Induction of MMP-2 activation, MT1-MMP expression, and cell invasion by HBx is sensitive to the COX-2 inhibitor NS398. (a) For 24 hours, CMX cells were grown in the presence of increasing amounts, and HepG2 and 2.2.15 cells were grown in the presence of 100 μM, of the COX-2–specific inhibitor NS398, along with 10 μM PGE₂ where indicated. The presence of activated MMP-2 in the cell lysates was analyzed by Western blot. (b) CMO, CMX, HepG2, and 2.2.15 cells, as well as 4pX cells in which HBx expression was induced by removing tetracycline (Tet) for 24 hours, were treated or not treated with 100 μM NS398 for 24 hours and lysed, and the amount of MT1-MMP protein was studied by Western blot. (c) CMX and CMO cells were treated or not treated with 100 μM NS398 for 24 hours, and the expression of MT1-MMP transcripts was analyzed by quantitative RT-PCR. (d) CMO, CMX, HepG2, 2.2.15, or 4pX cells (with or without tetracycline) were allowed to invade Matrigel-coated Transwells in the presence of 100 μM NS398, or DMSO as a control, and 10 μM PGE₂ where indicated. Cells that migrated to the lower chamber were quantified as in Figure 1.