Successful eradication of solid tumors and metastatic disease by immunotherapy requires efficient activation and mobilization of functional anti-tumor effector cells to tumor sites.Dendritic cells (DC), as the pivotal initiator and regulator of immune responses, have become the major targets and candidates for tumor immunotherapy.To increase the number of tumor antigen presenting DCs in lymphoid compartments and maximize their immune stimulatory effects on anti-tumor immunity, we employed a new stem cell based in vivo DC vaccine approach through transplantation of lentiviral vector engineered DC progenitors carrying a tumor antigen gene.