RESUMEN
Methylated promoter CpG islands (CGIs) can be used to find novel tumor-suppressor genes and disease markers. In this study, to identify promoter CGIs aberrantly methylated in human ovarian cancers, we performed a genome-wide screening for differentially methylated DNA fragments using methylation-sensitive-representational difference analysis (MS-RDA). MS-RDA isolated 185 DNA fragments specifically methylated in an ovarian cancer cell line (ES-2), compared with a normal human ovarian surface epithelial cell line (HOSE6-3), and 33 of them were derived from putative promoter CGIs. Ten ovarian cancer cell lines were analyzed by methylation-specific PCR, and seven (GPR150, LOC222171, PRTFDC1, LOC339210, ITGA8, C9orf64 and HOXD11) of the 33 CGIs were methylated in one or more of the cell lines. Their downstream genes were barely expressed in cell lines without unmethylated DNA molecules by quantitative reverse-transcription-PCR. Demethylation of methylated cell lines with 5-aza-2'-deoxycytidine restored expression of two genes (PRTFDC1 and C9orf64). In primary ovarian cancers, CGIs of GPR150 (in 4 of 15 cancers), ITGA8 (2/15), PRTFDC1 (1/15), and HOXD11 (1/15) were methylated. Silencing of PRTFDC1 was revealed here for the first time, and aberrant methylation of GPR150, ITGA8 and HOXD11 could be candidate tumor markers.
Asunto(s)
Biomarcadores de Tumor/genética , Islas de CpG/genética , Metilación de ADN , Regulación Neoplásica de la Expresión Génica , Neoplasias Ováricas/genética , Línea Celular Tumoral , Cartilla de ADN , Femenino , Genómica/métodos , Proteínas de Homeodominio/genética , Humanos , Cadenas alfa de Integrinas/genética , Receptores Acoplados a Proteínas G/genética , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
Aberrant methylation of CpG islands (CGIs) in promoter regions of tumor-suppressor genes causes their silencing, and aberrant demethylation of normally methylated CGIs in promoter regions causes aberrant expression of cancer-testis antigens. Here, we comprehensively analyzed aberrant methylation of 15 genes and demethylation of three normally methylated genes in 13 ovarian cancer cell lines. RASSF1A was most frequently methylated (complete methylation in 7 and partial methylation in 4 cell lines), followed by ESR1 (5 and 2, respectively), FLNC (4 and 4), HAND1 (4 and 2), LOX (3 and 2), HRASLS (3 and 2), MGMT (3 and 0), CDKN2A (3 and 0), THBD (2 and 1), hMLH1 (2 and 0), CDH1 (1 and 1) and GSTP1 (1 and 0). hTERC and TIMP3 were only partially methylated in 7 and 2 cell lines, respectively. BRCA1 was not methylated at all. Aberrant demethylation of MAGE-A3, -B2 and -A1 was detected in 8, 4 and 3 cell lines, respectively. Gene expression was consistently absent in cell lines without unmethylated DNA molecules. Aberrant methylation was frequently observed in MCAS, RMUG-L (mucinous cell carcinomas), RTSG (poorly-differentiated carcinoma) and TYK-nu (undifferentiated carcinoma) while infrequent in HTOA, JHOS-2, and OV-90 (serous cell carcinomas). Aberrant demethylation was frequently observed in OV-90, OVK-18, and ES-2 cell lines. It was shown that aberrant methylation and demethylation were frequently observed in ovarian cancer cell lines, and these data will provide a basis for further epigenetic analysis in ovarian cancers.
Asunto(s)
Metilación de ADN , ADN de Neoplasias/genética , Regulación Neoplásica de la Expresión Génica/genética , Genes Relacionados con las Neoplasias/genética , Neoplasias Ováricas/genética , Regiones Promotoras Genéticas/genética , Proteínas Supresoras de Tumor/genética , Epigénesis Genética , Femenino , Perfilación de la Expresión Génica , Humanos , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Células Tumorales CultivadasRESUMEN
OBJECTIVE: Uterine leiomyoma are very common benign tumors in women of reproductive age. However, the molecular mechanisms of cause and development of these tumors are poorly understood. This study attempts to examine whether or not aberrant DNA methylation occurred in these tumors. METHODS: We carried out a genome-wide screen for aberrant DNA methylation, adopting methylation-sensitive-representational difference analysis (MS-RDA) using normal adjacent myometria as tester and myoma tissue driver. CONCLUSION: A total of 192 clones identified by MS-RDA were sequenced, 27 DNA fragments derived from CpG islands (CGIs) were isolated, and seven of them were from CGI in the 5' regions of known genes, which include CHARC1, FAM44B, FLJ33655, HSUP, MLLT3, SLC16A1, and ZNF96. Then, methylation statuses of those CGIs were analyzed by methylation-specific polymerase chain reaction using 5 primary samples of human uterine leiomyoma. Aberrant DNA methylation did not observed in 7 genes in 5 human uterine leiomyoma eventually. This study is insufficient to identify aberrant DNA methylation occurring in the human uterine leiomyoma, a large population of primary samples and more attempts, such as the use of cell lines or primary monolayer cultures established from tissue samples, are warranted to clarify this issue.
Asunto(s)
Metilación de ADN , Leiomioma/genética , Neoplasias Uterinas/genética , Línea Celular Tumoral , Islas de CpG , Cartilla de ADN , Femenino , Regulación Neoplásica de la Expresión Génica , Estudio de Asociación del Genoma Completo , Humanos , Reacción en Cadena de la PolimerasaRESUMEN
The SFRP1 gene on chromosome 8p11.2 encodes a Wnt signaling antagonist, and was recently demonstrated to be a new tumor suppressor that is inactivated by promoter methylation in human colon cancers. Here, we analyzed promoter methylation of the SFRP1 gene in human ovarian cancers, in which loss of heterozygosity in 8p is frequently observed and involvement of the Wnt signaling pathway has been suggested. Methylation-specific PCR (MSP) analysis showed that four of 13 ovarian cancer cell lines and two of 17 primary ovarian cancers had methylated SFRP1, while an immortalized ovarian epithelial cell line, HOSE, and seven ovarian endometrial cyst samples did not. In the four ovarian cancer cell lines with the methylation, SFRP1 was not expressed at all as determined by quantitative RT-PCR analysis. A cell line with SFRP1 methylation, MCAS, was treated with a demethylating agent, 5-aza-2'-deoxycytidine, and demethylation of the promoter and re-expression of SFRP1 were observed. These results show that SFRP1 is inactivated by promoter methylation in human ovarian cancers, as well as colon cancers.