PTGS2 and neoplasm: The same investigators also found that inhibition of p38 MAPK blocked UVB-induced expression of COX-2, 15-LOX-2, and TNF-α, which demonstrate that UVB induces expression of COX-2, LOXs, and cytokines like TNF-α via MAPK signaling pathway.382 UVA upregulates the expression of COX-2 gene through MAPK/AP-1 mediated pathways.383 TPA/PMA, a tumor promoter, induces expression of COX-2 by activating MAPK/NF-κB/AP-1 mediated pathways whereas COX-2 inhibitors suppress.8,384,385 In addition, crystalline silica can promote lung tumor growth mediated by LTB4/BLT-1.386