Abstract 1782: Recombinant B7-DCIg enhances Bacillus Calmette-Guérin (BCG)-induced Th1 and anti-bladder cancer immune responses in vitro and in vivo

Abstract

Abstract Introduction and Objective: B7-DCIg, AMP-224, is a recombinant Fc fusion protein composed of the extracellular domain of B7-DC fused to the hinge and Fc domain of IgG. B7-DCIg interacts with PD-1, reduces the dysfunctional CD8+ T cells, and promotes an effective antitumor response. In vitro M. tuberculosis stimulation of human PBMC upregulates PD-1 expression in T cells. We proposed to test if B7-DCIg could enhance BCG-induced anti-bladder cancer immune responses. Methods: For in vitro evaluation of B7-DCIg on BCG induction of immune responses, mouse splenocytes were prepared and cultured in the absence or presence of Pasteur strain BCG and/or different doses of B7-DCIg for 3 days, followed by ELISA analysis of interferon gamma (IFN-γ) in culture supernatants. For in vivo evaluation of B7-DCIg on BCG induction of immune responses, mice were treated twice weekly with intravesical (i.b.) PBS plus intraperitoneal (i.p.) PBS, i.b. BCG (0.1 OD/dose) plus i.p. IgG2a (400 μg/dose), or i.b. BCG (0.1 OD/dose) plus i.p. B7-DCIg (400 μg/dose). The bladders were collected after treatments 2, 4 and 6, and analyzed for IFN- γ as well as other mRNAs by RT-PCR. ImageJ software was used to quantify PCR products on agarose gels. To evaluate the effect of B7-DCIg on BCG treatment of bladder cancer, C57BL/6 mice were implanted i.b. with luciferase-expressing MB49 (MB49-Luc) bladder cancer cells at day 0 and treated with i.b. BCG (0.1 OD/dose) plus i.p. B7-DCIg (400 μg/dose) twice weekly starting at day 1 for a total of 6 treatments. Control mice were treated with i.b. PBS plus i.p. PBS or i.b. BCG plus i.p. IgG2a. Bioluminescence was measured with Xenogen IVIS imaging at days 7, 14, and 21. At day 23 mice were euthanized and bladder weights measured. Results: B7-DCIg enhanced BCG-induced splenocyte IFN- γ production in a dose-dependent manner in vitro. B7-DCIg also enhanced BCG-induced bladder expression of IFN- γ and tumor necrosis factor related apoptosis-inducing ligand (TRAIL) mRNAs in vivo. In the orthotopic tumor model, BCG treatment reduced bladder weight by 53% (p = 0.0503 vs. PBS-treated group). Combination of BCG with B7-DCIg further reduced bladder weight by 5% (p = 0.0257 vs. PBS-treated group). In addition, the combination treatment also led to a delay in tumor growth by bioluminescence compared to BCG-treated group. Conclusions: B7-DCIg enhanced BCG-induced Th1 and anti-bladder cancer immune responses in mice. B7-DCIg may serve as a potential agent in combination with BCG for the treatment of bladder cancer in humans. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1782. doi:10.1158/1538-7445.AM2011-1782