listeria monocytogenes activated dendritic cell based vaccine for prevention of experimental tumor in mice

background: the use of dendritic cells (dcs) as a cellular adjuvant provides a promis-ing approach in immunotherapy of cancer. it has been demonstrated that listeria mono-cytogenes activated dcs pulsed ex vivo with tumor antigens trigger a systemic th1-biased specific immune response and a single dose of this vaccine will cause a consider-able anti tumor immunity. objective: the present study was designed to evaluate the ability of multiple doses of tumor antigen-pulsed dcs, matured in the presence of lis-teria monocytogenes components in induction of a potent anti-tumor response and the prevention of tumor formation in an experimental model. methods: bone-marrow de-rived dcs (bmdcs) were cultured in the presence of gm-csf and il-4. after 5 days, tumor lysates with/without listeria monocytogenes lysate were added to the culture media for another 2 days. mice received mature and tumor antigen pulsed dendritic cells subcutaneously in 3 groups. tumor growth was monitored and two weeks after immu-notherapy, cytotoxic activity of cd8+ t cells was evaluated in different groups. re-sults: according to the findings, repeated doses of vaccine did not lead to a significant increase in the activity of cytotoxic t cells and decreased tumor growth of immunized animals. conclusion: the current study suggests that increased doses of vaccine do not have sufficient efficiency for prevention of tumor induction. generation of t regulatory responses upon repeated doses of such vaccines should be considered in future investi-gations.