Nonviral gene delivery with the Sleeping Beauty transposon system

Effective gene therapy requires robust delivery of the desired genes into the relevant target cells, long-term gene expression and minimal risks of secondary effects. Non-viral gene transfer approaches typically result in only short-lived transgene expression in primary cells, due to the lack of nuclear maintenance of the vector over several rounds of cell division. The development of efficient and safe non-viral vectors equipped with an integrating feature would thus greatly facilitate clinical gene therapy studies. The latest generation transposon technology based on the Sleeping Beauty (SB) transposon may potentially overcome some of these limitations. SB was recently shown to provide efficient stable gene transfer after non-viral gene delivery into therapeutically relevant primary cell types, including human hematopoietic progenitors, mesenchymal stem cells, muscle stem/progenitor cells (myoblasts), iPSCs and T cells. These cells are relevant targets for stem cell biology and for regenerative medicine and gene- and cell-based therapies of complex genetic diseases. Moreover, the first-in-man clinical trial has recently been launched to use redirected T cells engineered with SB for gene therapy of B cell lymphoma. We discuss aspects of cellular delivery of the SB transposon system, transgene expression provided by integrated transposon vectors, target site selection of the transposon vectors and potential risks associated with random genomic insertion.