Role of Hyaluronan Metabolism in Prostate Tumor Aggresiveness and Stromal Transformation

Hyaluronan (HA) and one of its metabolic enzymes, Hyaluronidase1 (Hyal1) are clinically correlated to prostate cancer disease progression, and are known to be involved in the processes of proliferation, motility, adhesion and angiogenesis. In turn, these processes are well defined in terms of their ability to support invasion and metastasis of cancers. However, the exact molecular mechanisms that underlie Hyal1’s ability to affect these processes remain poorly defined, and detailed mechanistic studies will allow improvement of current therapies. It was previously shown that Hyal1 overexpression leads to increased tumor growth and metastasis in mice, which has been linked to increased proliferation and motility. It was further demonstrated that Hyal1 increased vesicular trafficking, and could alter cell surface molecule presentation. The aim of this work was to extend these findings, both in cancer cells and in stromal cells, and to thereby expand the mechanistic understanding of Hyal1’s role in disease progression. We determined that Hyal1 overexpressing cells grown in 3D culture grow larger in size and disengage from the spheroid and onto a substratum at an increased rate compared with controls. We showed that this is due to reduced E-cadherin engagement at the cell surface, and is marked by increased filopodia formation and redistribution of β1 integrin upon presentation with a substratum for adhesion. We also showed that Hyal1-containing exosomes from cancer cells are able to induce motility in stromal cells, without affecting proliferation. This was similar to the phenotype seen with the known cancer-associated fibroblast inducer, TGF-β1. The motile phenotype was also associated with increased adhesion of stromal cells, and increased activation of focal adhesion kinase (FAK). Using soluble HA and Hyal1, we demonstrated that these effects were specific to exosomally-contained Hyal1, and do not appear to depend on addition of HA to the system. Additionally, we demonstrate that the catalytic activity of Hyal1 is a requirement for phenotypic activation of stromal cells, since exosomes from cancer cells overexpressing a catalytically inactive mutant of the enzyme do not recapitulate this phenotype. These results further elucidate the mechanisms by which Hyal1 supports prostate tumor growth and motility