ABCB1 and neoplasm: Additionally, MCD@TMPyP4@DOX self-decomposes in the acidic tumor environment, releasing Mg2+-assisted DNAzymes that silence MDR1 mRNA and downregulate P-gp, while mitochondrial-targeted photodynamic therapy disrupts mitochondrial function, depleting ATP and further inhibiting P-gp activity, thus effectively reversing drug resistance 167.