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: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.
Project description:Basal-like breast cancer (BBC) 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 BBC 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 basal but not luminal breast cancer cells are exceptionally dependent on CDK7, a transcriptional cyclin-dependent kinase. BBC cells are unique in their dependence on this transcriptional CDK and suffer apoptotic cell death upon CDK7 inhibition. An “Achilles cluster” of BBC-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 BBC and CDK7 inhibition may be useful therapy for this challenging cancer. ChIP-Seq for H3K27ac in basal-like breast cancer and luminal-like breast cancer cell lines
Project description:Basal-like breast cancer (BBC) 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 BBC 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 basal but not luminal breast cancer cells are exceptionally dependent on CDK7, a transcriptional cyclin-dependent kinase. BBC cells are unique in their dependence on this transcriptional CDK and suffer apoptotic cell death upon CDK7 inhibition. An “Achilles cluster” of BBC-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 BBC and CDK7 inhibition may be useful therapy for this challenging cancer.
Project description:Triple-negative breast cancer (TNBC) has a highly aggressive nature and distinct molecular characteristics from other subtypes of breast cancer and lacks effective targeted therapy. The molecular and genetic basis of cysteine/cystine dependency in TNBC is complex. We found that cysteine addiction associates with the expression of a set of Claudin genes in TNBC. The Claudin-high TNBCs are independent on cystine, while the Claudin-low TNBCs undergo rapid ferroptosis upon cystine deprivation or inhibition of cystine transport by erastin. To overcome the resistance of Claudin-high TNBC and luminal breast cancer to the potential targeted cystine-addiction therapy, we explored the synthetic lethality of cysteine by an epigenetic compound library screen. Several potent HDAC6 inhibitors were identified and rendered the Claudin-high TNBCs and luminal cancer cells dependent on extracellular cystine and undergoing ferroptosis upon cystine deprivation. The transcriptomic profiling showed that the HDAC6 inhibitor tubacin in combination with erastin activates a synthetic-lethal transcriptional program. Together, we have identified the HDAC6 inhibitors as potent therapy-sensitizers to revive the targeted cysteine-addiction therapy for various subtypes of breast cancer, not limit in the Claudin-low TNBC.
Project description:Cyclin Dependent Kinase 7 (CDK7) is the core catalytic subunit of Cyclin Activating Kinase (CAK), a complex that has dual roles in cell cycle progression and transcription. While several CDK7 inhibitors are efficacious in preclinical models of cancer and have entered clinical trials, the mechanism(s) by which CDK7 promotes proliferation and cell viability is not well understood. Using triple negative breast cancer (TNBC) as a model, we found that inhibiting CDK7, either genomically or pharmacologically, induces mitotic dysfunction. Live and static cell imaging revealed that CDK7 inhibition prolongs mitosis and induces chromatin bridge formation, DNA double strand breaks, and abnormal nuclear features, all of which are indicative of mitotic catastrophe and chromosome instability. Transcriptome analyses revealed that CDK7 is essential for maintaining condensin complex gene expression, suggesting that CDK7 may sustain chromatin configuration, a role that extends beyond its impact on super-enhancers. Indeed, inhibiting CDK7 alters chromatin architecture consistent with condensin disruption. Confirming the importance of condensin regulation by CDK7, genetic suppression of a core subunit of this complex, structural maintenance of chromosome 2 (SMC2), phenocopies CDK7 inhibition. We report an undescribed role of CDK7 in maintaining chromatin structure and chromosome stability, as well as promoting proper mitoses, by sustaining condensin expression.