A Further Research And Analysis Of Hypermethylation At The PTEN CpG Island In Cervical Cancer Cell Lines And Cervical Tissues

PTEN (Phosphatase and tensin homologue) is a tumor suppressor gene with dual protein and lipid phosphatase activity. As is known to all that CpG island hypermethylation of gene promoter is another route to tumour suppressor gene inactivation. recently, many scholars made serious of studies on the mechanism of PTEN gene downregulated throw direction of promoter methylation. however, the literature regarding primer hypermethylation of PTEN in cervical cancer is controversial. Therefore, primer mehtylation and downregulated maybe caused by primer methylation in cervical cancer of PTEN need a further research.ObjectiveTo investigate methylation status at PTEN gene promoter and influence maybe caused by which on PTEN expression in cervical cancer cell lines and cervical tissues.MethodsMethylation status of2PTEN gene CpG islands were investigated in four kinds of cervical cancer cell lines HeLa, Caski, C-33A, HT-3,18cases of cervical cancer and8cases of normal cervical tissue throw bisulfite genomic sequencing PCR (BSP) combined with TA clone for sequencing.4cervical cancer cell lines were treated with5-Aza-2’-deoxycytidine (5-Aza-dC). Realtimefluores-cencequantitative PCR were used to compare the changes of PTEN gene expression on before and after the treatment of5-Aza-dC in cervical cell lines. And differences of PTEN gene expression between cervical cancer tissues and normal ones.Results①The2CpG island of PTEN promoter showed hypo-methylation in4kinds of cervical cancer cell lines, whose methylation rate has no difference(CpG1:t=2.83, P=0.11; CpG2:t=1.00, P=0.42) between HPV-positive cervical cancer cell lines (HeLa, Caski) and HPV-negative ones (C-33A,HT-3);②The2CpG island of PTEN promoter also showed hypo-methylation in both tissues of cervical cancer and normal ones, what’s more, their methylation rate has no significantly differences (CpG1:T=83.50, P=0.15; CpG2:T=34.5, P=0.720); ③Realtime-qPCR results shows no significant difference between before and after the treatment of5-Aza-dC in4kinds of cervical cell lines(HeLa:t=-1.18, P=0.36; Caski: t=2.07, P=0.18; C-33A:t=-0.07, P=0.95; HT-3:t=-0.53, P=0.65).Conclusions①Infection of HPV is unrelated with the hyper-methylation of PTEN promoter;②Hypermethylation of PTEN promoter is not the cause of cervical cancer.③Hypermethylation of promoter in tumor suppressor gene is believed to be a key mechanism in addition to mutations and deletions functional inactivation of tumor suppressor genes. But when we analysis methylation level of the gene promoter, MSP shows certain limitations. While, BSP combined with TA clone for sequencing could detect methylation status precisely.