Critical role of bad phosphorylation by Akt in cytostatic resistance of human bladder cancer cells.
BACKGROUND
Taxol is the most commonly used agent for salvage chemotherapy in transitional cell carcinoma of the urothelium. We examined mechanisms responsible for taxol resistance by using T24 human bladder carcinoma cells.


METHODS
We used an inhibitor and an activator of the phosphatidylinositol-3 kinase-Akt pathway in cell survival and caspase-3 assays, an HPLC method for determining released cytochrome c and immunoblotting for detecting protein phosphorylation.


RESULTS
Activation of Akt increased paclitaxel resistance by increasing Bad phosphorylation, leading to decreased release of mitochondrial cytochrome c and caspase-3-mediated apoptosis. On the other hand, inhibition of Akt prevented paclitaxel resistance by enhancing the effects of paclitaxel on Bad phosphorylation, mitochondrial cytochrome c release and caspase-3-mediated apoptosis, besides diminishing or abolishing the opposing effects of Akt activation.


CONCLUSIONS
Akt-mediated Bad phosphorylation plays an important role in preservation of mitochondrial membrane systems leading to paclitaxel resistance in T24 cells.
Szanto
Arpad
A
Department of Urology, Faculty of Medicine, University of Pecs, Hungary.
Bognar
Zita
Z
Szigeti
Andras
A
Szabo
Aliz
A
Farkas
Laszlo
L
Gallyas
Ferenc
F