Background

CDKs dysfunction has been recognized as the major contributor for abnormalities in cell cycle and transcription which underlie the majorities of human cancers. Unlike other CDKs, CDK9 does not regulate the cell cycle but promotes RNA synthesis. With the findings in anticancer and antiretroviral research, it is strongly believed that CDK9 inhibition would be a useful therapeutic strategy in these fields. A number of pharmacological CDK inhibitors have been identified and some of them are undergoing preclinical and clinical evaluation, but none of them selectively targets CDK9.

Method

A novel molecule CDKI-83 was designed and synthesized as CDK9 inhibitor and a series of in vitro study was done to investigate its inhibitory mechanism.

Results

Inhibitor activity in inhibiting CDK2/cyclin E, CDK7/cyclin H and CDK9/cyclin T1 was estimated by kinase assay and showed selectivity towards CDK9. Cytotoxic assay (72h MTT assay) showed CDKI-83 is a nano-molar inhibitors which has selectivity between tumour and normal human cell lines. It also demonstrated a dose and time dependent cell death in Annexin-V assay. CDKI-83 demonstrated potent anti-proliferative activity against human cancer cell lines, and also its selectivity towards CDK9 was confirmed. It can be further evaluated as a promising anti-tumour agent. It had no effect in cell cycle at 2 x GI₅₀ concentration and caused G₂/M arrest at 10 x GI₅₀ concentration. Western Blot showed it inhibited CDK9, but not CDK7 in cells. In combination of quantitative real time PCR, CDKI-83 suppressed the activity/expression of anti-apoptotic proteins regulated by CDK9 and stabilised the expression of tumour suppressor (p53).

Conclusion

CDKI-83 demonstrated potent anti-proliferative activity against human cancer cell lines, and also its selectivity towards CDK9 was confirmed. It can be further evaluated as a promising anti-tumour agent.