Phosphatidylinositol-3-OH kinase (PI3K) signaling is crucial to the viability of many cancers and represents a selective target for therapeutic intervention.Our strategy against cancer is based on the use of a newly identified cytokine (beta-GBP), a natural inhibitor of both class IA and class IB PI3K, whose physiological nature carries no chemotherapeutic disadvantages and which introduces a novel therapeutic concept that can be tested and utililised in clinical trials.Downregulation of PI3K by the beta-GBP cytokine results in inhibition of Ras-mitogen-activated signaling, negation of cell cycle controller genes and negation of akt gene expression.In a variety of tumor cells, but not in normal cells, downregulation of signaling and S phase block by beta-GBP leads to apoptosis ascribable to E2F 1 deregulation.In aggressive cancer cells where the strength of mitogenic input may not be affected by betaGBP, PI3K inhibition leads to akt gene suppression and apoptosis.We find that ERK, the akt gene, PI3K and betaGBP are functionally linked but only cancer cells, not normal cells, are vulnerable to apoptotic death by the betaGBP cytokine.By downregulating PI3K and affecting the cytokine network beta-GBP is alsoproving to be a controller of inflammation, an important contributor to the development of cancer.