In RA patients, a significant negative correlation has been shown between miR-26 serum level and expression of SMAD3 (r = −0.69, p = 0.02)/FOXP3 (r = −0.84, p = 0.004)/SMAD4 (r = −0.64, p = 0.04)/HIF1 (r = −0.65, p = 0.03) (Figure S2B–E). This evidence concerns the gene SMAD4 and rheumatoid arthritis.