title: Antimetastatic effect of suicide gene therapy for mouse mammary cancers requires T-cell-mediated immune responses.
abstract: These experiments were conducted to investigate whether the antimetastatic effects of HSVtk/GCV therapy involve T-cell-mediated immune responses. In the first experiment, immunocompetent syngeneic mice were inoculated with metastatic mammary cancers, then given a direct intratumoral injection of a plasmid vector containing a suicide gene (pHSVtk) or control vector once a week for 8 weeks. Gene electrotransfer treatment was applied to the tumors, and mice were administered ganciclovir (GCV) using a mini-osmotic pump. At the end of the experiment, tumor volume was significantly lower in the pHSVtk/GCV group. Macrophage accumulations were frequently observed in the peripheries of the necrotic regions in pHSVtk-transfected mice. Levels of CD4 and CD8 proteins in tumors were higher in the pHSVtk/GCV group than in the control group. Interleukin (IL)-12 mRNA levels tended to be higher in tumors in the pHSVtk/GCV group, but there were large variations. Tumor microvessel density was significantly lower in the pHSVtk/GCV group. The numbers of dilated lymphatic vessels containing intraluminal tumor cells tended to be higher in the pHSVtk/GCV group. However, vascular endothelial growth factor (VEGF)-A and VEGF-C mRNA levels in tumors were similar in the control and pHSVtk/GCV groups. In the second experiment, tumor volume and metastatic parameters were compared for immunocompetent syngeneic mice and immunodeficient athymic mice (without an intact T-cell system) given pHSVtk/GCV therapy. Although tumor volumes were significantly smaller in both syngeneic and athymic mice given pHSVtk/GCV therapy, the inhibition ratios (relative to control mice) were much greater in syngeneic mice than in athymic mice. No suppression of metastasis to the lymph nodes and lungs was observed for athymic mice given pHSVtk/GCV therapy. Our data suggest that HSVtk/GCV suicide gene therapy exerts an antimetastatic effect via a T-cell-mediated immune response.
authors.affiliation: Department of Anatomy and Cell Biology, Division of Basic Medicine I, Osaka Medical College, 2-7 Daigaku-machi, Takatsuki, Osaka 569-8686, Japan.
authors.forename: Masa-Aki
authors.initials: MA
authors.lastname: Shibata
authors.forename: Junji
authors.initials: J
authors.lastname: Morimoto
authors.forename: Kanako
authors.initials: K
authors.lastname: Akamatsu
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Otsuki
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000627:therapeutic use; D001483:Base Sequence; D015704:CD4 Antigens / Q000378:metabolism; D016827:CD8 Antigens / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D005260:Female; D015774:Ganciclovir / Q000627:therapeutic use; D015316:Genetic Therapy; D018259:Herpesvirus 1, Human / Q000201:enzymology / Q000235:genetics; D018664:Interleukin-12 / Q000235:genetics / Q000378:metabolism; D008175:Lung Neoplasms / Q000556:secondary; D008207:Lymphatic Metastasis; D008325:Mammary Neoplasms, Experimental / Q000235:genetics / Q000276:immunology* / Q000628:therapy*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology*; D013937:Thymidine Kinase / Q000235:genetics; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism; D042582:Vascular Endothelial Growth Factor C / Q000235:genetics / Q000378:metabolism
chemical_list: D000998:Antiviral Agents; D015704:CD4 Antigens; D016827:CD8 Antigens; D017931:DNA Primers; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D042582:Vascular Endothelial Growth Factor C; C467480:vascular endothelial growth factor A, mouse; C467483:vascular endothelial growth factor C, mouse; D018664:Interleukin-12; D013937:Thymidine Kinase; D015774:Ganciclovir