Prolonged early G(1) arrest by selective CDK4/CDK6 inhibition sensitizes myeloma cells to cytotoxic killing through cell cycle-coupled loss of IRF4

作者：Huang Xiangao; Di Liberto Maurizio; Jayabalan David; Liang Jun; Ely Scott; Bretz Jamieson; Shaffer Arthur L III; Louie Tracey; Chen Isan; Randolph Sophia; Hahn William C; Staudt Louis M; Niesvizky Ruben; Moore Malcolm A S; Chen Kiang Selina^*

来源：Blood, 2012, 120(5): 1095-1106.

DOI：10.1182/blood-2012-03-415984

Dysregulation of cyclin-dependent kinase 4 (CDK4) and CDK6 by gain of function or loss of inhibition is common in human cancer, including multiple myeloma, but success in targeting CDK with broad-spectrum inhibitors has been modest. By selective and reversible inhibition of CDK4/CDK6, we have developed a strategy to both inhibit proliferation and enhance cytotoxic killing of cancer cells. We show that induction of prolonged early-G(1) arrest (pG1) by CDK4/CDK6 inhibition halts gene expression in early-G1 and prevents expression of genes programmed for other cell-cycle phases. Removal of the early-G(1) block leads to S-phase synchronization (pG1-S) but fails to completely restore scheduled gene expression. Consequently, the IRF4 protein required to protect myeloma cells from apoptosis is markedly reduced in pG1 and further in pG1-S in response to cytotoxic agents, such as the proteasome inhibitor bortezomib. The coordinated loss of IRF4 and gain of Bim sensitize myeloma tumor cells to bortezomib-induced apoptosis in pG1 in the absence of Noxa and more profoundly in pG1-S in cooperation with Noxa in vitro. Induction of pG1 and pG1-S by reversible CDK4/CDK6 inhibition further augments tumor-specific bortezomib killing in myeloma xenografts. Reversible inhibition of CDK4/CDK6 in sequential combination therapy thus represents a novel mechanism-based cancer therapy. (Blood. 2012;120(5):1095-1106)

• 出版日期2012-8-2