Abstract A038: uPA/uPAR/MMP9 signaling hindered by heme oxygenase-1 in prostate cancer: Impact on cell invasiveness

Cell motility plays a crucial role in cancer metastasis. The actin cytoskeleton behaves as the cellular engine behind this process and is governed by complex signaling transduction cascades. Cancer cells have shown a variety of alterations both in the expression and localization of cytoskeleton-regulating proteins, which increase their capacity to migrate and invade homing organs. Heme oxygenase 1 (HO-1) is a stress response protein and a critical mediator of cellular homeostasis. Although HO-1’s role in cancer has been controversial, we have previously shown that its pharmacologic or genetic upregulation is associated with a less aggressive phenotype in PCa. HO-1 inhibits cell proliferation, migration, and invasion; impairs tumor growth and angiogenesis in vivo; and downregulates the expression of target genes associated with inflammation. We have also demonstrated that HO-1 is implicated in prostate cancer (PCa) cell adhesiveness and zippering (an increment in the number of filopodia between cells as well as a decrease in the levels of MMP9 (RTqPCR, Zimography, and Microarray analysis) favoring a more adhesive phenotype. However, the molecular mechanism behind this modulation was not yet deciphered. In this work we first assessed the presence of MMP9 in filopodia-like protrusions between neighboring cells to rule out that these increased protrusions were invadopodia structures. HO-1 was induced pharmacologically (hemin 80 uM, 24 h), fixed with PFA and stained with anti-HO-1 and anti-MMP9 antibodies. PCa cells were imaged by confocal microscopy. We observed that MMP9 did not colocalize with HO-1 and was absent at the leading edge of PCa cells. It is broadly known that MMP9 and the plasminogen activator urokinase (uPA) are important factors for cancer invasion and metastasis, both of them responsible for degrading the extracellular matrix (ECM). To assess whether the forced expression of HO-1 modulated the MMP9/uPA pathway, we studied the expression of several inhibitors and activators of this cascade through a transcriptomics approach. The RNAseq profiling for both PCa cells overexpressing HO-1 pharmacologically or genetically showed a direct regulation of the critical factors in the uPA/uPAR cascade, such as the downregulation of the axis activators uPA/uPAR (PLAU/PLAUR) and tPA (PLAT), and the upregulation of the axis inhibitors CPB2 (thrombin activator of fibrinolysis inhibitor), SERPINF2 (alpha 2 anti- plasmin), and F12 (factor XIIA). Our findings were further validated by an uPA ELISA revealing that under the same experimental conditions, the levels of this urokinase secreted to the conditioned media were significantly reduced. Altogether, our work delineates a molecular axis by which HO-1 potentially shuts down the acquisition of an invasive tumor cell phenotype, crucial for PCa cancer metastasis. Citation Format: Alejandra V. Paez, Javier H. Cotignola, Elba S. Vazquez, Geraldine Gueron. uPA/uPAR/MMP9 signaling hindered by heme oxygenase-1 in prostate cancer: Impact on cell invasiveness [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr A038.