Given the suggested role of JAK/STAT signaling pathway involved in MTX treatment, as well as a central role in RA (35), we checked whether genes encoding any of the four JAK proteins (JAK1, JAK2, JAK3 and TYK2) or the seven STAT proteins (STAT1, STAT2, STAT3, STAT4, STAT5A, STAT5B and STAT6) were among the genes annotated to the significant DMPs (Supplementary Table S4). Here, STAT4 is linked to rheumatoid arthritis.