In vitro and in vivo transfection of p21 gene enhances cyclosporin A-mediated inhibition of lymphocyte proliferation

Cyclosporine has potent antiproliferative properties, some of which may be via the induction of the cyclin inhibitor p21. In this study, we describe t he effects of in vitro and in vivo transfection of p21 in lymphoid and nonl ymphoid cells. For In vitro studies, p21 sense plasmid DNA was transfected in A-549 cells (lung adenocarcinoma cell line) and Jurkat cells (human lymp hoid cell line), This in vitro transfection of p21 resulted in the inhibiti on of spontaneous and mitogen-induced cellular proliferation ([H-3]thymidin e uptake) and also augmented the antiproliferative effects of cyclosporine, In vivo transfection of p21 was accomplished in mice via the i.m. injectio n of p21 sense plasmid DNA complexed with cationic lipids, As was the case in the cell lines, p21 mRNA was augmented in heart, lung, liver, and spleen 7 days after i.m. injection of p21 sense plasmid DNA, The mitogen (anti-CD 3)induced proliferation of splenocytes from p21-overexpressing mice was sig nificantly decreased, and again this effect was augmented by cotreatment wi th cyclosporine. These novel findings demonstrate the potential of targetin g the cell cycle directly to inhibit alloimmune activation in organ transpl antation. This may serve as an alternate strategy to induce immunosuppressi on, perhaps with less toxicity than that which is seen with conventional im munosuppressive agents.