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Comparison of the classical autoradiographic and the immunohistochemical methods with BrdU for measuring proliferation parameters in colon cancer.

In vivo labelling with bromodeoxyuridine (BrdU) was compared with 3H-thymidine (3HTdR) labelling for the study of cell proliferation in normal colon epithelium and in colon cancer tissue. Twenty-four BDIX rats with implanted subcutaneous tumors of DHD/K12 colon cancer cells were subdivided into 3 groups. Each rat received an intraperitoneal injection of either 5-bromo-2'deoxyuridine (50 mg/kg), or 3H-thymidine (1mCi/kg) or both precursors (double labelling). Immunoperoxidase staining with a monoclonal antibody to BrdU, or autoradiography were used. In the colonic crypts, similar patterns of spatial distributions of the labelled colonic epithelial cells were observed after each kind of labelling. The mean labelling indices (LI) by BrdU and by 3HTdR were similar in the normal colon as well as in the implanted tumors. The validity of BrdU labelling in vivo was further investigated by using BrdU+3HTdR double labelling technique. In the colonic crypts, the total BrdU labelled colonic epithelial cells were 11.85%, whereas the total 3HTdR labelled cells were 11.99% (p > 0.05). In the implanted tumors of colon cancer, the total BrdU and 3HTdR labelled cells accounted for 19.40% and 20.10% respectively of the colon cancer cells (p > 0.05). There was a close correlation between BrdU LI and 3HTdR LI in colonic epithelial cells (r = 0.99, p < 0.0001) as well as in colon cancer cells (r = 0.97, p < 0.001). There data indicate that the labelling index of BrdU is equivalent to that of 3HTdR not only in normal colonic epithelium but also in colon cancer. BrdU may thus be used for measuring proliferation parameters in cancer tissues.