Abstract:Objective:To examine the mutation frequencies ofKRAS,NRASandBRAFin colorectal cancer (CRC) among Chinese population, and to investigate their correlation with clinicopathological parameters and p53 protein expression.Methods:Tissue samples and pathological data of 110 CRC patients undergoing surgical excision were collected, and the clinical pathological features were summarized. Mutations inKRAS(codon 12/13 at exon 2, codon 61 at exon 3 and codon 117/146 at exon 4),NRAS(codon 12/13 at exon 2, codon 61 at exon 3 and codon 146 at exon 4) and BRAF (codon 600 at exon 15) genes were examined with ARMS-PCR. p53 protein expression was detected by immunohistochemistry.Results:45.4% (50/110) patients carriedKRASmutations; among them, almost all individuals had mutation inKRAScodon 12/13 at exon 2, except one individual had codon 117/146 at exon 4 mutated. 6.3% (7/110) patients carriedNRASmutations; among them, 3/110 patients had mutation inNRASexon 2 (condon 12/13), 3/110 patients had mutation inNRASexon 3 (condon 61), 1/110 patient had mutations in bothNRASexon 4 (condon 146) andKRAS.BRAFmutations were detected in 3 patients (2.7%), and were found to have V600E mutations. p53 expression was observed in 63 (57.3%) of 110 CRC patients. Within these 63 positive samples, 27 cases showedKRASmutations, 7 cases showedNRASmutations and 2 cases showedBRAFmutations.KRASmutation was significantly associated with lymph node metastasis (P<0.05) whileNRASmutation was significantly associated with histological type and p53 protein expression (P<0.05).BRAFmutation was significantly associated with right colon cancer (P<0.05).Conclusions:KRASis closely related to the molecular mechanism of occurrence and development of colorectal cancer.BRAFmutation is only found in right colon cancer, suggesting that the mechanism of right hemicolon cancer may have its particularity. The interaction between p53 protein expression andNRAS mutation is worthy of further study.

Key words:Colorectal cancer, KRAS , NRAS , BRAF , P53