Downregulation of Astrocyte Elevated Gene-1 Expression Combined with All-Trans Retinoic Acid Inhibits Development of Vasculogenic Mimicry and Angiogenesis in Glioma.

OBJECTIVE: This study aimed to investigate the effects of downregulating astrocyte elevated gene-1 (AEG-1) expression combined with all-trans retinoic acid (ATRA) on vasculogenic mimicry (VM) formation and angiogenesis in glioma. METHODS: U87 glioma cells were transfected with AEG-1 shRNA lentiviral vectors (U87-siAEG-1) and incubated in a medium containing 20 µmol/L ATRA. Matrigel-based tube formation assay was performed to evaluate VM formation, and the cell counting kit-8 (CCK-8) assay was used to analyze the proliferation of glioma cells in vitro. Reverse transcription-quantitative polymerase chain reaction and Western blot analysis were used to investigate the mRNA and protein expression of related genes, respectively. Glioma xenograft models were generated via subcutaneous implantation of glioma cells in nude mice. Tumor-bearing mice received an intraperitoneal injection of ATRA (10 mg/kg per day). Immunohistochemistry was used to evaluate the expression of related genes and the microvessel density (MVD) in glioma xenograft models. CD34/periodic acid-Schiff double staining was performed to detect VM channels in vivo. The volume and weight of tumors were measured, and a tumor growth curve was drawn to evaluate tumor growth. RESULTS: A combination of ATRA intervention and downregulation of AEG-1 expression significantly inhibited the proliferation of glioma cells in vitro and glioma VM formation in vitro and in vivo. It also significantly decreased MVD and inhibited tumor growth. Further, the expression levels of matrix metalloproteinase (MMP)-2, MMP-9, vascular endothelial-cadherin (VE-cadherin), and vascular endothelial growth factor (VEGF) in glioma significantly decreased in vivo and in vivo. CONCLUSION: Hence, a combinatorial approach might be effective in treating glioma through regulating MMP-2, MMP-9, VEGF, and VE-cadherin expression.

Combined elevation of TRIB2 and MAP3K1 indicates poor prognosis and chemoresistance to temozolomide in glioblastoma.

INTRODUCTION: Glioblastoma (GBM) is the most lethal primary malignant brain tumor in adults with poor survival due to acquired therapeutic resistance and rapid recurrence. Currently, the standard clinical strategy for glioma includes maximum surgical resection, radiotherapy, and temozolomide (TMZ) chemotherapy; however, the median survival of patients with GBM remains poor despite these comprehensive therapies. Therefore, the identification of new prognostic biomarkers is urgently needed to evaluate the malignancy and long-term outcome of glioma. AIMS: To further investigate prognostic biomarkers and potential therapeutic targets for GBM. RESULTS: In this study, we identified tribbles pseudokinase 2 (TRIB2) as one of the genes that is most correlated with pathological classification, radioresistance, and TMZ resistance in glioma. Additionally, the expression of mitogen-activated protein kinase kinase kinase 1 (MAP3K1) showed a strong correlation with TRIB2. Moreover, a combined increase in TRIB2 and MAP3K1 was observed in GBM and indicated a poor prognosis of patients with glioma. Finally, enriched TRIB2 expression and MAP3K1 expression were shown to be associated with resistance to TMZ and radiotherapy. CONCLUSION: Combined elevation of TRIB2 and MAP3K1 could be novel prognostic biomarkers and potential therapeutic targets to evaluate the malignancy and long-term outcomes of GBM.

PDZ-Binding Kinase-Dependent Transcriptional Regulation of CCNB2 Promotes Tumorigenesis and Radio-Resistance in Glioblastoma.

Increasing evidence has indicated that PDZ binding kinase (PBK) promotes proliferation, invasion, and therapeutic resistance in a variety of cancer types. However, the physiological function and therapy-resistant role of PBK in GBM remain underexplored. In this study, PBK was identified as one of the most therapy-resistant genes with significantly elevated expression level in GBM. Moreover, the high expression level of PBK was essential for GBM tumorigenesis and radio-resistance both in vitro and in vivo. Clinically, aberrant activation of PBK was correlated with poor clinical prognosis. In addition, inhibition of PBK dramatically enhanced the efficacy of radiation therapy in GBM cells. Mechanically, PBK-dependent transcriptional regulation of CCNB2 was critical for tumorigenesis and radio-resistance in GBM cells. Collectively, PBK promotes tumorigenesis and radio-resistance in GBM and may serve as a novel therapeutic target for GBM treatment.

Downregulation of AIF-2 Inhibits Proliferation, Migration, and Invasion of Human Glioma Cells via Mitochondrial Dysfunction.

Glioma remains the leading cause of brain tumor-related death worldwide. Apoptosis inducing factor (AIF) is a family of mitochondrial oxidoreductases that play important roles in mitochondrial metabolism and redox control. AIF-1 has been demonstrated to exert cell-killing effect via apoptosis in cancer cells, whereas the role of AIF-2 in cancer cells has not been determined. This study aimed to investigate the role of AIF-2 in human glioma cells. We found that AIF-2 was upregulated in human glioma tissues and cell lines, especially in U251 cells. Downregulation of AIF-2 using specific siRNA (Si-AIF-2) significantly reduced cell proliferation, induced G1 cell cycle arrest and differently regulated the expression of cell cycle regulator proteins in U251 cells. In addition, the results of Matrigel invasion assay and live-cell tracking assay showed that knockdown of AIF-2 inhibited cell invasion and migration. The results of immunocytochemistry indicated that knockdown of AIF-2 significantly attenuated the nuclear translocation of AIF-1, which was confirmed by western blot analysis. Furthermore, downregulation of AIF-2 resulted in mitochondrial dysfunction in U251 cells, as evidenced by reduced mitochondrial membrane potential (MMP), mitochondrial complex I activity, and mitochondrial Ca2+ buffering capacity. In conclusion, we found that AIF-2 plays a key role in promoting cell proliferation, invasion, and migration via regulating AIF-1-related mitochondrial cascades. Downregulation of the candidate oncogene AIF-2 might constitute a strategy to kill human glioma cells.

Salvianolic acid B renders glioma cells more sensitive to radiation via Fis-1-mediated mitochondrial dysfunction.

Glioma remains the leading cause of brain tumor-related death worldwide, and radiation is a standard adjuvant therapy with proven efficacy. Salvianolic acid B (SalB), a bioactive compound isolated from Radix Salviae, has been shown to exert anti-cancer effects in many cancer cell lines, including glioma. This study aimed to investigate whether SalB could affect response to radiation in human glioma cells. We found that SalB decreased cell viability of U87 cells in a-dose-dependent manner. A subthreshold dose of SalB at 0.5 µM, which had no effect on cell viability and apoptosis, significantly increased radiation sensitivity of U87 cells in a dose- and time-dependent manner, but had no effect on sensitivity to temozolomide (TMZ). Similar results were also observed in human glioma U373 cells. In addition, SalB aggravated the radiation-induced apoptosis and mitochondrial dysfunction, as measured by mitochondrial Ca2+ buffering capacity and mitochondrial swelling. SalB treatment markedly promoted mitochondrial fission and differently regulated the expression of fission proteins. Furthermore, downregulation of the fission protein Fis-1 using siRNA was found to partially reversed the SalB-induced effects on cell viability, apoptosis and mitochondrial fission in U87 cells. In conclusion, our results suggest that a subthreshold dose of SalB renders glioma cells more sensitive to radiation via Fis-1-mediated mitochondrial dysfunction, and radiotherapy combined with SalB might be a novel treatment for glioma patients.