Immune cells such as macrophages are drivers and
biomarkers of most
cancers. Scoring macrophage infiltration in
tumor tissue provides a prognostic assessment that is correlated with disease outcome and therapeutic response, but generally requires invasive biopsy. Routine detection of
hemosiderin iron aggregates in macrophages in other settings histologically and in vivo by MRI suggests that similar assessments in
cancer can bridge a gap in our ability to assess
tumor macrophage infiltration. Quantitative histological and in vivo MRI assessments of non-
heme cellular
iron revealed that preclinical prostate
tumor models could be differentiated according to
hemosiderin iron accumulation-both in
tumors and systemically. Monitoring cellular
iron levels during "off-label" administration of the FDA-approved
iron chelator deferiprone evidenced significant reductions in
tumor size without extensive perturbation to these
iron deposits. Spatial profiling of the
iron-laden infiltrates further demonstrated that higher numbers of infiltrating macrophage
iron deposits was associated with lower anti-
tumor chelation therapy response. Imaging macrophages according to their innate
iron status provides a new phenotypic window into the immune
tumor landscape and reveals a prognostic
biomarker associated with macrophage infiltration and therapeutic outcome.