Knockdown of DEC1 in human RA synovial fibroblast cell line (MH7A) significantly decreased cell migration and invasion as well as RA-related effector genes such as COX-2 (cyclooxygenase-2), OB-cadherin (osteoblast cadherin), and ICAM-1 (intercellular adhesion molecule 1). This evidence concerns the gene BHLHE40 and rheumatoid arthritis.