DETECTION OF K-RAS MUTATIONS IN STOOLS OF PATIENTS WITH COLORECTAL-CANCER BY MUTANT-ENRICHED PCR

Mutant-enriched PCR was applied to the detection of mutations at codon s 12 and 13 of K-ras genes in the stools of patients with colorectal c ancer. Mutations were analyzed in stool samples obtained prior to surg ery. Resected tumor specimens were screened for K-ras mutations by PCR -mediated RFLP analysis. Using normal stool samples, assay conditions were adjusted to optimal sensitivity and specificity. The following sp ecimens were included in the study: 16 stool samples corresponding to carcinomas in which K-ras mutations had been identified; 7 randomly se lected stool samples corresponding to carcinomas which were negative f or K-ras mutations; 1 stool sample from a patient with non-Hodgkin's l ymphoma. In 13 of the 16 stool samples (81%) corresponding to tumors i n which K-ras mutations had been identified previously, K-ras mutation s were detected. In 2 of the 7 stool samples corresponding to tumors i n which R-ras mutations had not been detected by previous PCR-mediated RFLP analysis, K-ras mutations were also present. Reanalyses of the t umors corresponding to these 2 positive stool samples by mutant-enrich ed PCR revealed a K-ras mutation in one of the tumors. The stool and t umor of the patient with non-Hodgkin's lymphoma were negative for K-ra s mutations. DNA sequence analysis revealed that, for each of the K-ra s mutations identified in stool samples, identical base substitutions were present in the corresponding tumor tissue. The results indicate t hat tumor cells harboring K-ras mutations can be detected in the stool s of patients with colorectal cancer by mutant-enriched PCR with high sensitivity and specificity. Because of the simplicity of the techniqu e, it may be suitable for screening of stool samples for mutations of the K-ras gene. (C) 1996 Wiley-Liss, Inc.