Dendritic cell (DC)-based immunotherapy has been clinically evaluated, however, still requires modification to improve its outcomes. We previously demonstrated that DCs activated by replication competent recombinant Sendai virus (SeV) showed dramatic efficacy over that seen in use of current DC vaccine for immunotherapy against malignancies; however, application of replication-deficient vector is more relevant in clinical setting. We here show that F-gene-deleted non-transmissible Sendai virus (SeV/dF)-activated DCs (DCs/SeV/ dF) has strong antitumor effects against murine SCCVII tumor, that was well-known as a less immunogenic cell line. SeV/dF shows high transfection efficiency to DCs and leads them to upregulate costimulatory molecules. Intratumoral injection of DCs/SeV/dF resulted in a marked and representative inhibition of the tumor, even when the tumors were well-vascularized. This is the first demonstration that non-transmissible SeV vector, SeV/dF, could be a DC-activator; DC/SeV/dF-based cancer immunotherapy may, therefore, warrant further investigation. (c) 2007 Elsevier Inc. All rights reserved.