RAL inhibits the proliferation of RA synoviocytes dose dependently and blocks the proliferation induced by u-PA, mainly by reducing u-PAR levels without affecting the Kd of the u-PA/u-PAR interaction (as shown in this study by ELISA and radioligand binding experiments) and, therefore, by reducing the specific interaction between u-PA and u-PAR following reduction of u-PAR. This evidence concerns the gene RALA and rheumatoid arthritis.