IFNγ Markedly Cooperates with Intratumoral Dendritic Cell Vaccine in Dog Tumor Models

Dendritic cell (DC)-based immunotherapy can trigger effective immune responses against cancer in human patients. Although accompanied by little toxicity, further improvements are needed to optimize immune responses for fully satisfactory clinical outcomes. IFN gamma, a potent inducer of T helper type 1 immune responses, is considered an important tool to realize improvements. In this study, we sought to clarify the effect of IFN gamma on the maturation and activation of DCs and the clinical outcome of DC-based cancer therapy in dogs. In vitro experiments indicated that IFN gamma significantly enhanced the expression of immune stimulatory molecules and interleukin-12 by DCs derived from canine monocytes. IFN gamma also significantly strengthened DC-mediated growth suppression against tumor cell lines. DC inoculation with concomitant delivery of IFN gamma into primary or recurrent tumors elicited significant clinical responses, including four complete responses and two partial responses against malignant tumors, also eliciting partial responses against benign but actively growing tumors. Together, our results indicate that combining IFN gamma and DCs could induce strong immune responses against tumors, significantly improving clinical outcomes. The present study of dogs bearing common types of cancer in humans offers a unique line of support for the development of human cancer therapies. Cancer Res; 70(18); 7093-101. (C)2010 AACR.