KLF4 and rheumatoid arthritis: It was subsequently concluded that KLF4 regulates the proliferation and apoptosis of fibroblast-like synoviocytes (FLSs) in RA and its role in modifying the expression of matrix metalloproteinases (MMPs) MMP2, MMP12, and MMP13 and proinflammatory cytokines such as B-cell lymphoma 2 (BCL2), IL-6, and IFNγ was suggested.