Pengxing Zhang

MicroRNA-101 inhibits proliferation, migration and invasion of human glioblastoma by targeting SOX9

Glioblastoma multiforme (GBM) is the most common primary malignant tumors originating in the brain parenchyma. At present, GBM patients have a poor prognosis despite the continuous progress in therapeutic technologies including surgery, radiotherapy, photodynamic therapy, and chemotherapy. Recent studies revealed that miR-101 was remarkably down-regulated in kinds of human cancers and was associated with aggressive tumor cell proliferation and stem cell self-renewal. Data also showed that miR-101 was down-regulated in primary glioma samples and cell lines, but the underlying molecular mechanism of the deregulation of miR-101 in glioma remained largely unknown. In this study, we found that miR-101 could inhibit the proliferation and invasion of glioma cells both in vitro and in vivo by directly targeting SOX9 [sex-determining region Y (SRY)-box9 protein]. Silencing of SOX9 exerted similar effects with miR-101 overexpression on glioma cells proliferation and invasion. Quantitative reverse transcription PCR and Western blotting analysis revealed a negative relationship between miR-101 and SOX9 in human glioma U251MG and U87MG cells, and the luciferase assay indicated that miR-101 altered SOX9 expression by directly targeting on 3′UTR. Taken together, our findings suggest that miR-101 regulates glioma proliferation, migration and invasion via directly down-regulating SOX9 both in vitro and in vivo, and miR-101 may be a potential therapeutic target for future glioma treatment.

A novel indication of thioredoxin-interacting protein as a tumor suppressor gene in malignant glioma

Malignant glioma, the most common form of primary brain tumor, is associated with substantial morbidity and mortality, owing to the lack of response shown by patients to conventional therapies. Additional therapeutic targets and effective treatment options for these patients are therefore required. In the present study, a possible association of thioredoxin-interacting protein (TXNIP) with malignant glioma was evaluated. Initially, semi-quantitative and quantitative analysis of the expression levels of TXNIP in clinical specimens of primary glioma was performed via immunohistochemistry (IHC) and reverse transcription-quantitative polymerase chain reaction (RT-qPCR), respectively, and expression levels were further correlated to the overall survival time of the patients. The proliferative, migratory and invasive properties of the glioblastoma U251 cell line, engineered to downregulate TXNIP by lentiviral transfection of a specific short hairpin RNA, were evaluated by means of in vitro assays. Consequently, IHC and RT-qPCR analysis revealed a negative association between the expression level of TXNIP and the histopathological grade of the tumor. Higher TXNIP expression level was associated with extended patient survival time. In vitro analysis revealed increased growth, migration and invasion in U251 cells with downregulated TXNIP expression compared with their non-transfected counterparts. These findings strongly indicate that TXNIP functions as a tumor suppressor in malignant glioma cells and underscore its potential as a novel therapeutic target and prognostic indicator of the condition.

ClC-3 Expression and Its Association with Hyperglycemia Induced HT22 Hippocampal Neuronal Cell Apoptosis

Although apoptosis plays an important role in the development of Diabetic Encephalopathy (DE), the underlying molecular mechanisms remain unclear. With respect to this, the present work aims to study the variation in chloride/proton exchanger ClC-3 expression and its association with HT22 hippocampal neuronal apoptosis under hyperglycemic condition in vitro. The cells were stimulated with added 0, 5, or 25 mM glucose or mannitol for up to 72 hours before assessing the rate of ClC-3 expression, cell viability, and apoptosis. In a consecutive experiment, cells received chloride channel blocker in addition to glucose. The rate of cellular death/apoptosis and viability was measured using Flow Cytometry and MTT assay, respectively. Changes in ClC-3 expression were assessed using immunofluorescence staining and western blot analysis. The results revealed a significant increase in cellular apoptosis and reduction in viability, associated with increased ClC-3 expression in high glucose group. Osmolarity had no role to play. Addition of chloride channel blocker completely abolished this effect. Thus we conclude that, with its increased expression, ClC-3 plays a major role in hyperglycemia induced hippocampal neuronal apoptosis. To strengthen our understanding of this aforesaid association, we conducted an extensive literature search which is presented in this paper.

The coexistence of VGluT2 and neurotensin or leu-enkephalin in the medullary dorsal horn: a confocal and electron microscopic immunohistochemical study in the rat.

Neuropeptides such as neurotensin (NT), and enkephalin (ENK) in the medullary dorsal horn (MDH) are involved in excitatory synaptic transmission to modulate nociceptive information. However, morphological evidence indicating that NT or ENK coexists with glutamate in the MDH is still meager. Using fluorescent immunohistochemistry, the results showed that double labeling of NT or ENK terminals with VGluT2 is mainly concentrated in the lamina II of the MDH, and many axon terminals exhibiting NT or ENK immunoreactivity in the superficial layers of the MDH showed VGluT2 immunoreactivity. Electron microscopy confirmed the coexpression of NT or ENK and VGluT2 in axon terminals within the laminae I and II of the MDH. These axon terminals make asymmetrical synapses with immunonegative neuronal cell bodies and dendrites. The findings suggest that glutamate is coreleased with NT or ENK from axon terminals of interneurons in the superficial layers of the MDH.

Hexokinase 2 (HK2), the tumor promoter in glioma, is downregulated by miR-218/Bmi1 pathway

In cancer, glycolysis driving enzymes and their regulating microRNAs are one of the key focus of oncology research lately. The glycolytic enzyme hexokinase 2 (HK2) is crucial for the Warburg effect in human glioma, the most common malignant brain tumor. In the present study, we studied the tumorigenic role of HK2 in glioma, and clarified the mechanism of miR-218 induced HK2 regulation in glioma development. The HK2 expression in patient derived glioma and non neoplastic brain tissue was quantified. The HK2 silenced U87 and U251 cell lines were assessed for their proliferation, migration and invasive potential in vitro, while the tumor forming potential of U87 cells was evaluated in vivo. The untreated cell lines served as control. The HK2 expression in (a) lentivirus-infected, miR-218 overexpressing and (b) shRNA mediated Bmi1 silenced U87 and U251 glioma cell lines were quantified. Luciferase reporter assay, qRT-PCR analysis and WB were employed as required. The HK2 expression was significantly increased in glioma tissues comparing with the non neoplastic brain tissues and was positively correlated with the glioma grade. Silencing HK2 in glioma cell lines significantly decreased their proliferation, migration, invasion and tumorigenic abilities. Although, overexpression of miR-218 significantly downregulated the HK2 expression, luciferase reporter assay failed to show HK2 as the direct target of miR-218. A direct correlation, however, was observed between HK2 and Bmi-1, the direct target of miR-218. Taken together, our findings confirmed the tumorigenic activity of HK2 in glioma, and the involvement of the miR218/Bmi1 pathway in the regulation of its expression.

The genomic organization and function of IRX1 in tumorigenesis and development

Iroquois homeobox (IRX), containing transcription factor family of homologous genes and proteins, is widely expressed in both vertebrates and invertebrates embryonic tissue expression profiles. They play a crucial role in the regionalization and patterning of tissues and organs during metazoan development. IRX1, belonging to the IRX gene family, codes for active proteins involved in the development of vertebrate nervous system and plays an important role in the development of various other organs during embryo development. It also plays a critical role in the tumor formation and is identified as both the oncogene or tumor suppressor gene in a variety of tumors. This review summarizes the recent discoveries on the genomic structure of IRX1 and the type classification in different species. More specifically, we focused on explaining the key role of IRX1 in tumorigenesis, and development of tumor and influence in biological processes of metazoans, which we hope will provide a better understanding of the mechanism of IRX1.

SOX9-PDK1 axis is essential for glioma stem cell self-renewal and temozolomide resistance

Glioblastoma multiforme (GBM) is the most common and aggressive brain tumor with limited therapeutic options. Glioma stem cell (GSC) is thought to be greatly responsible for glioma tumor progression and drug resistance. But the molecular mechanisms of GSC deriving recurrence and drug resistance are still unclear. SOX9 (sex-determining region Y (SRY)-box9 protein), a transcription factor expressed in most solid tumors, is reported as a key regulator involved in maintaining cancer hallmarks including the GSCs state. Previously, we have observed that silencing of SOX9 suppressed glioma cells proliferation both in vitro and in vivo. Here, we found that SOX9 was essential for GSC self-renewal. Silencing of SOX9 down-regulated a broad range of stem cell markers and inhibited glioma cell colony and sphere formation. We identified pyruvate dehydrogenase kinase 1 (PDK1) as a target gene of SOX9 using microarray analyses. PDK1 inactivation greatly inhibited glioma cell colony and sphere formation and sensitized glioma spheres to temozolomide (TMZ) toxicity. In addition, SOX9-shRNA and PDK1 inhibitor could greatly sensitize GSC to TMZ in vivo. Taken together, our data reveals that SOX9-PDK1 axis is a key regulator of GSC self-renewal and GSC temozolomide resistance. These findings may provide help for future human GBM therapy.

The mechanism of BMI1 in regulating cancer stemness maintenance, metastasis, chemo- and radiation resistance

BMI1 is involved in the occurrence and development of many types of cancer through a variety of signaling pathways. BMI1, which is overexpressed in cancer, is often associated with chemo- and radiation resistance and poor prognosis in cancer patients. This article reviews the current understanding of the mechanism of BMI1 in maintaining tumor stemness, promoting metastasis, and inducing chemo- and radiation resistance, aiming at providing updated information supportive of targeting BMI1 in cancer treatment.

Genetic variants of SOX9 contribute to susceptibility of gliomas among Chinese population

Gliomas make up about 80% of all malignant brain tumors, and cause serious public health problem. Genetic factors and environmental factors jointly caused the development of gliomas, and understanding of the genetic basis is a key component of preventive oncology. However, most genetic factors underlying carcinogenesis of gliomas remain largely unclear. In current study, we systematically evaluated whether genetic variants of SOX9 gene, a transcription factor that plays a central role in the development and differentiation of tumors, contribute to susceptibility of gliomas among Chinese population using a two-stage, case–control study. Results showed that SOX9 rs1042667 was significant associated with increased gliomas risk after adjusted by age, gender, family history of cancer, smoking status and alcohol status (Allele C vs A: OR=1.25; 95% CI=1.11-1.40; P=1.2×10−4). Compared with the carriers of genotype AA, both those of genotype AC (OR=1.37; 95% CI=1.13-1.66) and CC (OR=1.53; 95% CI=1.22-1.91) had significantly increased gliomas risk. This should be the first genetic association study which aims to evaluated the association between genetic variants of SOX9 and susceptibility of gliomas. Additional functional and association studies with different ethnic groups included are needed to further confirm our results.