In vivo bromodeoxyuridine incorporation in human gastric cancer: a study on formalin-fixed and paraffin-embedded sections.

Bromodeoxyuridine (BUDR) is a non-radioactive thymidine analogue which is incorporated into the DNA of proliferating cells. This allows evaluation of the size of the S-phase as the BUDR labelling index (BUDR-LI) not only in vitro but also in vivo, since BUDR is not toxic at the doses needed to label cells. To ascertain whether in vivo BUDR incorporation can be detected on routine histological material we tested several different procedures prior to immunoperoxidase staining, on formalin-fixed, paraffin-embedded sections from five patients with gastric cancer, who received BUDR (250 mg m-2, intravenous) 4 h before surgery. To determine the optimal conditions for detecting BUDR in formalin-fixed tissues, immunohistochemical testing for BUDR was performed simultaneously on duplicate sections fixed with 70% ethanol. It was found that hydrolysis with 3N HCl at 37 degrees C for 30 min and digestion with 0.5% in at 37 degrees C for 30 min were sufficient to detect BUDR immunoreactivity in formalin-fixed sections. The method presented extends the range of applications of the in vivo BUDR technique for cell kinetics studies in human neoplasms because it can be used on routinely fixed archival material, with the advantage of correlating the kinetic data with histopathological characters.