[Akt kinase: a key regulator of metabolism and progression of tumors].

The serine/threonine protein kinase Akt is a major transducer of the phosphoinositide 3-kinase pathway and plays a crucial role in regulation of cellular processes such as growth, metabolism, survival and proliferation. Mammalian cells are characterized by the expression of three different Akt isoforms (Akt1, Akt2, Akt3), encoded by distinct genes. Increased expression and activation of Akt observed in many human cancers is usually caused by amplification or mutation of Akt genes, amplification and activating mutation of the catalytic subunit of PI3K or deletion and mutations of phosphatidylinositol-3,4,5-triphosphate phosphatase--PTEN. Although activation of Akt alone is believed to be insufficient for tumorigenesis, it contributes to cancer progression by inhibiting apoptosis, promoting changes in metabolism and proliferation of cells and regulating their migration and invasion capabilities. Recent studies have provided evidence that depending on the cell type each specific Akt isoform may play a positive or negative role in cell migration and invasion. Akt is also involved in regulation of tumor angiogenesis.