PYGO2 Ablation Promotes Lymphoid Organization and STING-Dependent Antitumor Immunity in Prostate Cancer

Prostate cancer is an immunologically cold tumor with a limited response to immune checkpoint blockade. Although tertiary lymphoid structures (TLSs) are associated with favorable immunotherapeutic outcomes in various malignancies, the tumor-intrinsic mechanisms governing their formation in prostate cancer remain poorly defined. We investigated whether the frequently amplified chromatin effector PYGO2 regulates lymphoid organization and antitumor immunity. Using prostate-specific Pten/Smad4 double-knockout and Pten/Smad4/Pygo2 triple-knockout mice, syngeneic tumors, transcriptomics, single-cell RNA sequencing, and immunostaining, we found that Pygo2 ablation restored androgen receptor signaling, reduced neuroendocrine-associated features, delayed castration-resistant progression, and prolonged survival. Pygo2-deficient tumors expressed higher levels of tertiary lymphoid structure (TLS)-associated chemokines, exhibited greater T- and B-cell infiltration, and developed TLS-like structures. Single-cell profiling showed increased CD8/Treg ratios, B-cell abundance, TLS imprint scores, and antigen-presentation signatures, particularly after combination therapy. Pygo2 loss also increased DNA damage and was accompanied by activation of the STING-interferon axis. In RM1 syngeneic tumors, STING silencing attenuated the Pygo2-loss-associated increase in cytokine expression, immune infiltration, apoptosis, and tumor control. Combining Pygo2 ablation with castration, CXCR1/2 inhibition, and dual PD-1/CTLA-4 blockade produced durable disease control in more than 80% of Pygo2-deficient mice. These findings identify PYGO2 as a tumor-intrinsic regulator of castration resistance and antitumor immunity and support combining PYGO2-directed strategies with androgen deprivation, myeloid suppression, and immune checkpoint blockade in prostate cancer.