title: Intratumoral spread and increased efficacy of a p53-VP22 fusion protein expressed by a recombinant adenovirus.
abstract: In vitro experiments have demonstrated intercellular trafficking of the VP22 tegument protein of herpes simplex virus type 1 from infected cells to neighboring cells, which internalize VP22 and transport it to the nucleus. VP22 also can mediate intercellular transport of fusion proteins, providing a strategy for increasing the distribution of therapeutic proteins in gene therapy. Intercellular trafficking of the p53 tumor suppressor protein was demonstrated in vitro using a plasmid expressing full-length p53 fused in-frame to full-length VP22. The p53-VP22 chimeric protein induced apoptosis both in transfected tumor cells and in neighboring cells, resulting in a widespread cytotoxic effect. To evaluate the anti-tumor activity of p53-VP22 in vivo, we constructed recombinant adenoviruses expressing either wild-type p53 (FTCB) or a p53-VP22 fusion protein (FVCB) and compared their effects in p53-resistant tumor cells. In vitro, treatment of tumor cells with FVCB resulted in enhanced p53-specific apoptosis compared to treatment with equivalent doses of FTCB. However, in normal cells there was no difference in the dose-related cytotoxicity of FVCB compared to that of FTCB. In vivo, treatment of established tumors with FVCB was more effective than equivalent doses of FTCB. The dose-response curve to FVCB was flatter than that to FTCB; maximal antitumor responses could be achieved using FVCB at doses 1 log lower than those obtained with FTCB. Increased antitumor efficacy was correlated with increased distribution of p53 protein in FVCB-treated tumors. This study is the first demonstration that VP22 can enhance the in vivo distribution of therapeutic proteins and improve efficacy in gene therapy.
authors.affiliation: Canji, Inc., San Diego, California 92121, USA. ken.wills@canji.com
authors.forename: K N
authors.initials: KN
authors.lastname: Wills
authors.forename: I A
authors.initials: IA
authors.lastname: Atencio
authors.forename: J B
authors.initials: JB
authors.lastname: Avanzini
authors.forename: S
authors.initials: S
authors.lastname: Neuteboom
authors.forename: A
authors.initials: A
authors.lastname: Phelan
authors.forename: J
authors.initials: J
authors.lastname: Philopena
authors.forename: S
authors.initials: S
authors.lastname: Sutjipto
authors.forename: M T
authors.initials: MT
authors.lastname: Vaillancourt
authors.forename: S F
authors.initials: SF
authors.lastname: Wen
authors.forename: R O
authors.initials: RO
authors.lastname: Ralston
authors.forename: D E
authors.initials: DE
authors.lastname: Johnson
mesh_terms: D000260:Adenoviruses, Human; D000818:Animals; D017209:Apoptosis; D019556:COS Cells; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002522:Chlorocebus aethiops; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics; D004789:Enzyme Activation; D015870:Gene Expression; D005822:Genetic Vectors; D018259:Herpesvirus 1, Human / Q000378:metabolism*; D006801:Humans; D009374:Neoplasms, Experimental / Q000503:physiopathology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D015678:Viral Structural Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D011993:Recombinant Fusion Proteins; D016159:Tumor Suppressor Protein p53; D015678:Viral Structural Proteins; C073413:herpes simplex virus type 1 protein VP22; C506433:CASP9 protein, human; D053453:Caspase 9; D020169:Caspases