Synergistic Effect of Tumor Necrosis Factor-α and Interferon-α on the Induction of Apoptosis Detected by BM-I/JIMRO: A New Marker of Apoptosis

The effects of the combination of natural human tumor necrosis factor-alpha (nHuTNF-alpha) and natural human interferon-alpha (nHuIFN-alpha) on the induction of apoptosis were investigated by immunohistochemical analysis with BM-1/JIMRO monoclonal antibody in RPMI 4788 tumor cells. Few tumor cells in the control culture could spontaneously undergo apoptosis. The number of positive cells increased at 2 and 4 h after treatment with nHuTNF-alpha (1 x 10(5) U/ml) and nHulFN-alpha (1 x 10(5) IU/ml). This effect was clearly maintained from 8 h up to 72 h of culture. The number of apoptotic cells also greatly increased with doses, suggesting that the apoptosis induced by nHuTNF-alpha and nHuIFN-alpha in combination was dose-dependent. nHuTNF-alpha or nHuIFN-alpha alone could induce apoptosis, but the induction increased significantly when the two cytokines were combined. These findings indicate that by combining nHuTNF-alpha and nHuIFN-alpha apoptosis can be synergistically induced in RPMI 4788 tumor cells, and may have specific therapeutic implications for clinical treatments using these two cytokines.