Naproxen activates UPR signaling and blocks NFκB pathway. Activation of UPR signaling was characterized by the enhanced phosphorylation of eIF2α and increased ATF4 as well as its transcriptionally regulated CHOP. These pathways together block inflammatory response and induce apoptosis in UVB-induced BCC and SCCs. ↑ represents enhancement, ↓ represents decrease, → represents activating effect, ⊢ represents blocking effect, p – phosphorylation, ER – endoplasmic reticulum, UPR – unfolded protein response, ATF4 - activating transcription factor 4, eIF2α - eukaryotic initiation factor 2α, CHOP - C/EBP homologous protein, NFκB – nuclear factor kappa B, iNOS - inducible nitric oxide synthase, and COX2 – cyclooxygenase2.