It is well known that during ovarian cancer progression, the omentum transforms from a thin lacy organ to a thick tougher tissue. However, the mechanisms regulating this transformation and the implications of the altered microenvironment on ovarian cancer progression remain unclear. To address these questions, the global and local concentrations of collagen I were determined for normal and metastatic human omentum. Collagen I was increased 5.3-fold in omenta from ovarian cancer patients and localized to areas of activated fibroblasts rather than regions with a high density of cancer cells. Transforming growth factor beta 1 (TGFβ1) was detected in ascites from ovarian cancer patients (4 ng/mL), suggesting a potential role for TGFβ1 in the observed increase in collagen. Treatment with TGFβ1 induced fibroblast activation, proliferation, and collagen deposition in mouse omental explants and an in vitro model with human omental fibroblasts. Finally, the impact of increased collagen I on ovarian cancer cells was determined by examining proliferation on collagen I gels formulated to mimic normal and cancerous omenta. While collagen density alone had no impact on proliferation, a synergistic effect was observed with collagen density and heparin-binding epidermal growth factor treatment. These results suggest that TGFβ1 induces collagen deposition from the resident fibroblasts in the omentum and that this altered microenvironment impacts cancer cell response to growth factors found in ascites. Impact statement Using quantitative analysis of patient samples, in vitro models of the metastatic ovarian cancer microenvironment were designed with pathologically relevant collagen densities and growth factor concentrations. Studies in these models support a mechanism where transforming growth factor β1 in the ascites fluid induces omental fibroblast proliferation, activation, and deposition of collagen I, which then impacts tumor cell proliferation in response to additional ascites growth factors such as heparin-binding epidermal growth factor. This approach can be used to dissect mechanisms involved in microenvironmental modeling in multiple disease applications.
Keywords: TGFbeta; collagen; fibroblast; microenvironment; omentum; ovarian cancer.