PFN1 and rheumatoid arthritis: Accordingly, we performed the modular analysis of the PPI network using the MCODE plug-in of Cytoscape software with MCODE score > 2 as the threshold and identified Cluster1 including CFL1, COTL1, ACTG1, PFN1, and LCP1, and Cluster2 containing LCK, HLA-E, FYN, and HLA-DRA (Fig. 2e), suggesting that these nine genes may play critical roles in the development of RA.