The Development of a Selective Cyclin-Dependent Kinase Inhibitor That Shows Antitumor Activity

Abstract

Normal progression through the cell cycle requires the sequential action of cyclin-dependent kinases CDK1, CDK2, CDK4, and CDK6. Direct or indirect deregulation of CDK activity is a feature of almost all cancers and has led to the development of CDK inhibitors as anticancer agents. The CDKactivating kinase (CAK) plays a critical role in regulating cell cycle by mediating the activating phosphorylation of CDK1, CDK2, CDK4, and CDK6. As such, CDK7, which also regulates transcription as part of the TFIIH basal transcription factor, is an attractive target for the development of anticancer drugs. Computer modeling of the CDK7 structure was used to design potential potent CDK7 inhibitors. Here, we show that a pyrazolo[1,5-a ]pyrimidine-derived compound, BS-181, inhibited CAK activity with an IC 50 of 21 nmol/L. Testing of other CDKs as well as another 69 kinases showed that BS-181 only inhibited CDK2 at concentrations lower than 1 Mmol/L, with CDK2 being inhibited 35-fold less potently (IC 50 880 nmol/L) than CDK7. In MCF-7 cells, BS-181 inhibited the phosphorylation of CDK7 substrates, promoted cell cycle arrest and apoptosis to inhibit the growth of cancer cell lines, and showed antitumor effects in vivo. The drug was stable in vivo with a plasma elimination half-life in mice of 405 minutes after i.p. administration of 10 mg/kg. The same dose of drug inhibited the growth of MCF-7 human xenografts in nude mice. BS-181 therefore provides the first example of a potent and selective CDK7 inhibitor with potential as an anticancer agent. [Cancer Res 2009;69(15):6208-15]

The CDK Network: Linking Cycles of Cell Division and Gene Expression

“…This rethinking of Cdk7's place in the CDK network should prompt a reevaluation of its potential as an anticancer drug target. 15,41,42 CDK Activation during the Transcription Cycle…”

Why minimal is not optimal: Driving the mammalian cell cycle—and drug discovery—with a physiologic CDK control network

“…Any selectivity that does occur is usually dictated by CDK-drug interactions outside the ATP-binding site, and computer modeling based on that principle has aided in the development of compounds that are more specific for a selected CDK. 45,46 In one such study, the more specific inhibitor was less cytotoxic than the less specific one on which it was based, even though the IC 50 for the primary target, Cdk9, was the same for both compounds in vitro. 45 Therefore, developing specific CDK inhibitors and identifying…”

Transient over-expression of estrogen receptor-α in breast cancer cells promotes cell survival and estrogen-independent growth

“…Cells were seeded in six-well plates (10 5 /well) in DMEM containing 10% FCS and allowed to adhere for 48 h, followed by the addition of 1nM-100 M etoposide (Sigma-Aldrich) or DMSO and incubation for 48 h. Cells were harvested, cell cycle Annexin V/propidium iodide staining and analysis was carried out as previously described [16].…”

“…All of the markers used are highly polymorphic with multiple alleles. Assuming a conservative figure of 0.5 for the frequency of each allele at the ten loci examined, the probability that the cell lines are not derived from MCF-7 is 0.5 16 (p<0.0001) (Supplementary Table 1). …”