Targeting The Laminin Receptor / PEDF Interface to Treat Prostate Cancer Cells

Abstract

The non‐integrin laminin receptor (LAMR1) is a multifunctional protein localized in the cytosol and at the membrane. Recently, the potent antiangiogenic protein required for retinal development and maintenance, pigment epithelium derived factor (PEDF), was confirmed as a binding partner for LAMR1. LAMR1 is frequently overexpressed in cancer cells. Our lab and others have demonstrated that PEDF abolishes neo‐vasculature in prostate tumors, resulting in decreased tumor growth and burden and abatement of metastatic potential.Using crystal structures for PEDF and LAMR1, we mapped the interaction interface and screened the Maybridge HitFinder Database in silico (>14,000 compounds) using Docking@UTMB and AutoDock Vina. We selected seven hits and conducted a medium throughput screen in multiple cell lines. IC50s were generated using a six point dose curve and a four parameter non‐linear regression. Orthogonal validation was performed using luciferase assays against cancer specific promoters. Finally, we identified the 67 kDa species of LAMR1 and successfully knocked endogenous protein down using siRNA duplexes.Our phenotypic screen revealed three putative laminin antagonists, two agonists, and two ineffective compounds. We established that PEDF and the peptide P18 can mediate changes in gene expression. One compound significantly reduced Fas Ligand promoter activity and phenocopied PEDF, suggesting that these compounds may modify the tumor microenvironment. Next, we will confirm LamR specificity using cell‐surface binding assays and siRNA.Funding: UTMB CAR P50DA033935 Pilot Grant and Startup Funds