ARID1A loss shapes immunosuppression tumor microenvironment via NF-kB induced MDSC chemotaxis to promote prostate Cancer metastasis [RNA-seq II]

Chronic inflammation and immunosuppressive microenvironment promote prostate cancer (PCa) metastasis and diminish the responses to immune checkpoint blockade (ICB) therapies. However, it remains unclear how and to what extent these two events are coordinated. Here we show that ARID1A, a subunit of the SWI/SNF chromatin remodeling complex, functions downstream of inflammation induced IKKb activation to shape immunosuppressive tumor microenvironment (TME). Prostate-specific deletion of Arid1a cooperates with Pten loss to produce a metastasis-prone tumors. We identify that polymorphonuclear myeloid-derived suppressor cells (MDSCs) as the major infiltrating immune cell type to cause immune evasion, and neutralization of MDSCs restricts metastasis of Arid1a deficient tumors. Mechanistically, inflammation cues activate IKKß to phosphorylate ARID1A, leading to its degradation via b-TRCP. ARID1A downregulation in turn silences the enhancer of A20 deubiquitinase, a critical negative regulator of NF-kB signaling, and thereby unleashing CXCR2 ligands-mediated MDSC chemotaxis. Importantly, our results support the therapeutic strategy of anti-NF-kB or CXCR2 combined with ICB for advanced PCa. Together, our findings highlight a critical role of ARID1A in MDSCs recruitment and demonstrate IKKb/ARID1A/NF-kB feedback axis integrating inflammation and the immunosuppression to drive PCa metastasis. Overall design: Myc-CaP expressing sgARID1A and control vectors inoculated subcutaneously into FVB mice and treated with or without JSH-23 and epithelial cells were sorted for RNA-seq.