Fig. 4.

Constitutive activation of NF-κB accelerates cell growth and enhances the invasiveness of arthritic rFLS. (A) Constitutive activation of NF-κB accelerates cell growth. Cells were transduced as described for Fig. 2B, and proliferation was assessed by determining thymidine incorporation (a) or by MTT proliferation assay (b). (Ac) To directly assess cell growth, cells were plated at a low density and counted after 5 days in culture. The numbers of cells was adjusted to plating efficacy that was assessed 1 day after plating. Doubling times were calculated assuming an exponential cell growth. Representative data of three experiments are shown. ∗, P < 0.05 vs. Babe control. (B) The production of preproactive and active forms of MMP-13 protein by transduced cells was assessed by immunoblotting in lysates of cells that were unstimulated or stimulated for 4 h with IL-1β (100 units/ml). The blot was reprobed with β-actin Ab. (C) Constitutive activation of NF-κB enhances invasiveness. Cell motility was assessed in a transwell cell migration assay as described in Materials and Methods. The cells that migrated through the filter were stained and counted. One representative experiment from three independent experiments is shown.