Frequent activation of AKT2 and induction of apoptosis by inhibition of phosphoinositide-3-OH kinase/Akt pathway in human ovarian cancer

We previously demonstrated that AKT2, a member of protein kinase B family, is activated by a number of growth factors via Pas and PI 3-kinase signalin g pathways. Here,,ve report the frequent activation of AKT2 in human primar y ovarian cancer and induction of apoptosis by inhibition of phosphoinositi de-3-OH kinase (P1 3-kinase)/Akt pathway, Iii vitro AKT2 kinase assay analy ses in 91 ovarian cancer specimens revealed elevated levels of AKT2 activit y (>3-fold) in 33 cases (36.3%), The majority of tumors displaying activate d AKT2 were high grade and stages III and IV. Immunostaining and Western bl ot analyses using a phospho-ser-473 Akt antibody that detects the activated form of AKT2 (AKT2 phosphorylated at serine-474) confirmed the frequent ac tivation of AKT2 in ovarian cancer specimens, Phosphorylated AKT2 in tumor specimens localized to the cell membrane and cytoplasm but not the nucleus, To address the mechanism of AKT2 activation, we measured ill vitro PI 3-ki nase activity in 43 ovarian cancer specimens, including the 33 cases displa ying elevated AKT2 activation, High levels of PI 3-kinase activity were obs erved in 20 cases, 15 of which also exhibited AKT2 activation. The remainin g five cases displayed elevated AKT1 activation. Among the cases with eleva ted AKT2, but not PI 3-kinase activity (18 cases), three showed down-regula tion of PTEN protein expression. Inhibition of PI 3-kinase/AKT2 by wortmann in or LY294002 induces apoptosis in ovarian cancer cells exhibiting activat ion of the PI 3-kinase/AKT2 pathway, These findings demonstrate for the fir st time that activation of AKT2 is a common occurrence in human ovarian can cer and that PI 3-kinase/Akt pathway may be an important target for ovarian cancer intervention.