The potent Cdc7-Dbf4 (DDK) kinase inhibitor XL413 has limited activity in many cancer cell lines and discovery of potential new DDK inhibitor scaffolds

• Published in: PloS one Vol. 9; no. 11; p. e113300
• Main Authors: Sasi, Nanda Kumar, Tiwari, Kanchan, Soon, Fen-Fen, Bonte, Dorine, Wang, Tong, Melcher, Karsten, Xu, H Eric, Weinreich, Michael
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 20.11.2014; Public Library of Science (PLoS)
• Subjects: Apoptosis; Apoptosis - drug effects; Bioavailability; Biological activity; Biological Availability; Biology and Life Sciences; Biotechnology; Breast cancer; Cancer; Cell cycle; Cell Cycle Proteins - antagonists & inhibitors; Cell division; Cell Line, Tumor - drug effects; Cell Proliferation - drug effects; Chemotherapy; CHK1 protein; Cross-reactivity; Cyclin-dependent kinases; Deoxyribonucleic acid; DNA; DNA biosynthesis; DNA helicase; DNA repair; DNA replication; Drug Repositioning; Enzyme inhibitors; Gene Expression Regulation, Neoplastic - drug effects; Genomes; HCT116 Cells - drug effects; Health aspects; HeLa Cells - drug effects; Humans; Inhibition; Inhibitors; Kinases; Laboratories; Pharmaceutical industry; Phase transitions; Piperidones - pharmacology; Protein Kinase Inhibitors - pharmacology; Protein-Serine-Threonine Kinases - antagonists & inhibitors; Proteins; Pyrimidinones - pharmacokinetics; Pyrimidinones - pharmacology; Pyrroles - pharmacology; Reagents; RNA polymerase; Scaffolds; Thermal stability; Tumor cell lines; Tumor cells; Tumorigenesis; Yeast
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0113300

Cdc7-Dbf4 kinase or DDK (Dbf4-dependent kinase) is required to initiate DNA replication by phosphorylating and activating the replicative Mcm2-7 DNA helicase. DDK is overexpressed in many tumor cells and is an emerging chemotherapeutic target since DDK inhibition causes apoptosis of diverse cancer cell types but not of normal cells. PHA-767491 and XL413 are among a number of potent DDK inhibitors with low nanomolar IC50 values against the purified kinase. Although XL413 is highly selective for DDK, its activity has not been extensively characterized on cell lines. We measured anti-proliferative and apoptotic effects of XL413 on a panel of tumor cell lines compared to PHA-767491, whose activity is well characterized. Both compounds were effective biochemical DDK inhibitors but surprisingly, their activities in cell lines were highly divergent. Unlike PHA-767491, XL413 had significant anti-proliferative activity against only one of the ten cell lines tested. Since XL413 did not effectively inhibit DDK in multiple cell lines, this compound likely has limited bioavailability. To identify potential leads for additional DDK inhibitors, we also tested the cross-reactivity of ∼400 known kinase inhibitors against DDK using a DDK thermal stability shift assay (TSA). We identified 11 compounds that significantly stabilized DDK. Several inhibited DDK with comparable potency to PHA-767491, including Chk1 and PKR kinase inhibitors, but had divergent chemical scaffolds from known DDK inhibitors. Taken together, these data show that several well-known kinase inhibitors cross-react with DDK and also highlight the opportunity to design additional specific, biologically active DDK inhibitors for use as chemotherapeutic agents.