Abstract 5270: Androgen receptor blockade in macrophages primes NLRP3 inflammasome-mediated phagocytosis and tumor clearance in advanced prostate cancer

Abstract

Abstract Immune-based therapies induce durable remissions in subsets of patients across multiple malignancies. However, there is limited efficacy of immunotherapy in metastatic castrate-resistant prostate cancer (mCRPC), manifested by an enrichment of immunosuppressive (M2) tumor-associated macrophages (TAM) in the tumor immune microenvironment (TME). Therefore, therapeutic strategies to overcome TAM-mediated immunosuppression are critically needed in mCRPC. Our single-cell RNA sequencing analysis in human tumors revealed that NLR family pyrin domain containing 3 (NLRP3), an innate immune sensing protein, is differentially expressed in TAM from metastatic PC patients treated with standard-of-care androgen deprivation therapy (ADT), relative to other tumor types and untreated primary PC. Furthermore, bulk RNA sequencing analysis in human mCRPC samples revealed an inverse relationship between NLRP3 expression and AR activity, with high NLRP3 expression associated with an M1 signature and a favorable clinical response to ICI in mCRPC. Based on these findings, we hypothesized that androgen axis blockade could enhance NLRP3 expression and potentiate innate immune tumor control in advanced PC. Critically, we discovered that blockade of TAM-intrinsic androgen receptor (AR) activity enhanced NLRP3 expression, but not inflammasome activity in the immunosuppressive (M2) TAM. In contrast, anti-tumor (M1) TAM exhibited high de novo NLRP3 expression, regardless of AR activity. The combination of AR blockade and NLRP3 agonism significantly enhanced phagocytosis of cancer cells by M2 TAM, whereas NLRP3 agonist treatment alone was sufficient to induce phagocytosis in M1 TAM. Following AR blockade/NLRP3 agonist combination treatment, all TAM acquired a distinct phenotype with high PD-L1 and CD86 expression, indicative of phagocytic TAM. Critically, NLRP3 agonism in combination with ADT resulted in significant tumor control in an aggressive c-myc driven advanced PC model, with 55% of mice achieving complete tumor clearance, which was abrogated by concurrent clodronate treatment (which systemically depletes phagocytic macrophages), thus demonstrating TAM-mediated phagocytosis enhancement as a major driver of the observed anti-tumor response. Collectively, our results identify NLRP3 as an AR-regulated “macrophage phagocytic checkpoint” that can be inducibly expressed and activated in TAM following ADT and NLRP3 agonist treatment, respectively, the combination resulting in TAM-mediated phagocytosis and tumor control. Citation Format: Kiranj Chaudagar, Srikrishnan Rameshbabu, Shenglin Mei, Taghreed Hirz, Ya-Mei Hu, Anna Argulian, Brian Labadie, Kunal Desai, Sam Grimaldo, Doga Kahramangil, Rishikesh Nair, Sabina DSouza, Dylan Zhou, Raymond Chen, Jordan Shafran, Mayme Loyd, Zheng Xia, David Sykes, Amy Moran, Akash Patnaik. Androgen receptor blockade in macrophages primes NLRP3 inflammasome-mediated phagocytosis and tumor clearance in advanced prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5270.