title: Flt3 ligand antitumor activity in a murine breast cancer model: a comparison with granulocyte-macrophage colony-stimulating factor and a potential mechanism of action.
abstract: We have shown that Flk2/Flt3 ligand (Flt3L)-transduced tumor vaccine induces transferable T cell protection against a murine breast cancer cell line, but a direct comparison with the potent effector GM-CSF, the activity against preestablished tumors, and the mechanism of antitumor response in this breast cancer model are not known. We compared vaccination with C3L5 cells expressing Flt3L (C3Lt-Flt3L) and GM-CSF (C3L5-GMCSF) by injecting 1 x 10(4) cells subcutaneously into the chest wall and then, after 4 weeks, challenging the contralateral chest of tumor-free mice with parental C3L5 cells. C3L5-Flt3L and C3L5-GMCSF had reduced in vivo growth rates (25% tumor formation each) compared with 100% tumor formation of C3L5 cells expressing only neomycin phosphotransferase (C3L5-G1N). However, when tumor-free animals were challenged with parental C3L5 cells, C3L5-Flt3L vaccination was significantly better at preventing tumor growth (p < 0.05) than C3L5-GMCSF vaccination (33% of C3L5-Flt3L-vaccinated animals developed tumor compared with 77% of C3L5-GMCSF-vaccinated animals). Adoptive transfer of immunity for both vaccines was demonstrated; splenic T cells from tumor-free mice protected naive mice from parental tumor challenge. To simulate minimal disease, parental C3L5 cells at two concentrations (high, 5 x 10(3) cells; or low, 1 x 10(3) cells) were injected into the contralateral chest wall 4 days prior to treatment with C3L5-G1N or C3L5-Flt3L. C3L5-Flt3L treatment decreased contralateral parental tumor formation (high, 67% tumor free; low, 90% tumor free) compared with C3L5-G1N treatment (high and low, 0% tumor free). Immunodepletion of activated natural killer cells with anti-asialo-GM1 blocked C3L5-Flt3L- and C3L5 plus soluble Flt3L-mediated antitumor activity. Thus, Flt3L-transduced tumor cells manifest potent antitumor activity, apparently mediated, at least partially, by natural killer cells.
authors.affiliation: Department of Microbiology/Immunology, Indiana University School of Medicine, Indianapolis 46202, USA.
authors.forename: S E
authors.initials: SE
authors.lastname: Braun
authors.forename: K
authors.initials: K
authors.lastname: Chen
authors.forename: B R
authors.initials: BR
authors.lastname: Blazar
authors.forename: P J
authors.initials: PJ
authors.lastname: Orchard
authors.forename: G
authors.initials: G
authors.lastname: Sledge
authors.forename: M J
authors.initials: MJ
authors.lastname: Robertson
authors.forename: H E
authors.initials: HE
authors.lastname: Broxmeyer
authors.forename: K
authors.initials: K
authors.lastname: Cornetta
mesh_terms: D000818:Animals; D019496:Cancer Vaccines / Q000378:metabolism / Q000627:therapeutic use*; D003627:Data Interpretation, Statistical; D005260:Female; D018014:Gene Transfer Techniques; D015316:Genetic Therapy; D005822:Genetic Vectors; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism*; D016219:Immunotherapy, Adoptive; D007694:Killer Cells, Natural / Q000276:immunology; D008325:Mammary Neoplasms, Experimental / Q000276:immunology / Q000628:therapy*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008815:Mice, Inbred Strains; D011994:Recombinant Proteins; D012190:Retroviridae / Q000235:genetics; D014407:Tumor Cells, Cultured
chemical_list: D019496:Cancer Vaccines; D008565:Membrane Proteins; D011994:Recombinant Proteins; C084881:flt3 ligand protein; D016178:Granulocyte-Macrophage Colony-Stimulating Factor