IL6 and neoplasm: IL-6 is a pleiotropic cytokine that plays many roles in the tumor microenvironment: inducing immune checkpoint activation via PD-1/PD-L1 expression (51, 52), negatively regulating NK and effector T cells (12), and promoting functionally suppressive immune populations, such as MDSCs, which contribute to tumor progression and therapy resistance (53, 54).