Defeating Melanoma Through a Nano-Enabled Revision of Hypoxic and Immunosuppressive Tumor Microenvironment.

RATIONALE: Reversing the hypoxic and immunosuppressive tumor microenvironment (TME) is crucial for treating malignant melanoma. Seeking a robust platform for the effective reversion of hypoxic and immunosuppressive TME may be an excellent solution to revolutionizing the current landscape of malignant melanoma treatment. Here, we demonstrated a transdermal and intravenous dual-administration paradigm. A tailor-made Ato/cabo@PEG-TK-PLGA NPs were administrated transdermally to melanoma with the help of a gel spray containing a skin-penetrating material borneol. Nanoparticles encased Ato and cabo were released and thereby reversed the hypoxic and immunosuppressive tumor microenvironment (TME).

METHODS: Ato/cabo@PEG-TK-PLGA NPs were synthesized through a self-assembly emulsion process, and the transdermal ability was assessed using Franz diffusion cell assembly. The inhibition effect on cell respiration was measured by OCR, ATP, and pO2 detection and in vivo photoacoustic (PA) imaging. The reversing of the immunosuppressive was detected through flow cytometry analysis of MDSCs and T cells. At last, the in vivo anti-tumor efficacy and histopathology, immunohistochemical analysis and safety detection were performed using tumor-bearing mice.

RESULTS: The transdermally administrated Ato/cabo@PEG-TK-PLGA NPs successfully spread to the skin surface of melanoma and then entered deep inside the tumor with the help of a gel spray and a skin puncturing material borneol. Atovaquone (Ato, a mitochondrial-respiration inhibitor) and cabozantinib (cabo, a MDSCs eliminator) were concurrently released in response to the intratumorally overexpressed H2 O2 . The released Ato and cabo respectively reversed the hypoxic and immunosuppressive TME. The reversed hypoxic TME offered sufficient O2 for the intravenously administrated indocyanine green (ICG, an FDA-approved photosensitizer) to produce adequate amount of ROS. In contrast, the reversed immunosuppressive TME conferred amplified systemic immune responses.

CONCLUSION: Taken together, we developed a transdermal and intravenous dual-administration paradigm, which effectively reversed the hypoxic and immunosuppressive tumor microenvironment in the treatment of the malignant melanoma. We believe our study will open a new path for the effective elimination of the primary tumors and the real-time control of tumor metastasis.