Abstract 4742: BCG in combination with anti-IL-10R1 monoclonal antibody induces specific antitumor immunity in an orthotopic bladder cancer model.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Introduction and Objective: We previously demonstrated that combination therapy with BCG and anti-IL-10 receptor 1 monoclonal antibody (anti-IL-10R1 mAb) effectively prevented bladder cancer metastasis in a murine MB49 orthotopic tumor model. MB49 cells express the male minor histocompatibility (HY) antigen that, although is immunogenic, induces no tumor rejection in female mice. Here we investigated whether the combination therapy could enhance HY-specific immune responses and whether this HY-specific immunity contributed to the prevention of bladder cancer metastasis in this model. Methods: Four groups of female mice (n = 5) were inoculated intravesically (i.b.) with 1 X 106 luciferase–expressing MB49 (MB49-Luc) cells and treated intraperitoneally (i.p.) with PBS, control IgG (200μg), or anti-IL-10R1 mAb (200μg) at day 0. Starting at day 1, mice were treated twice weekly with i.b. PBS plus i.p. PBS (Group 1), i.b. PBS plus i.p. anti-IL-10R1 mAb (Group 2), i.b. BCG plus i.p. control IgG (Group 3), or i.b. BCG plus i.p. anti-IL-10R1 mAb (Group 4) for a total of 6 treatments. Tumor growth was monitored using the IVIS luminescence system. Mice were sacrificed for analysis at day 21. Splenocytes were prepared, pooled and cultured in the presence of a HY antigen peptide or a control ovalbumin (OVA) peptide. After 3 days culture supernatants were collected and analyzed for IFN-γ production by ELISA. After 5 days splenocytes were used as effector cells in a cytotoxicity assay. Results: Tumor implantation was confirmed for all groups. Splenocytes produced no IFNγ in response to OVA peptide stimulation. Splenocytes from Groups 1 and 3 (treated with no anti-IL-10R1 mAb) produced no IFN-γ in response to HY peptide stimulation. In contrast, splenocytes from Groups 2 and 4 (treated with anti-IL-10R1 mAb) produced significantly increased IFN-γ in a dose-dependent manner in response to HY peptide stimulation, with Group 4 (combination therapy) splenocytes being more potent. Accordingly, Group 4 splenocytes exhibited profound cytotoxicity against MB49-Luc cells with 69.8%, 51.2% and 25.6% killing at an E:T ratio of 50:1, 25:1 and 12.5:1, respectively. However, splenocytes from Group 2 (anti-IL-10R1 mAb monotherapy) showed marginal killing of MB49-Luc cells. Conclusions: BCG in combination with anti-IL-10R1 mAb induced HY-specific effector cells cytotoxic to MB49-Luc bladder cancer cells. Anti-IL-10R1 mAb may prove useful in clinical practice for the prevention of metastatic bladder cancer in high-risk patients. Citation Format: Eric J. Askeland, Mark R. Newton, Xu Wang, Xiaohong Chen, Ryan W. Askeland, Michael A. O'Donnell, Yi Luo. BCG in combination with anti-IL-10R1 monoclonal antibody induces specific antitumor immunity in an orthotopic bladder cancer model. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4742. doi:10.1158/1538-7445.AM2013-4742