Promoter hypermethylation contributes to frequent inactivation of a putative conditional tumor suppressor gene connective tissue growth factor in ovarian cancer.
Connective tissue growth factor (CTGF) is a secreted protein belonging to the CCN family, members of which are implicated in various biological processes. We identified a homozygous loss of CTGF (6q23.2) in the course of screening a panel of ovarian cancer cell lines for genomic copy number aberrations using in-house array-based comparative genomic hybridization. CTGF mRNA expression was observed in normal ovarian tissue and immortalized ovarian epithelial cells but was reduced in many ovarian cancer cell lines without its homozygous deletion (12 of 23 lines) and restored after treatment with 5-aza 2'-deoxycytidine. The methylation status around the CTGF CpG island correlated inversely with the expression, and a putative target region for methylation showed promoter activity. CTGF methylation was frequently observed in primary ovarian cancer tissues (39 of 66, 59%) and inversely correlated with CTGF mRNA expression. In an immunohistochemical analysis of primary ovarian cancers, CTGF protein expression was frequently reduced (84 of 103 cases, 82%). Ovarian cancer tended to lack CTGF expression more frequently in the earlier stages (stages I and II) than the advanced stages (stages III and IV). CTGF protein was also differentially expressed among histologic subtypes. Exogenous restoration of CTGF expression or treatment with recombinant CTGF inhibited the growth of ovarian cancer cells lacking its expression, whereas knockdown of endogenous CTGF accelerated growth of ovarian cancer cells with expression of this gene. These results suggest that epigenetic silencing by hypermethylation of the CTGF promoter leads to a loss of CTGF function, which may be a factor in the carcinogenesis of ovarian cancer in a stage-dependent and/or histologic subtype-dependent manner.
Kikuchi
Ryoko
R
Department of Molecular Cytogenetics, Medical Research Institute and School of Biomedical Science, Tokyo Medical and Dental University, Japan.
Tsuda
Hitoshi
H
Kanai
Yae
Y
Kasamatsu
Takahiro
T
Sengoku
Kazuo
K
Hirohashi
Setsuo
S
Inazawa
Johji
J
Imoto
Issei
I
D018262:Adenocarcinoma, Clear Cell / Q000235:genetics / Q000473:pathology; D002288:Adenocarcinoma, Mucinous / Q000235:genetics / Q000473:pathology; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D018269:Carcinoma, Endometrioid / Q000235:genetics / Q000473:pathology; D048708:Cell Growth Processes / Q000235:genetics; D045744:Cell Line, Tumor; D002869:Chromosome Aberrations; D055513:Connective Tissue Growth Factor; D018899:CpG Islands; D018284:Cystadenocarcinoma, Serous / Q000235:genetics / Q000473:pathology; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D016147:Genes, Tumor Suppressor; D006801:Humans; D017874:Immediate-Early Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D008875:Middle Aged; D009693:Nucleic Acid Hybridization; D020411:Oligonucleotide Array Sequence Analysis; D010051:Ovarian Neoplasms / Q000235:genetics* / Q000473:pathology; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism
D014408:Biomarkers, Tumor; C526317:CCN2 protein, human; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D055513:Connective Tissue Growth Factor