Inactivation of GPR30 reduces growth of triple-negative breast cancer cells: possible application in targeted therapy

Breast Cancer Res Treat. 2012 Jul;134(1):199-205. doi: 10.1007/s10549-012-1968-x.


Triple-negative breast cancers lack estrogen receptor α (ERα), progesterone receptor, and do not overexpress human epidermal growth factor receptor 2 (Her-2). They are neither susceptible to endocrine therapy nor to a therapy using the anti-Her-2 antibody, trastuzumab. Therefore, an efficient targeted therapy is warranted. Triple-negative breast tumors frequently express membrane bound estrogen receptor G-protein coupled receptor (GPR30). As proof of principle, we analyzed the consequences of a knock-down of GPR30 expression on the growth regulation of triple-negative breast cancer cell lines. Cells of triple-negative breast cancer cell lines were transfected with siRNA against GPR30 or control siRNA, and cell growth was stimulated either with 10(⁻⁹) M 17β-estradiol or 10(⁻⁶) M 4-hydroxytamoxifen. Cell proliferation was measured using Alamar blue staining. Activation of c-Src and epidermal growth factor (EGF)-receptor was assessed using western blot. Expression of c-fos was quantified by reverse transcription polymerase chain reaction. Seven days after transfection with siRNA, GPR30 mRNA in triple-negative breast cancer cell lines MDA-MB-435 and HCC1806 was reduced by 74 and 90%, respectively. 10(⁻⁸) M 17β-estradiol enhanced proliferation of MDA-MB-435 to 129.6±5.4% of control (p<0.05) and HCC1806 to 156.9±15.4% of control (p<0.05), respectively. 10(⁻⁶) M 4-hydroxytamoxifen increased cell number of MDA-MB-435 to 121.0±6.9% of control (p<0.05) and HCC1806 to 124.5±12.1% of control (n.s.), respectively. This increased proliferation by the two estrogenic compounds was completely prevented by knock-down of GPR30 expression in both cell lines. In control cells, activity of Src kinase was increased 3-fold by estradiol and 3.8-fold using 4-hydroxytamoxifen. Transactivation of the EGF-receptor was similarly increased in both cell lines by 17β-estradiol and 4-hydroxytamoxifen. Both compounds increased c-fos expression 1.5- and 3.1-fold, respectively. Knock-down of GPR30 expression completely abolished activation of all these signaling pathways responsible for enhanced proliferation. A pharmacological inhibition of GPR30 by specific small molecular inhibitors might prove to be an appropriate targeted therapy of triple-negative breast cancer in the future.

MeSH terms

  • Antineoplastic Agents, Hormonal / pharmacology*
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / pathology
  • Cell Line, Tumor / drug effects
  • Cell Proliferation*
  • Estradiol / pharmacology
  • Estradiol / physiology
  • Female
  • Gene Expression
  • Gene Knockdown Techniques
  • Humans
  • Molecular Targeted Therapy
  • Proto-Oncogene Proteins c-fos / metabolism
  • RNA Interference
  • Receptor, ErbB-2 / metabolism
  • Receptors, Estrogen / genetics
  • Receptors, Estrogen / metabolism*
  • Receptors, G-Protein-Coupled / genetics
  • Receptors, G-Protein-Coupled / metabolism*
  • Receptors, Progesterone / metabolism
  • Signal Transduction
  • Tamoxifen / analogs & derivatives*
  • Tamoxifen / pharmacology


  • Antineoplastic Agents, Hormonal
  • GPER1 protein, human
  • Proto-Oncogene Proteins c-fos
  • Receptors, Estrogen
  • Receptors, G-Protein-Coupled
  • Receptors, Progesterone
  • Tamoxifen
  • afimoxifene
  • Estradiol
  • ERBB2 protein, human
  • Receptor, ErbB-2