Synergistic interaction of natural human tumor necrosis factor-alpha/natural human interferon-alpha mixture alone and in combination with cisplatin against head and neck laryngeal squamous carcinoma multicellular tumor spheroids.

We evaluated the effects of each component, natural human tumor necrosis factor-alpha (nHuTNF-alpha) and natural human interferon-alpha (nHu-IFN-alpha), and the combined nHuTNF-alpha/nHuIFN-alpha preparation with or without cisplatin (DDP) at tumor mass level. Multicellular tumor spheroids (MTS) of approximately 500 microns in diameter were produced from HEp-2 laryngeal squamous carcinoma cell line by liquid overlay culture technique. Cell kill effects of 72 hr exposure to nHuTNF-alpha, nHuIFN-alpha, or nHuTNF-alpha/nHuIFN-alpha against cells in MTS were 2-3-fold less than those in monolayer. In MTS, does response curves become progressively flat at high drug concentrations, indicative of poor drug penetration into the MTS core. Combination nHuTNF-alpha/nHuIFN-alpha produced synergistic cell kill for both MTS and monolayers. For monolayer cells exposure to nHuTNF-alpha/nHuIFN-alpha first (72 hr) followed by DDP (1 hr) after 1 hr rest period was synergistic with combination index (CI) of approximately 0.8 at LD50. Simultaneous (72 hr in nHuTNF-alpha/nHuIFN-alpha with DDP in last 1 hr) or reverse order of exposure were antagonistic. In contrast, for MTS, DDP followed by nHuTNF-alpha/nHuIFN-alpha was most synergistic with CI of approximately 0.2. Simultaneous exposure or nHuTNF-alpha/nHuIFN-alpha followed by DDP showed synergism with CI of approximately 0.5 and 0.8, respectively. The improved efficacy of DDP followed by nHuTNF-alpha/nHuIFN-alpha sequence for MTS cells appears to be due to increased nHuTNF-alpha/nHuIFN-alpha penetration into the MTS core aided by DDP.