| Ovarian cancer is a complex disease, whose metastasis is both highly prevalent and an obstacle in treatment. In the ovarian cancer metastatic microenvironment multiple cell populations interact to impact tumor progression, including tumor cells, mesothelial cells, and alternatively activated macrophages (AAMs). The presence of AAMs correlates with prognosis and staging; however, mechanisms underlying these correlations are poorly understood. The central hypothesis of this thesis was that paracrine signaling from AAMs in the ovarian cancer microenvironment enhanced ovarian cancer metastatic behaviors to drive disease progression. To address this hypothesis, we developed multiple in vitro models to examine the impact of AAMs on ovarian cancer epithelial-to-mesenchymal transition (EMT), adhesion to mesothelial cells, clearance through mesothelial cells, and proliferation. To evaluate these behaviors, we first developed a novel micro-culture device that allows for dynamic, concentrated paracrine culture between AAMs and cells in the microenvironment. Next, the micro-culture device was revised to model AAM-tumor and AAM-tumor-mesothelial cell interactions to determine how the incorporation of AAMs enhances EMT, adhesion, clearance and proliferation in ovarian cancer. Preliminary studies performed with the THP-1 cell line showed that AAMs induced EMT by decreasing E-cadherin expression in ovarian cancer cells, increased early adhesion of ovarian cancer to mesothelial cells, variably enhanced spheroid clearance through the mesothelial barrier, and induced a heterogeneous proliferative response in the tumor cells. Computational modeling and systems analysis of ovarian cancer adhesion using primary AAMs was performed, and key findings illustrated a novel mechanism by which AAM-secreted MIP-1beta signaled to mesothelial cells via CCR5/PI3K to upregulate the expression of P-selectin, which enhanced adhesion of CD24+ ovarian cancer cells. Finally, the in vitro model of proliferation in established metastases was further explored in this thesis with primary AAMs and OVCA433. We identified a novel feedback loop between ovarian cancer cells and AAMs, where induced expression of MMP9 in tumor cells during co-culture increased the bioavailability of AAM-secreted HB-EGF, which in turn increased ovarian cancer proliferation. In combination, the studies reported in this thesis illustrate novel mechanisms by which AAMs drive ovarian cancer progression and identify targets within the microenvironment to inhibit ovarian cancer metastasis. |
