K-ras mutation in Greek patients with poorly and moderately differenciated tumours of the lower intestinal tract.

The K-ras protooncogene is activated via mutations in approximately 40% of primary colorectal adenocarcinoma. This finding suggests that these genetic alterations are important events in the genesis of colon cancer and should be correlated with other parameters in order to infer some conclusions relevant to the etiology and the pathogenesis of this type of cancer. In our study we examined whether the incidence of K-ras mutations detected in 23 samples with colorectal adenocarcinomas, was related to different anatomical sites within the lower intestinal tract (transverse colon, descending colon and rectosigmoid region) and also the correlation between K-ras mutations and depth of invasion, level of tumour cell differentiation and metastasis to the regional lymph nodes. For this study the critical regions for the activation of the K-ras protooncogene were amplified by the PCR technique and the particular sequences analysed, after their membrane transfer, by differential hybridization with selected synthetic oligonucleotides. Our results demonstrated that 39% of the adenocarcinomas examined contained point mutations, and 66.6% of these were located in the second position of K-ras codon 12, whereas the other 33.3% were located in the second position of codon 13. 77.8% of the mutations were located at the rectosigmoid region and the relevance of the mutations was higher in poorly differenciated tumours. The depth of invasion was associated with the presence of a mutation whereas no correlation was found between the presence of a mutation anb the regional lymph node metastasis.