Development of modified mismatch PCR-RFLP to screen mutations in codon 12 and 13 of K- ras gene of colorectal (CRC) patients in Sri Lanka

Abstract

INTRODUCTION AND OBJECTIVES: Mutations in K-ras codon 12, 13 of exon 2 are known to affect prognosis and impart resistance to anti EGFR monoclonal antibody therapy in CRC. Although several diagnostic tools have been developed for K-ras mutation testing, these procedures are too expensive or time consuming. Oufaim was to develop an effective, reliable and inexpensive method for the detection of K-ras mutations in codons 12 and 13 of exon 2 in CRC patients in Sri Lanka, and to relate the mutational status to liver metastasis, METHOD: The mismatch PCR-RFLP was developed and used to screen mutations in codon 12 and 13 for DMA isolated from paraffinized tumour tissue of 30 CRC patients followed up for 5 year after surgery to detect liver metastasis. Cross-tabulations were generated between K-ras mutations and the metastatic status. The Chi Square test was used to indicate statistical significance of the association. RESULTS: Analysis of banding pattern obtained from restriction digestion of PCR amplified region containing codon 12 and/or 13 of KRAS gene of 14(46.6%) CRC patients revealed the presence of mutations. Of the 30 patients, 13(43.3%) had developed liver metastases. There was a significant association between the presence of a K-ros mutation and the occurrence of liver metastasis (X2=4.693, p=0.003). CONCLUSION: This mismatch PCR-RFLP protocol is a suitable method to screen codon 12 and 13 mutation of K-ros gene to predict liver metastasis. Presence of these mutations is associated with the occurrence of liver metastasis during the first 5 years after surgery.