways.