Tracking Dendritic Cell Migration Using Magnetic Particle Imaging Enables Prediction of Anti-tumor Immune Efficacy

Dendritic cell (DC) cancer immunotherapy is of great interest if challenges associated with low DC migration to lymph nodes (LNs) can be overcome. Non-invasive quantification of DC migration could provide critical insight into mechanisms of treatment failure and in predicting response. Here we demonstrate the potential of magnetic particle imaging (MPI) for the quantitative evaluation of DC migration in the context of anti-tumor immunotherapy. Labeling of bone marrow-derived DCs (BMDCs) using a MPI tailored tracer was optimized to achieve high tracer uptake and reliable long-term tracking. Survival studies and RNA sequencing suggest that tracer labeling enhances therapeutic response by activating immune associated gene pathways. Heterogeneous DC to LN migration dynamics were observed in a cohort of 21 mice, with all animals showing varying levels of migration to the popliteal LN within 4 days, and some animals showing evidence of DCs in the inguinal LN. There was a strong correlation between DC migration to popliteal LN and their anti-tumor response.