Measuring PI3K lipid kinase activity.

Class IA phosphoinositide-3 kinases (PI3Ks) signaling has recently emerged as a key element in cancer development because of its ability to trigger a complex panoply of cellular responses controlling survival and proliferation. Many cancers show inappropriately activated PI3K pathway, and tumors with high PI3K activity are frequently resistant to traditional chemotherapy. Indeed, preclinical studies demonstrated a prominent role for the PI3K pathway in cancer cell survival and growth, thus validating PI3K as a potential drug target in cancer. The emerging interest in inhibiting PI3Ks in cancer have prompted the aggressive development of new selective PI3K pathway inhibitors as cancer therapy, and many of these molecules are currently in early-phase clinical trials. In this chapter, we describe methods to measure the PI3K lipid kinase activity in vitro, which is the standard procedure to test the efficacy of inhibitors.