In vitro antitumor properties of a novel cyclin-dependent kinase inhibitor, P276-00.

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.

• Authors: Kalpana S Joshi, Maggie J Rathos, Rajendra D Joshi, Meenakshi Sivakumar, Malcolm Mascarenhas, Shrikant Kamble, Bansi Lal, Somesh Sharma
• Journal: Molecular cancer therapeutics (Mol Cancer Ther) Vol. 6 Issue 3 Pg. 918-25 (Mar 2007) ISSN: 1535-7163 [Print] United States
• PMID: 17363486 (Publication Type: Journal Article)

Chemical References

• Antineoplastic Agents
• Enzyme Inhibitors
• Flavones
• P276-00
• Retinoblastoma Protein
• Cyclin D1
• Cyclin-Dependent Kinase 4
• Cyclin-Dependent Kinases
• Caspase 3

Topics

• Antineoplastic Agents (pharmacology)
• Breast Neoplasms (drug therapy, enzymology)
• Carcinoma, Non-Small-Cell Lung (drug therapy, enzymology)
• Caspase 3 (metabolism)
• Cell Cycle (drug effects)
• Cell Proliferation (drug effects)
• Cells, Cultured (drug effects)
• Cyclin D1 (metabolism)
• Cyclin-Dependent Kinase 4 (metabolism)
• Cyclin-Dependent Kinases (antagonists & inhibitors, metabolism)
• Down-Regulation
• Enzyme Inhibitors (pharmacology)
• Fibroblasts (cytology, drug effects, metabolism)
• Flavones (chemistry, pharmacology)
• HL-60 Cells (drug effects)
• Humans
• In Vitro Techniques
• Lung Neoplasms (drug therapy, enzymology)
• Molecular Structure
• Phosphorylation (drug effects)
• Retinoblastoma Protein (metabolism)