RESUMO
To study the effects of recombinant human tumor necrosis factor-alpha (rhTNF-alpha) on HL-60 cells in vitro and in vivo, MTT and colony forming assay were used to examine the effects of rhTNF-alpha on proliferation of HL-60 cells; AO/EB (acridine orange-ethidium bromide) staining, Annexin-V flow cytometry analysis and TUNEL assay were used to detect apoptotic cells. The effect of rhTNF-alpha on xenograft growth of HL-60 cells was evaluated by tumor inhibition rate, histology, ultrastructure and TUNEL assay. The results showed that rhTNF-alpha inhibited the proliferation of HL-60 cells in a dose-dependent manner. Staining of cells with AO/EB revealed that rhTNF-alpha induced nuclear chromatin condensation and fragmentation. Positive Annexin V-FITC on cell membrane showed that rhTNF-alpha induced apoptosis of HL-60 cells in a dose-dependent manner. TUNEL assay showed that the apoptotic percentage of HL-60 cells reached 37.5% when incubated with 3200 U/ml rhTNF-alpha for 48 hours. In vivo rhTNF-alpha inhibited xenograft growth of HL-60 cells with the highest inhibition rate of 60.33%. Pathologically it was found that there were necrotic areas in the tumors of groups treated with rhTNF-alpha. There were more apoptotic cells in treatment groups than in that control group by transmission electron microscopy (TEM) and TUNEL assay. It is concluded that rhTNF-alpha is able to inhibit the proliferation of HL-60 cells and to induce apoptosis of HL-60 cells in vitro and in vivo.