Direct identification of all oncogenic mutants in KRAS exon 1 by cycling temperature capillary electrophoresis

Over the past few decades, advances in genetics and molecular biology have revolutionized our understanding of cancer initiation and progression. Molecular progression models outlining genetic events have been developed for many solid tumors, including colon cancer. Previous reports in the literature have shown a relationship between different KRAS mutations and prognosis and response to medical treatment in colon cancer patients. Furthermore, the presence of a mutated KRAS has been correlated with different clinicopathological variables including age and gender of patients and tumor location. To our knowledge, few institutions screen for KRAS mutations on regular basis in colon cancer patients despite such evidence that knowledge of KRAS exon 1 status is informative. Here, we report on a mutation analysis method adapted to a 96-capillary electrophoresis instrument that allows identification of all 12 oncogenic mutations in KRAS exon 1 under denaturing conditions. To determine the optimal parameters, a series of DNA constructs generated by site-directed mutagenesis was analyzed and the migration times of all mutant peaks were measured. A classification tree was then made based on the differences in migration time between the mutants and an internal standard. A randomized series of 500 samples constructed with mutagenesis as well as 60 blind samples from sporadic colon carcinomas was analyzed to test the method. No wild-type samples were scored as mutants and all mutants were correctly identified. Post polymerase chain reaction (PCR) analysis time of 96 samples was performed within 40 min.