ABSTRACT
Cladribine, an analogue of deoxyadenosine, is highly toxic for both non-dividing and proliferating cells and has shown activity in the treatment of several malignancies. Therefore, the aim of the present study is to investigate the cytotoxicity effect of cladribine [2-CdA] on the breast cancer cell line, MCF-7 [estrogen receptor positive, ER+]. MTT assay, annexin V-Fluorescein/PI and Hoechst 33258 staining were used to detect cytotoxicity and cell apoptosis. The activation of caspase-3 and -9 was assayed using caspase activation assay kits. Gel electrophoresis was performed to detect DNA fragmentation. Treatment of MCF-7 cells with different concentrations of 2-CdA resulted in a significant increase in the cell death. Annexin V-Fluorescein/PI and Hoechst 33258 staining revealed that the cell death was mainly an apoptotic type. A significant [p<0.05] increase in the activity of caspase-9 was observed but Caspase-3 activity was unchanged and DNA laddering profile was not obtained. Pre-treatment of the cells with kinase inhibitor, 5 -amino-5 -deoxyadenosine inhibited the cytotoxicity effect of cladribine. In conclusion, this study has shown that high dose of cladribine [higher than 25 micro M] has an apoptotic effect on MCF-7 cells and that its intracellular phosphorylation is necessary