Project description:Cyclin-dependent kinase 7 (CDK7) plays a critical role in the general regulation of RNA polymerase II-mediated transcription. However, the absence of selective CDK7 inhibitors has hindered the ability to investigate the consequences of acute and prolonged inhibition of CDK7 under normal and pathological conditions. Here we present the discovery and characterization of the first covalent CDK7 inhibitor, CDK7-IN-1, that has the unprecedented ability to target a unique cysteine residue located outside of the canonical kinase domain, providing an unanticipated means of achieving selectivity for CDK7 amongst the 20 known CDKs. Cancer cell line profiling indicates that a subset of cancer cell lines, including T-cell acute lymphoblastic leukemia (T-ALL), exhibit 100-fold greater sensitivity to CDK7-IN-1 over other tumor and normal cell lines. Genome-wide expression analysis in Jurkat T-ALL indicates that CDK7-IN-1 disproportionally affects RUNX1 as well as other components of the TAL1 transcriptional network and its targets, downregulating key regulators of transcription and apoptosis critical for the T-ALL state. These oncogenes are encoded by short-lived mRNA transcripts, are associated with super-enhancers, and exhibit a strong dependency on continuous transcription for sustained expression. Therefore, pharmacological modulation of CDK7 kinase activity may define a method for the identification and treatment of tumor types exhibiting extreme dependencies on transcription for maintenance of the oncogenic state. Jurkat cells were treated with various drugs including a covalent inhibitor of CDK7 (CDK7-IN-1), a reversible inhibitor of CDK7 (CDK7-IN-1), Flavopiridol, Actinomycin D, and DMSO controls. Replicates are annotated.
Project description:Cyclin-dependent kinase 7 (CDK7) plays a critical role in the general regulation of RNA polymerase II-mediated transcription. However, the absence of selective CDK7 inhibitors has hindered the ability to investigate the consequences of acute and prolonged inhibition of CDK7 under normal and pathological conditions. Here we present the discovery and characterization of the first covalent CDK7 inhibitor, CDK7-IN-1, that has the unprecedented ability to target a unique cysteine residue located outside of the canonical kinase domain, providing an unanticipated means of achieving selectivity for CDK7 amongst the 20 known CDKs. Cancer cell line profiling indicates that a subset of cancer cell lines, including T-cell acute lymphoblastic leukemia (T-ALL), exhibit 100-fold greater sensitivity to CDK7-IN-1 over other tumor and normal cell lines. Genome-wide expression analysis in Jurkat T-ALL indicates that CDK7-IN-1 disproportionally affects RUNX1 as well as other components of the TAL1 transcriptional network and its targets, downregulating key regulators of transcription and apoptosis critical for the T-ALL state. These oncogenes are encoded by short-lived mRNA transcripts, are associated with super-enhancers, and exhibit a strong dependency on continuous transcription for sustained expression. Therefore, pharmacological modulation of CDK7 kinase activity may define a method for the identification and treatment of tumor types exhibiting extreme dependencies on transcription for maintenance of the oncogenic state. Jurkat, MM1S, Loucy, and HeLa (WT and Dox-inducible CDK7 mutant) cells were treated with various drugs including a covalent inhibitor of CDK7 (CDK7-IN-1), a reversible inhibitor of CDK7 (CDK7-IN-1), Flavopiridol, Actinomycin D, and DMSO controls. Replicates are annotated.
Project description:Cdk7, the CDK-activating kinase and transcription factor IIH component, is a target of inhibitors that kill cancer cells by exploiting tumor-specific transcriptional dependencies. However, whereas selective inhibition of analog-sensitive (AS) Cdk7 in colon cancer derived cells arrests division and disrupts transcription, it does not by itself trigger apoptosis efficiently. Here we show that p53 activation by 5-fluorouracil or nutlin-3 synergizes with a reversible Cdk7as inhibitor to induce cell death. Synthetic lethality was recapitulated with covalent inhibitors of wild-type Cdk7, THZ1 or the more selective YKL-1-116. The effects were allele-specific; a CDK7as mutation conferred both sensitivity to bulky adenine analogs and resistance to covalent inhibitors. Non-transformed colon epithelial cells were resistant to these combinations, as were cancer-derived cells with p53-inactivating mutations. Apoptosis was dependent on death receptor DR5, a p53 transcriptional target whose expression was refractory to Cdk7 inhibition. Therefore, p53 activation induces transcriptional dependency to sensitize cancer cells to Cdk7 inhibition.
Project description:Triple-negative breast cancer (TNBC) is a highly aggressive form of breast cancer that exhibits extremely high levels of genetic complexity and yet a relatively uniform transcriptional program. We postulate that TNBC might be highly dependent on uninterrupted transcription of a key set of genes within this gene expression program and might therefore be exceptionally sensitive to inhibitors of transcription. Utilizing a novel kinase inhibitor and CRISPR/Cas9-mediated gene editing, we show here that triple-negative but not ER/PR+ breast cancer cells are exceptionally dependent on CDK7, a transcriptional cyclin-dependent kinase. TNBC cells are unique in their dependence on this transcriptional CDK and suffer apoptotic cell death upon CDK7 inhibition. An “Achilles cluster” of TNBC-specific genes are extremely sensitive to CDK7 inhibition and frequently associated with super-enhancers. We conclude that CDK7 mediates transcriptional addiction to a vital cluster of genes in TNBC and CDK7 inhibition may be useful therapy for this challenging cancer. Expression microarrays in H3K27ac in triple-negative breast cancer +/- treatment with covalent CDK7 inhibitor THZ1 treatment
Project description:Small cell lung cancer (SCLC) is an aggressive disease with high mortality. The identification of effective pharmacological strategies to target SCLC biology represents an urgent need. Using a high-throughput cellular screen of a diverse chemical library we observe that SCLC is sensitive to transcription-targeting drugs, and in particular to THZ1, a newly identified covalent inhibitor of cyclin-dependent kinase 7 (CDK7). We find that expression of super-enhancer associated transcription factor genes including MYC family proto-oncogenes and neuroendocrine lineage-specific factors are highly vulnerability to THZ1 treatment. We propose that downregulation of these transcription factors contributes, in part, to SCLC sensitivity to transcriptional inhibitors and that THZ1 represents a novel treatment paradigm for targeted SCLC therapy. ChIP-Seq for H3K27ac in small cell lung cancer lines