Nonovarian origins of ovarian cancer

A role for G-protein coupled estrogen receptor (GPER) in estrogen-induced carcinogenesis: Dysregulated glandular homeostasis, survival and metastasis

Mechanisms of carcinogenesis by estrogen center on its mitogenic and genotoxic potential on tumor target cells. These models suggest that estrogen receptor (ER) signaling promotes expansion of the transformed population and that subsequent accumulation of somatic mutations that drive cancer progression occur via metabolic activation of cathecol estrogens or by epigenetic mechanisms. Recent findings that GPER is linked to obesity, vascular pathology and immunosuppression, key events in the development of metabolic syndrome and intra-tissular estrogen synthesis, provides an alternate view of estrogen-induced carcinogenesis. Consistent with this concept, GPER is directly associated with clinicopathological indices that predict cancer progression and poor survival in breast and gynecological cancers. Moreover, GPER manifests cell biological responses and a microenvironment conducive for tumor development and cancer progression, regulating cellular responses associated with glandular homeostasis and survival, invading surrounding tissue and attracting a vascular supply. Thus, the cellular actions attributed to GPER fit well with the known molecular mechanisms of G-protein coupled receptors, GPCRs, namely, their ability to transactivate integrins and EGF receptors and alter the interaction between glandular epithelia and their extracellular environment, affecting epithelial-to-mesenchymal transition (EMT) and allowing for tumor cell survival and dissemination. This perspective reviews the molecular and cellular responses manifested by GPER and evaluates its contribution to female reproductive cancers as diseases that progress as a result of dysregulated glandular homeostasis resulting in chronic inflammation and metastasis. This review is organized in sections as follows: I) a brief synopsis of the current state of knowledge regarding estrogen-induced carcinogenesis, II) a review of evidence from clinical and animal-based studies that support a role for GPER in cancer progression, and III) a mechanistic framework describing how GPER-mediated estrogen action may influence the tumor and its microenvironment.

Precursors of ovarian cancer in the fallopian tube: serous tubal intraepithelial carcinoma--an update

Ovarian tumors comprise a wide variety of entities. The largest group, epithelial ovarian carcinoma, can be classified into two main groups, type I and type II tumors. Recent advances in the understanding of ovarian cancer development have resulted in the finding of 'serous tubal intraepithelial carcinoma', which is believed to represent the precursor lesion in high-grade serous ovarian carcinoma. In this review, lines of evidence for this are discussed and possible future implications for clinical and research settings are outlined.

Membrane-type I matrix metalloproteinase-dependent ectodomain shedding of mucin16/ CA-125 on ovarian cancer cells modulates adhesion and invasion of peritoneal mesothelium

Mucin16 [MUC16/cancer antigen 125 (CA-125)], a high-molecular-weight glycoprotein expressed on the ovarian tumor cell surface, potentiates metastasis via selective binding to mesothelin on peritoneal mesothelial cells. Shed MUC16/CA-125 is detectable in sera from ovarian cancer patients. We investigated the potential role of membrane type 1 matrix metalloproteinase (MT1-MMP, MMP-14), a transmembrane collagenase highly expressed in ovarian cancer cells, in MUC16/CA-125 ectodomain shedding. An inverse correlation between MT1-MMP and MUC16 immunoreactivity was observed in human ovarian tumors and cells. Further, when MUC16-expressing OVCA433 cells were engineered to overexpress MT1-MMP, surface expression of MUC16/CA-125 was lost, whereas cells expressing the inactive E240A mutant retained surface MUC16/CA-125. As a functional consequence, decreased adhesion of cells expressing catalytically active MT1-MMP to three-dimensional meso-mimetic cultures and intact ex vivo peritoneal tissue explants was observed. Nevertheless, meso-mimetic invasion is enhanced in MT1-MMP-expressing cells. Together, these data support a model wherein acquisition of catalytically active MT1-MMP expression in ovarian cancer cells induces MUC16/CA-125 ectodomain shedding, reducing adhesion to meso-mimetic cultures and to intact peritoneal explants. However, proteolytic clearing of MUC16/CA-125, catalyzed by MT1-MMP, may then expose integrins for high-affinity cell binding to peritoneal tissues, thereby anchoring metastatic lesions for subsequent proliferation within the collagen-rich sub-mesothelial matrix.