title: Cyclin-dependent kinase inhibitors sensitize tumor cells to nutlin-induced apoptosis: a potent drug combination.
abstract: Current chemotherapy focuses on the use of genotoxic drugs that may induce general DNA damage in cancer cells but also high levels of toxicity in normal tissues. Nongenotoxic activation of p53 by targeting specific molecular pathways therefore provides an attractive therapeutic strategy in cancers with wild-type p53. Here, we explored the antitumor potential of cyclin-dependent kinase (CDK) inhibitors in combination with a small molecule inhibitor of p53-murine double minute 2 (MDM2) interaction. We show that low doses of CDK inhibitors roscovitine and DRB synergize with the MDM2 antagonist nutlin-3a in the induction of p53 activity and promote p53-dependent apoptosis in a dose- and time-dependent manner. Statistical measurement of the combination effects shows that the drug combination is additive on the reduction of cell viability and synergistic on inducing apoptosis, a critical end point of cytotoxic drugs. The degree of apoptosis observed 24 to 48 h after drug treatment correlated with the accumulation of p53 protein and concomitant induction of proapoptotic proteins Puma and PIG3. The antiproliferative and cytotoxic effects of this drug combination are validated in a range of tumor-derived cells including melanoma, colon carcinoma, breast adenocarcinoma, and hepatocarcinoma cells. Furthermore, this drug combination does not induce phosphorylation of Ser(15) on p53 and does not induce genotoxic stress in the cell. Given that many cytotoxic drugs rely on their ability to induce apoptosis via DNA damage-mediated activation of p53, the data presented here may provide a new therapeutic approach for the use of CDK inhibitors and MDM2 antagonists in combinatorial drug therapy.
authors.affiliation: Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673. cfcheok@imcb.a-star.edu.sg
authors.forename: Chit Fang
authors.initials: CF
authors.lastname: Cheok
authors.forename: Anwesha
authors.initials: A
authors.lastname: Dey
authors.forename: David P
authors.initials: DP
authors.lastname: Lane
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D004357:Drug Synergism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D009369:Neoplasms / Q000201:enzymology* / Q000473:pathology; D010879:Piperazines / Q000494:pharmacology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011687:Purines / Q000494:pharmacology*; D000077546:Roscovitine; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C438378:BBC3 protein, human; D007093:Imidazoles; D047908:Intracellular Signaling Peptides and Proteins; D010879:Piperazines; D011518:Proto-Oncogene Proteins; D011687:Purines; C411296:TP53I3 protein, human; D016159:Tumor Suppressor Protein p53; D000077546:Roscovitine; C482205:nutlin 3; D051736:Proto-Oncogene Proteins c-mdm2; D018844:Cyclin-Dependent Kinases