['Clofarabine, a purine nucleoside analogue and inhibitor of Ribonucleotide Reductase (RR), is used for treatment of leukemia. Clofarabine-induced defect in DNA replication, induces p53 and subsequently P53R2 genes as subunit of RR. clofarabine deregulated P53R2 gene expression leading to the elevated levels of P53R2 which impose resistance to DNA damaging drugs. In this study the apoptotic and cytotoxic effects of clofarabine has been investigated on breast cancer cell line.', 'Cofarabine cytotoxicity on T47D cells has been studied by MTT assay. T47D cells were exposed to the different concentrations of clofarabine for 24, 48 and 72 hours intervals. Relative expression of P53R2 gene has been studied using real-time PCR. Moreover, after treating with clofarabine the apoptotic and necrotic cells were detected using Annexin V and propodium iodide (PI) reagents by flowcytometry technique.', 'MTT assay results showed that the clofarabine IC50 on T47D cell line were 3 and 2.5µM after 48 and 72 h exposure, respectively. Clofarabine did not show any significant cytotoxic effect after 24 h exposure. The analysis of qRT-PCR showed a significant increase in P53R2 gene expression in treated cells with both 2.5 and 3 μM doses and also, the results of flowcytometry revealed 26.91 and 74.46 percent apoptosis induction in 48 and 72h treatments respectively in comparison to the control groups.'] Does clofarabine have Apoptotic Effect on T47D Breast Cancer Cell Line via P53R2 Gene Expression?