Vaccine-induced tumor necrosis factor-producing T cells synergize with cisplatin to promote tumor cell death.

Purpose: Cancer immunotherapy, such as vaccination, is an increasingly successful treatment modality, but its interaction with chemotherapy remains largely undefined. Therefore, we explored the mechanism of synergy between vaccination with synthetic long peptides (SLP) of human papillomavirus type 16 (HPV16) and cisplatin in a preclinical tumor model for HPV16. Experimental Design: SLP vaccination in this preclinical tumor model allowed the elucidation of novel mechanisms of synergy between chemo- and immunotherapy. By analyzing the tumor immune infiltrate, we focused on the local intratumoral effects of chemotherapy, vaccination, or the combination. Results: Of several chemotherapeutic agents, cisplatin synergized best with SLP vaccination in tumor eradication, without requirement for the maximum-tolerated dose (MTD). Upon SLP vaccination, tumors were highly infiltrated with HPV-specific, tumor necrosis factor-alpha (TNF alpha)- and interferon-gamma (IFN gamma)-producing T cells. Upon combined treatment, tumor cell proliferation was significantly decreased compared with single treated and untreated tumors. Furthermore, we showed that TNFa strongly enhanced cisplatin-induced apoptotic tumor cell death in a JNK-dependent manner. This is consistent with upregulation of proapoptotic molecules and with enhanced cell death in vivo upon combined SLP vaccination and cisplatin treatment. In vivo neutralization of TNFa significantly reduced the antitumor responses induced by the combined treatment. Conclusion: Taken together, our data show that peptide vaccination with cisplatin treatment leads to decreased tumor cell proliferation and TNF alpha-induced enhanced cisplatin-mediated killing of tumor cells, together resulting in superior tumor eradication. (C) 2014 AACR.