Abstract 528: CDK9 inhibition activates innate immune response in prostate cancer cells

Abstract

Abstract Hyper-activation of transcription is frequent in cancer, which often leads to increased sensitivity to compounds targeting the transcriptional kinases, in particular cyclin-dependent kinase 9 (CDK9). However, mechanistic details as to why CDK9 inhibition selectively kills cancer cells remain largely unknown. Here, we report that CDK9 inhibition activates innate immune response through viral mimicry. In MYC over-expressing prostate cancer cells, CDK9 inhibition leads to excessive accumulation of mis-spliced RNA. Double-stranded RNA (dsRNA)-activated kinase can recognize these mis-spliced RNAs, and we show that this kinase is required for the CDK9 inhibitor-induced anti-proliferative effects. Using time-resolved transcriptional profiling (SLAM-seq), targeted proteomics and ChIP-seq, we show that, similar to viral infection, CDK9 inhibition significantly suppresses transcription of most genes but allows selective transcription and translation of certain genes. In particular, CDK9 inhibition activates NFκB-driven cytokine-signaling at the transcriptional- and secretome-levels. Transcriptional signature induced by CDK9 inhibition identifies prostate cancers with high level of genome instability, and we propose that it is possible to induce similar effects using CDK9 inhibitors. In summary, here we show that inhibition of CDK9 activates innate immune response through viral mimicry. In the future, it is important to establish if CDK9 inhibitors can potentiate the effects of immunotherapy against the late-stage prostate cancer, a currently lethal disease. Citation Format: Shivani Yalala, Aishwarya Gondane, Ninu Poulose, Jing Liang, Ian G. Mills, Harri M. Itkonen. CDK9 inhibition activates innate immune response in prostate cancer cells [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 528.