Among the differentially expressed proteins in RA-FLSs treated with propionate, Forkhead Box K1 (FOXK1), attracted out attention as it was a transcription factor at the upstream of interferon pathway.37 FOXK1 was downregulated at protein level but not at mRNA level by propionate in RA-FLSs. This evidence concerns the gene FOXK1 and rheumatoid arthritis.