SM-induced MMP2 expression enhanced PC3 cell migration. (A) Effect of SM on the migration of siCTL and siMMP2 cells using a wound-healing assay. (B) Quantification of migrating siCTL and siMMP2 cells following SM treatment. Data are presented as the number of migrating cells, and represent the mean ± standard deviation of the number of migrating cells. *P<0.05 for siCTL cells vs. siMMP2 cells (with reduced MMP2 expression). CTL, control; si, small interfering; MMP2, matrix metallopeptidase; SM, cigarette smoke medium.