Abstract
Altered fibroblast GF receptor (FGFR) signaling has been shown to play a role in a number of cancers. However, the role of FGFR signaling in the development and progression of UVB-induced cutaneous squamous cell carcinoma remains unclear. In this study, the effect of UVB radiation on FGFR activation and its downstream signaling in mouse skin epidermis was examined. In addition, the impact of FGFR inhibition on UVB-induced signaling and skin carcinogenesis was also investigated. Exposure of mouse dorsal skin to UVB significantly increased the phosphorylation of FGFRs in the epidermis as well as the activation of downstream signaling pathways, including protein kinase B/mTOR, signal transducers and activators of transcription, and MAPK. Topical application of the pan-FGFR inhibitor AZD4547 to mouse skin before exposure to UVB significantly inhibited FGFR phosphorylation as well as mTORC1, signal transducer and activator of transcription 3, and MAPK activation (i.e., phosphorylation). Moreover, AZD4547 pretreatment significantly inhibited UVB-induced epidermal hyperplasia and hyperproliferation and reduced the infiltration of mast cells and macrophages into the dermis. AZD4547 treatment also significantly inhibited mRNA expression of inflammatory genes in the epidermis. Finally, mice treated topically with AZD4547 before UVB exposure showed decreased cutaneous squamous cell carcinoma incidence and increased survival rate. Collectively, the current data support the hypothesis that inhibition of FGFR in the epidermis may provide a new strategy to prevent and/or treat UVB-induced cutaneous squamous cell carcinoma.