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Abstract 1913: Role of glypican 1 in regulating fibroblast activation in the prostate cancer tumor microenvironment

Cancer is a heterogeneous collection of neoplastic cells, surrounded by non-malignant, stromal cells, and extracellular matrix (ECM), among other constituents. Cross-talk between tumor and stromal cells forms a dynamic tumor microenvironment (TME) that mediates cell growth, proliferation, and metastasis. The TME can inhibit cancer growth and proliferation during the initial stages of carcinogenesis; however, cancer cells can evade these inhibitory signals, and reshape the TME, making it more amenable to their own growth. This gives rise to cancer-associated stromal cells, including cancer-associated fibroblasts (CAFs). CAFs further modulate the TME by regulating the release of growth signals, cell death, ECM remodeling, angiogenesis, and epithelial-mesenchymal transition. Glypican-1 (GPC1) is a cell surface heparan sulfate proteoglycan (HSPG) that has both pro-mitogenic and pro-metastatic activity. GPC1’s role in regulating fibroblasts and their transformation into CAFs has not been investigated. We studied the ability of prostate cancer cells to alter the TME in vitro by exposing human bone fibroblasts (HS-5 cells) to tumor conditioned media (TCM) isolated from a human neuroendocrine (DU-145) and bone (PC-3) metastatic prostate cancer cell lines and assessed changes in cell morphology and cytotoxicity (using MTT). Exposure of HS-5 cells to TCM from DU-145 and PC-3 cells altered cellular morphology to a more mesenchymal phenotype similar to that seen in active myofibroblasts. TCM also decreased MTT staining in a time-dependent manner. We also determined the effect of GPC1 knockdown (KD) in HS-5 cells on cell morphology, migration and cytotoxicity. Interestingly, we saw phenotypic switching of GPC1 KD HS-5 cells to a myofibroblast like morphology akin to that when treated with TCM. There was no change in cytotoxicity in GPC1 KD HS-5 cells as compared to control cells. However, GPC1 KD enhanced the migration of HS-5 cells in wound healing assay. Migration was also increased in GPC1 KD HS-5 cells upon treatment with TCM. GPC1 KD also increased HS-5 cell contractility significantly. Collectively, these data support the hypothesis that GPC1 plays an inhibitory role in the TME of prostate cancer by regulating the activation of fibroblasts. Note: This abstract was not presented at the meeting. Citation Format: Sukhneeraj P. Kaur, Hee K. Lee, Robert D. Arnold, Brian S. Cummings. Role of glypican 1 in regulating fibroblast activation in the prostate cancer tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1913.