Detection of K-ras mutations in colon cancer by PHA-PHFA (preferential homoduplex formation assay)

The mutations of K-ras gene have been demonstrated at frequencies of about 40% in human colorectal cancer. We applied a developed PCR-preferential homoduplex formation assay (PCR-PHFA) to detect a point mutation of K-ras gene in the surgical specimens from thirty patients with colorectal cancer. This method is based on the strand competition during hybridization between a double labeled amplicon, prepared from biotin and DNP labeled primers, and an unlabeled amplicon. The procedure of this method is simple and speedy, and suitable to detect mutations in a small number of samples. By using this method, the mutations were found in 37% (11/30) and confirmed by sequencing analysis. The results suggest that the PCR-PHFA system may be useful for detecting low frequent mutation of K-ras gene even in the case of an early cancer.