Abstract 67: MMP-7 decreases E-cadherin localization at cell-cell contacts resulting in F-actin cytoskeletal remodeling in prostate cancer micro-tumors formed by perlecan/HSPG2

Introduction: Polarized epithelium is maintained by cell-cell interactions via cadherins and cell adhesion molecules (CAMs). These interactions are further stabilized by cell-matrix interactions on the basement membrane. Perlecan/HSPG2 is a major component of the basement membrane, controlling signaling in resting tissues with unperturbed matrices. During epithelial to mesenchymal transition in prostate cancer (PCa), cell-cell adhesions decrease and the cells acquire an invasive phenotype. Proteolytic cleavage of perlecan decreases cell-matrix interactions and dysregulates cell signaling, permitting migration. In vivo , patients with bone metastases were found to have circulating DmIV fragments, with a positive correlation between MMP-7 staining and loss of perlecan in tissue samples from these same patients. Recent studies showed perlecan domain IV-3 (DmIV-3) drives cell cohesion and, when digested with matrix metalloproteinase-7 (MMP-7), drives cell dyscohesion. MMP-7 can cleave cadherins and other CAMs disrupting cell-cell adhesions. Additionally, DmIV-3 fragments generated by MMP-7 cleavage may further induce cell dyscohesion by disrupting interactions between CAMs and/or cadherins. Methods: To evaluate the impact of MMP-7 and domain IV-3 fragments, uniformly sized PCa cell clusters were pre-formed using a microwell system, enabling control of cluster size and cell number. These pre-formed cell clusters were transferred to DmIV-3 coated wells for 16-24 hours. Clusters then were treated with MMP-7 alone or MMP-7 plus DmIV-3 fragments and stained for E-cadherin and F-actin. Results: Consistent with previous data, PCa cell clusters maintained strong cell-cell contacts in the presence of DmIV-3. In contrast, we showed that in pre-formed PCa cell clusters cultured in the presence of DmIV-3 cleaved by MMP-7, E-cadherin localization at cell-cell interfaces was reduced. Pre-formed PCa cell clusters treated with MMP-7 had increased F-actin stress fibers present, with a decrease in F-actin organization at cell-cell contacts. Conclusion: Creating PCa micro-tumors using a microwell system provides a good model to study dynamic changes in cell-cell interactions. The purpose of this study was to identify which cell adhesion complexes are perturbed by MMP-7 in these PCa cell clusters. E-cadherin is known to regulate the cortical actin cytoskeleton; thus, decreased E-cadherin at cell-cell contacts results in actin reorganization and an increase in F-actin stress fiber formation, promoting a migratory cell phenotype. Perlecan fragments may augment this behavior by increasing MMP-7 access to the ectodomains of CAMs. This study will be novel in its identification of a DmIV fragment(s) that may provide a prediction marker for PCa metastasis as well as fragments that are positively associated with tumor dyscohesion. Citation Format: Lissette A. Cruz, Tristen V. Tellman, Mary C. Farach-Carson, Brian Grindel, Daniel D. Carson. MMP-7 decreases E-cadherin localization at cell-cell contacts resulting in F-actin cytoskeletal remodeling in prostate cancer micro-tumors formed by perlecan/HSPG2 [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 67.