Compromised CDK12 activity causes dependency on the non-essential spliceosome components

Prostate cancer (PC) is the most common cancer in men and after development of the castration-resistant PC (CRPC), there are no curative treatment options. Inactivating mutations in cyclin-dependent kinase 12 (CDK12) define an aggressive sub-type of CRPC. We hypothesized that compromised CDK12 activity leads to significant rewiring of the CRPC cells, and that this rewiring results in actionable synthetic lethal interactions. MethodsWe used combinatorial lethal screening, ChIP-seq data, RNA-seq data, global alternative splicing analysis, and comprehensive mass spectrometry (MS) profiling to understand how the compromised CDK12 activity rewires the CRPC cells. In addition, we used DepMap-, PC- and CRPC-datasets as a strategy to identify factors that are selectively required by the CDK12-mutant cells. ResultsWe show that inhibition of O-GlcNAc transferase (OGT) and CDK12 induces cancer cell-selective growth-defect. OGT catalyzes all nucleocytoplasmic O-GlcNAcylation, and we use unbiased MS-profiling to show that the short-term CDK12 inhibition induces hyper-O-GlcNAcylation of the spliceosome-machinery in PC and CRPC cells. Integration of DepMap- and a small scale-drug screen data reveled that depletion of CDK12 activity causes addiction to non-essential spliceosome components (CLK1/4 and SRPK1). CDK12-mutant tumors overexpress CLK1/4 and SRPK1. Finally, we show that the genomes of the CDK12-mutant tumors have lower DNA methylation, and that CDK12 inhibition induces the expression of the genes marked by DNA methylation. ConclusionsCompromised CDK12 activity rewires DNA methylation, transcription and splicing, and this rewiring renders the affected cells addicted on the non-essential spliceosome components. We propose that inactivation of CDK12 is a biomarker for sensitivity against inhibitors of the non-essential spliceosome components just entering the clinical trials. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=85 SRC="FIGDIR/small/470703v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@a128e8org.highwire.dtl.DTLVardef@84a70dorg.highwire.dtl.DTLVardef@f37b10org.highwire.dtl.DTLVardef@1145f1b_HPS_FORMAT_FIGEXP M_FIG C_FIG