ABSTRACT
Objective To determine the correlation between Smad4 mRNA,protein expression,abnormal methylation of CpG islands of Smad4 and colorectal cancer.Methods The expression of Smad4 in 43 cases of colorectal cancer and its adjacent tissue.30 cases of colorectal adenoma and 12 normal colon mucosa were analyzed by RT-PCR,sequencing,semi-quantitative RT-PCR,methylation-specific PCR(MSP)and immunohistochemistry.Results The mRNA expression of Smad4 was detected in 25 cases of colorectal cancer(58.14%),with expression levels at 0.73±0.25,which was significantly lower than those in corresponding adjacent tissues(88.37%,0.95±0.29),eolorectal adenoma(90.63%,1.01±0.37)and normal mucosa(100.00%,1.18 ±0.33)(P＜0.05).The positive rates of Smad4 gone promoter methylation in colorectal caner(60.53%)was significantly higher than that in other tissues(27.03%,25.00%and 16.67%,respectively,P＜0.05).The expression of Smad4 protein was significantly lower in colorectal cancer(44.19%)than that in other tissues(81.40%,87.50%,91.67%,respectively,P＜0.05),which was correlated with tumor invasion and lymph node metastasis.Conclusion Down-regulation of Smad4 expression may be associated with the development,the biological behavior and prognosis of colorectal cancer,and it can be an important biological marker in evaluation of disease progression.