Figure 4.

Tumor recruitment of innate immune cells is essential for tumor development, invasion and metastasis. Tumor cells or tumor-associated cells attract and retain protumoral innate immune cells by secreting chemokines, complement, leukotrienes (e.g., LTB4), and damage-associated molecular patterns (e.g., adenosine and HMGB1) or via platelets as a bridge. Recruited myeloid cells support tumorigenesis by suppressing antitumoral T cell response, promoting angiogenesis and genomic instability, clearing dying cells via efferocytosis, and by facilitating tumor invasion and metastasis to neighboring and remote tissue sites. PMN-MDSC, neutrophil-derived myeloid-derived suppressor cell; M-MDSC, monocyte/macrophage-derived myeloid derived suppressor cell.