title: The mechanism of exogenous B7.1-enhanced IL-12-mediated complete regression of tumors by a single electroporation delivery.
abstract: Electroporation-based mono-gene therapy has received great interest in recent years but coadministration of different therapeutic genes for treatment of tumors has not been well explored. We hypothesize that electroporation is capable of delivering multiple genes that induce an additive or synergistic antitumor effect. To test this hypothesis, we used mice that were bearing SCCVII or TRAMP tumors. Established tumors with a diameter of 4-5 mm were injected with control plasmid DNA or plasmid DNA encoding B7.1, IL-12 or both via electroporation. Tumor regression, CTL activity and the level of B7.1, IL-12 and Stat1 expression were determined in both wild-type mice and in mice with a knock-out of the Stat1 gene. Remarkably, a single coadministration of the plasmids that encoded IL-12 and B7.1 eradicated tumors in 80% of mice. The therapeutic effect was associated with high levels of endogenous B7.1 expression, activity of cytotoxic lymphocytes, and activation of Stat1. Both exogenous B7.1 and IL-12 were required for inducing a high level of Stat1 activation in tumors, which occurred through a mechanism that was independent of the host Stat1. Both stimulators were also required for inducing the strong cytotoxic lymphocyte activity and for increasing the level and extending the duration of endogenous B7.1 expression. We therefore propose a 2-signal stimulation model to explain the synergistic effect of the coadministration of IL-12 and B7.1 on the regression of the tumors.
authors.affiliation: Department of Comparative Biomedical Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
authors.forename: Jianguo
authors.initials: J
authors.lastname: Liu
authors.forename: Xueqing
authors.initials: X
authors.lastname: Xia
authors.forename: Marina
authors.initials: M
authors.lastname: Torrero
authors.forename: Robin
authors.initials: R
authors.lastname: Barrett
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Shillitoe
authors.forename: Shulin
authors.initials: S
authors.lastname: Li
mesh_terms: D000818:Animals; D018122:B7-1 Antigen / Q000502:physiology*; D045744:Cell Line, Tumor; D017931:DNA Primers; D018274:Electroporation; D015972:Gene Expression Regulation, Neoplastic; D018664:Interleukin-12 / Q000502:physiology*; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D009374:Neoplasms, Experimental / Q000235:genetics*; D010957:Plasmids; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D018122:B7-1 Antigen; D017931:DNA Primers; D018664:Interleukin-12