title: Bispecific antibody-mediated lysis of placental and germ cell alkaline phosphatase targeted solid tumors in immunocompetent mice.
abstract: Recently, an immunocompetent in vivo mouse model was developed based on germ cell alkaline phosphatase (GCAP) transgenic (FVB/N x C3H) mice in which both placental alkaline phosphatase (PLAP)+ and GCAP+ solid MO4 tumors develop. A bispecific anti-PLAP/GCAP anti-mouse CD3 antibody (Ab) 7E8 x 7D6, previously shown to induce efficient dose-dependent T-cell proliferation and PLAP+ tumor cell lysis in the presence of recombinant IL-2 and the anti-mouse CD3 Ab 7D6, was used in this report in in vivo lysis experiments targeting GCAP+ tumors grown in GCAP+ transgenic mice. Mice received injections i.v. twice a week with PBS (group 1) or with 10 micrograms of the bispecific Ab 7E8 x 7D6, either alone (group 2) or combined with 1 microgram of the anti-CD3 Ab 7D6 (group 3), starting 7 days after the tumor inoculation. A fourth group received a local treatment with mouse splenocytes precoated with 10 micrograms 7E8 x 7D6 and 1 microgram 7D6. In between Ab injections, groups 2, 3, and 4 received 10(4) units recombinant IL-2 (i.v.) every day. Two weeks of treatment with the bispecific Ab either alone or combined with 7D6 resulted in a significant decrease of GCAP+ tumor cells in groups 2 and 3 (4 +/- 3% and 10 +/- 11% GCAP+ cells/tumor) as compared to the nontreated tumors (95 +/- 5% GCAP+ cells), although tumor volumes were not significantly different (12 +/- 15 cm3 and 14 +/- 11 cm3 versus 16 +/- 7 cm3). Apparently, the elimination of GCAP+ cells from the tumor seemed to favor conditions enabling the outgrowth of the few GCAP- cells originally present in the tumor inoculate. In contrast, tumor volumes in group 4 (local treatment) were significantly smaller (P < 0.03; 5 +/- 10 cm3, 8 +/- 11% GCAP+ cells) as compared to the nontreated group, probably due to the presence of higher amounts of Ab and infiltrated activated T cells (567 +/- 322 CD5+ cells/mm2) capable of secreting cytostatic cytokines like tumor necrosis factor alpha and IFN-gamma as compared to groups 2 and 3 (266 +/- 135 and 198 +/- 86 CD5+ cells/mm2, respectively). In summary, this study clearly demonstrated that bispecific antibodies specifically concentrate cytotoxic T cells into a solid tumor in vivo, with subsequent elimination of the targeted tumor cell.
authors.affiliation: Department of Nephrology-Hypertension, University of Antwerp, Edegem, Belgium.
authors.forename: K A
authors.initials: KA
authors.lastname: Smans
authors.forename: M F
authors.initials: MF
authors.lastname: Hoylaerts
authors.forename: S
authors.initials: S
authors.lastname: Narisawa
authors.forename: J L
authors.initials: JL
authors.lastname: Millán
authors.forename: M E
authors.initials: ME
authors.lastname: De Broe
mesh_terms: D000469:Alkaline Phosphatase / Q000032:analysis / Q000276:immunology*; D000818:Animals; D018033:Antibodies, Bispecific / Q000276:immunology*; D014408:Biomarkers, Tumor / Q000276:immunology*; D003602:Cytotoxicity, Immunologic; D005260:Female; D058851:GPI-Linked Proteins; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000276:immunology*; D008213:Lymphocyte Activation; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008822:Mice, Transgenic; D009374:Neoplasms, Experimental / Q000276:immunology / Q000628:therapy*; D010920:Placenta / Q000201:enzymology*; D016176:T-Lymphocyte Subsets; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D018033:Antibodies, Bispecific; D014408:Biomarkers, Tumor; D058851:GPI-Linked Proteins; D007527:Isoenzymes; D000469:Alkaline Phosphatase; C019839:alkaline phosphatase, placental