CD4 and neoplasm: ZnO can not only guard pH-responsive targeted drug delivery and privileged phagocytic ability to melanoma cells but also play an immune-stimulating adjuvant role as they produce pro-inflammatory cytokines such as IFN-γ or TNF-α and induce an ICD effect, promoting DC maturation and the infiltration of effector CD4+ and CD8+ T cells into tumor sites, ultimately inhibiting tumor growth and distant lung metastases [63].