PCR-based assessment of the recovery rate of exfoliated colonocytes or cancer cells from fecal samples depends on the storage conditions after defecation

We recently developed a new methodology for isolating colonocytes from fecal samples. We then applied a DNA-based analysis to the isolated colonocytes to detect colorectal cancer cells originating from any part of the colorectum. The purpose of the present study was to determine how long after defecation and at what temperature the fecal samples should be stored to isolate the colonocytes successfully. Fecal samples were collected from 6 patients with colorectal cancer and 6 healthy volunteers soon after defecation at the National Cancer Center Hospital. The fecal samples were stored at 4 degrees C, room temperature or 40 degrees C for 0, 24 or 48 hours. Colonocytes were then isolated from the fecal samples, and the DNA was purified. Finally, PCR for p53, K-ras and APC was conducted to determine whether the corresponding PCR products could be obtained. The colonocyte recovery rate was not reduced, when compared with the data for successful PCR amplification, if the fecal samples were kept at 4 degrees C after defecation and if the colonocytes were isolated within 48 hours after defecation. The present data provided important clinical knowledge regarding the storage of fecal samples for future mass screening tests.