Colorectal carcinomas in mice lacking the catalytic subunit of PI(3)Kγ

Phosphoinositide-3-OH kinases (PI(3)Ks) constitute a family of evolutionarily conserved lipid kinases that regulate a vast array of fundamental cellular responses, including proliferation, transformation, differentiation and protection from apoptosis1,2. PI(3)K-mediated activation of the cell survival kinase PKB/Akt, and negative regulation of PI(3)K signalling by the tumour suppressor PTEN (refs 3, 4) are key regulatory events in tumorigenesis5,6,7. Thus, a model has arisen that PI(3)Ks promote development of cancers. Here we report that genetic inactivation of the p110γ catalytic subunit of PI(3)Kγ (ref. 8) leads to development of invasive colorectal adenocarcinomas in mice. In humans, p110γ protein expression is lost in primary colorectal adenocarcinomas from patients and in colon cancer cell lines. Overexpression of wild-type or kinase-dead p110γ in human colon cancer cells with mutations of the tumour suppressors APC and p53 , or the oncogenes β-catenin and Ki-ras, suppressed tumorigenesis. Thus, loss of p110γ in mice leads to spontaneous, malignant epithelial tumours in the colorectum and p110γ can block the growth of human colon cancer cells.