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.
Valerie M Jansen  1 ,  Neil E Bhola  1 ,  Joshua A Bauer  2  3 ,  Luigi Formisano  1 ,  Kyung-Min Lee  1 ,  Katherine E Hutchinson  1 ,  Agnieszka K Witkiewicz  4 ,  Preston D Moore  1 ,  Mónica Valéria Estrada  5 ,  Violeta Sánchez  5 ,  Paula G Ericsson  5 ,  Melinda E Sanders  6 ,  Paula R Pohlmann  7 ,  Michael J Pishvaian  7 ,  David A Riddle  1 ,  Teresa C Dugger  1 ,  Wenyi Wei  8 ,  Erik S Knudsen  9 ,  Carlos L Arteaga  10  5  11
Affiliations
  • 1. Department of Medicine, Vanderbilt-Ingram Cancer Center, Vanderbilt University Medical Center, Nashville, Tennessee.
  • 2. Department of Biochemistry, Vanderbilt-Ingram Cancer Center, Vanderbilt University Medical Center, Nashville, Tennessee.
  • 3. Vanderbilt Institute of Chemical Biology, Vanderbilt-Ingram Cancer Center, Vanderbilt University Medical Center, Nashville, Tennessee.
  • 4. Department of Pathology, University of Arizona, Tucson, Arizona.
  • 5. Breast Cancer Program, Vanderbilt-Ingram Cancer Center, Vanderbilt University Medical Center, Nashville, Tennessee.
  • 6. Department of Pathology, Microbiology and Immunology, Vanderbilt-Ingram Cancer Center, Vanderbilt University Medical Center, Nashville, Tennessee.
  • 7. Department of Medicine, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC.
  • 8. Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
  • 9. Department of Medicine, University of Arizona, Tucson, Arizona.
  • 10. Department of Medicine, Vanderbilt-Ingram Cancer Center, Vanderbilt University Medical Center, Nashville, Tennessee. [email protected].
  • 11. Department of Cancer Biology, Vanderbilt-Ingram Cancer Center, Vanderbilt University Medical Center, Nashville, Tennessee.
PMID: 28249908 DOI: 10.1158/0008-5472.CAN-16-2653
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.

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