The PTEN/PI3K-AKT pathway – one of the most commonly activated metabolic drivers of cancer – is an upstream regulator of autocrine prolactin production in the normal mammary gland; moreover, autocrine prolactin production is a direct mechanism by which PI3K-AKT activation results in PRLR/JAK2/STAT5 pathway activation [123]. This evidence concerns the gene PTEN and cancer.