[Quantitative evaluation of the activity of nuclear Ca2+/Mg2+-dependent endonucleases in hyperplasia and cancer of the endometrium].

Endometrial carcinoma is the most incident cancer of human reproductive system. There are unequivocal evidences of relationship between complex and atypical hyperplasia and development of cancer. Apoptosis plays a significant role in the maintenance of equilibrium between cell death and proliferation and contributes to prevention of tumorigenesis. Internucleosomal DNA fragmentation known as one of the most important criteria of apoptosis cannot be used for evaluating the risk of cancer development because it reflects the current level of apoptosis but is useless for evaluating the real limits of apoptosis intensity in certain types of tissue. For estimating the possibility of apoptosis development in endometrial tissues, a new method of quantitation of nuclear Ca(2+)/Mg(2+)-dependent endonuclease (NCME) activity has been developed. Fifteen samples of normal endometrial tissues at middle proliferative, secretory, premenstrual, and menstrual phases, 43 samples of hyperplastic endometrial tissues, 13 samples of endometrial polyps, and 17 samples of endometrial adenocarcinoma were collected by diagnostic curettage of the uterine cavity and by hysterectomy (carcinomas). The material was examined by 1) TUNEL method and 2) agarose gel electrophoresis of DNA cleaved by nuclear CME in isolated cell nuclei in the presence of Ca(2+) and Mg(2+) ions, followed by quantitation of CME activity. The activity of NCME was found to decrease from normal endometrium (1.1 +/- 0.12 U, without significant changes throughout the menstrual cycle) through polyps (0.9 +/- 0.15 U), cystic hyperplasia (0.45 +/- 0.06 U, p < 0.01), and adenomatous hyperplasia (0.32 +/- 0.08 U, p < 0.01) to adenocarcinoma (0.37 +/- 0.11 U, p < 0.01 for well differentiated, 0.16 +/- 0.08 U, p < 0.01 for moderately differentiated, and 0.03 +/- 0.02 U, p < 0.01 for poorly differentiated samples). The TUNEL-specific staining pattern in normal endometrium varied in a wide range during the menstrual cycle (from poorly stained individual cells in the proliferative phase to intensely stained cell clusters in the premenstrual phase). At the same time the difference between the normal endometrium in the proliferative phase and pathologically changed endometrium (hyperplasia or cancer) could not be detected by the TUNEL technique. Hence, TUNEL is useless for predicting cancer development in hyperplasia and precancer. By contrast, evaluation of NCME activity helps detect the early disorders in the proliferative processes coursing in endometrial tissues and thus prevent tumor development.