Preliminary Study On The Relationship Between K-ras Gene Mutation Of Sporadic Colorectal Cancer And Its Clinicopathological Features And Prognosis

Backround and objectiveColorectal carcinoma (CRC) is a common malignant tumor of digestive system. With improvement of people living standard, the fatality and incidence of CRC are getting higher and higher in recent years in the world. Modern molecular genetics reveals that the occurrence and development of CRC are a multi-stage and multi-step process involved by multiple genes. Ras/MAPK pathway is one of the key survival and anti-apoptotic signal transduction pathway. Current researches have showed, in Ras gene families, that K-ras gene is most closely related with CRC, but the relationship between K-ras gene mutation and CRC clinicopathological features as well as prognosis is not completely clear. Continuous development of molecular targeted therapy has showed that the state of K-ras gene is closely related to the efficacy of epidermal growth factor receptor(EGFR) monoclonal antibody which is a targeted drug. Therefore, the appropriate technology to detect K-ras gene mutation is very important. This study observed the CRC pathological morphology and detected K-ras gene mutation from the gene level in order to find the relationship between sporadic CRC K-ras gene status and its clinicopathological characteristics as well as prognosis, to clear the function of K-ras genes in the process of CRC occurrence, development and prognosis.This study will demonstrate the initial map of the K-ras gene mutation spectrum of Chinese sporadic CRC, and provide theoretical basis for rational use of gene targeted drugs and prediction of clinical efficacy.MethodsThis study collected 112 cases sporadic colorectal adenocarcinoma of Zhe jiang Cancer Hospital Department of Pathology from January 2003 to December 2009.A11 specimens were fixed by neutral buffered formalin, paraffin-embedded, hematoxylin-eosin stained and then, observed morphologically by light microscope. Genomic DNA was extracted from paraffin-embedded tissues and K-ras gene mutations were analyzed by Pyrosequencing after Polymerase Chain Reaction amplification. The SPSS 17.0 statistical software for statistical analysis was used. The survival of 112 patients was followed up and analysed by Kaplan-Meier survival analysis method.ResultsOf 112 cases, K-ras gene mutations were detected in 45 cases, including 33 cases at codon 12 and 12 cases at codon 13. In additional, seven types of K-ras mutation were found, including G12D,G12S,G12V,G12R,G12A,G12C and G13D.The predominant mutations were G12D and G13D.K-ras gene mutations had no relationship with sex,age,tumor size,tumor location,histologic subtype,tumor grade,infiltrating depth, metastasis, clinical stage and vascular invation(P>0.05). The mean follow-up time of 112 Cases was 34.06 months, mean postoperative progression-free survival (PFS) was 31.47±3.06 months. No significant differences were observed for postoperative PFS with respect to K-ras gene mutation. The groups of 12 G→T K-ras mutation had a poorer prognosis, its mean postoperative PFS was 14.6 months, than that of the 13G→A groups with statistical significance (P=0.021).Conclusions1. K-ras gene mutation rate and mutation characteristics in Chinese sporadic colorectal carcinoma are similar to that in foreign counterparts, in which G12D and G13D were more common. 2. K-ras gene mutations of sporadic colorectal carcinoma have no correlation with its clinicopathological features and prognosis.3. The patients with K-ras mutation of codon 12 G→T have poorer prognosis than that with other types of K-ras mutation.