Dual Targeting of CDK4/6 and BCL2 Pathways Augments Tumor Response in Estrogen Receptor-Positive Breast Cancer

James R Whittle, François Vaillant, Elliot Surgenor, Antonia N Policheni, Göknur Giner, Bianca D Capaldo, Huei-Rong Chen, He K Liu, Johanna F Dekkers, Norman Sachs, Hans Clevers, Andrew Fellowes, Thomas Green, Huiling Xu, Stephen B Fox, Marco J Herold, Gordon K Smyth, Daniel H D Gray, Jane E Visvader, Geoffrey J Lindeman

Onderzoeksoutput: Bijdrage aan wetenschappelijk tijdschrift/periodieke uitgaveArtikelWetenschappelijkpeer review


PURPOSE: Although cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors significantly extend tumor response in patients with metastatic estrogen receptor-positive (ER+) breast cancer, relapse is almost inevitable. This may, in part, reflect the failure of CDK4/6 inhibitors to induce apoptotic cell death. We therefore evaluated combination therapy with ABT-199 (venetoclax), a potent and selective BCL2 inhibitor.

EXPERIMENTAL DESIGN: BCL2 family member expression was assessed following treatment with endocrine therapy and the CDK4/6 inhibitor palbociclib. Functional assays were used to determine the impact of adding ABT-199 to fulvestrant and palbociclib in ER+ breast cancer cell lines, patient-derived organoid (PDO), and patient-derived xenograft (PDX) models. A syngeneic ER+ mouse mammary tumor model was used to study the effect of combination therapy on the immune system.

RESULTS: Triple therapy was well tolerated and produced a superior and more durable tumor response compared with single or doublet therapy. This was associated with marked apoptosis, including of senescent cells, indicative of senolysis. Unexpectedly, ABT-199 resulted in Rb dephosphorylation and reduced G1-S cyclins, most notably at high doses, thereby intensifying the fulvestrant/palbociclib-induced cell-cycle arrest. Interestingly, a CRISPR/Cas9 screen suggested that ABT-199 could mitigate loss of Rb (and potentially other mechanisms of acquired resistance) to palbociclib. ABT-199 did not abrogate the favorable immunomodulatory effects of palbociclib in a syngeneic ER+ mammary tumor model and extended tumor response when combined with anti-PD1 therapy.

CONCLUSIONS: This study illustrates the potential for targeting BCL2 in combination with CDK4/6 inhibitors and supports investigation of combination therapy in ER+ breast cancer.

Originele taal-2Engels
Pagina's (van-tot)4120-4134
Aantal pagina's15
TijdschriftClinical Cancer Research
Nummer van het tijdschrift15
StatusGepubliceerd - 01 aug. 2020


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