Modulating therapeutic effects of the c-Src inhibitor via oestrogen receptor and human epidermal growth factor receptor 2 in breast cancer cell lines.
OBJECTIVE
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.
Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, 3970 Reservoir Road NW, Washington, DC 20057, USA.
Ping
P
Fan
Russell E
RE
McDaniel
Helen R
HR
Kim
Dionyssia
D
Clagett
Bassem
B
Haddad
V Craig
VC
Jordan
D000230:Adenocarcinoma / Q000737:chemistry / Q000473:pathology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology; D001943:Breast Neoplasms / Q000737:chemistry / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor / Q000187:drug effects / Q000378:metabolism; D004273:DNA, Neoplasm / Q000032:analysis; D019008:Drug Resistance, Neoplasm; D020847:Estrogen Receptor Modulators / Q000494:pharmacology; D004967:Estrogens; D005260:Female; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D058990:Molecular Targeted Therapy; D009363:Neoplasm Proteins / Q000032:analysis / Q000037:antagonists & inhibitors* / Q000502:physiology; D009376:Neoplasms, Hormone-Dependent / Q000737:chemistry / Q000473:pathology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D011374:Progesterone; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000037:antagonists & inhibitors*; D011743:Pyrimidines / Q000494:pharmacology*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis / Q000502:physiology*; D011960:Receptors, Estrogen / Q000032:analysis / Q000502:physiology*; D011980:Receptors, Progesterone / Q000032:analysis; D015398:Signal Transduction / Q000187:drug effects*; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000494:pharmacology
D000970:Antineoplastic Agents; D018931:Antineoplastic Agents, Hormonal; D004273:DNA, Neoplasm; D020847:Estrogen Receptor Modulators; D004967:Estrogens; D009363:Neoplasm Proteins; D019869:Phosphatidylinositol 3-Kinases; D011374:Progesterone; D047428:Protein Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D016392:Proto-Oncogene Proteins pp60(c-src); D011743:Pyrimidines; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D013629:Tamoxifen; C412373:AG 1879; C016601:afimoxifene; C508053:ERBB2 protein, human; C494918:AKT1 protein, human