Kinome-Wide RNA Interference Screen Reveals a Role for PDK1 in Acquired Resistance to CDK4/6 Inhibition in ER-Positive Breast Cancer

Cancer Res. 2017 May 1;77(9):2488-2499. doi: 10.1158/0008-5472.CAN-16-2653. Epub 2017 Mar 1.

Abstract

Acquired resistance to cyclin-dependent kinases 4 and 6 (CDK4/6) small-molecule inhibitors in breast cancer arises through mechanisms that are yet uncharacterized. In this study, we used a kinome-wide siRNA screen to identify kinases that, when downregulated, yield sensitivity to the CDK4/6 inhibitor ribociclib. In this manner, we identified 3-phosphoinositide-dependent protein kinase 1 (PDK1) as a key modifier of ribociclib sensitivity in estrogen receptor-positive MCF-7 breast cancer cells. Pharmacologic inhibition of PDK1 with GSK2334470 in combination with ribociclib or palbociclib, another CDK4/6 inhibitor, synergistically inhibited proliferation and increased apoptosis in a panel of ER-positive breast cancer cell lines. Ribociclib-resistant breast cancer cells selected by chronic drug exposure displayed a relative increase in the levels of PDK1 and activation of the AKT pathway. Analysis of these cells revealed that CDK4/6 inhibition failed to induce cell-cycle arrest or senescence. Mechanistic investigations showed that resistant cells coordinately upregulated expression of cyclins A, E, and D1, activated phospho-CDK2, and phospho-S477/T479 AKT. Treatment with GSK2334470 or the CDK2 inhibitor dinaciclib was sufficient to reverse these events and to restore the sensitivity of ribociclib-resistant cells to CDK4/6 inhibitors. Ribociclib, in combination with GSK2334470 or the PI3Kα inhibitor alpelisib, decreased xenograft tumor growth more potently than each drug alone. Taken together, our results highlight a role for the PI3K-PDK1 signaling pathway in mediating acquired resistance to CDK4/6 inhibitors. Cancer Res; 77(9); 2488-99. ©2017 AACR.

MeSH terms

  • Aminopyridines / administration & dosage*
  • Animals
  • Apoptosis / drug effects
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / genetics
  • Breast Neoplasms / pathology
  • Cell Cycle Checkpoints / drug effects
  • Cell Proliferation / drug effects
  • Cyclin-Dependent Kinase 4 / antagonists & inhibitors
  • Cyclin-Dependent Kinase 4 / genetics
  • Cyclin-Dependent Kinase 6 / antagonists & inhibitors
  • Cyclin-Dependent Kinase 6 / genetics
  • Drug Resistance, Neoplasm / drug effects
  • Drug Resistance, Neoplasm / genetics*
  • Drug Synergism
  • Female
  • Humans
  • Indazoles / administration & dosage
  • MCF-7 Cells
  • Mice
  • Phosphatidylinositol 3-Kinases / genetics
  • Piperazines / administration & dosage
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors
  • Protein-Serine-Threonine Kinases / genetics*
  • Purines / administration & dosage*
  • Pyridines / administration & dosage
  • Pyrimidines / administration & dosage
  • Pyruvate Dehydrogenase (Acetyl-Transferring) Kinase
  • Receptors, Estrogen / antagonists & inhibitors
  • Receptors, Estrogen / genetics
  • Xenograft Model Antitumor Assays

Substances

  • Aminopyridines
  • GSK 2334470
  • Indazoles
  • PDK1 protein, human
  • Pdk1 protein, mouse
  • Piperazines
  • Purines
  • Pyridines
  • Pyrimidines
  • Pyruvate Dehydrogenase (Acetyl-Transferring) Kinase
  • Receptors, Estrogen
  • Protein-Serine-Threonine Kinases
  • CDK4 protein, human
  • Cyclin-Dependent Kinase 4
  • Cyclin-Dependent Kinase 6
  • palbociclib
  • ribociclib