Regulation of HSulf-1 expression by variant hepatic nuclear factor 1 in ovarian cancer

We recently identified HSulf-1 as a down-regulated gene in ovarian carcinomas. Our previous analysis indicated that HSulf-1 inactivation in ovarian cancers is partly mediated by loss of heterozygosity and epigenetic silencing. Here, we show that variant hepatic nuclear factor 1 (vHNF1), encoded by transcription factor 2 gene (TCF2, HNF1β), negatively regulates HSulf-1 expression in ovarian cancer. Immunoblot assay revealed that vHNF1 is highly expressed in HSulf-1-deficient OV207, SKOV3, and TOV-21G cell lines but not in HSulf-1-expressing OSE, OV167, and OV202 cells. By short hairpin RNA-mediated down-regulation of vHNF1 in TOV-21G cells and transient enhanced vHNF1 expression in OV202 cells, we showed that vHNF1 suppresses HSulf-1 expression in ovarian cancer cell lines. Reporter assay and chromatin immunoprecipitation experiments showed that vHNF1 is specifically recruited to HSulf-1 promoter at two different vHNF1-responsive elements in OV207 and TOV-21G cells. Additionally, down-regulation of vHNF1 expression in OV207 and TOV-21G cells increased cisplatin- or paclitaxel-mediated cytotoxicity as determined by both 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and clonogenic assays and this effect was reversed by down-regulation of HSulf-1. Moreover, nude mice bearing TOV-21G cell xenografts with stably down-regulated vHNF1 were more sensitive to cisplatin- or paclitaxel-induced cytotoxicity compared with xenografts of TOV-21G clonal lines with nontargeted control short hairpin RNA. Finally, immunohistochemical analysis of 501 ovarian tumors including 140 clear-cell tumors on tissue microarrays showed that vHNF1 inversely correlates to HSulf-1 expression. Collectively, these results indicate that vHNF1 acts as a repressor of HSulf-1 expression and might be a molecular target for ovarian cancer therapy.