Introduction: It has been reported that platelets can eradicate tumor cells in vitro, although the mechanism of this effect has not been determined. The effect of platelets on the induction of apoptosis in tumor cells is largely unknown.

Materials and methods: To investigate this effect, two human hematologic cell lines, K562 and Daudi, were independently faced with unstimulated and thrombin-activated platelets. After the elapsed co-culture time, the levels of caspase-3 and CD95 were evaluated as a sign of cell death and apoptosis. In addition, immortalized cells were evaluated using trypan blue, 7-AAD and WST-1 methods.

Results: CD95 and caspase-3 levels were significantly increased in both cell lines compared with the control cells (P<0.05). Beside, considerably lower number of living cells were shown by trypan blue, 7-AAD and WST-1 in the treatment groups compared with the control group (P<0.05).

Conclusion: This study demonstrated the role of apoptosis in tumor inhibition and implied the ability of platelets to induce apoptosis in tumor cell lines.