The epithelial-to-mesenchymal transition (EMT) program is critical for epithelial cell cancer progression and fibrotic diseases. FOXO1 influences a broad range of physiological and pathological processes. However, the mechanism by which FOXO1 inhibits EMT is not fully understood. In this study, we demonstrated that FOXO1 overexpression inhibited cell motility and invasiveness in vitro and inhibited lung metastasis in vivo. In addition, we found that FOXO1 couldreverse the EMT program. FOXO1 silencing by siRNA in hepatocellular carcinoma (HCC) cell lines enhanced the expression of mesenchymal markers and decreased the expression of the epithelial markers. Consistent with these findings, FOXO1 overexpression exerted opposite effects. Furthermore, we found that FOXO1 levels were inversely correlated with the levels of EMT inducers, including Snail, Slug, ZEB1, ZEB2 and Twist1 in HCC cells. Co-immunoprecipitation and immunohistochemistry assays revealed that an interaction between FOXO1 and ZEB2. A dual-luciferase reporter assay and a ChIP assay further demonstrated that FOXO1 binds to the ZEB2 promoter. Together, these findings suggest that FOXO1 overexpression or ZEB2 inhibition might be potential therapeutic strategies for treating HCC.
Background
Nuciferine (NF), extracted from the leaves of
N. nucifera Gaertn
, has been shown to exhibit anti-tumor and anti-viral pharmacological properties. It can also penetrate the blood brain barrier (BBB). However, the mechanism by which NF inhibits glioblastoma (GBM) progression is not well understood. We aimed to determine the anti-tumor effect of NF on GBM cell lines and clarify the potential molecular mechanism involved.
Methods
U87MG and U251 cell lines were used in vitro to assess the anti-tumor efficacy of NF. Cytotoxicity, viability, and proliferation were evaluated by MTT and colony formation assay. After Annexin V-FITC and PI staining, flow cytometry was performed to evaluate apoptosis and cell cycle changes in NF-treated GBM cells. Wound healing and Transwell assays were used to assess migration and invasion of GBM cells. Western blot analysis, immunofluorescence staining, immunohistochemistry, and bioinformatics were used to gain insights into the molecular mechanisms. Preclinical therapeutic efficacy was mainly estimated by ultrasound and MRI in xenograft nude mouse models.
Results
NF inhibited the proliferation, mobility, stemness, angiogenesis, and epithelial-to-mesenchymal transition (EMT) of GBM cells. Additionally, NF induced apoptosis and G2 cell cycle arrest. Slug expression was also decreased by NF via the AKT and STAT3 signaling pathways. Interestingly, we discovered that NF affected GBM cells partly by targeting SOX2, which may be upstream of the AKT and STAT3 pathways. Finally, NF led to significant tumor control in GBM xenograft models.
Conclusions
NF inhibited the progression of GBM via the SOX2-AKT/STAT3-Slug signaling pathway. SOX2-targeting with NF may offer a novel therapeutic approach for GBM treatment.
Electronic supplementary material
The online version of this article (10.1186/s13046-019-1134-y) contains supplementary material, which is available to authorized users.
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