Chromatin remodeling geneARID2targets cyclin D1 and cyclin E1 to suppress hepatoma cell progression

Abstract

Exome and whole-genome sequencing studies have drawn attention to the role of somatic mutations in SWI/SNF chromatin remodeling complexes in the carcinogenesis of hepatocellular carcinoma (HCC). Here, we explored the molecular mechanisms underlying the biological roles of AT-rich interactive domain 2 (ARID2) in the pathogenesis of HCC. We found that ARID2 expression was significantly downregulated in HCC tissues compared with non-tumorous tissues. Restoration of ARID2 expression in hepatoma cells was sufficient to suppress cell proliferation and tumor growth in mice, whereas ARID2 knockdown contributed to the enhancement of cellular proliferation and tumorigenicity. Suppression of ARID2 expression accelerated G1/S transition associated with upregulation of cyclin D1, cyclin E1, CDK4, and phosphorylation of the retinoblastoma protein (Rb). Furthermore, we demonstrated that ARID2 physically interacts with E2F1 and decreases binding of E2F1/RNA Pol II to the promoters of CCND1 and CCNE1. Taken together, these results demonstrate that ARID2 suppresses tumor cell growth through repression of cyclin D1 and cyclin E1 expression, thereby retarding cell cycle progression and cell proliferation in hepatoma cells. These findings highlight the potential role of ARID2 as a tumor growth suppressor in HCC.

HBx protein‐mediated ATOH1 downregulation suppresses ARID2 expression and promotes hepatocellular carcinoma

“…Previously, we and others reported that ARID2 deficiency is prevalent in human HCC, suggesting that ARID2 deletion may play an important role in the pathogenesis of HCC. (15,20) However, the relationship between HBV infection and ARID2 expression in hepatoma cell lines is unclear. We first examined the levels of ARID2 in an HBV-expressing hepatoma cell line.…”

“…Following elution, DNA was extracted and subjected to PCR analysis. Isolated chromatin immunoprecipitated by E2F1 antibody was amplified with ARID2 primers and CCND1 (cyclin D1) primers used us positive control . For ChIP‐qPCR, the immunoprecipitated DNA was quantified by real‐time PCR.…”

“…Recombinant adenoviruses AdHBx and AdARID2 were constructed as previously described. (20,24) The full-length cDNA of ATOH1 (coding sequence of NM_005172) was subcloned from the pPCR-Script-ATOH1 plasmid (GeneCopoeia #FL30148) and inserted into the shuttle vector pAdTrack-TO4 or His-tagged vector pSEB-3His vector. HBx (genotype C) was cloned into the Flag-tagged pSEB-3Flag vector (from Dr. T-C He, University of Chicago, IL, USA).…”

“…Isolated chromatin immunoprecipitated by E2F1 antibody was amplified with ARID2 primers and CCND1 (cyclin D1) primers used us positive control. (20) For ChIP-qPCR, the immunoprecipitated DNA was quantified by real-time PCR. Enrichment of ATOH1 at the examined regions of the ARID2 promoter was quantified relative to the input control.…”

“…(11) Recently, ARID2 was identified as a tumor suppressor and found to be frequently mutated in various cancers, such as HCC, (12)(13)(14)(15) melanoma, (16) nonsmall lung carcinoma, (17) and gastric adenomas. (18) Recent studies have revealed that loss of ARID2 expression owing to inactivating mutations promotes hepatoma cell proliferation (19,20) and may be associated with tumor recurrence. (21) Adenomatous polyposis coli (APC) and ARID2 inactivating mutations have recently been reported to be involved in the early stages of gastric carcinogenesis.…”