Induction of AKT phosphorylation by a small molecule AKT inhibitor

Proc Amer Assoc Cancer Res, Volume 46, 2005 5476 AKT (PKB) is a serine/threonine that plays an important role in apoptosis, cell proliferation and survival. The AKT gene has been amplified in a number of human cancers. Furthermore, AKT activity is elevated in cells with a mutated PTEN tumor suppressor gene. These studies establish AKT as an attractive target for cancer therapy. We have identified a small molecule that specifically inhibits AKT1 with an IC50 of < 1 nM. When MiaPaCa cells (PTEN+) were treated with the inhibitor for 2h, AKT phosphorylation (at 473 site) was induced in a dose dependent manner. This induction was observed as early as 15 min with 1 μM compound treatment. AKT phosphorylation induction was seen in several cancer cell lines. In PTEN (-) cells such as PC3, there was an additional increase in AKT phosphorylation after treatment by the inhibitor. To examine the mechanim(s) for the induction of AKT phosphroylation, we employed LY294002, a PI3-kinase inhibitor. Pre-incubation of MiaPaCa cells with Ly294002 at 50 μM completely inhibited the AKT phosphorylation induction. Our results suggest that the PI3-kinase pathway is involved in the drug-related induction of AKT phosphorylation. Furthermore, there may be a feed-back mechanism involved in the up-regulation of phosphorylation in response to AKT inhibition.