CXCL2 and neoplasm: On the other hand, CAFs promote the expression of PD-L1 in tumor cells by secreting CXCL2 and CXCL5 (Inoue et al., 2019; Li et al., 2019), and macrophages upregulate PD-L1 expression through TGF-β–induced EMT (Vakili-Ghartavol et al., 2018; Jiang and Zhan, 2020), which plays a critical role in tumor immunosuppression and immune evasion.