Abstract: 【Abstract】 Objective To evaluate regulatory effects of fibroblast growth factor receptor 3 （FGFR3） and human papillomavirus type 2 （HPV2） E2 protein on the differentiation of an immortalized human keratinocyte line HaCaT and a normal human epidermal keratinocyte line NHEK. Methods In both HaCaT and NHEK cells, HPV2 E2-stably transfected cell lines （HPV2 E2-transfected groups） were established by using the lentivirus transfection method, wide-type FGFR3-overexpressing cells （FGFR3-WT transfected groups） and FGFR3-K650E mutant-overexpressing cells （FGFR3-K650E transfected groups） were constructed by using the plasmid transfection method, and cells transfected with blank vectors served as control groups （blank vector control groups）. Real-time fluorescence-based quantitative PCR was performed to determine the mRNA expression of HPV2 E2, and Western blot analysis to determine the protein expression of HPV2 E2, FGFR3, and keratinocyte differentiation markers including loricrin, filaggrin, as well as involucrin. Laser scanning confocal microscopy was conducted to observe the spatial localization of HPV2 E2 and FGFR3 in HaCaT cells. Statistical analysis was carried out by using two-independent-sample t test for the comparison between two groups, one-way analysis of variance for the comparison among multiple groups, and Dunnett t-test for multiple comparisons. Results The HPV2 E2 -stably transfected cell lines were successfully constructed, and the expression of HPV2 E2 FLAG protein was significantly higher in the HPV2 E2-transfected groups than in the blank vector control groups in both HaCaT and NHEK cells （t = 13.71, 25.91, respectively, both P < 0.001）; both FGFR3-WT and FGFR3-K650E were successfully overexpressed in both HaCaT and NHEK cells, and the FGFR3 protein expression was significantly higher in the FGFR3-WT transfected groups and the FGFR3-K650E transfected groups than in the blank vector control groups （F = 473.90, 579.90, respectively, both P < 0.001）. In both HaCaT and NHEK cells, the expression of keratinocyte differentiation markers including loricrin, filaggrin, and involucrin was significantly upregulated in the HPV2 E2-transfected groups, the FGFR3-WT transfected groups, and the FGFR3-K650E transfected groups than in the blank vector control groups （all P < 0.05）. In the HPV2 E2-stably transfected HaCaT and NHEK cells, the expression of loricrin, filaggrin, and involucrin was significantly down-regulated in the HPV2 E2 + FGFR3-WT transfected groups and the HPV2 E2 + FGFR3-K650E transfected groups than in the HPV2 E2 + blank vector groups （all P < 0.05）. Laser scanning confocal microscopy showed the spatial co-localization of HPV2 E2 and FGFR3 in the nuclear membrane and cytoplasm of HaCaT cells. Conclusion HPV2 E2 and FGFR3 could both induce the differentiation of HaCaT and NHEK cells, while FGFR3 could inhibit HPV2 E2-induced differentiation trend of HaCaT and NHEK cells, which may be related to the cellular spatial co-localization of HPV2 E2 and FGFR3.

Key words: Keratinocytes, Receptor, fibroblast growth factor, type 3, Human papillomavirus 2, Antigens, differentiation, Human papillomavirus 2 E2, Keratinocyte differentiation, Cellular spatial localization