CCL2 and melanoma: In addition, we found that conditioned MCs could be a source of the pro-tumorigenic cytokine IL-8 (53); CCL2, a potent chemokine that recruits MDSCs and TAMs (54, 55); IL-33 that modulates melanoma cell proliferation, angiogenesis, and regulatory T cells (11, 56, 57); and the pro-angiogenic cytokine IL-1β (58, 59).