A dual role for genetically modified lymphocytes in cancer immunotherapy.

T cells as the ultimate effectors of adaptive immune responses are currently used to treat patients affected by infectious diseases and certain tumors. Recently, T cells have been manipulated ex vivo with viral vectors coding for chimeric antigen receptors, exogenous T cell receptors, or 'suicide' genes to potentiate their efficacy and minimize possible side effects. However, the introduction of exogenous genes into T lymphocytes, particularly bacterial or viral transgene products, has occasionally produced immune-mediated elimination of transduced lymphocytes. This immune effect has recently been exploited in a trial of active immunotherapy in melanoma patients. In this opinion article, we discuss the therapeutic possibilities presented by the dual aspects of genetically modified lymphocytes used to treat cancer patients.