Detection And Clinic Study Of K-ras Mutations And MGMT Methylations In Rectal Cancer Undergone Preoperative Radiotherapy

Objective:To detect K-ras mutations and MGMT methylations in rectal carcinoma before and after preoperative radiotherapy,and study genetic changes of radiotherapy in rectal cancer.Methods:Twenty-five patients with rectal cancer in pTNM stage II or III were enrolled.All patients received preoperative adjuvant radiotherapy.The treatment time is 4 weeks for 40Gy in 2.0 Gy fractions and it is usually followed by an interval of 2 weeks before the operation.Tumor tissue and normal mucosa were collected from patients before preoperative adjuvant radiotherapy and after operation.The K-ras mutations in codon 12 were investigated using polymerase chain reaction -restriction fragment length polymorphism (PCR-RFLP) and the MGMT methylations were detected by nested methylation specific PCR (MS-PCR) in tumor and normal mucosa.Results:The frequencies of K-ras mutations and MGMT methylations before preoperative adjuvant radiotherapy in tumor tissue were 44.0%and 36.0%.After radiotherapy ,the frequencies of K-ras mutations and MGMT methylations in tumor tissue became 12.0% and 8.0%.No K-ras mutations...