LPA stimulates and S1P inhibits migration of most tumor cell lines. Tumor cell migration analysis was performed on 8 μm polycarbonate gelatin-coated membranes and 20 μg/ml of fibronectin. LPA and/or S1P (1 μM) were added to the lower chambers and cells were allowed to migrate for 4 hours. Membranes were removed, stained, and migrating cells were quantitated using Scion® software and Microsoft Excel®. Data are expressed as mean number of migrating cells × 103 (± S.D.) and represent the results of quadruplicate experiments.