Listeria monocytogenes-Derived Membrane Vesicles Suppress Melanoma Growth via Macrophage Activation Involving NF-κB Signaling

Melanoma is an aggressive skin cancer with rapid progression and high metastatic potential, and resistance to current therapies remains a major clinical challenge. In this study, Listeria monocytogenes-derived membrane vesicles (LM MVs) were isolated, characterized, and evaluated for their immunomodulatory and antitumor activities. LM MVs showed an average diameter of approximately 160 nm and contained multiple bacterial proteins, including listeriolysin O. In vitro, LM MVs promoted pro-inflammatory activation of RAW264.7 macrophages, as indicated by increased CD80/CD86 expression and enhanced transcription of inflammatory mediators. LM MV treatment was accompanied by IκB-α degradation and NF-κB p65 nuclear translocation, whereas pharmacological inhibition of NF-κB attenuated macrophage activation. In a macrophage–melanoma co-culture system, LM MVs-activated macrophages reduced the viability, migration, and invasion of B16 melanoma cells and increased tumor cell apoptosis. Additional inhibition and immunofluorescence analyses suggested that iNOS and TNF-α-associated mechanisms contributed to these tumor-suppressive effects. In a murine melanoma model, LM MVs significantly inhibited tumor growth without overt systemic toxicity, whereas macrophage depletion markedly weakened this effect. These findings indicate that LM MVs exert antitumor activity against melanoma, at least in part through macrophage activation involving NF-κB signaling.