Despite the pressing need for novel cancer treatments, our improved understanding of tumor biology is not being successfully translated into better therapies. Here we present a lentiviral vector that enables in vivo validation of cancer therapeutic targets when combined with existing cancer animal models that faithfully reproduce the natural history of human disease. Unlike the conventional genetic approaches with targeted alleles, the outlined experimental strategy could be used to assess the preclinical efficacy of a growing number of putative therapeutic hits in a rapid and cost-effective manner.