title: Both soluble and membrane-bound forms of Flt3 ligand enhance tumor immunity following "suicide" gene therapy in a murine colon carcinoma model.
abstract: In prodrug-activated ("suicide") gene therapy, tumor cells are transfected with the gene for an enzyme that converts an inactive prodrug, such as ganciclovir (GCV), to a toxic compound. Transfected cells are killed on administration of GCV, as also are untransfected "bystander" cells. The ability of the dendritic cell stimulatory cytokine Flt3 ligand (Flt3-L) to modulate prodrug-activated gene therapy has been investigated. Transfectants of the murine colon carcinoma MC26 were generated expressing soluble (FLS) and membrane-bound forms of Flt3-L. They were inoculated together with wild-type MC26 cells and cells expressing herpes simplex virus-1 (HSV1) thymidine kinase into BALB/c mice, which were then administered GCV. Expression of Flt3-L or FLS prevented regrowth of tumor in most mice, which was comparable to the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF), while tumors recurred in all mice receiving "suicide" gene therapy alone. Recurring tumor cells were resistant to direct killing by GCV but sensitive to "bystander" killing in vitro. Mice without tumor recurrence were rechallenged with unmodified MC26 cells. Of those mice given transfectants expressing GM-CSF, Flt3-L, or FLS, approximately 50% were immune to rechallenge. These mice also showed cytotoxic and proliferative responses to MC26 cells. These experiments show that both soluble and membrane-bound forms of Flt3-L were able to induce a protective immune response to colon carcinoma cells in a fashion similar to GM-CSF.
authors.affiliation: Department of Immunology, University of Liverpool Medical School, Daulby St., L69 3GA, Liverpool, UK.
authors.forename: Abdul-Razzak
authors.initials: AR
authors.lastname: Alsheikhly
authors.forename: Jehad
authors.initials: J
authors.lastname: Zweiri
authors.forename: Alice J
authors.initials: AJ
authors.lastname: Walmesley
authors.forename: Alastair J M
authors.initials: AJ
authors.lastname: Watson
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Christmas
mesh_terms: D000818:Animals; D002277:Carcinoma / Q000628:therapy*; D002455:Cell Division; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism*; D003110:Colonic Neoplasms / Q000628:therapy*; D003713:Dendritic Cells / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D015774:Ganciclovir / Q000494:pharmacology; D015316:Genetic Therapy / Q000379:methods*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism; D018259:Herpesvirus 1, Human / Q000201:enzymology; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental; D011355:Prodrugs; D012008:Recurrence; D013154:Spleen / Q000166:cytology; D013937:Thymidine Kinase / Q000378:metabolism; D013997:Time Factors; D014162:Transfection
chemical_list: D008565:Membrane Proteins; D011355:Prodrugs; C084881:flt3 ligand protein; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D013937:Thymidine Kinase; D015774:Ganciclovir