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|Ref Type||Journal Article|
|Authors||Herrera-Abreu MT, Palafox M, Asghar U, Rivas MA, Cutts RJ, Garcia-Murillas I, Pearson A, Guzman M, Rodriguez O, Grueso J, Bellet M, Cortés J, Elliott R, Pancholi S, Baselga J, Dowsett M, Martin LA, Turner NC, Serra V|
|Title||Early Adaptation and Acquired Resistance to CDK4/6 Inhibition in Estrogen Receptor-Positive Breast Cancer.|
|Date||2016 04 15|
|Abstract Text||Small-molecule inhibitors of the CDK4/6 cell-cycle kinases have shown clinical efficacy in estrogen receptor (ER)-positive metastatic breast cancer, although their cytostatic effects are limited by primary and acquired resistance. Here we report that ER-positive breast cancer cells can adapt quickly to CDK4/6 inhibition and evade cytostasis, in part, via noncanonical cyclin D1-CDK2-mediated S-phase entry. This adaptation was prevented by cotreatment with hormone therapies or PI3K inhibitors, which reduced the levels of cyclin D1 (CCND1) and other G1-S cyclins, abolished pRb phosphorylation, and inhibited activation of S-phase transcriptional programs. Combined targeting of both CDK4/6 and PI3K triggered cancer cell apoptosis in vitro and in patient-derived tumor xenograft (PDX) models, resulting in tumor regression and improved disease control. Furthermore, a triple combination of endocrine therapy, CDK4/6, and PI3K inhibition was more effective than paired combinations, provoking rapid tumor regressions in a PDX model. Mechanistic investigations showed that acquired resistance to CDK4/6 inhibition resulted from bypass of cyclin D1-CDK4/6 dependency through selection of CCNE1 amplification or RB1 loss. Notably, although PI3K inhibitors could prevent resistance to CDK4/6 inhibitors, they failed to resensitize cells once resistance had been acquired. However, we found that cells acquiring resistance to CDK4/6 inhibitors due to CCNE1 amplification could be resensitized by targeting CDK2. Overall, our results illustrate convergent mechanisms of early adaptation and acquired resistance to CDK4/6 inhibitors that enable alternate means of S-phase entry, highlighting strategies to prevent the acquisition of therapeutic resistance to these agents. Cancer Res; 76(8); 2301-13. ©2016 AACR.|
|Molecular Profile||Treatment Approach|
|Gene Name||Source||Synonyms||Protein Domains||Gene Description||Gene Role|
|Therapy Name||Drugs||Efficacy Evidence||Clinical Trials|
|Drug Name||Trade Name||Synonyms||Drug Classes||Drug Description|
|Gene||Variant||Impact||Protein Effect||Variant Description||Associated with drug Resistance|
|Molecular Profile||Indication/Tumor Type||Response Type||Therapy Name||Approval Status||Evidence Type||Efficacy Evidence||References|
|RB1 loss||estrogen-receptor positive breast cancer||resistant||Palbociclib||Preclinical - Cell culture||Actionable||In a preclinical study, RB1 loss was associated with acquired resistance to Ibrance (palbociclib) in an estrogen-receptor positive breast cancer cell line in culture (PMID: 27020857).||27020857|
|PIK3CA mutant||triple-receptor negative breast cancer||sensitive||Palbociclib + Pictilisib||Preclinical||Actionable||In a preclinical study, Ibrance (palbociclib) and Pictilisib (GDC-0941) worked synergistically to inhibit the survival of triple-receptor negative breast cancer cell lines harboring PIK3CA mutations in culture (PMID: 27020857).||27020857|
|PIK3CA wild-type||triple-receptor negative breast cancer||no benefit||Palbociclib + Pictilisib||Preclinical||Actionable||In a preclinical study, the combination of Ibrance (palbociclib) and Pictilisib (GDC-0941) did not improve growth inhibition compared to single drug treatment in PIK3CA wild-type, triple-receptor negative breast cancer cell lines in culture (PMID: 27020857).||27020857|
|ERBB2 pos PIK3CA act mut||Her2-receptor positive breast cancer||sensitive||Palbociclib + Pictilisib||Preclinical||Actionable||In a preclinical study, Ibrance (palbociclib) and Pictilisib (GDC-0941) worked synergistically to inhibit survival of ERBB2 (HER2)-positive breast cancer cell lines harboring PIK3CA mutations in culture (PMID: 27020857).||27020857|