New complement roles revealed by immune gene profiling in endometriosis and endometriosis-associated ovarian cancer (TUM7P.957)

Endometriosis is a largely benign, chronic inflammatory disease that may predispose to some of the ovarian tumors histotypes, collectively called endometriosis-associated ovarian cancers (EAOC). Although it is widely accepted that chronic inflammation drives cancer, the immune deregulation in chronic precursors of ovarian cancer has not been systematically studied. We performed here the first comprehensive gene profile of the tissue immune microenvironment in normal endometrium, benign endometriosis and EAOC (n=133), using Nanostring and the nCounter® GX Human Immunology Kit comprising probes for 511 immune genes. We found that the complement pathway was most prominently upregulated, suggesting its involvement in the transition from chronic endometriosis to atypical (premalignant) endometriosis and to EAOC. Complement protein expression was confirmed via immunohistochemistry, which identified upregulation of complement in epithelial cells. To explore the roles of complement in early EAOC carcinogenesis, we derived several novel ovarian cell lines with conditional mutations that can be turned on and off, using the Cre-loxP system. Using this in vitro model we demonstrate that genetic instability triggers upregulation of complement genes in epithelial cells, but without an advantage on cell death. These findings reveal an early link between epithelium and innate immune environment and further support a paradigm shift on complement roles in supporting cancer growth.