找出这句话近3年的参考文献并提供pmid号：IL-6和TNF-α 可以促进肿瘤微环境中免疫抑制细胞如调节性T细胞和髓样抑制细胞的产生并进一步增加肿瘤细胞的PD-L1表达

Wang Y, Wang L, Li H, et al. Targeting Programmed Death-1/Programmed Death-Ligand 1 Through Glycoengineering Technology: Current Status and Future Perspectives. Frontiers in oncology. 2020;10:585241. PMID: 33194699.

Ye Y, Zhou L, Xie X, et al. Targeting the Tumor Microenvironment: Current Status and Future Perspectives. Signal transduction and targeted therapy. 2021;6(1):260. PMID: 34290451.

Yang X, He J, Wang L, et al. Targeting the Tumor Microenvironment: New Strategies in Cancer Immunotherapy. Journal of hematology & oncology. 2020;13(1):1-21. PMID: 32028923