Identification and regulation of c-Myb target genes in MCF-7 cells

BMC Cancer. 2011 Jan 25;11:30. doi: 10.1186/1471-2407-11-30.

Abstract

Background: The c-Myb transcription factor regulates differentiation and proliferation in hematopoietic cells, stem cells and epithelial cells. Although oncogenic versions of c-Myb were first associated with leukemias, over expression or rearrangement of the c-myb gene is common in several types of solid tumors, including breast cancers. Expression of the c-myb gene in human breast cancer cells is dependent on estrogen stimulation, but little is known about the activities of the c-Myb protein or what genes it regulates in estrogen-stimulated cells.

Methods: We used chromatin immunoprecipitation coupled with whole genome promoter tiling microarrays to identify endogenous c-Myb target genes in human MCF-7 breast cancer cells and characterized the activity of c-Myb at a panel of target genes during different stages of estrogen deprivation and stimulation.

Results: By using different antibodies and different growth conditions, the c-Myb protein was found associated with over 10,000 promoters in MCF-7 cells, including many genes that encode cell cycle regulators or transcription factors and more than 60 genes that encode microRNAs. Several previously identified c-Myb target genes were identified, including CCNB1, MYC and CXCR4 and novel targets such as JUN, KLF4, NANOG and SND1. By studying a panel of these targets to validate the results, we found that estradiol stimulation triggered the association of c-Myb with promoters and that association correlated with increased target gene expression. We studied one target gene, CXCR4, in detail, showing that c-Myb associated with the CXCR4 gene promoter and activated a CXCR4 reporter gene in transfection assays.

Conclusions: Our results show that c-Myb associates with a surprisingly large number of promoters in human cells. The results also suggest that estradiol stimulation leads to large-scale, genome-wide changes in c-Myb activity and subsequent changes in gene expression in human breast cancer cells.

Publication types

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

MeSH terms

  • Blotting, Western
  • Breast Neoplasms / genetics
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / pathology
  • Cell Line, Tumor
  • Chromatin Immunoprecipitation
  • Estradiol / pharmacology
  • Estrogens / pharmacology
  • Female
  • Gene Expression Regulation, Neoplastic / drug effects
  • Gene Expression Regulation, Neoplastic / genetics*
  • Humans
  • Promoter Regions, Genetic / genetics*
  • Protein Binding / drug effects
  • Proto-Oncogene Proteins c-myb / genetics*
  • Proto-Oncogene Proteins c-myb / metabolism*
  • RNA Interference
  • Receptors, CXCR4 / genetics
  • Reverse Transcriptase Polymerase Chain Reaction

Substances

  • CXCR4 protein, human
  • Estrogens
  • Proto-Oncogene Proteins c-myb
  • Receptors, CXCR4
  • Estradiol