GSE202744
Selective CDK9 inhibition by natural compound toyocamycin in cancer cell
Aberrant transcription in cancer cells is characterized by silencing of tumor suppressor genes (TSG) and activation of oncogenes. Transcriptomic changes are associated with epigenomic alterations such as DNA hypermethylation, histone deacetylation, and chromatin condensation in promoter regions of silenced TSG. To discover novel drugs that trigger tumor suppressor genes reactivation in cancer cells, we used a GFP reporter system whose expression is silenced by promoter DNA hypermethyation and histone deacetylation. After screening a natural product drug library, we identified toyocamycin, an adenosine analog that induced potent GFP reactivation and loss of clonogenicity in human colon cancer cells. Toyocamycin induced a downregulation in gene pathways involved in RNA pol II transcription regulation. Connectivity mapping analysis revealed that toyocamycin produced a pharmacological signature mimicking cyclin-dependent kinase (CDK) inhibitors. Using RNA-sequencing, we showed that toyocamycin transcriptomic signature closely resembled the profile of a specific CDK9 inhibitor (HH1). Specific inhibition of RNA pol II phosphorylation level and enzymatic kinase assays confirmed that toyocamycin inhibits specifically CDK9 (IC50 = 79nM) with a greater efficacy than other CDKs (IC50 values between 0.67-15µM). Molecular docking showed that toyocamycin binds efficiently CDK9 catalytic site with a different pose than in other CDKs, which was explained by the binding contribution of specific amino acids within the catalytic pocket and the backbone of the protein. Altogether, we demonstrated that toyocamycin exhibits specific CDK9 inhibition in cancer cells, highlighting its potential for cancer chemotherapy. Overall design: YB5 cells were treated with either DMSO or Toyocamycin (250 nM) for various time points. Cells were harvested posy incubation with the drug and RNA was extracted and sent for sequencing.