Abstract:

Objective To study the expression of the tumor suppressor gene RAS in papillary thyroid carcinoma(PTC) and the correlation between the expression and the aberrant promoter methylation of RAS gene.
Methods RT-PCR was used to detect the mRNA expression of RAS in 50 cases of PTC, 20 cases of nodular goiter and 12 cases of thyroid adenoma tissue. We examined the promoter methylation status of RAS gene by using methylation-specific PCR technique(MSP).
Results Hypermethylation of RAS gene in promoter region was detected in 30 of 50 cases with PTC(60%) and in 10 of 32 cases of control group(31.3%), the difference in methylation of RAS promoter was significantly higher in PTC patients than that in controls(χ²=6.46, P<0.05). The mRNA expression of RAS genes was significantly lower in PTCs than that in controls(the t value was 2.83, P<0.05). The sequencing confirmed that there was the CG →TG transmission in promoter of RAS genes.
Conclusion Methylation of RAS gene in promoter region is a common molecular event and may be involved in the genesis and development of human PTC.

Key words: papillary thyroid carcinoma, hypermethylation, RAS, promoter