An epigenetic link from CXCL12-CXCR4 axis through nuclear LASP-1 in breast cancer

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 DESCRIPTION (provided by applicant): The goal of the proposed research is to investigate the role of CXCL12-driven nuclear LASP1 in modulation of epigenetic events in breast cancer. LASP-1 mediates cell migration, proliferation and survival in several breast cancer cell lines. Silencing of LASP-1 inhibits proliferation and migration by 45%. Previously, LASP-1 was demonstrated to directly interact with CXC chemokine receptors, CXCR1, CXCR2, CXCR3 and CXCR4 that play a key role in the tumor microenvironment facilitating breast cancer progression and metastasis. In particular, LASP-1 augmented CXCR2-mediated cell migration. Epigenetic alterations in breast cancer cells convert them into aggressive and metastatic phenotype. In this study, through proteomics, UHRF1 was discovered as a novel LASP-1 associating protein. Subsequently, DNMT1, G9a and Snail1 were also observed to associate with LASP-1. In particular, Snail1 was found to directly bind to LASP-1. The biological implication of this direct interaction is unclear. First, I propose to map the interaction sites between LASP-1 and Snail1 by mutational and biochemical approaches. I further propose to study the LASP1-Snail1 complex for its ability to modulate the E-cadherin promoter. Additionally, as Snail1 directly binds to lysine demethyalse1 (LSD1), LSD1 will be analyzed whether it associates with LASP1-Snail1 complex by biochemical studies. Functionally, I propose to perform a chromatin immunoprecipitation (ChIP) analysis for LASP-1, LSD1, and K4/9 methylation of histone H3 to see if LASP-1/LSD1 co-localize to regions with demethylated histones upon stimulation with CXCL12. Alternatively, recombinant LASP-1 will be mixed with purified LSD-1 and see if LASP-1 enhances in vitro demethylation activity on labeled histone H3 or nucleosome substrates. Additionally, non-silenced and LASP1-knock down basal- like breast cancer cells will be tested for their ability to facilitate bone resorption in a dentine disk assay. LASP1-Snail1 axis would become a novel drug target for small molecule inhibitors with the aim of prolonging the survival rate especially in triple-negative breast cancer patients. Novel inhibitors might be even more useful in cases of breast cancer that are resistant to current chemotherapeutic agents.