Background: Cancer vaccines employing DC in their capacity as APC have been tolerated well and have shown some efficacy in clinical studies. IL-12, a cytokine critical for type 1 T-helper (Th1) lymphocyte and cytotoxic T-lymphocyte (CTL) differentiation, when released from a DC-based cancer vaccine, may support the generation of a cellular T-cell response.
Methods: We applied tumor cell lysate plus keyhole limpet hemocyanin (KLH)-loaded and 48-h lipopolysaccharide (LPS) plus IFN-gamma-stimulated fully mature DC, which do not release IL-12, subcutaneously to eight patients, and maximally 6-h stimulated semi-mature (sm) DC, which are potent producers of IL-12, subcutaneously (n=6) or intranodally (n=8) as a cancer vaccine to patients suffering from advanced solid pediatric malignancies.
Results: No serious adverse events were observed following application of IL-12-releasing smDC. Following immunization the majority of patients responded positively to KLH in a delayed-type hypersensitivity (DTH) test. In addition, three of six intranodally treated patients responded to the tumor Ag in the DTH test.
Discussion: We conclude that treatment with a DC-based cancer vaccine enabled to release the immune regulatory cytokine IL-12 is safe and feasible and has the potential to induce a cellular immune response in pediatric cancer patients.