Different expression patterns of Bcl-2 family genes in breast cancer by estrogen receptor status with special reference to pro-apoptotic Bak gene

Cell Death Differ. 2000 May;7(5):439-46. doi: 10.1038/sj.cdd.4400675.


Oncogenic and anti-apoptotic Bcl-2 is expressed much less in estrogen receptor alpha (ERalpha) negative breast cancers, which show more malignant phenotypes, than ERalpha-positive, indicating that some other Bcl-2 family member(s) are involved in the apoptotic balance of the cancer cells. We first analyzed mRNA expression of pro-apoptotic Bak and Bax along with that of anti-apoptotic Bcl-2 and Bcl-xL, using breast cancer specimens of 27 patients. Bak mRNA was expressed much less in ERalpha negative breast cancers, along with reduced expression of Bcl-2. Immunostaining of sections of 108 patients confirmed the observation. Next, stable transformants of MCF-7 cells with sense Bak expression vector showed fewer colonies in soft agar compared with the parental cells, while stable introduction of antisense Bak vector enhanced colony formation at lower estradiol concentrations. The reduction of Bak may play important roles in malignant development of breast cancer to acquire estrogen independency, counteracting the reduced Bcl-2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / genetics*
  • Base Sequence
  • Breast Neoplasms / genetics*
  • Breast Neoplasms / metabolism*
  • Breast Neoplasms / pathology
  • DNA Primers / genetics
  • Female
  • Gene Expression
  • Genes, bcl-2*
  • Humans
  • Immunohistochemistry
  • Membrane Proteins / genetics*
  • Membrane Proteins / metabolism
  • Multigene Family
  • Neoplasms, Hormone-Dependent / genetics*
  • Neoplasms, Hormone-Dependent / metabolism*
  • Neoplasms, Hormone-Dependent / pathology
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins c-bcl-2 / genetics
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • RNA, Neoplasm / genetics
  • RNA, Neoplasm / metabolism
  • Receptors, Estrogen / metabolism*
  • Transformation, Genetic
  • Tumor Cells, Cultured
  • bcl-2 Homologous Antagonist-Killer Protein
  • bcl-2-Associated X Protein
  • bcl-X Protein


  • BAK1 protein, human
  • BAX protein, human
  • BCL2L1 protein, human
  • DNA Primers
  • Membrane Proteins
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • RNA, Messenger
  • RNA, Neoplasm
  • Receptors, Estrogen
  • bcl-2 Homologous Antagonist-Killer Protein
  • bcl-2-Associated X Protein
  • bcl-X Protein