GLI2/Hedgehog Signaling Contributes to the Induction of Malignant Phenotype of Gallbladder Cancer

Abstract

Background: We have previously shown that Hedgehog (Hh) signaling is reactivated in GBC. However, which and how three GLI proteins; GLI1. GLI2 and GLI3 contribute to the induction of malignant phenotype of GBC is still unclear. To develop a new therapeutic strategy for refractory GBC, the biological significance of GLI1, GLI2 and GLI3 was investigated. Materials: 1) In vitro experiment; GLI proteins were inhibited using siRNA. GLI expressing 3 GBC cell lines (NOZ, TGBC2TKB, and TYGBK−1) were used for invasion assay and proliferation assay. 2) In vivo experiment; In xenograft mice model, tumorigenesis of GLI inhibited cells (NOZ) was analyzed. 3) Clinical experiment; 67 patients with GBC who underwent curative surgical resection were enrolled in this study. Correlation between GLI expression and clinicopathological findings was analyzed immunohistochemically. Results: 1) In vitro results; GLI2 siRNA but not GLI1/GLI3 siRNA transfection significantly inhibited the invasiveness and proliferation ability of GBC cells. 2) In vivo results; Tumor volume from mice injected with GLI2 siRNA transfected cells was significantly lower than that in control tumors. 3) Clinical results; The expression levels of GLI2 in human GBC specimens were higher than those in normal gallbladder tissue. GBC specimens with high GLI2 expression had significantly high level of PD-L1 expression and low number of infiltrated CD3 positive lymphocytes. Conclusion: GLI2 contributes to the induction of malignant phenotype of GBC and could be a potential therapeutic target for GBC.