Characterizing the role of ADAM10 and 15 disintegrins in prostate biology and disease

Abstract

During the progression of prostate cancer, the adhesion molecule epithelial (E)-cadherin can be lost from the cell surface by ADAM15 proteolytic processing, generating an extracellular 80kDa fragment referred to as soluble E-cadherin (sE-cad). Contrary to observations in cancer, the generation of sE-cad appears to correlate with ADAM10 activity in benign prostatic epithelium. The ADAM10-specific inhibitors INCB008765 and proA10 inhibit sE-cad generation, downstream signaling, and cell proliferation. Addition of EGF or amphiregulin to benign prostatic hyperplasia cells (BPH-1) or immortalized prostate epithelial cells (PrEC) increases the amount of sE-cad shed into the conditioned media and bound to EGFR. EGF-associated shedding appears to be mediated by ADAM10 as shRNA knockdown of ADAM10 results in reduced sE-cad generation. To examine the physiologic consequence of sE-cad on prostatic epithelium, we treated cells with a sE-cad analog (Fc-Ecad), which resulted in phosphorylation of EGFR, signaling through ERK, and cell proliferation. Pre-treating cells with cetuximab, a therapeutic antibody against EGFR, decreased the ability of Fc-Ecad to induce EGFR phosphorylation, downstream signaling and proliferation. These data demonstrate that ADAM10-generated sE-cad may have a role in EGFR signaling independent of traditional EGFR ligands. In order to better characterize the role of ADAM10 in normal prostate biology, we generated prostate specific knockout mice utilizing probasin (Pb) driven Cre. Preliminary analysis of Adam10 loxP/loxP Pb-Cre mice indicates an unexpected epithelial hyperplasia into the luminal space and areas of continued ADAM10 expression. However, cell lines generated from Adam10 loxP/loxP Pb-Cre mouse prostates express no ADAM10. Because of our interest in targeting ADAM15 in prostate cancer, we initiated studies investigating potential inhibitors and domain requirements for E-cadherin cleavage. In these preliminary studies, the EGF-like domain of ADAM15 appears to be critical for sE-cad generation. We have also observed that the ADAM10 inhibitor, INCB08765, can inhibit ADAM15 activity during in vitro and CD23 peptide cleavage assays. Furthermore, ADAM15 and ADAM10 co-immunoprecipitate as a catalytically active unit. These studies suggest a novel role for the EGF-like domain of ADAM15 and present an interesting observation of functional interaction between ADAM10 and ADAM15.PhDCellular & Molecular BiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/89823/1/mmgrabow_1.pd