Modulating therapeutic effects of the c-Src inhibitor via oestrogen receptor and human epidermal growth factor receptor 2 in breast cancer cell lines

Eur J Cancer. 2012 Dec;48(18):3488-98. doi: 10.1016/j.ejca.2012.04.020. Epub 2012 Jun 2.


Purpose: c-Src is an important adapter protein with oestrogen receptor (ER) and human epidermal growth factor receptor 2 (HER2), which validates it as an attractive target for the treatment of breast cancer. A specific c-Src inhibitor, 4-amino-5-(4-chlorophenyl)-7(t-butyl)pyrazolo[3,4-d]pyrinidine (PP2), was utilised to block c-Src activity to identify targeted vulnerabilities affected by ER and HER2 in a panel of breast cancer cell lines.

Methods: ER, growth factor receptors and signalling pathways were detected by Western-blot. The DNA content of the cells was determined by using a DNA fluorescence quantitation kit. Cell cycles were analysed by flow cytometry.

Results: The antiproliferative effect of PP2 closely correlated with the inhibition of c-Src mediated extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) and/or phosphoinositide 3-kinase (PI3K)/Akt growth pathways. Inhibition of c-Src tyrosine kinase predominantly blocked ER negative breast cancer cell growth, particularly the triple (i.e. ER, progesterone receptor (PR), and HER2) negative cells. In contrast, ER negative Sk-Br-3 cells with highest HER2 phosphorylation were resistant to PP2, in which hyper-activated HER2 directly regulated growth pathways. However, blocking c-Src recovered ER expression and down-regulated HER2 which made Sk-Br-3 cells regain responsiveness to 4-hydroxytamoxifen. The majority of ER positive cells were not sensitive to PP2 regardless of wild-type or endocrine resistant cell lines.

Conclusions: c-Src mediates the essential role of growth pathways in ER negative breast cancer cells. The ER positive and HER2 over-activation are two important predictive biomarkers for the resistance to a c-Src inhibitor. These data provided an important therapeutic rationale for patient selection in clinical trials with c-Src inhibitors in breast cancer.

Publication types

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

MeSH terms

  • Adenocarcinoma / chemistry
  • Adenocarcinoma / pathology*
  • Antineoplastic Agents / pharmacology*
  • Antineoplastic Agents, Hormonal / pharmacology
  • Breast Neoplasms / chemistry
  • Breast Neoplasms / pathology*
  • Cell Division / drug effects
  • Cell Line, Tumor / drug effects
  • Cell Line, Tumor / metabolism
  • DNA, Neoplasm / analysis
  • Drug Resistance, Neoplasm
  • Estrogen Receptor Modulators / pharmacology
  • Estrogens*
  • Female
  • Humans
  • MAP Kinase Signaling System / drug effects
  • Molecular Targeted Therapy*
  • Neoplasm Proteins / analysis
  • Neoplasm Proteins / antagonists & inhibitors*
  • Neoplasm Proteins / physiology
  • Neoplasms, Hormone-Dependent / chemistry
  • Neoplasms, Hormone-Dependent / pathology*
  • Phosphatidylinositol 3-Kinases / physiology
  • Progesterone*
  • Protein Kinase Inhibitors / pharmacology*
  • Proto-Oncogene Proteins c-akt / physiology
  • Proto-Oncogene Proteins pp60(c-src) / antagonists & inhibitors*
  • Pyrimidines / pharmacology*
  • Receptor, ErbB-2 / analysis
  • Receptor, ErbB-2 / physiology*
  • Receptors, Estrogen / analysis
  • Receptors, Estrogen / physiology*
  • Receptors, Progesterone / analysis
  • Signal Transduction / drug effects*
  • Tamoxifen / analogs & derivatives
  • Tamoxifen / pharmacology


  • AG 1879
  • Antineoplastic Agents
  • Antineoplastic Agents, Hormonal
  • DNA, Neoplasm
  • Estrogen Receptor Modulators
  • Estrogens
  • Neoplasm Proteins
  • Protein Kinase Inhibitors
  • Pyrimidines
  • Receptors, Estrogen
  • Receptors, Progesterone
  • Tamoxifen
  • afimoxifene
  • Progesterone
  • Phosphatidylinositol 3-Kinases
  • ERBB2 protein, human
  • Receptor, ErbB-2
  • Proto-Oncogene Proteins pp60(c-src)
  • AKT1 protein, human
  • Proto-Oncogene Proteins c-akt