Abstract 4587: Utility of recombinant MUC4 domains as potential therapeutic agents

Pancreatic cancer (PC) is a highly aggressive malignancy with limited therapeutic options and is characterized by aberrant overexpression of mucins. Mucin 4 (MUC4) is a multi-domain transmembrane mucin which is differentially overexpressed in pancreatic cancer. MUC4 expression increases progressively during PC and high expression correlates with poor prognosis. MUC4 functionally contributes to pathobiology and aggressiveness of the disease by promoting cell proliferation, migration and inducing chemotherapy resistance. MUC4 is putatively cleaved at GDPH site protein resulting in two subunits, MUC4α and MUC4β. MUC4α comprises of highly glycosylated tandem repeat region, followed by NIDO and AMOP domains. The NIDO domain is known to play a role in cancer metastasis and tumor growth by interacting with other proteins. MUC4β comprises of vWD domain, three EGF-like domains, and a transmembrane domain. Following cleavage, MUC4β remains tethered to the cell membrane as a functional protein, and is thus an attractive target for therapeutic intervention. We have cloned and expressed various recombinant domains of MUC4 for the generation of monoclonal antibodies and development of therapeutic vaccine. We observed that recombinant MUC4β (rMUC4β) interacts with several cellular proteins including Ezrin, EGFR, HER2 and HER3. On the basis of these protein-protein interactions, we hypothesized that exogenous soluble MUC4β acts as a competitive inhibitor of endogenous MUC4 and disrupts its tumor-promoting functions. To determine the utility of rMUC4β as a therapeutic agent, we examined its effect on the proliferation, aggregation, migration, apoptosis and downstream signaling pathways in MUC4 expressing (CD18/HPAF) and non-expressing (MiaPaCa) human pancreatic cancer cell lines. We observed that rMUC4β induced alterations in cell morphology, including higher membrane blebbing, detachment from the plate, and disrupted homotypic cell-cell interactions. Further, exogenous MUC4β significantly inhibited (p value=0.0001) the proliferation of MUC4 expressing CD18/HPAF cells in a dose and time dependent manner. In contrast, no significant change was observed in growth rates and cells-cell interactions in MUC4 negative MiaPaCa cells. We also observed that MUC4β induced significantly higher apoptosis (> 15%) in MUC4 expressing cells as compared to MUC4 negative. Additionally, treatment of MUC4 expressing cells with rMUC4β inhibited their migration by up to 30 percent in a dose-dependent manner while no significant effect was observed in MUC4 non-expressing cells. Recombinant MUC4β treatment resulted in decreased phosphorylation of ERK-1 and AKT. Overall these studies suggest that rMUC4β can competitively inhibit some of the functions of endogenous MUC4 and disrupt the growth and migration promoting signaling pathways. Thus, MUC4β is an attractive therapeutic agent that can potentially inhibit tumorigenesis and metastasis in MUC4-positive PC. Citation Format: Mansi Gulati. Utility of recombinant MUC4 domains as potential therapeutic agents [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4587.