TNF and fibrosarcoma: Moreover, concomitant treatment with LPS and 33 resulted in three to four tumor‐free mice out of five.184 The exact mechanism underlying antitumor activity was not identified in this study, but could, at least in part, be attributed to macrophage activation and induction of TNF‐α secretion, as was observed in an experiment on mouse peritoneal exudate macrophages.184 Furthermore, 33 potentiated cytotoxic activity of TNF‐α against L929 murine fibrosarcoma cells.