Prussian blue staining revealed blue signals in the tumor regions of CHOL-PEG-SPIO-IL19-treated mice but not in CHOL-PEG-SPIO-isotype-treated mice (Fig. 8B), indicating the presence of iron oxide nanoparticles in tumor tissue after CHOL-PEG-SPIO-IL19 injection (Fig. 8C). The gene discussed is IL19; the disease is neoplasm.