Specific regulatory effects of IL4 in fludarabine-induced apoptosis in B-CLL cells.

PAULA FERNANDEZ CALOTTI; ROMINA GAMBERALE; CARLOS GALMARINI; MARIA LAURA GABELLONI; JEREMIAS GALLETI; JULIO SANCHEZ AVALOS; MIRTA GIORDANO

Cuidad de Cordoba, Argentina

Congreso; VII congreso latinoamericano de inmunologia; 2005

Fludarabine is a nucleoside analogue employed for the treatment of B-CLL, which enters the cell through the nucleoside transported hENT1. We have previously reported that, although IL4 is a prototypic anti-apoptotic cytokine for B-CLL cells, the acute stimulation of PKC (PMA 500nM, 10min) increased FLU-induced apoptosis in IL-4 treated cells. In this study we aimed to determine the specificity of IL-4 effect by testing two other anti-apoptotic cytokines: IFNa and IL-8.Apoptosis was evaluated by fluorescence microscopy and flow cytometry. We found that incubation with IFNa or IL-8 for 24hs plus acute stimulation of PKC protected cells from FLU (10ug/ml) induced apoptosis (42±1.2 vs 16.5±2; PMA+FLU vs IFNa+PMA+FLU and 42±1.2 vs 18±1.5; PMA+FLU vs IL-8+PMA+FLU p<0.01, n=8). We also tested the possibility that IL-4 plus PMA sensitizes cells to undergo drug-induced apoptosis. To this aim, we evaluated pro-apoptotic effects of the following anti-neoplastic agents that do not enter cells via hENT1: Velcade, Etoposide, Idarubicin and Dexamethasone. We found that acute stimulation of PKC in IL-4 treated B-CLL cells did not enhance but rather inhibit apoptotic rates induced by these agents (p<0.05, n=4). Whether therapeutic PKC activators, such as Bryostatin, are also able to enhance pro-apoptotic effects of FLU on IL-4 treated B-CLL cells, remains to be determined.