P043

1:Universitat Autònoma de Barcelona

Mycobacteria play a relevant role as immunotherapy agents, however the immunological mechanisms behind this effect in not completely understood. This is particularly relevant for Mycobacterium bovis BCG, widely used in non-muscle invasive bladder cancer treatment, for which the crosstalk with innate immune cells is crucial to antitumoral efficacy. Mycobacteria modulate immune responses through lipid recognition from their well-characterized lipid-rich cell wall. In this interaction, the C-type lectin receptor Mincle plays an essential role in sensing glycolipids such as trehalose-6,6-dimycolate. However, the function of Mincle-mediated signaling in tumor therapy is unknown.

To investigate the role of glycolipids in the antitumor responses, murine J774A.1 macrophages were stimulated with different glycolipids: glycerol-monomycolate, trehalose-dimycolate, and trehalose-monomycolate purified from M. bovis BCG and Mycobacterium brumae. Cell cultures were performed under various conditions, including Mincle blockade and/or TLR2/TLR4 activation, to explore the contribution of pattern recognition receptors to macrophage-mediated immune responses. Macrophage activation was assessed through proliferation assays, nitric oxide production, and analysis of cytokines/chemokines released (TNF-α, IL-6, IP-10, IL-12, IL-1β, RANTES). The antitumoral effect was evaluated by exposing MB49 bladder cancer cells to macrophage-conditioned media.

Certain mycobacterial glycolipids induced robust production of TNF-α, IP-10, IL-6, and nitric oxide in J774A.1 macrophages. Secretion levels varied depending on lipid exposure and receptor modulation. Mincle blockade significantly reduced cytokine and NO production, reinforcing its role in sensing mycobacterial lipids. High levels of TNF-α, IP-10, and NO correlated with decreased MB49 proliferation, suggesting an antitumoral effect of activated macrophages. These results highlight Mincle’s role in mycobacteria-driven cancer immunotherapy responses.