Active Immunization of Patients With Stage III and IV Melanoma in Whom a Regional Lymph Node Dissection is Planned, With Peptide-Pulsed Dendritic Cells: Evaluation of in Vivo Immune and Clinical Response and Migration

Dendritic cells (DCs) are the professional antigen-presenting cells of the immune system. As such they are currently used in clinical vaccination protocols in cancer patients, and both immunological and clinical responses have been observed. For these therapies accurate delivery to target organs is essential. Correct delivery and subsequent migration of vaccinated DCs to regional lymph nodes is of paramount importance for effective stimulation of the immune system. Currently it is not known what the best route of administration is for DC vaccines.

Using magnetically labeled DCs, we investigate the potential of MRI cell tracking to monitor DC therapy. This is investigated in stage III/IV melanoma patients in whom a regional lymph node dissection is scheduled. Autologous monocyte-derived DCs are labeled with the clinically approved superparamagnetic iron oxide (SPIO) formulation Endorem and 111In-oxine and injected either in the skin or directly in lymph nodes under ultrasound guidance. Two days after vaccination patients are monitored with scintigraphy and MR imaging. Lymph nodes are then resected. Subsequently patients receive 3 more vaccination with DCs. During and after therapy immune responses against the used melanoma peptides are monitored.