Dried Feces Spots as an Alternative DNA Source: Detection of K-ras Mutations in Colorectal Cancer Screening

Detection of genetic alterations in exfoliated intestinal cells into feces is expected to be a novel approach to colorectal cancer screening. We aimed here to detect cancer-related gene mutations in routine fecal specimen; dried feces spots (DFS) on a filter paper especially designated for an automated fecal occult blood (FOB) test. DNA was simply extracted from a 3 mm disc of DFS (including around 10 mg feces) with a boiling procedure followed by a cationic surfactant extraction. K-ras common mutations, as the typical cancer-related gene alterations, were detected with a nested allele specific PCR with microfluorometry (ASP/MFL). Adequate DNA was recovered from 363/451 (80.5%) DFS specimens tested. The K-ras mutations were detected in 2/24 (8.3%) from patients with colorectal cancer and 13/315 (4.1%) from screening participants with positive FOB. No mutations were detected in 24 DFS specimens with negative FOB. The results of K-ras mutation frequency were not encouraging to achieve practically a specific and reliable method for colorectal cancer screening. However this report, identifying for the first time a cancer related gene alteration in feces using identical samples with routine FOB test, will be a step to realize a molecular genetic testing for the cancer screening.