In vitro antitumor properties of a novel cyclin-dependent kinase inhibitor, P276-00
Kalpana S Joshi1, Maggie J Rathos, Rajendra D Joshi
1Department of Pharmacology, Nicholas Piramal Research Center, Nicholas Piramal India Limited, 1-Nirlon Complex, Goregaon (E), Mumbai 400 063, India. kjoshi@nicholaspiramal.co.in
Abstract:
Cyclin-dependent kinases (Cdk) and their associated pathways represent some of the most attractive targets for the development of anticancer therapeutics. Based on antitumor activity in animal models, a variety of Cdk inhibitors are undergoing clinical evaluation either as a single agent or in combination with other approved drugs. In our anticancer drug discovery program, a novel series of flavones have been synthesized for evaluation against the activity of Cdk4-D1. This enzyme catalyzes the phosphorylation of retinoblastoma protein, thus inhibiting its function. We have identified a series of potent Cdk4-D1 inhibitors with IC(50) below 250 nmol/L. In this report, we have described the properties of one of the best compound, P276-00 of the flavone's series. P276-00 shows 40-fold selectivity toward Cdk4-D1, compared with Cdk2-E. The specificity toward 14 other related and unrelated kinases was also determined. P276-00 was found to be more selective with IC(50)s <100 nmol/L for Cdk4-D1, Cdk1-B, and Cdk9-T1, as compared with other Cdks, and less selective for non-Cdk kinases. It showed potent antiproliferative effects against various human cancer cell lines, with an IC(50) ranging from 300 to 800 nmol/L and was further compared for its antiproliferative activity against cancer and normal fibroblast cell lines. P276-00 was found to be highly selective for cancer cells as compared with normal fibroblast cells. To delineate its mechanism of action, the effect of P276-00 on cell cycle proteins was studied in human breast cancer cell line (MCF-7) and human non-small cell lung carcinoma (H-460). A significant down-regulation of cyclin D1 and Cdk4 and a decrease in Cdk4-specific pRb Ser(780) phosphorylation was observed. P276-00 produced potent inhibition of Cdk4-D1 activity that was found to be competitive with ATP and not with retinoblastoma protein. The compound also induced apoptosis in human promyelocytic leukemia (HL-60) cells, as evidenced by the induction of caspase-3 and DNA ladder studies. These data suggest that P276-00 has the potential to be developed as an anti-Cdk chemotherapeutic agent.
Insights
A novel flavone compound, P276-00, effectively inhibits Cyclin-dependent kinase 4-D1 (Cdk4-D1), demonstrating potent anticancer activity. This Cdk4-D1 inhibitor shows high selectivity for cancer cells and induces apoptosis, suggesting its potential as a new chemotherapeutic agent.
Area of Science:
- Oncology
- Medicinal Chemistry
- Molecular Biology
Background:
- Cyclin-dependent kinases (Cdks) are key regulators of the cell cycle and are attractive targets for anticancer drug development.
- Several Cdk inhibitors are in clinical trials, highlighting the therapeutic potential of targeting these pathways.
Purpose of the Study:
- To synthesize and evaluate a novel series of flavone derivatives as inhibitors of Cdk4-D1.
- To characterize the preclinical anticancer properties of the lead compound, P276-00.
Main Methods:
- Synthesis of novel flavone derivatives.
- In vitro enzyme inhibition assays to determine IC50 values against Cdk4-D1 and other kinases.
- Antiproliferative assays against various human cancer cell lines and normal fibroblasts.
- Cell cycle analysis and apoptosis assays (caspase-3, DNA laddering).
Main Results:
- Identified potent Cdk4-D1 inhibitors with IC50 values below 250 nmol/L.
- P276-00 demonstrated high selectivity for Cdk4-D1 over other Cdks and kinases.
- P276-00 exhibited potent antiproliferative effects against cancer cells (IC50 300-800 nmol/L) with selectivity over normal fibroblasts.
- Mechanism of action involves down-regulation of cyclin D1 and Cdk4, decreased pRb phosphorylation, and induction of apoptosis.
Conclusions:
- P276-00 is a potent and selective Cdk4-D1 inhibitor with promising anticancer activity.
- The compound demonstrates a favorable selectivity profile for cancer cells over normal cells.
- P276-00 warrants further development as a potential chemotherapeutic agent targeting Cdk pathways.
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