Guan Sun

MicroRNA-21 inhibitor sensitizes human glioblastoma U251 stem cells to chemotherapeutic drug temozolomide.

MicroRNAs (miRNAs) are small noncoding RNA molecules that regulate protein expression by cleaving or repressing the translation of target mRNAs. In mammals, their function mainly represses the target mRNA transcripts via imperfect complementary sequences in the 3′UTR of target mRNAs. Several miRNAs have been recently reported to be involved in modulation of glioma development, especially some upregulated miRNAs, such as microRNA-21 (miR-21), which has been found to function as an oncogene in cultured glioblastoma multiforme cells. Temozolomide (TMZ), an alkylating agent, is a promising chemotherapeutic agent for treating glioblastoma. Although chemotherapy with temozolomide may contain tumor growth for some months, invariable tumor recurrence suggests that cancer stem cells maintaining these tumors persist. Previous research showed that TMZ could inhibit the proliferation of human glioblastoma stem cells (GSC), but not induced apoptosis, which could supply the chance for glioblastoma recurrence. Accumulating evidence indicated that downregulation of miR-21 in glioblastoma cells caused repression of growth and increased apoptosis, all of which could theoretically enhance the chemotherapeutic effects of cancer therapy. In this study, we aimed to explore whether miR-21 downregulation could enhance the chemotherapeutic effects of TMZ and induce apoptosis on GSC. Interestingly, the results demonstrated that either miR-21 inhibitor or TMZ could not induce apoptosis on GSC. However, miR-21 inhibitor combined with TMZ significantly enhanced GSC apoptosis. Taken together, a combination of miR-21 inhibitor and TMZ could be an effective therapeutic strategy for GSC apoptosis to prevent potential glioblastoma recurrence.

MiR‐21 Modulates hTERT Through a STAT3‐Dependent Manner on Glioblastoma Cell Growth

As an important oncogenic miRNA, miR‐21 has been reported to play crucial roles in glioblastoma (GBM) carcinogenesis. However, the precise biological function and molecular mechanism of miR‐21 in GBM remain elusive. This study is designed to explore the mechanism of miR‐21 involved in the control of GBM cell growth.

Circulating MicroRNAs as Novel Potential Biomarkers for Early Diagnosis of Acute Stroke in Humans

BACKGROUND Many diseases include microRNAs (miRNAs) as reported biomarkers. The significance of circulating miRNAs for early diagnosis of acute stroke in humans is unknown. We aim to determine whether circulating miRNAs potentially serve as novel biomarkers for acute stroke. METHODS We prospectively recruited patients with acute stroke and those with nonstroke disease. Patients with acute stroke were identified using magnetic resonance imaging (MRI) for early diagnosis. If the patient suffered from acute stroke that was detected with diffusion-weighted imaging, the patient was defined as an MRI(+) patient. Otherwise, it was defined as an MRI(-) patient. Circulating miRNAs were measured by miRNA microarray and real-time polymerase chain reaction (PCR) analysis. RESULTS A total of 136 patients were included in the study. Testing by miRNA microarray and real-time PCR analyses showed that hsa-miR-106b-5P and hsa-miR-4306 were present with markedly high abundance in patients of acute stroke, whereas hsa-miR-320e and hsa-miR-320d were present with quite low abundance in patients compared with healthy individuals. Compared with healthy individuals, the miRNAs were increased as in patients with acute stroke as follows: hsa-miR-106b-5P, 3.63-fold in MRI(-) patients and 23.90-fold in MRI(+) patients; hsa-miR-4306, 3.19-fold in MRI(-) patients and 5.30-fold in MRI(+) patients; hsa-miR-320e, .33-fold in MRI(-) patients and .13-fold in MRI(+) patients; and hsa-miR-320d, .23-fold in MRI(-) patients and .07-fold in MRI(+) patients. CONCLUSIONS Elevated hsa-miR-106b-5P and hsa-miR-4306 and decreased hsa-miR-320e and hsa-miR-320d in plasma may be novel biomarkers for the early detection of acute stroke in humans.

miR-145 Inhibits Migration and Invasion of Glioma Stem Cells by Targeting ABCG2

Abstract Despite advances in clinical therapies and technologies, the prognosis for patients with malignant glioma is poor. Our previous research demonstrated that glioma stem cells (GSCs) were crucial for glioma malignancy and accelerated tumor migration and invasion. The migration and invasion of malignant glioma cells into the surrounding normal brain tissues cause the poor outcome. miR-145, a miRNA found to be expressed in neurons, was recently found to have reduced expression in glioblastoma multiforme tumors. And miR-145 loss in glioma cells led to increased cell proliferation and invasion. However, its function on the migration and invasion of GSCs was still unknown. In this study, we aimed to identify the effects and mechanisms of miR-145 on the migration and invasion of GSCs. Our investigations revealed that miR-145 was low expressed in malignant glioma tissues and their corresponding GSCs. Knockdown of miR-145 in vitro could enhance the migration and invasion of GSCs, while up-regulation of miR-145 had the opposite effects. Further investigation of the potential mechanism demonstrated that the function of miR-145 in regulating the migration and invasion of GSCs is mediated by its targeting of ABCG2 mRNA. ABCG2 is an ATP-binding cassette transporter protein, which was identified to be overexpressed in GSCs and higher-grade glioma tissues. We found that miR-145 was negative correlated with ABCG2 levels in GSCs, and reduction in ABCG2 expression decreased the cell migration and invasion of GSCs. Further, a luciferase reporter proved that ABCG2 was a direct target of miR-145 in GSCs. Thus, these findings underscore the potential of miR-145 to regulate the migration and invasion of GSCs through targeting ABCG2.

Functional Differences of miR-125b on the Invasion of Primary Glioblastoma CD133-Negative Cells and CD133-Positive Cells

MicroRNAs (miRNAs) are small noncoding RNAs whose function as modulators of gene expression is crucial for the proper control of cell development, differentiation, and homeostasis. The total number and composition of miRNAs expressed per cell at different stages of development varies widely, and the same miRNA may function differently at different stages of development. In this prospective study, we evaluated the function of miR-125b at different developmental stages of glioblastoma cells, such as primary glioblastoma cells and the corresponding stem cells. CD133 is an important surface marker in glioblastoma stem cells. We found that the upregulation of miR-125b had no effects on the invasion of primary glioblastoma CD133-negative cells but that it could inhibit the invasion of corresponding CD133-positive cells; however, the downregulation of miR-125b also had no effects on the invasion of primary glioblastoma CD133-negative cells but promoted the invasion of CD133-positive cells. Further research into the underlying mechanism demonstrated that the effects of miR-125b on the invasion of glioblastoma CD133-positive cells were associated with the alteration of the expression of MMPs (MMP-2 and MMP-9) and corresponding inhibitors (RECK and TIMP3). Our results demonstrate that miR-125b expression plays an essential role in the invasion of glioblastoma CD133-positive cells but not CD133-negative cells. Therefore, miR-125b may represent a novel target for therapy targeting the invasion of glioblastoma stem cells in the future.

MicroRNAs involved in the EGFR/PTEN/AKT pathway in gliomas

Gliomas are the most common type of malignant primary brain tumor. Despite advances in surgery, radiation therapy, and chemotherapy, the prognosis of patients with gliomas has not significantly improved. MicroRNAs (miRNAs), a class of non-coding RNAs, 21–25 nucleotides long, negatively regulate the expression of target genes by interacting with specific sites in mRNAs, and play a critical role in the development of gliomas. The EGFR/PTEN/AKT pathway is a promising target for anti-glioma therapy. Recent studies have showed that regulation of the EGFR/PTEN/AKT pathway by miRNAs plays a major role in glioma progression, indicating a novel way to investigate the tumorigenesis, diagnosis, and therapy of gliomas. Here, we focus on recent findings of miRNAs with respect to the EGFR/PTEN/AKT pathway in gliomas.

MiR-15b Targets Cyclin D1 to Regulate Proliferation and Apoptosis in Glioma Cells

Aim. To investigate the role and mechanism of miR-15b in the proliferation and apoptosis of glioma. Methods. The miR-15b mimics were transfected into human glioma cells to upregulate the miR-15b expression. Cyclin D1 was determined by both western blotting analysis and luciferase reporter assay. Methylthiazol tetrazolium (MTT) and flow cytometry were employed to detect the cell proliferation, cell cycle, and apoptosis. Results. Overexpression of miR-15b inhibits proliferation by arrested cell cycle progression and induces apoptosis, possibly by directly targeting Cyclin D1. Both luciferase assay and bioinformatics search revealed a putative target site of miR-15b binding to the 3′-UTR of Cyclin D1. Moreover, expression of miR-15b in glioma tissues was found to be inversely correlated with Cyclin D1 expression. Enforced Cyclin D1 could abrogate the miR-15b-mediated cell cycle arrest and apoptosis. Conclusions. Our findings identified that miR-15b may function as a glioma suppressor by targeting the Cyclin D1, which may provide a novel therapeutic strategy for treatment of glioma.

Overexpressed miRNA-137 Inhibits Human Glioma Cells Growth by Targeting Rac1

Previous studies have shown that miR-137 functions as a tumor suppressor in various cancers, but its role in the initiation and development of gliomas is still unknown. Currently, we found that miR-137 exhibited the most significant increase in normal brain tissues compared with glioma specimens, and the miR-137 expression was greatly decreased with the ascending of tumor pathological grades. Furthermore, overexpression of miR-137 in vitro by chemically synthesized miR-137 mimics suppressed the proliferation, inhibited cell cycle arrest in the G1/G0 phase, and induced cell apoptosis. The tumor-suppressive effects of miR-137 were indeed induced by Rac1, which was verified as a direct target of miR-137. These findings indicate that miR-137 inhibits the growth of gliomas cells by directly targeting Rac1, suggesting that miR-137 could be a new important therapeutic strategy for glioma treatment and warrants further investigation.

miR-125b Inhibitor May Enhance the Invasion-Prevention Activity of Temozolomide in Glioblastoma Stem Cells by Targeting PIAS3

BackgroundTemozolomide, an alkylating agent, is a promising chemotherapeutic agent for treating glioblastoma. Although chemotherapy with temozolomide may restrain tumor growth for some months, invariable tumor recurrence suggests that cancer stem cells maintaining these tumors persist. Previous research has shown that temozolomide can inhibit the proliferation of human glioblastoma stem cells (GSCs); however, no research has focused on the invasion of GSCs, which is an important factor for glioblastoma recurrence. Accumulating evidence indicates that microRNA (miR)-125b over-expression in GSCs may increase their invasiveness.ObjectiveOur objective was to identify the effects and mechanism of action of an miR-125b inhibitor combined with temozolomide in the invasive pathogenesis of GSCs.MethodsWe modified the levels of miR-125b expression in primary GSCs in order to observe the effect on sensitivity to temozolomide on invasion, and we further analyzed the differences in mechanism between miR-125b treatment alone and treatment with miR-125b plus temozolomide using the Cancer PathwayFinder PCR Array.ResultsOur results demonstrated that either an miR-125b inhibitor or temozolomide could modestly inhibit the invasiveness of GSCs. Furthermore, GSCs that were pre-transfected with an miR-125b inhibitor, then treated with temozolomide, showed significantly decreased invasiveness when compared with GSCs treated with an miR-125b inhibitor or temozolomide alone. Further research into the underlying mechanism demonstrated that the miR-125b inhibitor enhanced the invasion-prevention activity of temozolomide in GSCs through targeting PIAS3 (protein inhibitor of activated STAT [signal transducer and activator of transcription]), which contributed to reduced STAT3 transcriptional activity and subsequent decreased expression of matrix metalloproteinase (MMP)-2 and -9.ConclusionsmiR-125b could play a role in the development of temozolomide resistance in GSCs. Inhibition of miR-125b expression may enhance sensitivity of GSCs to temozolomide by targeting PIAS3 on cell invasion.

miR-125b promotes cell proliferation by directly targeting Lin28 in glioblastoma stem cells with low expression levels of miR-125b.

MicroRNAs (miRNAs) are small noncoding RNA molecules that regulate protein expression by cleaving or repressing the translation of target mRNAs. Our previous studies have revealed that miR-125b is a typical overexpressed miRNA in human primary glioblastoma stem cells (GSCs). Here, we report that miR-125b was also found to be significantly underexpressed in three primary GSCs. Characterization of the effects of the underexpressed miR-125b in GSCs showed that elevated levels of miR-125b inhibited cell growth and induced cell cycle arrest in the G0/G1 phase in vitro; a reduction in miR-125b levels had the opposite effect on tumour growth and progression. Further research into the underlying mechanism demonstrated that miR-125b acts by targeting Lin28 to regulate cell growth. Lin28 is highly expressed in human embryonic stem cells and glioblastomas. We showed that the specific repression of Lin28 results in decreased GSC proliferation, and that the overexpression of Lin28 accelerates cell proliferation. Our results highlight a novel molecular interaction between miR-125b and Lin28, and miR-125b may represent a potential novel therapeutic agent for targeting the proliferation of GSCs. In view of our previous research showing that miR-125b was overexpressed in GSCs and functioned as an oncogene, here our finding was not in agreement with our previous report, which implies that the personalized treatment on GSCs may be necessary and important.