Myeloid-derived suppressor cells (MDSC) are generated during tumor progression and suppress the anti-tumor functions of T and natural killer (NK) cells. Their enrichment is associated with a bad prognosis and a worse outcome of immunotherapy in cancer patients. The cytokine interleukin (IL)-6 was found to be a crucial regulator of MDSC accumulation and activation as well as a factor, stimulating tumor cell proliferation, survival, invasiveness and metastasis. Accordingly, IL-6 can serve as a negative prognostic marker in cancer. On the other hand, this cytokine is also involved in T cell activation. This review discusses the pleiotropic effects of IL-6 on immune cell populations that are critical for tumor development, such as MDSC and T cells, and summarizes the data on targeting IL-6 or IL-6 receptor (IL-6R) for tumor immunotherapy to block MDSC-mediated immunosuppression in cancer patients.

骨髓来源的抑制细胞（MDSC）在肿瘤进展过程中产生，并抑制T细胞和自然杀伤（NK）细胞的抗肿瘤功能。它们的富集与癌症患者的不良预后和免疫疗法的较差结果相关。发现细胞因子白介素（IL）-6是MDSC积累和激活以及刺激肿瘤细胞增殖，存活，侵袭性和转移的重要因素。因此，IL-6可作为癌症的阴性预后标志物。另一方面，该细胞因子也参与T细胞活化。这篇综述讨论了IL-6对免疫细胞群（如MDSC和T细胞）的多效性作用，