Avaliação comparativa da atividade antitumoral de diferentes β-d-glucanas em modelo experimental de melanoma: uma abordagem imunológica

Abstract

Melanoma is an aggressive type of skin cancer, and its treatment faces several limitations, such as therapeutic resistance. (1→3)(1→6)-β-D-glucans, especially those of fungal origin, stimulate the immune response through interaction with pattern recognition receptors and are considered promising adjuvants in cancer treatment. The objective of this study was to evaluate whether the (1→3)(1→6)-β-D-glucan extracted from the cell wall of S. cerevisiae (Wellmune, WM) and that produced by the ascomycete fungus B. rhodina (Botryospheran, BOT) exhibited antitumor activity against murine B16-F10 melanoma. To this end, female C57BL/6 mice were subcutaneously inoculated with 2×10⁵ B16-F10 melanoma cells and treated starting on the 5th day post-tumor implantation, followed by treatments every 3 days until euthanasia on day 17. Treatments were administered either orally or intraperitoneally (IP) with saline (control group), 30 mg/kg of BOT (oral or IP), or 30 mg/kg of WM (oral or IP). The BOT oral group showed a reduction in tumor volume starting from day 14 compared to the control group, while in the WM oral and WM IP groups this effect was only observed on day 17. BOT administered intraperitoneally did not affect tumor volume compared to the control. A reduction in tumor weight on day 17 was observed only in the BOT oral group compared to the control (p = 0.005), although all treatment protocols significantly reduced the mitotic index. No changes were observed in the semiquantitative evaluation of the tumor necrosis area. Regarding cytokine levels in the tumor microenvironment (TME), IFN-γ increased threefold in the BOT oral group compared to the control group. mRNA expression of Ifnb1 increased in the WM oral group compared to the control. To determine the influence of TLR2, TLR4, and IFN-γ, the same experimental model was applied in knockout mice for these molecules. Tumor weight reduction by the end of the experimental period was found to be dependent on the TLR4 receptor in the BOT oral treatment group. Moreover, the absence of TLR4 led to increased tumor weight in the WM oral group compared to the control. The antiproliferative effect of orally administered BOT and WM was shown to be dependent on the cytokine IFN-γ. The results of this study demonstrated that the antitumor effect of BOT depends on oral administration and the TLR4 receptor. Furthermore, the absence of this receptor was capable of promoting the growth of subcutaneous B16-F10 melanoma in the WM oral group. The antiproliferative action of BOT and WM was shown to be dependent on IFN-γ. These findings reinforce the potential of β-glucans as immunomodulatory adjuvants in melanoma treatment and highlight the importance of TLR4 and IFN-γ in mediating their biological activity.