HA-induced regulation of protease gene expression is attenuated by a p38 MAPK inhibitor. (A) Representative immunoblot characterizing the time-dependent phosphorylation of p38 MAPK in MDA-MB-231Hi cells after stimulation with 100 μg/ml HA. Equal protein loading in immunoblots was confirmed by reprobing the membranes for p38 MAPK and β-tubulin. Bar graphs illustrate the magnitude of HA-induced increases in the mRNA transcript levels for (B) uPA, (C) cathepsin K, and (D) MT1-MMP, in the absence or presence of the p38 MAPK inhibitor SB203580 (2 μM). The effect of the DMSO vehicle on the response was adjusted. Data shown are the mean ± SEM values calculated from three independent experiments. Statistically significant differences between data points in quantitative assays were determined by using a Student two-tailed t test. *P < 0.05; **P < 0.01.