FIGURE 4 (A) Schematic illustration of brain-targeted HFn-Cu-REGO. (B) Immunoblotting analysis of copper transporter in cells after different treatments. (C) Immunoblotting analysis of cuproptosis-related indicators in cells after different treatments. (D) The bioluminescence intensity of tumor-bearing mice after different treatments. (A-D) Reproduced with permission.44Copyright 2022, Wiley-VCH.
Because complicated pathophysiology involves multiple mechanisms, cancer exhibits similar acidic environments compared with other diseases such as inflammation, cardiovascular disease, leading to nonspecific accumulation of single-pH-responsive nanomaterials.45,46 Multi-stimuli responsive nanomaterials have been explored to achieve responsiveness to multiple pathological environmental variations for improved specificity and targeting.47,48 For example, Suo et al . designed a GSH/pH-responsive hollow amorphous metal organic framework (HaMOF) (DOX@Fe/CuTH) consisting of Cu2+, disulfide bond (S-S)-bearing 3,3′-dithiobis(propionohydrazide) (TPH) and Fe3+ encapsulated by hyaluronan shell with a good doxorubicin (DOX) loading ability for cuproptosis/ferroptosis/apoptosis synergistic cancer therapy (Figure 5A ).49Because of the high affinity between hyaluronan and CD44 receptor overexpressing on the surface of cancer cells, hyaluronan endowed the DOX@Fe/CuTH with cancer site-specific targeting capability, resulting in thus enhanced tumor-site accumulation and preferential internalization within cancer cells. After cell internalization, DOX@Fe/CuTH showed GSH/pH-responsive cargo (Cu2+, Fe3+and DOX) release due to the GSH-triggered fracture of disulfide bonds and acidic pH-triggered weakening of ion coordination. The Cu2+ released from DOX@Fe/CuTH bound to DLAT, resulting in abnormal oligomerization of DLAT, with a more obvious DLAT foci than PBS-treated cells. In addition, the expression levels of FDX1 and LIAS in the DOX@Fe/CuTH-treated cells were 0.18-fold and 0.35-fold than those of PBS-treated cells, respectively, showing significant loss of FDX1 and LIAS (Figure 5B ). Meanwhile, the poor cell vitality after DOX@Fe/CuTH treatment was significantly restored by the copper chelating agent (Figure 5C ). These results collectively confirmed that Cu2+ induced cancer cell death through the cuproptosis pathway. Apart from Cu2+-mediated cuproptosis, Fe3+-mediated ferroptosis and DOX-mediated apoptosis also exhibited synergistic therapeutic effects. Therefore, after intravenous injection, the tumor volume after nanodurg treatment was 0.7-fold that before treatment, remarkably smaller than those of control (4.1-fold), DOX (3.0-fold), CuTH (2.4-fold) and Fe/CuTH (1.4-fold) groups. The results demonstrated that DOX@Fe/CuTH had potent anti-cancer effect via cuproptosis/ferroptosis/apoptosis synergistic therapy (Figure 5D ).