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AIM:To investigate the effects of DNA methylation on theexpression of tumor suppressor genes and proto-oncogenein human colon cancer cell lines.METHODS:Three colon cancer cell lines(HT-29,SW1116and Colo-320)treated with different concentrations of DNAmethyltransferase inhibitor,5-aza-2’-deoxycytidine(5-aza-dC)were used to induce DNA demethylation.The expressionsof p16(INK4A),p21~(WAF1),APC and c-rnyc genes were observedby using RT-PCR.The methylation status of p16~(INK4A)promoterin HT-29 cells was also determined by methylation-specificPCR(MSP).RESULTS:Weak expressions of p16(INK4A)and APCin thethree colon cancer cells were detected,and p21(WAF1)expressionwas not found in SW1116 and Colo-320 cells beforetreatment.After treatment of I μmol/L but not 10 μmol/L of5-aza-dC,the methylation level of p16(INK4A)gene promoterdecreased significantly,and the hypomethylation led to theup-regulation of p16~(INK4A)gene transcription in HT-29 cells.In the cell lines of SW1116 and Colo-320,p16(INK4A)and APCmRNA expressions were obviously enhanced after treatmentof either 10 μmol/L or 5 μmol/1 5-aza-dC for 24 h.However,no evidence was found that methylation regulated theexpression of p21~(WAF1)and c-mycgenes in human colon cancercell lines.CONCLUSION:Expression of p16~(INK4A)and APC genes isregulated by DNA methylation in three human colon cancercell lines.
AIM: To investigate the effects of DNA methylation on theexpression of tumor suppressor genes and proto-oncogenein human colon cancer cell lines. METHODS: Three colon cancer cell lines (HT-29, SW1116 and Colo-320) treated with different concentrations of DNAmethyltransferase inhibitors, 5-aza-2’-deoxycytidine (5-aza-dC) were used to induce DNA demethylation.The expressions of p16 (INK4A), p21 WAF1, APC and c-rnyc genes were observed by using RT-PCR.The methylation status of p16 INK4A promoterin HT-29 cells was also determined by methylation-specific PCR (MSP) .RESULTS: Weak expressions of p16 (INK4A) and APCin thethree colon cancer cells were detected, and p21 (WAF1) expressionwas not found in The methylation level of p16 (INK4A) gene promoter was significantly increased, and the hypomethylation led to the up-regulation of p16 ~ (+) cells treated with 1 μmol / L but not 10 μmol / L of 5-aza- (INK4A) gene transcription in HT-29 cells. In the cell lines of SW1116 and Colo-320, p16 (INK4A ) and APC mRNA expressions were obviously enhanced after treatment of either 10 μmol / L or 5 μmol / 1 5-aza-dC for 24 h. Of the no evidence was found that methylation regulated the expression of p21 WAF1 and c-mycgenes in human colon cancercell lines. CONCLUSION: Expression of p16 ~ (INK4A) and APC genes isregulated by DNA methylation in three human colon cancer cells line.