title: Aberrant TGFβ/SMAD4 signaling contributes to epigenetic silencing of a putative tumor suppressor, RunX1T1 in ovarian cancer.
abstract: Aberrant TGFβ signaling pathway may alter the expression of down-stream targets and promotes ovarian carcinogenesis. However, the mechanism of this impairment is not fully understood. Our previous study has identified RunX1T1 as a putative SMAD4 target in an immortalized ovarian surface epithelial cell line, IOSE. In this study, we report that transcription of RunX1T1 was confirmed to be positively regulated by SMAD4 in IOSE cells and epigenetically silenced in a panel of ovarian cancer cell lines by promoter hypermethylation and histone methylation at H3 lysine 9. SMAD4 depletion increased repressive histone modifications of RunX1T1 promoter without affecting promoter methylation in IOSE cells. Epigenetic treatment can restore RunX1T1 expression by reversing its epigenetic status in MCP3 ovarian cancer cells. When transiently treated with a demethylating agent, the expression of RunX1T1 was partially restored in MCP3 cells, but gradual re-silencing through promoter re-methylation was observed after the treatment. Interestingly, SMAD4 knockdown accelerated this re-silencing process, suggesting that normal TGF-beta signaling is essential for the maintenance of RunX1T1 expression. In vivo analysis confirmed that hypermethylation of RunX1T1 was detected in 35.7% (34/95) of ovarian tumors with high clinical stages (P=0.035) and in 83% (5/6) of primary ovarian cancer-initiating cells. Additionally, concurrent methylation of RunX1T1 and another SMAD4 target, FBXO32 which was previously found to be hypermethylated in ovarian cancer was observed in this same sample cohort (P< 0.05). Restoration of RunX1T1 inhibited cancer cell growth. Taken together, dysregulated TGFβ/SMAD4 signaling may lead to epigenetic silencing of a putative tumor suppressor, RunX1T1, during ovarian carcinogenesis.
authors.affiliation: Department of Pathology, Changhua Christian Hospital, Changhua, Republic of China.
authors.forename: Kun-Tu
authors.initials: KT
authors.lastname: Yeh
authors.forename: Tze-Ho
authors.initials: TH
authors.lastname: Chen
authors.forename: Hui-Wen
authors.initials: HW
authors.lastname: Yang
authors.forename: Jian-Liang
authors.initials: JL
authors.lastname: Chou
authors.forename: Lin-Yu
authors.initials: LY
authors.lastname: Chen
authors.forename: Chia-Ming
authors.initials: CM
authors.lastname: Yeh
authors.forename: Yu-Hsin
authors.initials: YH
authors.lastname: Chen
authors.forename: Ru-Inn
authors.initials: RI
authors.lastname: Lin
authors.forename: Her-Young
authors.initials: HY
authors.lastname: Su
authors.forename: Gary C W
authors.initials: GC
authors.lastname: Chen
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Deatherage
authors.forename: Yi-Wen
authors.initials: YW
authors.lastname: Huang
authors.forename: Pearlly S
authors.initials: PS
authors.lastname: Yan
authors.forename: Huey-Jen
authors.initials: HJ
authors.lastname: Lin
authors.forename: Kenneth P
authors.initials: KP
authors.lastname: Nephew
authors.forename: Tim H-M
authors.initials: TH
authors.lastname: Huang
authors.forename: Hung-Cheng
authors.initials: HC
authors.lastname: Lai
authors.forename: Michael W Y
authors.initials: MW
authors.lastname: Chan
mesh_terms: D045744:Cell Line, Tumor; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D005260:Female; D020868:Gene Silencing; D006657:Histones / Q000378:metabolism; D006801:Humans; D009367:Neoplasm Staging; D010051:Ovarian Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D000075142:RUNX1 Translocation Partner 1 Protein; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*
chemical_list: D006657:Histones; D011518:Proto-Oncogene Proteins; D000075142:RUNX1 Translocation Partner 1 Protein; C082222:RUNX1T1 protein, human; D014157:Transcription Factors; D016212:Transforming Growth Factor beta