Effect of p53 siRNA on function of fibroblast-like synoviocytes (FLS). (a) Cell growth. p53 was knocked down by using siRNA, and cell growth was determined with an Alamar Blue assay in triplicate wells (n = 3 separate cell lines) The relative number of cells is quantified using arbitrary fluorescence units, and the fold induction in p53 siRNA-transfected FLS is shown relative to mock-transfected cells. Similar results were observed with 5 μg of siRNA (data not shown). *p < 0.001 for p53 siRNA-transfected cells compared with scrambled (sc) siRNA. RFU, relative fluorescence units. (b) p21 protein expression. p53 siRNA was knocked down by using siRNA, and p21 expression was determined by Western blot analysis. p21 expression decreased in cells with deficient p53 expression (n = 2 separate cell lines).