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Cancer Cell. 2014 Jul 14;26(1):136-49. doi: 10.1016/j.ccr.2014.05.020. Epub 2014 Jul 4.

CDK 4/6 inhibitors sensitize PIK3CA mutant breast cancer to PI3K inhibitors.

Author information

1
Massachusetts General Hospital Cancer Center, Boston, MA 02120, USA; Department of Medicine, Harvard Medical School, Boston, MA 02115, USA.
2
Massachusetts General Hospital Cancer Center, Boston, MA 02120, USA; Department of Pathology, Harvard Medical School, Boston, MA 02115, USA.
3
Department of Pathology, Harvard Medical School, Boston, MA 02115, USA.
4
Novartis Institutes for BioMedical Research, Cambridge, MA 02139, USA.
5
Novartis Institutes for BioMedical Research, Cambridge, MA 02139, USA. Electronic address: alan.huang@novartis.com.
6
Massachusetts General Hospital Cancer Center, Boston, MA 02120, USA; Department of Medicine, Harvard Medical School, Boston, MA 02115, USA. Electronic address: jengelman@partners.org.

Abstract

Activation of the phosphoinositide 3-kinase (PI3K) pathway occurs frequently in breast cancer. However, clinical results of single-agent PI3K inhibitors have been modest to date. A combinatorial drug screen on multiple PIK3CA mutant cancers with decreased sensitivity to PI3K inhibitors revealed that combined CDK 4/6-PI3K inhibition synergistically reduces cell viability. Laboratory studies revealed that sensitive cancers suppress RB phosphorylation upon treatment with single-agent PI3K inhibitors but cancers with reduced sensitivity fail to do so. Similarly, patients' tumors that responded to the PI3K inhibitor BYL719 demonstrated suppression of pRB, while nonresponding tumors showed sustained or increased levels of pRB. Importantly, the combination of PI3K and CDK 4/6 inhibitors overcomes intrinsic and adaptive resistance leading to tumor regressions in PIK3CA mutant xenografts.

TRIAL REGISTRATION:

ClinicalTrials.gov NCT01219699.

PMID:
25002028
PMCID:
PMC4155598
DOI:
10.1016/j.ccr.2014.05.020
[Indexed for MEDLINE]
Free PMC Article

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