Pygo2 Loss Induces Tertiary Lymphoid Structure Formation and Enhances Immunotherapy and Castration Responses in Prostate Cancer

Prostate cancer (PCa) is widely regarded as an immunologically "cold" tumor, and the presence and regulation of tertiary lymphoid structures (TLSs) in it remain poorly understood. Using a prostate-specific Pten/Smad4 knockout (DKO) model, we found that additional deletion of Pygo2 (TKO) markedly enhanced TLS formation, increased TLS-associated chemokines and cytokines, and promoted lymphocyte organization within the tumor microenvironment. Pygo2 loss also restored androgen receptor (AR) signaling and sensitized tumors to castration. Importantly, combination therapy with castration, CXCR2 inhibition, and immune checkpoint blockade (CSI) further matured TLSs, strengthened B and T cell responses, and induced durable disease control in >80% of TKO mice for more than 42 weeks. Mechanistically, Pygo2 deletion led to DNA damage accumulation and activation of the STING-interferon pathway, whereas STING silencing abolished this response. Collectively, these findings identify Pygo2 as a key regulator of TLS formation, immune activation, and therapy resistance, highlighting it as a promising therapeutic target in castration-resistant prostate cancer.