salmonella typhimurium , a facultative anaerobe , has been shown to accumulate at tumor sites when injected intravenously into mouse tumor models attenuated s. typhimurium were engineered to express fas ligand ( fasl ) to deliver this toxic , antitumor cytokine to tumor sites and to thereby enhance therapeutic potential . s. typhimurium expressing fasl dramatically inhibited the growth of d2f2 murine breast carcinoma and ct-26 murine colon carcinoma tumors , as well as the growth of d2f2 pulmonary metastases in mice . these experiments involved murine tumor models , and the effects of fasl - expressing s. typhimurium on human tumor models are not yet known . salmonella typhimurium , a facultative anaerobe , has been shown to accumulate at tumor sites when injected intravenously into mouse tumor models attenuated s. typhimurium were engineered to express fas ligand ( fasl ) to deliver this toxic , antitumor cytokine to tumor sites and to thereby enhance therapeutic potential . s. typhimurium expressing fasl dramatically inhibited the growth of d2f2 murine breast carcinoma and ct-26 murine colon carcinoma tumors , as well as the growth of d2f2 pulmonary metastases in mice . these experiments involved murine tumor models , and the effects of fasl - expressing s. typhimurium on human tumor models are not yet known . nih - ca69381 ; austrian program for advanced research and technology ( austrian academy of sciences ) .