Tumor ABCC4-mediated release of PGE2 induces CD8+ T cell dysfunction and impairs PD-1 blockade in prostate cancer.

Prostate cancer presents as an immunologically "cold" malignancy, characterized by a lack of response to immunotherapy in the majority of patients. The dysfunction of prostate tumor metabolism is recognized as a critical factor in immune evasion, resulting in reduced effectiveness of immunotherapeutic interventions. Despite this awareness, the precise molecular mechanisms underpinning metabolic dysregulation in prostate cancer and its intricate relationship with immune evasion remain incompletely elucidated. In this study, we introduce the multi-drug resistance protein ABCC4/MRP4 as a key player prominently expressed in prostate cancer, exerting a pivotal role in suppressing the activity of intratumoral CD8⁺ T cells. Depletion of ABCC4 in prostate cancer cells halts the release of prostaglandin E2 (PGE2), a molecule that diminishes the population of CD8⁺ T cells and curtails their cytotoxic capabilities. Conversely, constraining the activation of PGE2 signaling in CD8⁺ T cells effectively improved the efficacy of prostate cancer treatment with PD-1 blockade. During this process, downregulation of the JAK1-STAT3 pathway and depolarization of mitochondria emerge as crucial factors contributing to T cell anergy. Collectively, our research identifies the ABCC4-PGE2 axis as a promising target for reversing dysfunction within tumor-infiltrating lymphocytes (TILs) and augmenting the suboptimal responsiveness to immunotherapy in prostate cancer.