Occurrence of apoptotic DNA fragmentation in quiescent and proliferating cells in human endometrial adenocarcinoma tissues and the influence of apoptosis-suppressing effects of bcl-2 products.

ABSTRACT

In situ estimation of DNA fragmentation by the nick end labelling (NEL) method, and immunohistochemical examination of Ki-67 proliferative antigen and bcl-2 products in human endometrial adenocarcinoma tissues were performed to provide answers to the following two questions; a) does apoptotic DNA fragmentation occur specifically in quiescent cells or in proliferating cells or randomly in both?, b) does the bcl-2 product exert its apoptosis-suppressing effects differentially on carcinoma cells depending on their cell cycle condition?. Serial sections, one micrometer in thickness, from formalin-fixed and paraffinembedded tissues of 9 cases of human endometrial adenocarcinoma were examined. Apoptotic DNA fragmentation was observed in both quiescent (Ki-67 negative) and proliferating (Ki-67 positive) cells. Bcl-2 product-positive tumor cell islands tended to be NEL negative, although a few but non-negligible number of carcinoma cells, including both Ki-67 positive and negative ones, were NEL positive. These results indicate that, at least in human endometrial adenocarcinomas, apoptotic DNA fragmentation and bcl-2 product-independent (DNA) fragmentation occurs non-specifically with respect to the cell proliferation status. Further, the results suggest an altered regulation of cell death processes in human solid tumor tissue in vivo.