Background: Tumor cell lysate has been considered as a preferential antigen source for the therapeutic dendritic cell pulsing. Our experiences with in vivo study with animal tumor model indicate the tumor cell lysate dependent differential effect of DC therapy. Our previous data show that MC38 lysate pulsed-DC induced stronger ag-specific immunity than CT26 lysate pulsed-DC in vitro. In this study we tried to reveal the mechanism for differential induction of ag-specific immunity of different colon cancer cell lysate pulsed-DCs. Methods: MC38 and CT26 cell lines were prepared as lysate by freezing-thawing procedure. Tumor cell antigenicity was confirmed by detecting the surface expression of MHC I/II & B7.1/2 molecules. IL-10, IL-12 and TGF-beta in the tumor cell lysate were detected by ELISA and the presence of heat shock proteins were analysed by western blotting. Results: The secretion of IL-10, a immune-inhibitory cytokine was about 470% higher in CT26 lysate than in MC38. Hsp 70 was detected only in the MC38 lysate but not in the CT26. On the other hand, Hsp 60 and 90 expression were not different in two colon cancer cell lysates. Conclusion: In two different colon cancer cell lysate, immune inhibitory IL-10 (higher in CT26) and Hsp70 (MC38 superiority) were differentially expressed. These data indicate that higher agspecific immunity induction by MC38 lysate pulsed-DC may due to the expression of hsp70 and lower secretion of IL-10, a immune-inhibitory cytokine than CT26 lysate. The significance of other cytokine and the surface marker expression will be discussed.