Engineering of murine dendritic cells (DCs) with an adenovirus encoding IL12p70 was shown to augment DC expression of TNF family ligands and the capacity of these cells to kill the CMS4 sarcoma in vitro. To evaluate the impact of this DC-tumor interaction in vivo, we injected Ad.IL-12- engineered DCs derived from EGFP transgenic (green) mice directly into established day 7 CMS4 tumors in Balb/c mice. After 24 h, tumors were resected and OCT embedded, then sectioned and analyzed for apoptotic tumor cells by TUNEL staining (red). In the figure, DCs can be observed in areas of elevated tumor apoptosis (lower right inset), with some DCs observed to have take up apoptotic tumor bodies (arrow; higher magnification inset). For details, see the article by Tatsumi et al. on p. 6252 of this issue.