TNFα, IL-1β, and hypoxia also up-regulate the expression of cytokines, including IL-6, CXCL8 (namely, IL-8), CCL2, CXCL11, CXCL12, and VEGF, as well as the expression of cytokine receptors such as TNFRSF9 in synovial fibroblasts derived from rheumatoid arthritis (RA) patients (49, 50). Here, CXCL8 is linked to rheumatoid arthritis.