Expression of the bcl-2 gene family in normal and malignant breast tissue: low bax-alpha expression in tumor cells correlates with resistance towards apoptosis

Int J Cancer. 1995 Mar 16;60(6):854-9. doi: 10.1002/ijc.2910600622.


We have studied the expression of the apoptosis-regulating genes bcl-2, bcl-x, bax and APO-1/fas (CD95) in human breast cancer. The expression pattern of these genes in human breast-cancer tissues and breast-cancer-derived cell lines was compared to that seen in normal breast epithelium and breast epithelial cell lines. No difference with regard to bcl-2 and bcl-xL expression was observed between normal breast epithelium and tumor tissue or breast cancer and non-malignant epithelial cell lines. In contrast, bax-alpha, a splice variant of bax, which promotes apoptosis, is expressed in high amounts in normal cell lines and breast tissue, whereas only weak or no expression could be detected in cancer-cell lines and malignant tissue. In contrast to malignant cell lines, which express low levels of bax-alpha, non-malignant epithelial cell lines displaying high amounts of bax-alpha were highly sensitive to induction of programmed cell death by both serum starvation and APO-1/fas (CD95) triggering. We therefore propose that dysregulation of apoptosis contributes to the pathogenesis of breast cancer, at least in part, due to an imbalance between anti-apoptosis genes (such as bcl-2/bcl-x) and apoptosis-promoting genes (bax).

MeSH terms

  • Apoptosis / genetics*
  • Base Sequence
  • Breast Neoplasms / genetics*
  • Breast Neoplasms / metabolism
  • Gene Expression Regulation, Neoplastic / genetics*
  • Humans
  • Molecular Sequence Data
  • Proto-Oncogene Proteins / biosynthesis*
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins c-bcl-2
  • RNA, Messenger / genetics
  • Tumor Cells, Cultured
  • bcl-2-Associated X Protein


  • BAX protein, human
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • RNA, Messenger
  • bcl-2-Associated X Protein