FLT1 and rheumatoid arthritis: Because the data that VEGF165 stimulated ADAM15 expression only in HUVECs suggested that the effect is dependent on the expression of VEGF receptors, we tried to induce VEGF receptors by treating RA SFs with cytokines and growth factor and found that TNF-α, but not IL-1α or TGF-β, can induce VEGFR-2 expression without affecting the expression of VEGFR-1 or neuropilin-1 (Fig. 9b).