The activation of hypoxia-inducible factor 1alpha by delta-opioid receptors promoted cyclooxygenase 2 expression, through phosphatidylinositol 3 kinase (PI3k)/protein kinase B (Akt) stimulation, in breast cancer cells (MCF-7, T47D) causing a paracrine activation of the vascular endothelial cells by prostaglandin E2 receptors [18]. This evidence concerns the gene AKT1 and breast cancer.