Cu2+-Pyropheophorbide a-Cystine Conjugate: Synergistic Photodynamic/Chemodynamic Therapy and Glutathione Depletion Improves the Antitumor Efficacy and Downregulates the Hypoxia-Inducing Factor

Cancerimmune escape, metastasis, recurrence, and multidrugresistanceare all associated with hypoxia in the tumor microenvironment (TME).We synthesized a CuPPaCC conjugate for reactive oxygen species (ROS)-mediatedcancer therapy. CuPPaCC continuously produced cytotoxic ROS and oxygenthrough a photo-chemocycloreaction, alleviated hypoxia, and inhibitedthe expression of a hypoxia-inducing factor (HIF-1 & alpha;). CuPPaCCwas synthesized from pyromania phyllophyllic acid a (PPa), cystine(CC), and copper ions, and its structure was characterized by nuclearmagnetic resonance (NMR) and mass spectrometry (MS). The ability ofCuPPaCC to produce ROS and oxygen after photodynamic therapy (PDT)in vitro and in vivo was investigated. The ability of CuPPaCC to consumeglutathione was investigated. CuPPaCC toxicity (light and dark) inCT26 cells was analyzed by MTT and live/dead cell staining. The anticancereffect of CuPPaCC in vivo was investigated in CT26 Balb/c mice. Whenstimulated by the TME, CuPPaCC released Cu2+ and PPaCC,and the singlet oxygen yield increased from 34 to 56.5%. The dualROS-generating mechanism via a Fenton-like reaction/photoreactionand dual glutathione depletion via Cu2+/CC multiplied theantitumor efficacy of CuPPaCC. The photo-chemocycloreaction continuedto produce oxygen and maintained high ROS levels even after PDT, significantlyalleviating hypoxia in the TME and downregulating the expression ofHIF-1 & alpha;. CuPPaCC thus showed excellent antitumor activity invitro and in vivo. These results showed that the strategy could beeffective in improving the antitumor efficacy of CuPPaCC and couldbe used as a synergistic regimen for cancer therapy.

Automated summary

In this study, CuPPaCC conjugate was synthesized for ROS-mediated cancer therapy. CuPPaCC continuously produced cytotoxic ROS and oxygen through a photo-chemocyclo reaction, alleviated hypoxia, and inhibited HIF-1α expression. The results showed that CuPPaCC has excellent antitumor activity.