Combination therapy with cisplatin and anti-4-1BB: synergistic anticancer effects and amelioration of cisplatin-induced nephrotoxicity.

Anti-4-1BB and cisplatin showed synergistic anticancer effects in the CT-26 colon carcinoma model, producing complete regression in >60% of mice with either preventive or therapeutic treatment. The tumor-free mice formed long-lasting CD8(+) T cell-dependent tumor-specific memory. Anti-4-1BB induced rapid repopulation of T and B cells from cisplatin-mediated lymphopenia and differentiation and expansion of IFN-gamma(+)CD11c(+)CD8(+) T cells. Cisplatin facilitated expansion of naïve, effector, and memory CD8(+) T cells; combination therapy produced almost twice as many lymphoid cells as anti-4-1BB alone. Cisplatin increased 4-1BB on antigen-primed T cells and induced 4-1BB de novo on kidney tubular epithelium. Cross-linking of 4-1BB protected the T cells and kidney epithelium from cisplatin-mediated apoptosis by increasing expression of antiapoptotic molecules. Thus, cisplatin-induced 4-1BB provided a mechanism for amelioration of the lymphopenia and nephrotoxicity inherent in cisplatin treatment. We concluded that chemoimmunotherapy with anti-4-1BB and cisplatin is synergistic in tumor killing and prevention of organ-specific toxicity.