Furthermore, qRT-PCR was used to analyze the mRNA expression of three upregulated proteins (fold change > 4 and p < 0.05): Tumor necrosis factor-α (TNF-α) converting enzyme (TACE), matrix metalloproteinase 2 (MMP2), and platelet derived growth factor subunit AA (PDGF-AA), all of which might promote RA-FLS invasion. Here, TNF is linked to rheumatoid arthritis.