Abstract 66: MMP-7 cleavage of the Perlecan-Sema3A-Plexin(A1)-Neuropilin-1 complex promotes the progression of metastatic prostate cancer
Authors: Tellman Tristen V. , Cruz Lissette A. , Grindel Brian J. , Chung Leland W.K. , Farach-Carson Mary C. 
Published: August 2019

Abstract
Introduction: Perlecan/HSPG2 is a major component of the basement membrane and of reactive stroma. PCa relies on matrix metalloproteinase activity to pass through five perlecan-rich boundaries to metastasize to bone. Semaphorin 3A (Sema3A), a secreted factor, complexes with perlecan at the cell surface and binds to a plexin-neuropilin receptor, resulting in a cohesive tumor state. In prostate cancer (PCa) metastasis, cleavage of this complex and disruption of the perlecan-rich stroma promotes migration to secondary sites. Loss of the Perlecan-Sema3A-Plexin(A1)-Neuropilin-1 (PSPN)-complex by MMP-7 cleavage of perlecan disrupts PCa cohesion and enables the formation of circulating tumor cells (CTCs). Downstream FAK, Akt, and FOXM1 are activated by loss of the PSPN-complex in the tumor microenvironment, promoting growth and metastasis. The extent of MMP-7 cleavage of the other components of the PSPN-complex was unknown.
Methods: Knockdowns using shRNA of various PSPN-complex components were used to identify the perlecan-Sema3A binding partners (plexin A1 and neuropilin-1) on the PCa cell surface. Both in silico and in vitro analysis of plexin A1 and neuropilin-1 revealed potential MMP-7 cleavage sites within the PSPN-complex. Silver staining was used to analyze the extent of cleavage of the PSPN-complex components by MMP-7. Western blot analysis was used to probe for any resulting molecular changes in downstream signaling from PSPN-complex components (FAK, Akt, and FOXM1). Changes in cell cohesion were monitored to associate changes in signaling with phenotypic changes in cell behavior.
Results: Knockdowns of the plexin A1 component of the PSPN-complex prevented tumoroid-like formation of PCa cells, implicating this plexin as having a key role in maintaing PCa cohesion mediated through the PSPN-complex. MMP-7 cleavage of various PSPN-complex components resulted in complex destruction, PCa dyscohesion, and the activation of downstream metastasis-promoting factors FAK, Akt, and FOXM1.
Conclusion: The dynamic interactions between the PSPN-complex and MMP-7 at the PCa cell surface governs the cohesion-dyscohesion behavior of PCa cells. Loss of the PSPN-complex by MMP-7 cleavage results in a dyscohesive and metastatic phenotype. Downstream factors FAK, Akt, and FOXM1 can be activated by loss of the PSPN-complex, further implicating the importance of this complex in the metastasis of PCa. These components offer a novel target to perturb the progression of metastatic disease and to prevent CTC formation in PCa patients.
Citation Format: Tristen V. Tellman, Lissette A. Cruz, Brian J. Grindel, Leland W.K. Chung, Mary C. Farach-Carson. MMP-7 cleavage of the Perlecan-Sema3A-Plexin(A1)-Neuropilin-1 complex promotes the progression of metastatic prostate cancer [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 66.