Topoisomerase IIα inhibition following DNA transfection greatly enhances random integration in a human pre-B lymphocyte cell line

DNA transfection can be too inefficient to establish a desired number of stable transfectants, particularly in lymphocytes; however, this could be circumvented by increasing the absolute frequency of random integration. In this paper, we show that treating cells with topoisomerase II inhibitor following electroporation greatly (∼10- to 20-fold) enhances random integration of input DNA in a human pre-B lymphocyte cell line, Nalm-6. With the use of various kinds of topoisomerase II-targeting agents, we also present evidence that topoisomerase IIα inhibition is critical for the enhancement of random integration, while the contribution of topoisomerase IIβ may be negligible. As topoisomerase IIα is highly expressed in vigorously growing cells, our results show that topoisomerase IIα inhibition provides a promising way of enhancing random integration in virtually all cultured cell lines.