CD44 and neoplasm: DOX/siGCN5@HPMSNs could target drug‐resistant breast cancer cells; after CD44‐mediated endocytosis, the released siGCN5 epigenetically abolished P‐glycoprotein (P‐gp) to enhance the intracellular DOX concentration in response to intratumoral pH/GSH; thus, reversing cancer drug resistance and markedly suppressing tumor growth.[101]