Quantification of human DNA in feces as a diagnostic test for the presence of colorectal cancer.

Abstract

Analysis of nuclear DNA extracted from stool specimens (1) is a recent addition to cancer diagnostics (2)(3)(4). Most studies have focused on the detection of sequence variations in tumor suppressor genes and oncogenes and on their correlation with clinical stage. In addition, however, the amount of human DNA in feces may be increased in individuals with colorectal cancer. Villa et al. (5) found that β-globin sequences were amplified by PCR more frequently in patients with either colorectal carcinoma or adenomas than in healthy individuals. Ahlquist et al. (6) demonstrated that large DNA fragments were amplified from DNA in stool samples from colorectal cancer patients more frequently than from healthy volunteers. In view of these results, we developed a real-time PCR assay for quantification of human DNA in stool samples. Human stool samples were collected from 15 healthy adult volunteers (mean age, 46 years; range, 21–78 years) not on any dietary restrictions or antibiotic treatment and from 13 patients (mean age, 71 years; range, 49–81 years) who were diagnosed with colorectal cancer. All volunteers and patients gave informed oral consent. Stools were collected before any preparation for colonoscopy. Absolute care was taken to avoid hydration of the samples until further processing (1). Under these circumstances, solid stool samples can be stored at 4 °C for several days without significant degradation of the DNA. All stool samples from both groups were processed within 48 h after collection. DNA was isolated from 200-mg fresh solid human stool samples with use of the QIAamp …