HIF1A and breast carcinoma: DOX-BSA/MnO2 NPs can interact with H2O2 and H+ in TME to form oxygen and exhibit excellent photothermal effect to further alleviate hypoxia due to MnO2, reversing DOX resistance by down-regulating HIF-1α expression and significantly improving the antitumor efficiency in DOX-resistant human breast carcinoma cell line (MCF-7/ADR) tumor model.