The nuclear transporter importin-11 regulates the Wnt/β-catenin pathway and acts as a tumor promoter in glioma

Basic mechanism of mobilizing cell movement during invasion of glioblastoma and target selection of targeted therapy

BACKGROUND

Glioblastoma (GBM), also known as glioblastoma multiforme, is a rapidly growing and highly invasive malignant tumor. Due to the inability to clearly distinguish between glioblastoma and normal tissue, surgery cannot achieve safe resection, often leading to poor patient prognosis and inevitable tumor recurrence. According to previous studies, GBM invasion is related to intercellular adhesion, matrix degradation, extracellular matrix and its related adhesion molecules, as well as the molecular matrix of protein hydrolases in the microenvironment of GBM cells and stromal cells.

AIM OF REVIEW

The aim is to enhance our understanding of the molecular mechanisms underlying GBM invasion and to advance research on targeted therapies for inhibiting GBM invasion.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This article describes the protein hydrolases that may affect GBM cell invasion, changes in the cytoskeleton during motility, and the regulatory mechanisms of intracellular signaling pathways in GBM invasion. In addition, we also explored the possibility of targeted therapy against invasion related molecules in GBM.

Wnt/β-catenin-driven EMT regulation in human cancers

Metastasis accounts for 90% of cancer-related deaths among the patients. The transformation of epithelial cells into mesenchymal cells with molecular alterations can occur during epithelial-mesenchymal transition (EMT). The EMT mechanism accelerates the cancer metastasis and drug resistance ability in human cancers. Among the different regulators of EMT, Wnt/β-catenin axis has been emerged as a versatile modulator. Wnt is in active form in physiological condition due to the function of GSK-3β that destructs β-catenin, while ligand-receptor interaction impairs GSK-3β function to increase β-catenin stability and promote its nuclear transfer. Regarding the oncogenic function of Wnt/β-catenin, its upregulation occurs in human cancers and it can accelerate EMT-mediated metastasis and drug resistance. The stimulation of Wnt by binding Wnt ligands into Frizzled receptors can enhance β-catenin accumulation in cytoplasm that stimulates EMT and related genes upon nuclear translocation. Wnt/β-catenin/EMT axis has been implicated in augmenting metastasis of both solid and hematological tumors. The Wnt/EMT-mediated cancer metastasis promotes the malignant behavior of tumor cells, causing therapy resistance. The Wnt/β-catenin/EMT axis can be modulated by upstream mediators in which non-coding RNAs are main regulators. Moreover, pharmacological intervention, mainly using phytochemicals, suppresses Wnt/EMT axis in metastasis suppression.

Effect of Licochalcone-A Combined with Rab23 Gene on Proliferation of Glioma U251 Cells

This research aimed to explore the effect of Licochalcone-A (LCA) combined with Rab23 gene on the proliferation, migration, and invasion of glioma U251 cells through the Wnt/β-catenin signaling pathway. The glioma U251 cell line was taken as the research object, and the Rab23 overexpression plasmid was constructed. According to the treatment method, U251 cells were rolled into blank control group (BC), Rab23 overexpression plasmid transfection group (Rab23), 25 μmol·L⁻¹ LCA treatment group (LCA), and Rab23 overexpression plasmid transfection combined with 25 μmol·L⁻¹ LCA treatment group (Rab23 + LCA). Subsequently, the ability of cell proliferation, migration, and invasion of each group was detected by methyl thiazolyl tetrazolium (MTT) assay, scratch healing test, and Transwell cell invasion test, respectively. Western blot was implemented to detect the expression differences of cell proliferation antigen Ki-67, apoptosis-related proteins Bcl-2 and Bax, and Wnt/β-catenin pathway-related proteins β-catenin, glycogen synthase kinase-3 (GSK3β), Axin2, and c-myc. The results showed the successful construction of Rab23 overexpression and stable transfection U251 cell line. After grouping and treatments, the cell proliferation, migration, and invasion ability of the Rab23 group, LCA group, and Rab23 + LCA group was substantially reduced relative to BC group (P < 0.05). In addition, the cell proliferation, migration, and invasion ability of Rab23 + LCA group decreased relatively more significantly. The expression levels of Ki-67, Bcl-2, β-catenin, and c-myc in the Rab23, LCA, and Rab23 + LCA groups were greatly lower versus those of BC group. Moreover, the protein expression levels of Bax, GSK3β, and Axin2 were considerably increased (P < 0.05), while the expression of protein in Rab23 + LCA group increased notably. These findings indicate that LCA combined with Rab23 gene can inhibit the proliferation, migration, and invasion of glioma U251 cells through the Wnt/β-catenin signaling and can promote cell apoptosis.

LASS2 impairs proliferation of glioma stem cells and migration and invasion of glioma cells mainly via inhibition of EMT and apoptosis promotion

LAG1 longevity assurance homolog 2 (LASS2), a highly conserved transmembrane protein, has been reported in several cancer types. However, the roles of LASS2 in glioma biology remain elusive. In the present study, we investigated the expression of LAAS2 in human glioma tissues and the effects of LASS2 on glioma stem cell (GSC) proliferation. Roles of LASS2 in glioma cell migration and invasion were also researched both in vitro and in vivo. Our results demonstrated that the level of LASS2 is gradually reduced with the increase of glioma grade. The level of LASS2 is significantly lower in GSCs than in non GSCs, whereas LASS2 overexpression reduced the sphere formation and promoted the differentiation of CD133⁺ glioblastoma cells, as was indicated by reduced levels of CD133 and Nestin. In addition, LASS2 overexpression significantly reduced colony formation, migration, and invasion of glioma cells by promoting tumor cell apoptosis and inhibiting epithelial-mesenchymal transition (EMT). Overexpression of LASS2 inhibited U-87 MG cell-derived glioma xenograft growth in nude mice in a manner similar to in vitro. Our findings indicate that LASS2 can function as a suppressor of glioma growth, suggesting that modulation of LASS2 expression may contribute to a novel strategy for the management of glioma via inhibition of GSCs.