Hbo1 is a cyclin E/CDK2 substrate that enriches breast cancer stem-like cells

Cancer Res. 2013 Sep 1;73(17):5556-68. doi: 10.1158/0008-5472.CAN-13-0013. Epub 2013 Aug 16.

Abstract

Expression of cyclin E proteolytic cleavage products, low-molecular weight cyclin E (LMW-E), is associated with poor clinical outcome in patients with breast cancer and it enhances tumorigenecity in mouse models. Here we report that LMW-E expression in human mammary epithelial cells induces an epithelial-to-mesenchymal transition phenotype, increases the CD44(hi)/CD24(lo) population, enhances mammosphere formation, and upregulates aldehyde dehydrogenase expression and activity. We also report that breast tumors expressing LMW-E have a higher proportion of CD44(hi)/CD24(lo) tumor cells as compared with tumors expressing only full-length cyclin E. In order to explore how LMW-E enriches cancer stem cells in breast tumors, we conducted a protein microarray analysis that identified the histone acetyltransferase (HAT) Hbo1 as a novel cyclin E/CDK2 substrate. The LMW-E/CDK2 complex phosphorylated Hbo1 at T88 without affecting its HAT activity. When coexpressed with LMW-E/CDK2, wild-type Hbo1 promoted enrichment of cancer stem-like cells (CSC), whereas the T88 Hbo1 mutant reversed the CSC phenotype. Finally, doxorubicin and salinomycin (a CSC-selective cytotoxic agent) synergized to kill cells expressing LMW-E, but not full-length cyclin E. Collectively, our results suggest that the heightened oncogenecity of LMW-E relates to its ability to promote CSC properties, supporting the design of therapeutic strategies to target this unique function.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Antibiotics, Antineoplastic / pharmacology
  • Apoptosis / drug effects
  • Blotting, Western
  • Breast Neoplasms / drug therapy
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / pathology*
  • CD24 Antigen / genetics
  • CD24 Antigen / metabolism
  • Cell Proliferation / drug effects
  • Cyclin E / genetics
  • Cyclin E / metabolism*
  • Cyclin-Dependent Kinase 2 / genetics
  • Cyclin-Dependent Kinase 2 / metabolism*
  • Doxorubicin / pharmacology
  • Drug Synergism
  • Drug Therapy, Combination
  • Epithelial-Mesenchymal Transition*
  • Female
  • Flow Cytometry
  • Fluorescent Antibody Technique
  • Histone Acetyltransferases / antagonists & inhibitors
  • Histone Acetyltransferases / genetics
  • Histone Acetyltransferases / metabolism*
  • Humans
  • Hyaluronan Receptors / genetics
  • Hyaluronan Receptors / metabolism
  • Immunoprecipitation
  • Molecular Weight
  • Neoplastic Stem Cells / drug effects
  • Neoplastic Stem Cells / metabolism
  • Neoplastic Stem Cells / pathology*
  • Phosphorylation
  • Protein Array Analysis
  • Pyrans / pharmacology
  • RNA, Messenger / genetics
  • RNA, Small Interfering / genetics
  • Real-Time Polymerase Chain Reaction
  • Reverse Transcriptase Polymerase Chain Reaction
  • Tumor Cells, Cultured

Substances

  • Anti-Bacterial Agents
  • Antibiotics, Antineoplastic
  • CD24 Antigen
  • Cyclin E
  • Hyaluronan Receptors
  • Pyrans
  • RNA, Messenger
  • RNA, Small Interfering
  • salinomycin
  • Doxorubicin
  • Histone Acetyltransferases
  • KAT7 protein, human
  • CDK2 protein, human
  • Cyclin-Dependent Kinase 2