The therapeutic potential of SA-sCD40L in the orthotopic model of superficial bladder cancer

Abstract

Background. Intravesical administration is an important treatment against superficial bladder cancer and CD40L is essential for the protective anti-tumor immunity. In situ gene therapy with CD40L was demonstrated to successfully inhibit tumor cell growth in the orthotopic mouse model of bladder cancer. In the present study, we prepared streptavidin (SA)-tagged sCD40L and developed a novel immunotherapy for superficial bladder cancer based on the strong interaction between streptavidin and biotin. Material and methods. The SA-sCD40L fusion protein was expressed in E. coli and purified on the Ni-NTA column. After refolding with dialysis, the bi-function of the fusion protein was determined by flow cytometric analysis for streptaidin-mediated surface modification of MB49 bladder cancer cells and a mouse B cell CD40L-dependent proliferation assay. The mouse orthotopic model of MB49 superficial bladder cancer was used to evaluate the efficacy of SA-sCD40L immunotherapy. Results. The SA-sCD40L fusion protein exhibited both full biotin-binding property and CD40L bioactivity. After intravesical instillation, the SA-sCD40L bi-functional fusion protein was durably immobilized on the biotinylated mucosal surface of bladder wall for up to four days. The SA-sCD40L treatment significantly prolonged the survival of MB49 tumor-bearing mice and cured 50% of mice with MB49 superficial bladder cancer without significant adverse effects. In addition, more tumor-infiltrating CD4⁺or CD8⁺ T cells were observed in SA-sCD40L–treated group. Conclusion. Intravesical immobilization of SA-sCD40L elicited a strong and long-lasting immunity against the MB49 bladder cancer.