We divided mice into four groups including saline (G1), HBO (G2), HHD‐Cu NPs (G3), and HHD‐Cu NPs (G4), immunofluorescence staining for major components of tumor ECM including fibronectin, type I collagen, and α‐smooth actin (α‐SMA) in different groups are presented in Figure 6D–G, which reveal that HBO treatment significantly reduces tumor ECM, with decreases over 50% in all of these components. The gene discussed is ACTA1; the disease is neoplasm.