New strategies for active immunotherapy with genetically engineered tumor cells.

While previous tumor vaccine strategies have shown intriguing results, clearcut efficacy has been difficult to establish in human trials. Recently, newer approaches have been developed in animal systems that modify tumor cells genetically so that they express new antigens or secrete certain cytokines. Engineering tumor cells to secrete cytokines in a paracrine fashion can induce powerful local cytokine effects without producing significant systemic toxicity. In addition to local inflammation, this approach can alter the presentation of tumor antigen or activation of tumor antigen-specific T lymphocytes, resulting in systemic antitumor immunity.