| Summary: | 碩士 === 國立中正大學 === 分子生物研究所 === 101 === Ovarian cancer is the fifth leading cause of cancer death and the most deadly gynecological malignancies in women. Epigenetic modifications play an important role in regulating gene transcription. Specifically, aberrant promoter hypermethylation has been implicated as a hallmark of cancer. In order to identify genes that are differentially methylated in ovarian cancer, we performed differential methylation hybridization (DMH) in various ovarian cancer cell lines using Agilent 244K CpG island microarray. One of the targets, ARNTL which is a core component of the circadian clock is methylated in a sub-set of ovarian cancer cell lines. COBRA assay and epigenetic treatment confirmed the results of the microarray. ChIP-PCR revealed that histone modifications trimethyl-H3K4 in IOSE and trimethyl-H3K27 is enriched in MCP3 ovarian cancer cells. Overexpression of ARNTL restored the rhythmic activity of c-myc in ovarian cancer cells. Further functional analysis demonstrated that over-expression of ARNTL inhibited cell growth and enhanced chemosensitivity to cisplatin. These results suggested that ARNTL may be a tumor suppressor and is epigenetically silenced in ovarian cancer. Additionally, we have investigated the promoter methylation of DCC by methylation specific PCR (MSP) in 4 normal ovary, 8 benign and 55 ovarian cancer patient samples. Except for normal ovary and benign tumor, methylation of DCC was detected in 55% of the cancer patients. Kaplan meier survival analysis also found that patient samples with DCC methylation have significantly shorter survival.
In conclusion, ARNTL and DCC are epigenetically silenced in ovarian cancer. The diagnostic potential of the methylation of ARNTL and DCC deserves further investigation.
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