Extracellular Vesicles Derived from MDA-MB-231 Cells Trigger Neutrophils to a Pro-Tumor Profile.

Immune system cells, including neutrophils, are recruited by the tumor microenvironment as a site of chronic inflammation and begin to favor tumor growth. Neutrophils present in the tumor site are called tumor-associated neutrophils (TAN) and can present two phenotypes: N1 (antitumor) or N2 (pro-tumor). Evidence shows the high capacity of immune system cells to interact with extracellular vesicles (Evs) released by tumor cells. Evs can modulate the phenotype of cells within the immune system, contributing to tumor development. Here, we investigated the role of MDA-MB-231-derived Evs upon the polarization of neutrophils towards an N2 phenotype and the underlying mechanisms. We observed that neutrophils treated with Evs released by MDA cells (MDA-Evs) had their half-life increased, increased their chemotactic capacity, and released higher levels of NETs and ROS than neutrophils treated with non-tumoral Evs. We also observed that neutrophils treated with MDA-Evs released increased IL-8, VEGF, MMP9, and increased expression of CD184, an N2-neutrophil marker. Finally, neutrophils treated with MDA-Evs increased tumor cell viability. Our results show that MDA-Evs induce an N2-like phenotype, and the blockage of phosphatidylserine by annexin-V may be an essential agent counter-regulating this effect.

Melanoma-derived extracellular vesicles skew neutrophils into a pro-tumor phenotype.

Evidence shows that tumor cells abundantly produce and release extracellular vesicles (EVs) that can interact with stromal cells and modulate their functions. In the tumor neighborhood, neutrophils can assume both antitumor and pro-tumor phenotypes, known as TAN-N1 and TAN-N2, respectively. Nevertheless, the contribution of tumor-derived EVs to the modulation of TAN phenotypes is still poorly understood. The effects of EVs produced by a metastatic human melanoma cell line (MV3) on the differentiation and functional changes in human neutrophils were investigated. Treatment with MV3-derived EVs induced neutrophil chemotaxis through a signaling pathway involving the CXCR2/PI3K-Akt axis, prolonged neutrophil life span, promoted formation of neutrophil extracellular traps with poor elastase activity, and increased reactive oxygen species production. In contrast, EVs also increased the expression of TAN-N2 molecular markers (such as ARG1, CXCR4, and VEGF) in neutrophils. They also impaired oxide nitric and peroxynitrite production and diminished cytotoxic activity against melanoma cells, inducing neutrophils into a pro-tumor profile. Remarkably, EV-stimulated neutrophils did not exhibit phagocytic activity. These data suggested that melanoma-derived EVs could activate neutrophils, allowing their migration toward the tumor microenvironment, and driving these cells to a pro-tumor/N2 polarization, thus contributing to tumor progression.

Effect of Lonomia obliqua Venom on Human Neutrophils.

The significant incidence of deforestation in South America culminates in the contact of humans with typical forests species. Among these species, one may highlight Lonomia obliqua caterpillar, which, when touched by humans, can poison them through their bristles. Therefore, better acknowledging the mechanisms involved in envenomation caused by Lonomia obliqua caterpillar bristle extract (LOCBE) may contribute to further treatments. Recently, we demonstrated that LOCBE induces a pro-inflammatory profile in endothelial cells; thus, we decided to investigate the effects of LOCBE on human polymorphonuclear neutrophils (PMN), which are the first leukocytes that migrate to the inflammatory focus. Our results showed that treatment with LOCBE induced PMN chemotaxis together with alterations in actin cytoskeleton and focal adhesion kinase (FAK) activation, favoring migration. Concurrently, LOCBE induced PMN adhesion to matrix proteins, such as collagen IV, fibronectin, and fibrinogen. Moreover, we observed that LOCBE attenuated PMN apoptosis and increased reactive oxygen species (ROS) production together with nuclear factor kB (NF-κB) activation-a redox-sensitive transcription factor-as well as interleukin (IL)-1ß and IL-8 release. We call attention to the ROS-dependent effect of LOCBE on increased cell migration once an antioxidant treatment reverted it. In summary, we report that LOCBE activates PMN, inducing pro-inflammatory responses modulated by ROS.