1. ¹Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
2. ²Cancer Biology Program, Graduate School of Biomedical Science, The University of Texas, Health Science Center at Houston, Houston, TX, USA

Correspondence: Dr M-C Hung, Department of Molecular and Cellular Oncology, Box 108, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA. E-mail: mhung@mdanderson.org

³Visiting Scientist from the Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan, Republic of China.

⁴These authors contributed equally to this work.

Received 22 June 2005; Revised 4 October 2005; Accepted 9 October 2005; Published online 6 January 2006.

Abstract

Antitumor vaccination therapies using attenuated Salmonella typhimurium carrying plasmid DNA encoding tumor-associated antigens are currently under preclinical development. In the present study, we first established a useful method to facilitate in vivo monitoring of attenuated S. typhimurium uptake using a bioluminescent lux gene operon plasmid. Following transformation with the lux gene operon construct, mice were fed with various amounts of attenuated S. typhimurium-lux to monitor in vivo clearance over a period of 24 h. We found that the ingested attenuated S. typhimurium-lux cells were almost cleared out 9 h postfeeding, as judged by a significant decrease in bioluminescence. We further examined the therapeutic efficacy of vaccination using attenuated S. typhimurium carrying the mouse -fetoprotein (AFP) gene against a cancer line CT26-murine -feto protein (mAFP) that stably expresses AFP and mouse hepatocellular carcinoma (HCC) Hepa1-6. Attenuated S. typhimurium oral DNA vaccine was found to promote protective immunity against both CT26-mAFP and Hepa1-6 tumor cells growth. The oral DNA vaccine significantly increased the life span of tumor-challenged mice in both tumor models. Together, these results suggest that vaccination with the attenuated S. typhimurium oral DNA vaccine that carries the AFP gene could be a promising strategy to prevent HCC development.