Mediator Kinase Inhibitor Selectivity and Activity in Colorectal Cancer.

Area of Science:

• Molecular Biology
• Gene Regulation
• Cancer Research

Background:

• The Mediator complex regulates gene expression by influencing chromatin structure and transcription.
• Cyclin-dependent kinases 8 and 19 (CDK8/19) form a protein kinase module controlling Mediator complex activity.
• CDK8/19 phosphorylates RNA polymerase II and transcription factors, impacting gene expression.

Purpose of the Study:

• To develop and validate selective small-molecule inhibitors for CDK8/19.
• To investigate the role of Mediator kinases in human colorectal cancer.
• To explore the mechanisms by which Mediator kinases regulate gene expression.

Main Methods:

• Utilized orthogonal approaches combining chemical inhibitors and genetic knockout models (CDK8/19 double knockout).
• Employed human colorectal cell culture and tumor xenograft models.
• Performed phospho-proteome profiling and promoter reporter assays.

Main Results:

• Demonstrated selectivity of novel pyridine and pyrazolo[3,4-b]pyridine inhibitors for CDK8/19 in colorectal cancer models.
• Confirmed inhibitor specificity and dependence on CDK8/19 through knockout studies.
• Identified key substrates and transcription factors (TCF/LEF, AP1) regulated by Mediator kinases.
• Revealed altered phosphorylation of Mediator subunits, suggesting rapid regulatory mechanisms.

Conclusions:

• CDK8 and CDK19 are pivotal in regulating gene expression linked to oncogene activation and signaling pathways in colorectal cancer.
• Selective inhibitors developed in this study are valuable tools for mechanistic investigations.
• Further research is needed to fully elucidate the cellular roles and regulatory mechanisms of Mediator kinases for therapeutic potential.