We used a label-free quantitative mass spectrometry method to obtain unbiased phosphoproteomic profiles from primary MEFs, which either heterozygously express the endogenous Pik3caH1047R mutant allele or have homozygous loss of Pten. The aim of our screen was to faithfully mimic mutational activation of the PI3K pathway as observed in cancer. This evidence concerns the gene PTEN and cancer.