Background: Ankaferd Blood Stopper (ABS) is a preparation of plant extracts originally used as a hemostatic agent. It has pleiotropic effects in many cellular processes such as cell cycle regulation, apoptosis, angiogenesis, signal transduction, inflammation, immunologic processes and metabolic pathways as well as hemostatic activity. This unique preparation has been widely investigated for its properties. However there are no studies investigating its action on leukemic cells.Aim: Aim of the study was to examine the ABS action on PAR1 and EPCR in leukemia cells. However, during the experiments, we observed the apoptotic effect of ABS on leukemic cells, particularly Jurkat cells. As a result the mechanism of apoptosis induced by ABS treatment was also explored in the study.Material and method: Two leukemia cell lines, K-562 and Jurkat, were utilized for the study. Expression analyses of PAR1, EPCR and p21 upon ABS treatment were performed by quantitative real time PCR. Annexin V method was used for apoptosis detection.Results: Our results demonstrated that ABS alters PAR1 and EPCR expression in K-562 and Jurkat cells in a time and dose dependent manner. Additionally it was found that ABS treatment induces apoptosis in leukemia cells. Possible involvement of PAR1 and p21 in this apoptotic process was observed in Jurkat cells.Conclusion: This study concludes that depending on the concentration and duration of the application, ABS causes apoptosis by regulating PAR1 and p53-independent p21 involvement in Production and hosting by Elsevier B.V. on behalf of Ain Shams University. apoptosis stimulation in leukemia cells. The composition of ABS plant extracts might be responsible from the apoptotic effect that was observed. We think that our results could contribute to the development of new treatment for leukemia therapy.Ó 2014 Production and hosting by Elsevier B.V. on behalf of Ain Shams University.