PTGS2 and melanoma: In “COX-2-positive” (A2058) and “COX-2- negative” (Mel-Juso) human melanoma cell lines showing upregulated COX-2 expression under experimental hypoxic conditions and after irradiation, NO-COXIBs 5a and 5e showed more potent radiosensitizing efficacy compared to the COXIB 3a under normoxic and hypoxic conditions at low applied inhibitor concentrations of 10 μM.