UTMD Enhances Targeting of Diclofenac and Doxil® to Boost Tumor Immunotherapy.

Objective: The tumor immune microenvironment (TIME) limits antitumor therapy efficacy. Improving TIME enhances immune responses and improves drug effectiveness. The study designed nanobubble-encapsulated diclofenac (DNBs) and used ultrasound-targeted microbubble destruction (UTMD), referred to as DNBs-UTMD, to improve TIME and enhancing the efficacy of Doxil®.

Methods: DNBs were characterized using scanning electron microscope and particle size analysis. Encapsulation efficiency and loading capacity were measured via spectro-photometry. Cell activity was evaluated by CCK-8 assays. Lactate concentrations by lactate detection kit, extracellular pH were measured by pH meter, and flow cytometry assessed Doxil® uptake, M2 tumor-associated macrophages (M2), myeloid-derived suppressor cells (MDSCs), CD8+ cells and CD4+ T cells.

Results: DNBs had an average size of 331.6 nm, a zeta potential of 15.9 mV, and smooth spherical morphology. Encapsulation efficiency of 12.6% and loading capacity of 24.75%. DNBs-UTMD promoted Doxil® uptake, inhibited lactate secretion, and improved the acidic microenvironment. DNBs-UTMD reduces the proportion of immune-suppressive cells, with M2 of 22% and MDSCs of 5.3%. In addition, combination therapy group of Doxil ® + DNBs-UTMD reduced cell viability to 31%, with CD8+T cells of 51.1% and CD4+T cells of 24.1%, developing a synergistic anti-tumor effect.

Conclusion: DNBs-UTMD regulates TIME and alleviates immune suppression (M2 and MDSCs ↓) by improving the acidic tumor microenvironment. DNBs-UTMD also can promote cellular uptake of Doxil® and enhance T cell response (CD8+T cells and CD4+T cells ↑) to exert synergistic therapeutic effects.