The best characterized RTK-GPCR heteromer is produced by HER2 and β2-adrenergic receptors in the heart and it is essential for the cardiac homeostasis (Negro et al., 2006); by fibroblast growth factor receptor and adenosine A2A receptors (Flajolet et al., 2008) or serotonin 5-HT1A receptors (Borroto-Escuela et al., 2012), which take part in synaptic plasticity; and by EGFR and GPR54, which seem to induce breast cancer cell invasiveness (Zajac et al., 2011). This evidence concerns the gene ERBB2 and breast cancer.