PLX069512

GSE146788: Functional determinants of sensitivity to CDK4/6 inhibition or cell-cycle plasticity

• Organsim human
• Type RNASEQ
• Target gene
• Project ARCHS4

Intrinsic or acquired resistance to clinically approved CDK4/6 inhibitors have emerged as a major obstacle that hinders their utility beyond ER+ breast cancer. Palbociclib-sensitive ER+ breast cancer models and pancreatic ductal adenocarcinoma (PDAC) models were employed to identify functional determinants of response.; In all models tested the activation of RB and inhibition of CDK2 activity emerged as determinants of sensitivity. While depleting CDK4 and 6 was sufficient to limit proliferation in specific resistance setting, RB loss renders cells completely CDK4/6 independent. The main down-stream target in this context is the activation status of CDK2 which is suppressed with CDK4/6 inhibition in an RB-dependent fashion.The P27KIP1 protein levels are associated with plasticity/rigidity of the cell cycle and correlates with sensitivity to CDK4/6 inhibiion. Exogenous overexpression and pharmacological induction of P27KIP1 by targeting the MEK/ERK pathway enhances the cytostatic effect of palbociclib.; Similar to cell-culture data, in vivo experiments revealed that combination treatment of palbociclib and trametinib in mice bearing PDAC PDXs elicited a robust anti-proliferative effect with a corresponding increase in p27 expression. Mice bearing MCF7 xenografts displayed a durable response in the presence of palbociclib; however, over the course of treatment few cells begin to evade the negative cell-cycle regulation.; Based on multispectral staining, the MCF7 tumor cells that underwent RB inactivation in the presence of palbociclib harbored low p27 expression. Finally, we demonstrate that the cell-cycle plasticity that enables tumor models to evade the palbociclib mediated RB activation could be potently targeted using a clinically applicable CDK2 inhibitor. SOURCE: Ram,Mohan,Nambiar (ram.nambiar@RoswellPark.org) - Roswell Park