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

Background: 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.

Methods: 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.

Results: 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.

Conclusions: 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.