PTGS2 and melanoma: Interestingly, addition of exogenous PGE2 (given at 10 and 100 ng/ml) to B16M cells for only 2 h significantly (P < 0.01) increased melanoma cell adhesion to an immobilized rhVCAM-1 substrate, which further suggests that VLA-4-dependent adhesion in VEGF-stimulated B16M cells was mediated by COX-2-dependent PGE2 (Figure 5A)