Purpose: We analyzed the anti-tumor effect and the mechanism of action of perifosine, an orally active alkylphospholipid AKT inhibitor using in vitro models of human ovarian cancer.
Methods: Ovarian cancer cells OAW42, PA-1, SKOV3, and A2780 as well as platinum resistant A2780cis cells were incubated with increasing concentrations of perifosine, with and without multi-caspase inhibitor zVAD-FMK. The effect of a combined treatment with cisplatin and perifosine was investigated in OAW42, SKOV3, A2780 and A2780cis cells. Cytotoxic effects of perifosine were analyzed using crystal violet staining, FACS analysis of DNA content as well as Annexin V/propidium iodide-double staining. The effect of perifosine on AKT phosphorylation was determined by Western blotting.
Results: Perifosine displayed anti-tumor activity in all five cell lines, which increased time-dependently. While IC(50) values at 24 h were >40 μM, IC(50) values after 72 h decreased to 10 μM in OAW42 and 25 μM in PA-1 and 30 μm in SKOV3 cells. In platinum resistant A2780cis cells perifosine showed good antiproliferative activity (IC(50) = 3 μm). At adequate doses, perifosine increased cytotoxic effects of cisplatin in OAW42, A2780 and A2780cis cell. Anti-tumor activity of perifosine was not confined to a specific phase of the cell cycle and could not be decreased by the pan-caspase inhibitor zVAD-FMK. AnnexinV/propidium iodide-double staining after treatment with perifosine was not indicative of classical apoptosis. AKT phosphorylation was dose-dependently inhibited by perifosine.
Conclusions: Perifosine showed substantial cytotoxic effects in various in vitro models of ovarian cancer. Since anti-tumor effects were not confined to platinum-sensitive cells perifosine seems to be a good candidate for clinical studies in patients especially with platinum resistant ovarian cancer.