Exploring Anti-Neoplastic Activity of Chitosan Nanobubbles Decorated with ICOS-Fc and Loaded with Paclitaxel in a Human and Murine Model of Melanoma

<b>Background:</b> Paclitaxel (PTX) is an anti-neoplastic drug that inhibits not only melanoma cell proliferation but also migration and angiogenesis. ICOS-Fc is a recombinant molecule that triggers ICOS ligand (ICOSL) on tumor cells and cells of the tumor microenvironment and inhibits tumor growth, angiogenesis, and metastasis. This study investigated the effects of chitosan nanobubbles loaded with low doses of PTX and surface decorated with ICOS-Fc (ICOS-Fc-NB-PTX) in inhibiting in vitro and in vivo melanoma cell growth and invasiveness. <b>Methods:</b> Preparation and characterization of nanoformulations, as well as in vitro drug release studies, were carried out. Nanoformulations were studied both in vitro and in vivo. In melanoma cells, viability, migration, and invasion assays were analyzed. For the in vivo experiments, C57BL/6 Wild-type (WT) male mice were injected subcutaneously with D4M-3A cells, a murine melanoma cell line engineered to carry the BRAF^V600E mutation. After treatments, in vivo tumor growth, proliferation, and angiogenesis markers were studied. <b>Results</b>: In vitro tests showed the great ability of ICOS-Fc-NB-PTX to inhibit cell viability, migration, and invasion. These results were confirmed in vivo, where the tumors of mice treated with ICOS-Fc-NB-PTX displayed decreased growth accompanied by downregulation of the proliferation marker Ki-67 and reduced development of CD31⁺ blood vessels. <b>Conclusions</b>: In conclusion, the ICOS-Fc-NB-PTX formulation deserves to be further analyzed as a highly effective combination for melanoma, exerting multifaceted anti-tumor activities.