PI3K inhibitor reverses curcumin-induced phosphorylation of Akt and enhances MCF-7 cell death
Since curcumin enhances Akt phosphorylation in MCF-7 cells (Fig. 3A), we investigated whether the combined treatment with curcumin and LY290042, a selective PI3K inhibitor, would reverse curcumin-induced phosphorylation of Akt. MCF-7 cells were treated with LY290042 and curcumin for 12 h. LY290042 markedly down regulated curcumin-induced Akt phosphorylation at Ser473 (Fig. 4A). Moreover, LY290042 synergistically enhanced the curcumin-induced apoptosis as measured by MTT assay (Fig. 4B), and PARP cleavage (Fig. 4C). In order to examine the effect of the combined treatment with LY290042 and curcumin on Akt downstream targets, GSK3b was investigated. As shown in Fig. 4D, the combined treatment with LY290042 and curcumin down regulates curcumininduced GSK3b phosphorylation at Ser9. These results suggest that the combined treatment of MCF-7 cells with LY290042 and curcumin, induces the inactivation of Akt and activation of GSK3b, and subsequently promotes MCF-7 apoptosis.