Oleandrin

Oleandrin, also known as PBI-05204 , is a lipid soluble cardiac glycoside with potential antineoplastic activity. Upon administration, oleandrin specifically binds to and inhibits the alpha3 subunit of the Na/K-ATPase pump in human cancer cells. This may inhibit the phosphorylation of Akt, upregulate MAPK, inhibit NF-kb activation and inhibit FGF-2 export and may downregulate mTOR thereby inhibiting p70S6K and S6 protein expression. All of this may lead to an induction of apoptosis. (In Vitro) :Study of Na, K-ATPase inhibition shows an IC50 (nM) of 620 for Oleandrin. The inhibition of Na, K-ATPase by Oleandrin confirms that it likely exert its toxic effect through inhibition of sodium pump activity. When treated with a series of concentrations of Oleandrin (0.2-25 nM), the undifferentiated CaCO-2 cells are sensitive as evidenced by an IC50 of 8.25 nM. In contrast, a maximum growth inhibition of only 20% is reached in differentiated CaCO-2 cells even though they are treated with Oleandrin concentrations as high as 25 nM. (In Vivo) :The effect of Oleandrin is investigated on glioma growth in vivo. To this aim, SCID or C57BL/6 mice are transplanted, respectively, with human U87MG (5x104), U251, GBM19 (5x105), or murine (syngeneic) GL261 (7.5x104) cells into the right striatum and, after 10 d, treated daily with intraperitoneal Oleandrin for an additional 7 d. Oleandrin significantly reduces tumor sizes in human and murine glioma cell models in vivo in a dose-dependent way. High concentrations of Oleandrin (3 mg/kg) are fatal in both models, as expected from the known lethal dose for rodents. Doses of Oleandrin below the lethal dose (0.3 mg/kg) significantly increase the survival time from 32.6±1.4 d to 53.8±9.6 d in mice injected with U87MG cells (n=5-11; p<0.01, log-rank test) and from 23.37±1.2 d to 34.38±3.3 d (n=5-11; p<0.01, log rank test) in mice injected with GL261 cells.