Interplay of Perlecan and MMP-7/Matrilysin Regulates Metastatic Prostate Cancer Cell Behavior: Basic and Clinical Implications

Perlecan/HSPG2 is a large extracellular heparan sulfate proteoglycan concentrated at tissue borders and separating epithelium and stroma. Along with its proteolytic consumers, the matrix metalloproteinases (MMPs), perlecan helps orchestrate development and homeostasis in nearly all studied multicellular organisms. However, both molecule classes can be coopted by prostate cancer (PCa) to advance the disease to its most deadly metastatic form. This work aimed to understand that relationship both at the basic and clinical level. Perlecan with its HS chains and tight domain structure is generally resistant to proteolysis, but a PCa cell must produce an associated enzyme to cleave the border proteoglycan in order to metastasize. This work was the first to identify an active protease produced by PCa cells that can completely digest intact perlecan. Following in silico proteolytic analysis, matrilysin/MMP-7, was identified as a likely candidate for in vitro assays. MMP-7, unlike other enzymes tested, cleaved perlecan when presented in multiple contexts. Perlecan and a subdomain, domain IV-3 (Dm IV-3), but not other subdomains (Dm I, IV-1 and IV-2), induced a striking clustering phenotype. MMP-7 incubation completely reversed this effect to favor cell dispersion and adhesion. Proteomic signaling arrays point towards global Src kinase activation as a major influence of perlecan DmIV-3 effects. To determine if this perlecan/MMP-7 relationship exists in PCa subjects, I performed a tissue microarray, along with β2-microglobulin (β2M), a GF that binds perlecan and induces MMP secretion. Besides increased levels of the two proteins within the patients (cancer/normal), MMP-7 and perlecan levels statistically correlated in multiple grades and localized at tissue interfaces. Additionally, I developed a new assay probing the perlecan fragment signature in the same PCa subjects’ serum. Perlecan fragments were largely increased in PCa and some of the fragments were associated with MMP-7 expression in the subjects. Overall, this work demonstrates a unique interplay between perlecan and its efficient proteolyzer, MMP-7, a relationship that is relevant from the cell and tissue to the clinic and which is likely to contribute to PCa progression to metastatic lethal disease