Dual Targeting of CDK4/6 and BCL2 Pathways Augments Tumor Response in Estrogen Receptor–Positive Breast Cancer James R
Published OnlineFirst April 3, 2020; DOI: 10.1158/1078-0432.CCR-19-1872 CLINICAL CANCER RESEARCH | TRANSLATIONAL CANCER MECHANISMS AND THERAPY Dual Targeting of CDK4/6 and BCL2 Pathways Augments Tumor Response in Estrogen Receptor–Positive Breast Cancer James R. Whittle1,2,3, Francois¸ Vaillant1,3, Elliot Surgenor1, Antonia N. Policheni3,4,Goknur€ Giner3,5, Bianca D. Capaldo1,3, Huei-Rong Chen1,HeK.Liu1, Johanna F. Dekkers1,6,7, Norman Sachs6, Hans Clevers6,7, Andrew Fellowes8, Thomas Green8, Huiling Xu8, Stephen B. Fox8,9, Marco J. Herold3,10, Gordon K. Smyth5,11, Daniel H.D. Gray3,4, Jane E. Visvader1,3, and Geoffrey J. Lindeman1,2,12 ABSTRACT ◥ Purpose: Although cyclin-dependent kinase 4 and 6 (CDK4/6) Results: Triple therapy was well tolerated and produced a super- inhibitors significantly extend tumor response in patients with ior and more durable tumor response compared with single or þ metastatic estrogen receptor–positive (ER ) breast cancer, relapse doublet therapy. This was associated with marked apoptosis, includ- is almost inevitable. This may, in part, reflect the failure of CDK4/6 ing of senescent cells, indicative of senolysis. Unexpectedly, ABT- – inhibitors to induce apoptotic cell death. We therefore evaluated 199 resulted in Rb dephosphorylation and reduced G1 S cyclins, combination therapy with ABT-199 (venetoclax), a potent and most notably at high doses, thereby intensifying the fulvestrant/ selective BCL2 inhibitor. palbociclib–induced cell-cycle arrest. Interestingly, a CRISPR/Cas9 Experimental Design: BCL2 family member expression was screen suggested that ABT-199 could mitigate loss of Rb (and assessed following treatment with endocrine therapy and the potentially other mechanisms of acquired resistance) to palbociclib.
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