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.
Glioblastoma multiforme (GBM) has been considered the most aggressive glioma type. Temozolomide (TMZ) is the main first-line chemotherapeutic agent for GBM. Decreased mutS homolog 6 (MSH6) expression is clinically recognized as one of the principal reasons for GBM resistance to TMZ. However, the specific functions of MSH6 in GBM, in addition to its role in mismatch repair, remain unknown.
Methods:
Bioinformatics were employed to analyze MSH6 mRNA and protein levels in GBM clinical samples and to predict the potential cancer-promoting functions and mechanisms of MSH6. MSH6 levels were silenced or overexpressed in GBM cells to assess its functional effects
in vitro
and
in vivo
. Western blot, qRT-PCR, and immunofluorescence assays were used to explore the relevant molecular mechanisms. Cu
2
(OH)PO
4
@PAA nanoparticles were fabricated through a hydrothermal method. Their MRI and photothermal effects as well as their effect on restraining the MSH6-CXCR4-TGFB1 feedback loop were investigated
in vitro
and
in vivo
.
Results:
We demonstrated that
MSH6
is an overexpressed oncogene in human GBM tissues. MSH6, CXCR4 and TGFB1 formed a triangular MSH6-CXCR4-TGFB1 feedback loop that accelerated gliomagenesis, proliferation (G1 phase), migration and invasion (epithelial-to-mesenchymal transition; EMT), stemness, angiogenesis and antiapoptotic effects by regulating the p-STAT3/Slug and p-Smad2/3/ZEB2 signaling pathways in GBM. In addition, the MSH6-CXCR4-TGFB1 feedback loop was a vital marker of GBM, making it a promising therapeutic target. Notably, photothermal therapy (PTT) mediated by Cu
2
(OH)PO
4
@PAA + near infrared (NIR) irradiation showed outstanding therapeutic effects, which might be associated with a repressed MSH6-CXCR4-TGFB1 feedback loop and its downstream factors in GBM. Simultaneously, the prominent MR imaging (T1WI) ability of Cu
2
(OH)PO
4
@PAA could provide visual guidance for PTT.
Conclusions:
Our findings indicate that the oncogenic MSH6-CXCR4-TGFB1 feedback loop is a novel therapeutic target for GBM and that PTT is associated with the inhibition of the MSH6-CXCR4-TGFB1 loop.
Green synthesized 3D CuS hollow nanoflowers are for the first time proved to be a T1 positive MRI contrast agent for imaging-guided thermochemotherapy.
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