Abstract 1903: Enhanced antitumor effect of coincident combination intravesical MMC plus BCG therapy in an orthotopic bladder cancer model

Abstract

Abstract Introduction and Objective: Intravesical immunotherapy with bacillus Calmette-Guerin (BCG) is currently the most successful adjuvant agent for the treatment and/or prophylaxis of superficial bladder tumors. However, superficial bladder tumors recur in 60 to 70% of all cases, and 30 % of these recurrent tumors present with a higher grade with invasive properties. We evaluated the combination of intravesical MMC plus BCG treatment against bladder tumors in a model of orthotopic murine bladder cancer. Methods: An orthotopic murine bladder cancer model was established using the simple instillation of 1 × 106 MBT-2 cells into the lumen of the bladder of a female C3H/HeN mouse through a urethral catheter. To assess the antitumoral effect of MMC, intravesical MMC therapy was administered at various dose-escalating concentrations: 0μg (control: PBS), 25μg, 50μg, 100μg, and 200μg, (n = 8 for each group; a total of 5 groups). Next, a comparative evaluation of tumor growth in a control group(PBS), a MCC-alone group, a BCG-alone group(100μg), and a combined MMC plus BCG (100μg) group were performed (n= 8 for each group; a total of 4 groups). Intravesical therapy was administered at 3-day intervals starting on day 5 and repeated 5 times. On day 60 after the initial implantation of the MBT-2 cells, all the surviving mice were sacrificed and necropsied. To evaluate macrophage infiltration in the tumor and the proliferative activity among the different groups, immunohistochemical staining analysis of the tumor cells utilizing CD68 and Ki-67 was performed in animal model. Results: In the MMC groups of 8 mice each treated with a dose of 0μg (survival; 26.4 ± 3.2 days), 25μg (34.8 ± 7.0 days) and 50μg (40.0 ± 13.2 days), 0, 0 and 2 of the mice failed to develop tumor and survived, respectively. In both the 100μg (17.3 ± 2.8 days) and 200μg (11.9 ± 3.0 days) groups, all eight mice died from adverse events. A significant survival advantage was observed in the combined MMC (50μg) plus BCG (100μg) group (51.5 ± 8.1 days), compared with that in the BCG-alone group (33.4 ± 16.8 days; p = 0.03) and the MMC-alone group (39.5 ± 13.5 days; p = 0.04). BCG significantly suppressed while MMC increased macrophage infiltration in the tumors, compared with in the control groups. The Ki-67 expression level, which is regarded as a proliferation index was significantly lower in the combined MMC (50μg) plus BCG (100μg) group (31.1 ± 5.2%) than in the BCG-alone group (50.9 ± 4.1%; p <0.001) and the MCC-alone group (39.2 ± 2.5%; p <0.05). Conclusion: Combining BCG plus MMC treatment decreased the tumor appearance rate, improved the survival period and reduced the proliferation rate in tumors, as compared with BCG-alone and MMC-alone treatment, possibly providing a greater therapeutic benefit over either agent alone. Immunochemotherapy with a combination of intravesical MMC plus BCG may be a promising alternative treatment for bladder tumors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1903.