Cytotoxicity induced by manipulation of signal transduction pathways is associated with down-regulation of Bcl-2 but not Mcl-1 in MCF-7 human breast cancer

Breast Cancer Res Treat. 2001 Nov;70(1):11-20. doi: 10.1023/a:1012564620853.


We examined the role of Mcl-1 and Bcl-2 expression in the induction of apoptosis. through blocking protein tyrosine kinase (PTK), protein kinase C (PKC), phosphatidylinositol 3-kinase (P13-K) and mitogen-activated protein kinase (MAPK)/Erk kinase (MEK) signaling pathways by various kinase inhibitors in MCF-7 breast cancer cells. The PTK inhibitor genistein (GEN) and PKC inhibitor staurosporine (STP) down-regulated Mcl-1 and Bcl-2 expression, and induced growth inhibition by blocking at the G2/M phase of cell cycle, followed by apoptosis, leading to chromatin condensation and DNA fragmentation. LY294002 (LY)-mediated inhibition of P13-K activity down-regulated Bcl-2 but not Mcl-1 expression. triggered growth arrest at the G1/G0 phase of cell cycle and also led to apoptosis marked with chromatin condensation and DNA fragmentation. The MEK inhibitor U0126 (U0) decreased Bcl-2 expression but not Mcl-1 expression, inhibited cells growth and induced G1/G0 arrest. but in this case cell death occurred without significant apoptotic features. The kinase inhibitor concentration dependence of cytotoxicity correlated well with down-regulation of Bcl-2 but not with changes in Mcl-1 levels. This suggests that Bcl-2 plays a predominant role in the regulation of cell death induced by cell signaling alterations whereas Mcl-1 does not appear to control cell survival under these conditions in MCF-7 cells. Further studies showed that the combination of GEN, STP and LY with U0 can produce synergetic cytotoxic effects on MCF-7 cells. Our results suggest that PTK, PKC, P13-K and MEK signaling pathways can regulate Bcl-2 expression and form an integrated network that plays a critical role in cell survival.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / pharmacology*
  • Apoptosis*
  • Blotting, Western
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / enzymology
  • Breast Neoplasms / metabolism*
  • Breast Neoplasms / pathology
  • Butadienes / pharmacology
  • Chromones / pharmacology
  • Down-Regulation / drug effects
  • Enzyme Inhibitors / pharmacology*
  • Female
  • Flow Cytometry
  • Genistein / pharmacology
  • Humans
  • Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • Morpholines / pharmacology
  • Myeloid Cell Leukemia Sequence 1 Protein
  • Neoplasm Proteins / metabolism*
  • Nitriles / pharmacology
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase Inhibitors*
  • Protein-Tyrosine Kinases / antagonists & inhibitors
  • Proto-Oncogene Proteins c-bcl-2 / metabolism*
  • Signal Transduction / drug effects*
  • Staurosporine / pharmacology
  • Tumor Cells, Cultured


  • Antineoplastic Agents
  • Butadienes
  • Chromones
  • Enzyme Inhibitors
  • Morpholines
  • Myeloid Cell Leukemia Sequence 1 Protein
  • Neoplasm Proteins
  • Nitriles
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Kinase Inhibitors
  • Proto-Oncogene Proteins c-bcl-2
  • U 0126
  • 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
  • Genistein
  • Protein-Tyrosine Kinases
  • Protein Kinase C
  • Mitogen-Activated Protein Kinases
  • Staurosporine