For example, the use of manganese dioxide (MnO2) and gold–platinum (Au-Pt) NPs helps to modify the tumor immunosuppressor microenvironment because they act as generators of radioactive nano-oxygen (nanobubbles composed of gas such as oxygen), improving the infiltration of cytotoxic T cells, affecting the cancer cells’ metabolism and reducing their proliferation by downregulating the expression of hypoxia-inducible factor 1α (HIF-1α) and C-MYC [183], and consequently, tumor progression [184,185]. This evidence concerns the gene HIF1A and neoplasm.