CDK4/6 Inhibitor PD 0332991 Sensitizes Acute Myeloid Leukemia to Cytarabine-Mediated Cytotoxicity

• Published in: Cancer research (Chicago, Ill.) Vol. 75; no. 9; pp. 1838 - 1845
• Main Authors: Yang, Chenyi, Boyson, Cynthia A, Di Liberto, Maurizio, Huang, Xiangao, Hannah, Jeffrey, Dorn, David C, Moore, Malcolm A S, Chen-Kiang, Selina, Zhou, Pengbo
• Format: Journal Article
• Language: English
• Published: United States 01-05-2015
• Subjects: Animals; Antineoplastic Agents - pharmacology; Apoptosis - drug effects; Apoptosis - genetics; Cell Line; Cyclin-Dependent Kinase 4 - antagonists & inhibitors; Cyclin-Dependent Kinase 4 - genetics; Cyclin-Dependent Kinase 4 - metabolism; Cyclin-Dependent Kinase 6 - antagonists & inhibitors; Cyclin-Dependent Kinase 6 - genetics; Cyclin-Dependent Kinase 6 - metabolism; Cytarabine - pharmacology; DNA Damage - drug effects; DNA Replication - drug effects; HEK293 Cells; HL-60 Cells; Humans; Leukemia, Myeloid, Acute - drug therapy; Leukemia, Myeloid, Acute - genetics; Leukemia, Myeloid, Acute - metabolism; Mice, Inbred NOD; Mice, SCID; Phosphorylation - drug effects; Piperazines - pharmacology; Protein Kinase Inhibitors - pharmacology; Proto-Oncogene Proteins c-pim-1 - genetics; Proto-Oncogene Proteins c-pim-1 - metabolism; Pyridines - pharmacology; S Phase - drug effects; S Phase - genetics; Transcription, Genetic - drug effects; Tumor Cells, Cultured; Xenograft Model Antitumor Assays
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/0008-5472.CAN-14-2486

Cyclin-dependent kinase (CDK)4 and CDK6 are frequently overexpressed or hyperactivated in human cancers. Targeting CDK4/CDK6 in combination with cytotoxic killing therefore represents a rational approach to cancer therapy. By selective inhibition of CDK4/CDK6 with PD 0332991, which leads to early G1 arrest and synchronous S-phase entry upon release of the G1 block, we have developed a novel strategy to prime acute myeloid leukemia (AML) cells for cytotoxic killing by cytarabine (Ara-C). This sensitization is achieved in part through enrichment of S-phase cells, which maximizes the AML populations for Ara-C incorporation into replicating DNA to elicit DNA damage. Moreover, PD 0332991 triggered apoptosis of AML cells through inhibition of the homeobox (HOX)A9 oncogene expression, reducing the transcription of its target PIM1. Reduced PIM1 synthesis attenuates PIM1-mediated phosphorylation of the proapoptotic BAD and activates BAD-dependent apoptosis. In vivo, timely inhibition of CDK4/CDK6 by PD 0332991 and release profoundly suppresses tumor growth in response to reduced doses of Ara-C in a xenograft AML model. Collectively, these data suggest selective and reversible inhibition of CDK4/CDK6 as an effective means to enhance Ara-C killing of AML cells at reduced doses, which has implications for the treatment of elderly AML patients who are unable to tolerate high-dose Ara-C therapy.