PTGS2 and neoplasm: However, given that UVB irradiation enhances the expression of inflammatory mediators (e.g. chemokine (C-X-C motif) ligand 5, cyclooxygenase-2) in murine and human skin in an AHR-dependent manner (106, 116), and that a transgenic overexpression of a constitutively active AHR in mice is associated with inflammatory skin lesions (117), it seems to be likely that cutaneous AHR signaling also exhibits tumor-promoting effects.