Combination of tumor necrosis factor-alpha with sulindac augments its apoptotic potential and suppresses tumor growth of human carcinoma cells in nude mice.

Abstract

Resistance to apoptosis may be responsible for a principal mechanism by which cancer cells overcome anticancer therapies. Among antiapoptotic signals, the transcription factor, NF-kappaB, plays a pivotal role in the resistance because it is frequently activated in many primary carcinoma cells. However, NF-kappaB is also activated by several anticancer therapies, including tumor necrosis factor-alpha (TNF-alpha). The NF-kappaB-mediated survival signals are supposed to evade these therapies. Recently, a nonsteroidal antiinflammatory drug, sulindac, and its metabolites have been shown to inhibit the NF-kappaB pathway and to enhance TNF-alpha-mediated apoptosis in lung carcinoma cell lines. In the current study, the authors investigated whether sulindac can augment TNF-alpha-mediated apoptosis in other human carcinoma cells and whether it can be applied for in vivo clinical usage. Human gastric MKN45 and cervical HeLa carcinoma cells were treated with sulindac and/or TNF-alpha. Proapoptotic effects of these agents were evaluated by trypan blue exclusion assay, DNA fragmentation, and caspase-3 activity. The effect of sulindac on NF-kappaB activation was evaluated by luciferase reporter and gel-shift assays. The suppressive effects of these reagents on the subcutaneous tumor growth of MKN45 cells were evaluated by measuring tumor size in nude mice. Sulindac inhibited TNF-alpha-mediated NF-kappaB activation and greatly sensitized MKN45 and HeLa cell lines to TNF-alpha. Moreover, in vivo tumor growth of MKN45 cells was inhibited most strongly by a combination of TNF-alpha with sulindac compared with TNF-alpha or sulindac alone. The current study data strongly suggest that combination therapy of TNF-alpha with sulindac may sensitize tumor cells to TNF-alpha and augment its proapoptotic potential. Therefore, in combination with sulindac, TNF-alpha may become a potentially useful anticancer agent to suppress tumor growth in a wide range of carcinomas.