Abstract: Objective: To determine the effect of exogenous signal transduction pathway JAK/STAT on apoptosis of human SCC cells induced by 5-ALA-PDT. Methods: Squamous cell carcinoma cell line A431 and COLO-16 cells were cultured in vitro, and then were divided into blank control group, negative control group, PDT group, negative control+PDT group, STAT3 high expression vector group, STAT3-siRNA group, STAT3 high expression vector+PDT group and STAT3-siRNA+ PDT group. The survival rate and apoptosis rate were detected by CCK-8 method and flow cytometry method (FCM). The expression level of mRNA and protein of STAT3 and the downstream gene of Bax and Bcl-2 were detected by qRT-PCR and Western Blot. Results: The apoptosis rate of A431 and COLO-16 cells were 24% and 22% in PDT group, which were higher than in the STAT3 high expression vector+PDT group (11% and 10.5%), but lower than those in the STAT3-siRNA+ PDT group (36% and 39%).The level of STAT3 and Bcl-2 mRNA and protein in the PDT group were higher than those in the STAT3 high expression vector+PDT group, but lower than those in the STAT3-siRNA+ PDT group. The level of BCL-2mRNA and protein in PDT group was lower than that in the STAT3 high expression vector+PDT group, but higher than that in the STAT3-siRNA+ PDT group. Conclusion: Exogenous apoptotic pathway JAK-STAT3 may involved in the apoptosis of squamous cancer cells induced by 5-ALA-PDT.

Key words: photodynamic therapy (PDT), 5-aminolevulinic acid, skin squamous cell carcinoma, JAK/STAT3