title: Regulation of Transgene Expression in Tumor Cells by Exploiting Endogenous Intracellular Signals.
abstract: Recently, we have proposed a novel strategy for a cell-specific gene therapy system based on responses to intracellular signals. In this system, an intracellular signal that is specifically and abnormally activated in the diseased cells is used for the activation of transgene expression. In this study, we used protein kinase C (PKC)alpha as a trigger to activate transgene expression. We prepared a PKCalpha-responsive polymer conjugate [PPC(S)] and a negative control conjugate [PPC(A)], in which the phosphorylation site serine (Ser) was replaced with alanine (Ala). The phosphorylation for polymer/DNA complexes was determined with a radiolabel assay using [gamma-(32)P]ATP. PPC(S)/DNA complexes were phosphorylated by the addition of PKCalpha, but no phosphorylation of the PPC(A)/DNA complex was observed. Moreover, after microinjection of polymer/GFP-encoding DNA complexes into HepG2 cells at cation/anion (C/A) ratios of 0.5 to 2.0, significant expression of GFP was observed in all cases using PPC(S)/DNA complexes, but no GFP expression was observed in the negative control PPC(A)/DNA complex-microinjected cells at C/A ratios of 1.0 and 2.0. On the other hand, GFP expression from PPC(S)/DNA complexes was completely suppressed in cells pretreated with PKCalpha inhibitor (Ro31-7549). These results suggest that our gene regulation system can be used for tumor cell-specific expression of a transgene in response to PKCalpha activity.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Asai
authors.forename: Jeong-Hun
authors.initials: JH
authors.lastname: Kang
authors.forename: Riki
authors.initials: R
authors.lastname: Toita
authors.forename: Akira
authors.initials: A
authors.lastname: Tsuchiya
authors.forename: Takuro
authors.initials: T
authors.lastname: Niidome
authors.forename: Hideki
authors.initials: H
authors.lastname: Nakashima
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Katayama