Multifunctional Nano Immunostimulant: Overcoming Immunosuppressive Microenvironment for Antitumor Immunotherapy

Area of Science:

• Biomedical Engineering
• Immunology
• Cancer Research

Background:

• Antitumor immunotherapy is vital but limited by the immunosuppressive tumor microenvironment (TME).
• Key immunosuppressive factors in the TME include hypoxia, high glutathione (GSH) levels, and immune evasion.
• Tumor heterogeneity and TME complexity necessitate multifaceted therapeutic strategies beyond monotherapy.

Purpose of the Study:

• To develop a multifunctional immune stimulator (3IZH) capable of simultaneously boosting immunity, downregulating GSH, and alleviating hypoxia within the TME.
• To investigate the synergistic effects of 3IZH with a hypoxia-inducible factor 1-alpha (HIF-1α) inhibitor (digoxin) for enhanced antitumor responses.

Main Methods:

• Design and synthesis of a multifunctional immune stimulator (3IZH) releasing photosensitizer (3ICy5) and Fe ions in the TME.
• Investigation of Fe ion-mediated GSH consumption and hypoxia alleviation via redox reactions.
• Evaluation of 3ICy5-induced endoplasmic reticulum (ER) stress, DAMPs release, immunogenic cell death (ICD), and ferroptosis.
• Assessment of combined therapy with digoxin in bilateral tumor-bearing mouse models.

Main Results:

• 3IZH effectively consumed GSH and alleviated hypoxia in the TME.
• 3ICy5 induced ER stress, DAMPs release, ICD, and ferroptosis by reducing GPX4.
• The combination of 3IZH and digoxin enhanced immune cell infiltration and demonstrated significant antitumor efficacy.
• The developed strategy effectively modulated the immunosuppressive TME and showed a favorable safety profile.

Conclusions:

• The multifunctional immune stimulator (3IZH) shows promise for overcoming TME-mediated resistance in cancer immunotherapy.
• Simultaneous targeting of GSH, hypoxia, and immune evasion represents a potent strategy for enhancing antitumor responses.
• This design strategy offers a potential platform for developing novel combination therapies against complex tumors.