title: 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.affiliation: Department of Pharmacology, Nicholas Piramal Research Center, Nicholas Piramal India Limited, 1-Nirlon Complex, Goregaon (E), Mumbai 400 063, India. kjoshi@nicholaspiramal.co.in
authors.forename: Kalpana S
authors.initials: KS
authors.lastname: Joshi
authors.forename: Maggie J
authors.initials: MJ
authors.lastname: Rathos
authors.forename: Rajendra D
authors.initials: RD
authors.lastname: Joshi
authors.forename: Meenakshi
authors.initials: M
authors.lastname: Sivakumar
authors.forename: Malcolm
authors.initials: M
authors.lastname: Mascarenhas
authors.forename: Shrikant
authors.initials: S
authors.lastname: Kamble
authors.forename: Bansi
authors.initials: B
authors.lastname: Lal
authors.forename: Somesh
authors.initials: S
authors.lastname: Sharma
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000201:enzymology; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000201:enzymology; D053148:Caspase 3 / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured / Q000187:drug effects; D019938:Cyclin D1 / Q000378:metabolism; D051358:Cyclin-Dependent Kinase 4 / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D047309:Flavones / Q000737:chemistry / Q000494:pharmacology*; D018922:HL-60 Cells / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000201:enzymology; D015394:Molecular Structure; D010766:Phosphorylation / Q000187:drug effects; D016160:Retinoblastoma Protein / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D047309:Flavones; C520467:P276-00; D016160:Retinoblastoma Protein; D019938:Cyclin D1; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases; D053148:Caspase 3