Expression of apoptosis-related proteins in peritoneal, ovarian and colorectal endometriosis

Endometriosis is defined as the presence of endometrial glands and stroma outside the uterus. Apoptosis, a physiological process by which multicellular organisms eliminate superfluous cells, is altered in tumor tissue. Here we studied the expression of the apoptosis-related proteins p53, bcl-2, bax, p21 and fas in proliferative (n = 9) and secretory (n = 9) endometrium, and in peritoneal (n = 11), ovarian (n = 20) and colorectal (n = 20) endometriosis, by qualitative and semi-quantitative immunohistochemical methods using the percentage of positive cells and HSCORE analysis.In endometrium, p53, p21 and fas expression was low, whereas bax and bcl-2 expression was elevated. Using HSCORE analysis, only bcl-2 expression varied during the menstrual cycle (48.9 ± 34.2% in the proliferative phase, 11.5 ± 24.7% in the secretory phase, p = 0.01).Using HSCORE analysis, p53 expression was higher in ovarian endometriosis than in peritoneal (p < 0.0001) and colorectal endometriosis (p = 0.03). P21 expression was higher in ovarian endometriosis than in peritoneal (p = 0.01) and colorectal endometriosis (p = 0.01). Bcl-2 expression was lower in ovarian endometriosis than in peritoneal (p = 0.0002) and colorectal endometriosis (p < 0.0001). Fas expression was higher in peritoneal endometriosis than in ovarian (p = 0.02) and colorectal endometriosis (p = 0.008).In conclusion, these results confirm the involvement of apoptosis in the pathogenesis of endometriosis. Moreover, expression of apoptosis-related proteins varies according to the location of endometriosis suggesting the involvement of different apoptotic pathways.