American Association for Cancer Research
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Supplementary Materials and Methods from Kinome-Wide RNA Interference Screen Reveals a Role for PDK1 in Acquired Resistance to CDK4/6 Inhibition in ER-Positive Breast Cancer

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journal contribution
posted on 2023-03-31, 01:24 authored by Valerie M. Jansen, Neil E. Bhola, Joshua A. Bauer, Luigi Formisano, Kyung-Min Lee, Katherine E. Hutchinson, Agnieszka K. Witkiewicz, Preston D. Moore, Mónica Valéria Estrada, Violeta Sánchez, Paula G. Ericsson, Melinda E. Sanders, Paula R. Pohlmann, Michael J. Pishvaian, David A. Riddle, Teresa C. Dugger, Wenyi Wei, Erik S. Knudsen, Carlos L. Arteaga

Supplementary Materials and Methods and Figure Legends for Supplementary Figures S1-6


Cure Foundation

Breast Cancer Research Foundation





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.