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Dissertation/Thesis Abstract

The Paracaspase MALT1 is a Critical Mediator of PAR1-Driven NF-κB Activation and Tumor Metastasis
by McAuley, James Randall, Ph.D., University of Pittsburgh, 2017, 113; 10692563
Abstract (Summary)

Protease Activated Receptor 1 (PAR1), a G-protein coupled receptor that is stimulated via thrombin-mediated proteolytic cleavage, is implicated in promoting metastasis in a variety of tumor types, including both carcinomas and sarcomas. The molecular mechanisms underlying PAR1-driven tumor metastasis remain largely unknown. Our laboratory previously discovered that PAR1 stimulation in endothelial cells leads to activation of the NF-κB transcription factor, and this is mediated by a protein complex comprised of the CARMA3 scaffolding protein, the Bcl10 adaptor protein, and the protease MALT1 (CBM). Given the strong association between NF-κB and tumor metastasis, we hypothesized that this CBM complex also mediates PAR1- driven, NF-κB-dependent tumor metastasis. In support of our hypothesis, we demonstrated that PAR1 stimulation in both osteosarcoma and in breast cancer cells results in NF-κB activation. siRNA-mediated MALT1 knockdown suppresses this NF-κB activation, suggesting that an intact CBM complex is required for PAR1-induced NF-κB activity in both tumor cell types. We identified several metastasis-associated genes that are significantly upregulated after PAR1 stimulation of osteosarcoma cells, and found that expression of the matrix remodeling protein MMP9, and the inflammatory cytokine IL-1β are both abrogated by MALT1 knockdown. We identified a similar, though distinct, PAR1-induced, MALT1-dependent gene expression profile in breast cancer cells. We next used CRISPR/Cas9 to knock out MALT1 in MCF7 breast cancer cells engineered to express PAR1 (MCF7-N55). In contrast to control MCF7 cells, which do not express PAR1, MCF7-N55 cells are highly invasive in vitro and in vivo. We found that MALT1 knockout significantly blunts MCF7-N55 invasion and metastasis. Excitingly, we demonstrate that PAR1 stimulation induces MALT1 proteolytic activity in both osteosarcoma and breast cancer cells. Several small molecule MALT1 protease inhibitors have recently been described, and our study suggests that MALT1 could represent a promising new pharmaceutical target for the prevention/treatment of PAR1-driven tumor metastasis.

Indexing (document details)
Advisor: McAllister-Lucas, Linda
School: University of Pittsburgh
School Location: United States -- Pennsylvania
Source: DAI-B 79/04(E), Dissertation Abstracts International
Subjects: Cellular biology, Medicine, Oncology
Keywords: PAR1, breast cancer, osteosarcoma
Publication Number: 10692563
ISBN: 978-0-355-41036-5
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