Document Type: Original Paper
Cancer Research Laboratory, Department of Clinical Biochemistry, School of Medical Sciences, University of Tarbiat Modarres, Tehran, Islamic Republic of Iran
The purpose of the present study is to investigate the cytotoxicity/apoptotic effect of 2-chloro-2′-deoxyadenosine, cladribine, (2-CdA) in the human breast cancer cell line, MDA-MB468 (estrogen receptor negative, ER−). MTT [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide] 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 MDA-MB468 cells with different concentrations of 2-CdA (50, 100 and 500 µM) resulted in a significant increase in the cell death. Annexin V-Fluorescein/PI and Hoechst 33258 staining revealed that the cell death was mainly of apoptotic type. DNA laddering profile was also obtained in the treated MDA-MB468 cells using DNA fragmentation analysis. A significant (p<0.05) increase in the activity of caspase-3 and -9 was observed. Pre-treatment of the cells with kinase inhibitor, 5′-amino-5′-deoxyadenosine inhibited the cytotoxicity effect of 2-CdA. This suggests that intracellular phosphorylation activation reaction plays a key role in the 2-CdA-induced apoptosis. In conclusion, this study showed that high dose of cladribine has an apoptotic effect on ER−MDA-MB468 breast cancer cells and its intracellular phosphorylation is necessary for cytotoxicity.