PTEN and cancer: The PTEN protein has emerged as one of the most important tumor suppressors in human cancer, with a high potential as prognostic and prediction-of-response marker in several human cancers, including those with high prevalence such as breast or prostate cancer.14–18 PTEN exerts its tumor suppressor functions mainly through the negative regulation of the activity of the PI3K/AKT pro-survival pathway, by dephosphorylating at cell membranes the PI(3,4,5)P3 (PIP3) reaction product of the oncogenic PI3K.