Apoptosis and the Expression of Bcl-2 and Bax in Patients with Endometrioid, Clear Cell, and Serous Carcinomas of the Uterine Endometrium

Abstract Objectives. Clear cell and serous carcinoma of the uterus are rare types of endometrial carcinomas. This study was designed to investigate the differential occurrence of apoptosis, Bcl-2, and Bax in endometrioid, clear cell, and serous carcinomas. Methods. In a total of 28 endometrial carcinomas as well as 4 samples of normal postmenopausal endometria, apoptotic changes were examined using molecular biochemical techniques. The expression of Bcl-2 and Bax proteins was also investigated by immunohistochemical staining with appropriate antibodies. Results. Labeling of DNA in situ indicated that apoptotic cells were sporadically seen in postmenopausal endometrium (5.2 ± 2.1, n = 4). In contrast, cells undergoing apoptosis apparently were detected in endometrioid carcinoma (29.3 ± 3.7, n = 20), and their numbers increased intensely in clear cell (49.5 ± 5.6, n = 5) and serous carcinomas (50.8 ± 6.0, n = 3). Autoradiographic analysis revealed that high-molecular-weight DNA was predominant in postmenopausal endometrium. However, a DNA ladder was identified in 7 of 10 carcinomas. Although Bcl-2 was immunonegative or faintly immunopositive in all cases, many cases of endometrioid carcinoma (43.6 ± 4.1%, n = 20) were immunopositive for Bax, unlike postmenopausal endometrium (17.6 ± 6.7%, n = 4). Moreover, the number of cells expressing Bax increased in clear cell (60.4 ± 6.5%, n = 5) and serous carcinomas (66.8 ± 7.6%, n = 3) compared with that in endometrioid carcinoma. Conclusions. These results indicate that apoptosis occurs in a specific population of cells in different histologic components of endometrial carcinomas. The expression of Bax, but not of Bcl-2, might suggest histologic differentiation in endometrial carcinomas.