The anti-tumor activity and mechanisms of a GLI1 inhibitor FL18 in suppression of glioblastoma growth / 药学学报

ABSTRACT

The abnormal activation of hedgehog (HH) signaling pathway plays an important role in the development and progression of glioblastoma (GBM). As a transcription factor at the end of the HH pathway, the final effector of glioma-associated oncogene homoglog-1 (GLI1) is an important target in the treatment of GBM. The study was designed to evaluate the anti-tumor activities and mechanisms of a novel GLI1 inhibitor FL18 in GBM. MTT and colony formation assay were performed to determine anti-proliferation activity of FL18 in vitro. The effect of FL18 on cell apoptosis was measured by flow cytometry (FCM) analysis. Transwell experiment was used to explore the inhibitory activity of FL18 in cell invasion. In vivo experiments, the subcutaneously transplanted and orthotopic U-87 MG GBM xenograft model were used to study the activity of FL18 on tumor growth. The optimized dual report gene screening model was used to detect the effect of FL18 on the transcriptional activity of GLI1. Western blot assay was used to study the mechanisms of action of FL18. The results showed that the IC50 of FL18 in glioblastoma was in the nanomole level in vitro. It was observed that 22.5 and 45 mg·kg-1 FL18 reduced the tumor volume with the rate of 55.4% and 89.8% in xenograft model in mice in situ. The IC50 of FL18 on the inhibition of GLI1 transcriptional activity was 3.32×10-11 mol·L-1 analyzed by the optimized dual report gene screening model. By the Western blot experiments, it was proved that FL18 inhibited expression of GLI1 without influencing the upstream canonical HH/SMO signaling and cross-talk oncogenic pathway, such as ERK and AKT signaling. The results also demonstrated that FL18 significantly downregulated GLI1 target genes such as Bcl-2, MMP2 and MMP9 and increased the expression of c-caspase3, c-PARP and Bax. These data suggest that FL18 may generate the anti-glioma activity by inhibition of GLI1.