PTGS2 and neoplasm: A linear regression analysis of cell viability showed the EC50 values for enhancement of tumor cell growth by COX-2 (concentration required to increase growth by ~50% after a 24-hour treatment) were 8.95 × 10-3, 11.20 × 10-3, and 8.44 × 10-3 μM for A549, H460 and A431 cells, respectively.