RT-PCR showed that expression of CYLD in mRNA levels was remarkably downregulated in RA-FLSs transfected with sh-CYLD, compared with those transfected with sh-GFP (Fig. 3a; 0.20 ± 0.04 vs. 1.00 ± 0.00; P < 0.01). Here, CYLD is linked to rheumatoid arthritis.