Rheumatoid arthritis synovial fibroblasts are more resistant to proteasome and autophagy/lysosome inhibitors than other fibroblasts. Fibroblasts (n = 6 rheumatoid arthritis (RA), n = 3 osteoarthritis, n = 3 dermal), stimulated or not with 10 ng/ml TNFα, were cultured with (a) 2 μg/ml tunicamycin, (b) 0.5 μM MG132, (c) 4 mM 3-methyladenine (3-MA) or (d) 12.5 μM chloroquine (CQ) for 72 hours. An XTT assay was performed and the survival of the cells was determined. Bars show standard error of the mean. Significant differences in control fibroblasts compared with RA synovial fibroblasts or the response of TNFα-stimulated cultures compared with non-induced cultures: *P < 0.05, **P < 0.01.