drug resistance

cell proliferation

cellular senescence

cycle progression

cell cycle

Pharmacological Research

Cyclins and cyclin-dependent protein kinases (CDKs) are important proteins that are required for the regulation and expression of the large number of components necessary for the passage through the cell cycle. The concentrations of the CDKs are generally constant, but their activities are controlled by the oscillation of the cyclin levels during each cell cycle. Additional CDK family members play significant roles in a wide range of activities including gene transcription, metabolism, and neuronal function. In response to mitogenic stimuli, cells in the G1-phase of the cell cycle produce D type cyclins that activate CDK4/6. These activated enzymes catalyze the monophosphorylation of the retinoblastoma protein. Subsequently, CDK2-cyclin E catalyzes the hyperphosphorylation of Rb that promotes the release and activation of the E2F transcription factor, which in turn lead to the biosynthesis of dozens of proteins required for cell cycle progression. Consequently, cells pass the G1-restriction point and are committed to complete cell division in the absence of mitogenic stimulation. CDK2-cyclin A, CDK1-cyclin A, and CDK1-cyclin B are required for S-, G2-, and M-phase progression. A crucial mechanism in controlling cell cycle progression is the precise timing of more than 32,000 phosphorylation and dephosphorylation reactions catalyzed by a network of protein kinases and phosphoprotein phosphatases as determined by mass spectrometry. Increased cyclin or CDK expression or decreased levels of endogenous CDK modulators/inhibitors such as INK4 or CIP/KIP have been observed in a wide variety of carcinomas, hematological malignancies, and sarcomas. The pathogenesis of neoplasms because of mutations in the CDKs are rare. Owing to their role in cell proliferation, CDKs represent natural targets for anticancer therapies. Palbociclib, ribociclib, and abemaciclib are FDA-approved CDK4/6 inhibitors used in the treatment of breast cancer. These drugs have IC50 values for CKD4/6 in the low nanomolar range. These inhibitors bind in...

Cyclin-dependent protein serine/threonine kinase inhibitors as anticancer drugs