Characterization of stable NCI/ADR-Res and SKOV3 matriptase-expressing (Mat) or vector alone (Vec) cell lines. (A) Activity. NCI/ADR-Res and SKOV3 Vec and Mat cells were characterized for cell surface protease activity using the Boc-QAR-AMC fluorogenic substrate over 4 h; representative time course is shown, and the plot shows average fold change of activity at the endpoint relative to Vec from three independent experiments performed in triplicate (error bars are ± SEM; *P < 0.05). (B) Proliferation. Stable ES-2, NCI/ADR-Res, and SKOV3 matriptase-expressing (Mat) or vector alone (Vec) cell lines were seeded onto six-well plates in triplicate and cells were counted after 48 and 72 h. Cell counts at 0, 48, and 72 h showed no significant difference (ns). (C) A11 antibody blocks Boc-QAR-AMC matriptase activity. ES-2 Mat cells were analyzed for AEBSF-sensitive cell surface serine protease activity in the presence of the matriptase-blocking antibody A11 to determine the optimal dose for matriptase inhibition. Representative time course over 4 h shows average cell surface serine protease activity; error bars show ± SEM from triplicate wells (left panel). Right panel graph shows the average fold change of cell surface protease activity at the endpoint from three independent experiments performed in triplicate (error bars are ± SEM; *P < 0.05; ns = not significant). All P values were calculated according to two-tailed, unpaired Student’s t tests.