Date of this Version
Progression of Prostate cancer (CaP), depends on a complex series of interactions between the tumor and extracellular matrix (ECM) leading to tumor growth and metastasis. Hyaluronan (HA), an ECM component, is elevated in CaP and its accumulation in the tumor microenvironment is dependent on its synthetic enzyme, hyaluronan synthase (HAS), and turnover enzyme, hyaluronidase (Hyal). Although Hyal1 expression can independently prognosticate CaP, and HAS expression shows increase in aggressive prostate cancer cells, the functional relevance of this correlation is unexplored. In these studies we aim to dissect the roles of HAS and Hyal1 in prostate cancer.
Stably overexpressed hyaluronan synthases (HAS2, HAS3), and Hyal1, individually or concurrently (Hyal1+HAS2 and Hyal1+HAS3) in a non-metastatic prostate tumor cell line, were characterized by subcutaneous and orthotopic injections in NOD/SCID mice and assayed for cell proliferation, adhesion, and motility in vitro. Subcutaneous tumors were larger for Hyal1+HAS2 cells and smaller in Hyal1+HAS3 cells, potentially due to effective HA dissipation in the former. With orthoptopic injections, Hyal1+HAS transfectants were maximally tumorigenic and metastatic. Contrastingly, HAS expression suppressed tumor growth and metastasis, while Hyal1 promoted metastasis without significant tumor growth. These in vitro characterizations suggested tumor suppression by HAS was due to reduced growth with slower cell cycle kinetics, and the enhanced metastasis of Hyal1+HAS ascribed to increased adhesion and motility of the transfectants.
We tested ERK activation and cell cycle proteins as potential targets and found that Hyal1 showed modestly decreased sustained ERK activation compared to HAS3. Furthermore, in asynchronous and cycling cells, cyclin-dependent kinase inhibitors (CKIs) p21cipM and p27kip were elevated with HAS expression while p21cip expression was reduced in Hyal1 and Hyal1+HAS3 cells.
We demonstrate the dual requirement of both HAS and Hyal for maximum prostate tumorgenesis and metastasis mediated via altered adhesion, motility, and cell cycle progression. Our studies are the first comprehensive examination of the role of HAS and Hyal1 in prostate tumor progression thereby establishing a new paradigm for HA metabolism in CaP.