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EMBO J. 2018 May 15;37(10). pii: e98359. doi: 10.15252/embj.201798359. Epub 2018 Apr 18.

Thermal proteome profiling of breast cancer cells reveals proteasomal activation by CDK4/6 inhibitor palbociclib.

Author information

1
Division of Cell and Developmental Biology, University of Dundee, Dundee, UK.
2
MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Dundee, UK.
3
MRC Laboratory for Molecular Cell Biology, University College London, London, UK.
4
Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA.
5
Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, UK.
6
Division of Computational Biology, University of Dundee, Dundee, UK.
7
Division of Hematology-Oncology, Vanderbilt University Medical Center, Nashville, TN, USA.
8
MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Dundee, UK matthias.trost@ncl.ac.uk mikael.bjorklund.lab@gmail.com.
9
Division of Cell and Developmental Biology, University of Dundee, Dundee, UK matthias.trost@ncl.ac.uk mikael.bjorklund.lab@gmail.com.

Abstract

Palbociclib is a CDK4/6 inhibitor approved for metastatic estrogen receptor-positive breast cancer. In addition to G1 cell cycle arrest, palbociclib treatment results in cell senescence, a phenotype that is not readily explained by CDK4/6 inhibition. In order to identify a molecular mechanism responsible for palbociclib-induced senescence, we performed thermal proteome profiling of MCF7 breast cancer cells. In addition to affecting known CDK4/6 targets, palbociclib induces a thermal stabilization of the 20S proteasome, despite not directly binding to it. We further show that palbociclib treatment increases proteasome activity independently of the ubiquitin pathway. This leads to cellular senescence, which can be counteracted by proteasome inhibitors. Palbociclib-induced proteasome activation and senescence is mediated by reduced proteasomal association of ECM29. Loss of ECM29 activates the proteasome, blocks cell proliferation, and induces a senescence-like phenotype. Finally, we find that ECM29 mRNA levels are predictive of relapse-free survival in breast cancer patients treated with endocrine therapy. In conclusion, thermal proteome profiling identifies the proteasome and ECM29 protein as mediators of palbociclib activity in breast cancer cells.

KEYWORDS:

CDK4; breast cancer; palbociclib; proteasome; thermal proteome profiling

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