| Background Colorectal Cancer(CRC) is one of the most common malignant neoplasms and the3rd leading cause of cancer-related deaths globally. It is estimated that approximately1.23million new cases are diagnosed annually worldwide which seriously threats to the public health worldwide. The pathogenesis of CRC is very complicated, In addition to multiple genetic alterations, it is now recognized that the development and progression of CRC is associated with epigenetic mechanisms. It is reported that epigenetic inactivation of multiple tumor suppressor genes involved with colorectal carcinogenesis, especially DNA methylation. Recent findings suggest that epigenetic alterations of Rassf gene family play important roles in the tumorigenesis of colorectal carcinoma. Rassf gene family disregulate RAS signaling pathyway and and may serve as tumour suppressor gene,which consists of ten members, several of the members are expression missing due to hypermethylation of their CpG island promoter in various tumors. It is reported that RassflO is frequently methylated in gastric cancer, thyroid cancer, Malignant Melanoma, in childhood leukaemias and prostate carcinoma, and is considered as potential candidate tumor suppress gene. However, there is no similar report in colorectal cancer. The methylation status of Rassf10remains unclear. Objectives Our research aimed to explore the methylation and expression status of Rassf10in colorectal cancer, to explore the relationship of Rassf10gene methylation and human colorectal cancer and provide a new target for the diagnosis and treatment of human colorectal cancer.Methods In this study,7colorectal cancer cell lines (LOVO, RKO, DLD1, HCT116, HT29,SW620andSW480)were supplied by Department of Gastroenterology,Chinese PLA General Hospital. The methylation status of Rassf10promoter region of the7colorectal cancer cell lines and human primary colorectal cancer tissues were examined by MSP (methylation special PCR). Rassf10expression in mRNA was detected by semi-quantity RT-PCR before and after5-aza-2’-deoxycytidine(5-aza-dc) treatment in colorectal cancer cell lines.Expression of Rassf10was detected by Immunohistochemistry(IHC)in20cases of available matched colorectal cancer and adjacent tissues samples. The association of Rassf10methylation and clinical factors of CRC patients was analyzed by SPSS17.0software, p<0.05was regarded as significant difference.Results1.The promoter region of Rassf10was completely methylated in LOVO, RKO and HCT116cells. DLD1,HT29,SW620and SW480were metyhlated partially.2. Loss of Rassf10mRNA expression was found in LOVO,RKO and HCT116cells. Rassf10mRNA expression was restored after5-aza-2’-deoxycytidine treatment and expression increased was found in the other4cell lines. Combined with the MSP results suggest that expression of Rassf10was down regulated in colorectal cancer.3. The results of IHC of20cases of available matched colorectal cancer and adjacent tissues samples displayed expression of Rassf10was down-regulated in the colorectal cancer tissues compare to adjacent tissues, and the difference has statistical significance. 4. RassflO methylation was found in60%(54/90) of colorectal cancer and no methylation was detected in normal colorectal mucosa. No association was found between promoter region hypermethylation and gender, age or tumor differentiation (P>0.05). Promoter region methylation was related to lymph node metastasis and TNM staging (P<0.05).Conclusions1. The promoter region of RassflO is aberrantly hypermethylated in colorectal cancer. Rassf10is frequently methylated in human colorectal cancer. The promoter region of Rassf10methylation is related to lymph node metastasis and TNM staging and may play an important role in the development and progression of CRC.2. The expression of Rassf10is down-regulated in the colorectal cancer tissues compare to adjacent tissues, and the difference has statistical significance.3. The expression of Rassf10is down regulated by the promoter hypermethylation in colorectal cancer. |
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