The Clinical Significance And Detection Of K-ras, BRAF And PIK3CA Genes Mutation In Colorectal Cancer

Objcet: To investigate the K-ras,BRAF and PIK3CA gene mutations in the colorectal cancer(CRC) and the relationship between the K-ras,BRAF,PIK3CA gene mutations and clinical pathological factors of CRC, trying to provide some theoretical basis for establishing a simple,rapid and economical method of testing gene status in the clinical practice.Methods: Took 37 cases of postoperative tumor tissues and 27 cases of preoperative peripheral vein blood of colorectal cancer patients with surgical treatment as experimental materials, which were from the First Affiliated Hospital of Suzhou University in July to November of 2010. Genomic Deoxyribonucleic acid (DNA) from peripheral vein blood was extracted with kit,while the tumor tissues embedded in paraffin, DNA was extracted with the method of manual microdissection and DNA extraction kit for paraffin specimen.After the perimental steps of polymerase chain reaction (PCR) amplification, sequencing,Codon 12,13 of exon 1 of the K-ras gene and exon 15 of BRAF gene and exon 9,20 of PIK3CA gene mutations were identified and analyzed with the corresponding clinical pathological datas.Later,take another 8 cases of tissue specimens after PPH operation for hemorrhoid patients as controls.Results:(1)In the tumor tissues of CRC , a total of 4 out of 37 cases were identified with mutations at codon 12 of exon 1 of K-ras gene,the mutation rate was 10.8%, no one was found point-mutation at codon 13;There were 2 cases with PIK3CA gene mutations ,the mutation rate was 5.4%;no mutations were detected at exon 15 of BRAF gene, they were all wide type, the mutation rate was 0%; the total mutation rate of the three genes was 16.2%.(2)In 27 cases of preoperative peripheral vein blood, no mutations of the K-ras, BRAF and PIK3CA genes were detected, all the mutation rate was 0%.(3)The mutation pattern of the K-ras gene was a kind of G>A and were all heterozygotic mutations.1 case of the 2 patients with PIK3CA gene mutation at exon 9 was A1634C (E545A) and the other at exon 20 was the type of A3140G(H1047R).(4)In the 8 cases of patients after the PPH operation ,no mutations of the three genes were detected in the control group.(5)The frequency of K-ras and PIK3CA gene mutation has no significant correlation with the pathological histological types,location of tumors,clinical stage, or with lymph nodes or remote metastasis in CRC.Conclusion(:1)The quality and quantity of DNA extracted from Formaldehyde-fixed paraffin-embedded (FFPE) with the method of manual microdissection and FFPE DNA kit can meet the need for the clinical detection of gene mutation.(2)K-ras and PIK3CA gene mutations in colorectal cancer are common molecular biological events and may play an important role in the occurring of colorectal cancer,while BRAF gene mutations may not be the major molecular mechanism in CRC.(3)K-ras gene mutations mainly occur at codon 12 of exon1, the mutation of the G>A was the main type.(4)Exon9 and Exon20 of PIK3CA gene were the two major mutational hotspots.(5)In this study, no significant correlation was observed between mutations of K-ras,PIK3CA gene and the clinicopathoiogic characteristics of colorectal cancer, so the further study concerning the relationships needs to be done.BRAF gene mutational types,the exact rate of mutation and the relationship between BRAF gene mutations and clinicopathological factors need to be further studied.