The changes in the proportions of 22 subtypes of immune cells in the high and low hepcidin expression groups in tumor samples showed that immune cells, such as eosinophils, Tregs, CD8+ T cells, plasma cells, M1 macrophages and monocytes, were significantly positively correlated with hepcidin expression, and CD4+ naïve T cells and M2 macrophages were significantly negatively correlated with hepcidin expression in CGGA dataset (p < 0.05) (Figures 7B, C). The gene discussed is HAMP; the disease is neoplasm.