Abstract
Inactivation of cyclin-dependent kinase 12 (CDK12) defines an immunogenic molecular subtype of prostate cancer characterized by genomic instability and increased intratumoral T cell infiltration. This study revealed that genetic or pharmacologic inactivation of CDK12 and its paralog CDK13 robustly activates stimulator of interferon genes (STING) signaling across multiple cancer types. Clinical cohort analysis showed that reduced CDK12/13 expression correlates with improved survival and response to immune checkpoint blockade (ICB). Mechanistically, CDK12/13 depletion or targeted degradation induced cytosolic nucleic acid release, triggering STING pathway activation. CDK12/13 degradation delayed tumor growth and synergized with anti-PD-1 therapy in syngeneic tumor models, enhancing STING activity and promoting CD8+ T cell infiltration and activation within tumors. Notably, the antitumor effects of this combination required STING signaling and functional CD8+ T cells. These findings establish STING activation as the key driver of T cell infiltration and the immune-hot tumor microenvironment in CDK12-mutant cancers, suggesting that dual CDK12/13 inhibitors and degraders activate antitumor immunity and potentiate responses to immunotherapies.