A rapid and simple in vitro method for evaluating human colorectal epithelial proliferation.

Assessment of colonic epithelial proliferation is a biomarker of risk for large-bowel neoplasia. Until now, in vitro labeling of S-phase crypt cells was usually performed by incorporation of tritiated thymidine. Its major disadvantage is the lengthy period of autoradiography before results can be evaluated. The thymidine analogue bromodeoxyuridine, which is detectable by immunohistochemical examination, allows evaluation of epithelial proliferation within 3 days. Pinch rectal biopsy specimens, from the unprepared bowel, are incubated under 1 atm additional pressure in a medium containing bromodeoxyuridine. The tissue is then fixed in 70% ethanol and embedded in paraffin, and the slides are prepared. The labeled nuclei are revealed using indirect immunoperoxidase staining and are easily counted by light microscopy. Assessment of proliferation is rapidly available for determining cancer risk and response in ongoing experimental and human dietary intervention studies.