Abstract 202: CRISP3 and PSP94 as soluble mediators shaping P2RX7 mediated signalling probably via CITED2 in tumor microenvironment

Abstract The dynamic interplay between the tumor and the infiltrating immune cells within the tumor microenvironment (TME) critically shapes cancer progression, particularly through mechanisms of immune evasion and tumor cell survival. Cysteine Rich Secretory Protein 3 (CRISP3) is elevated in prostate cancer and linked to poor prognosis. Originally identified in neutrophilic granules and body secretions, CRISP3 levels are frequently dysregulated in inflammation. Whether overexpressed CRISP3 modulates tumor immune microenvironment remains largely unexplored. Our study unravelled a potential mechanism whereby CRISP3 controlled the expression of P2RX7 (Purinergic Receptor X7), a key player in the inflammasome pathway, in tumor cells as well as in macrophages. Using antibody array, we identified CITED2 (cAMP-responsive element-binding protein (CBP)/p300-interacting transactivator with glutamic acid (E) and aspartic acid (D)-rich tail) levels to be upregulated in cells exposed to CRISP3. CITED2 is a transcriptional coregulator and a potent molecular switch that promotes macrophage polarisation. In silico analysis of human P2RX7 promoter demonstrated presence of p300/CBP binding sites suggesting possible sequestration of p300/CBP in presence of CITED2, thus downregulating P2RX7. Publicly available single cell RNA-seq data also highlighted the involvement of CITED2 in regulating the expression of P2RX7. Ectopically added CRISP3 significantly altered ATP-induced cytotoxicity and IL-1β maturation due to downregulation of P2RX7. Interestingly, when CRISP3 was complexed with its binding partner, PSP94 (Prostate Secretory Protein of 94 amino acids), its regulatory action on P2RX7 was inhibited. The presence of PSP94 also affected CRISP3 endocytosis which was via flotillin-2 dependent pathway. Together, our data provides evidence for an important role for CRISP3 and PSP94 in regulating P2RX7 levels. Upregulated CRISP3, in prostate tumorigenesis, suppresses P2RX7 expression, impacting IL-1β maturation and potentially driving macrophage polarization to M2 like by upregulating CITED2. This supports poor prognostic outcomes in prostate cancer patients showing upregulated CRISP3. Inhibition of CRISP3 can be an interesting therapeutic strategy in alleviating immunosuppressive tumor milieu. Citation Format: Vaidehi Miya, Bhakti Rajesh Pathak. CRISP3 and PSP94 as soluble mediators shaping P2RX7 mediated signalling probably via CITED2 in tumor microenvironment. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 202.