CXCL12 and rheumatoid arthritis: 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).