The method disclosed herein describes a novel technology offering unparalleled efficiency, flexibility, utility and speed for the stable integration of transgenes into lymphocytes and other mammalian cells. The novel method is based on the use of an mRNA-encoded transposase (e.g. sleeping beauty transposase) in combination with a minicircle DNA-encoded transposable element. The novel method enables higher gene-transfer rates and is at the same time less toxic than the conventional approach, which is the use of plasmid DNA- encoded transposase in combination with a plasmid DNA-encoded transposable element. Applications of the invention include but are not limited to the stable integration of a transgene encoding an immune receptor (e.g. a T-cell receptor or synthetic chimeric antigen receptor) into human T lymphocytes, with the immune receptor conferring specificity for a molecule expressed by a tumor cell. The transposase mRNA and transposon minicircle DNA may be introduced into lymphocytes by methods including but not limited to electrotransfer such as electroporation and nucleofection.
