Resumen de Potenciación de la inmunoterapia frente al cáncer de pulmón mediante la modulación del microambiente tumoral
Complement C5a has been proposed as a major regulator of myeloid-derived suppressor cells (MDSCs). In this thesis, we aimed to evaluate the mechanisms by which the C5a/C5aR1 axis endows MDSCs with properties that facilitate tumor growth and metastatic spread. Local C5a production in primary tumors seems to promote the recruitment of MDSCs, which results in a decrease in the frequency and activity of CD8 T cytotoxic lymphocytes. For this reason, we hypothesized that combined inhibition of C5a/C5aR1 and programmed cell death protein 1 (PD-1) signaling may have a synergistic antitumor effect. Using syngeneic models of lung cancer, we demonstrate that the combined blockade of C5a (AON-D21) and PD-1 (RMP1-14) markedly reduced tumor growth and led to prolonged survival. This effect was accompanied by a negative association between the frequency of CD8 T cells and MDSCs within tumors, which may result in a more complete reversal of CD8 T-cell exhaustion. This study provides support for the clinical evaluation of antiPD-1 and anti-C5a drugs as a novel combination therapeutic strategy for lung cancer. We also characterized the role of C5a on the two distinct subsets of MDSCs: polymorphonuclear MDSCs (PMN-MDSCs) and monocytic MDSCs (MON-MDSCs). Using ex vivo generated MDSCs and antagonists for C5a (AON-D21) and C5aR1 (PMX53), we demonstrate that C5a promoted an integrin-independent amoeboid mode of migration on PMN-MDSCs, while had no apparent effect on MON-MDSCs. In association with the effect on PMN-MDSC migration, C5a downregulated the expression of β1 and β3 integrins (mediators of cell-matrix adhesion) and upregulated the expression of the mediator of leukocyte extravasation CD11b. Moreover, stimulation of PMN-MDSCs with C5a favored the invasion of cancer cells via a process dependent on the extrusion of neutrophil extracellular traps (NETs). C5a/C5aR1 blockade or NET inhibition reduced the number of circulating tumor cells (CTCs) and the metastatic burden in a lung metastasis model. In support of the relevance of these findings obtained in mice, C5a was able to stimulate invasion and NETosis of PMN-MDSCs obtained from lung cancer patients. Moreover, myeloperoxidase (MPO)-DNA complexes, markers of NETosis, were elevated in lung cancer patients and correlated with C5a levels. We conclude that blockade of C5a results in a substantial improvement in the efficacy of antiPD-1 antibodies against lung cancer growth, and that C5a induces the formation of NETs by MDSCs to facilitate the dissemination, colonization and metastasis of cancer cells.
