AdCD40L is an adenoviral nonreplicating vector carrying the human CD40L gene. AdCD40L infects tumor cells upon intratumoral injection and deliver the CD40L gene into the cells whereupon the virus is destroyed. CD40L is then expressed as a membrane-bound protein and interacts with the CD40 receptor expressed by for example dendritic cells (DCs) in the tumor area. DCs mature upon CD40/CD40L interactions and activates tumor-specific T cell responses.