Abstract 2385: Characterization of ECM remodeling in disseminated ovarian cancer as a result of loss of HtrA1 and deregulated TGFB signaling
Authors: Cooley Megan , Chien Jeremy , Mitra Anirban , Baldi Alfonso , Czirok Andras , Kosa Edina 
Published: August 2015

Abstract
Dissemination of ovarian cancer is promoted by deregulated cell adhesion that selectively enhances detachment at primary site and attachment and invasion at secondary sites. Modifications in the extracellular matrix composition within tumor microenvironment can facilitate deregulated cell adhesion, migration, and invasion. We aim to understand how tumor-intrinsic changes affect expression and composition of ECM proteins in disseminated ovarian cancer. The serine protease HtrA1 has been shown to inhibit TGFB by targeting TGFB family ligands and receptors for proteolysis. In addition, HtrA1 also degrades ECM proteins, such as decorin, fibronectin, and collagens. We have shown that HtrA1 is down-regulated in ovarian cancer cells with loss contributing to chemotherapy resistance. We propose that loss of HtrA1 in the ovarian tumor microenvironment enhances TGFB signaling that in turn facilitate compositional changes in ECM proteins from stromal cells and promote cancer dissemination. To characterize compositional changes that occur in ECM proteins as a result of increased TGFB signaling, stable isotope amino acid labeling (SILAC) and LC-MS analysis were used. Mesothelial cells were cultured in heavy or light isotopically labeled media to confluence. Tumor cells expressing HtrA1 (NT) or stably transfected with HtrA1-targeting shRNA (sh1) were added to either heavy or light mesothelial cultures with or without TGFB (10 ng/ml). Cells were lifted by EDTA and the remaining matrix proteins were subjected to LC-MS. The data show that ECM compositional changes in fibronectin, laminin and collagen were up regulated in mesothelial cells co-cultured with sh1 compared to NT cells. All extracted proteins with ≥ 4 fold change were analyzed by Ingenuity Pathway Analysis. Proteins up regulated in co-cultures with HtrA1-deficient cancer cells (sh) were determined to be associated with migration, invasion and tumorogenesis whereas proteins upregulated in co-culture with HtrA1-expressing cancer cells (NT) were associated with protein modifications and ER stress. HtrA1-deficient cells show decreased adhesion to collagen I/III matrix and enhanced adhesion to collagen I/VI matrix. HtrA1-deficient cancer cells show morphology characteristics of epithelial-mesenchymal transition and shows higher motility and invasion through mesothelial cell layer. Finally, in clinical samples, decreased HtrA1 expression in primary tumor was significantly associated with higher incidence of carcinomatosis and nodal metastasis in ovarian cancer. We conclude that loss of HtrA1 in ovarian cancer cells results in compositional changes in ECM within the tumor microenvironment, and these changes may contribute to the dissemination of ovarian cancer.
Citation Format: Megan Cooley, Jeremy Chien, Anirban Mitra, Alfonso Baldi, Andras Czirok, Edina Kosa. Characterization of ECM remodeling in disseminated ovarian cancer as a result of loss of HtrA1 and deregulated TGFB signaling. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2385. doi:10.1158/1538-7445.AM2015-2385