The pivotal role of microRNA-155 in the control of cancer

Knockdown of LMP1-induced miR-155 sensitizes nasopharyngeal carcinoma cells to radiotherapy in vitro

The present study aimed to confirm the promotion of microRNA (miR)-155 expression by latent membrane protein 1 (LMP1), and to recognize the oncogenic role of LMP1 and LMP1-promoted miR-155 in nasopharyngeal carcinoma (NPC), particularly the influence of miR-155 knockdown on the radiosensitivity of CNE-2 cells. Following the regulation of the levels of LMP1 or miR-155 and/or subsequent to radiation treatment, the proliferation ability of CNE-2 cells was examined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, colony formation and Cell Counting Kit-8 assays. The results demonstrated that miR-155 was upregulated by overexpression of LMP1 in CNE-2 cells, and LMP1 overexpression and miR-155 mimic transfection increased CNE-2 cell proliferation, whereas miR-155 knockdown attenuated the promotion of CNE-2 cell growth induced by LMP1 overexpression. Furthermore, knockdown of miR-155 enhanced the radiosensitivity of CNE-2 cells. In conclusion, the present study confirmed the oncogenic role of miR-155 in NPC, and demonstrated that knockdown of miR-155 inhibited the growth of NPC cells and sensitized NPC cells to radiotherapy.

MicroRNA-155 expression inversely correlates with pathologic stage of gastric cancer and it inhibits gastric cancer cell growth by targeting cyclin D1

PURPOSE

MicroRNAs (miRs) have been frequently reported dysregulating in tumors and playing a crucial role in tumor development and progression. However, the expression of miR-155 and its role in gastric cancer (GC) are still obscure.

METHODS

qRT-PCR was applied to detect miR-155 expression in 60 matched GC samples and four GC cell lines, and the relationship between miR-155 levels and clinicopathological features of GC was analyzed. Next, the effects of miR-155 on GC cell growth were evaluated by gain- and loss-of-function analysis. Finally, the target gene(s) of miR-155 in GC cells were explored.

RESULTS

Our results revealed that miR-155 levels were significantly lower in both GC tissues and GC cell lines than in their normal controls, and its expression inversely correlated with tumor size and the pathologic stage. Moreover, our study showed that enforced expression of miR-155 impaired GC cell proliferation, promoted G1 phase arrest and induced apoptosis in vitro. In addition, we identified cyclin D1 as the direct target of miR-155, and knockdown of cyclin D1 partially phenocopied the role of miR-155 in GC cells.

CONCLUSIONS

Our findings suggest that miR-155 may act as a potential diagnostic marker for early-stage GC and may represent a novel therapeutic target for GC treatment.

MicroRNA-155 expression is independently predictive of outcome in chordoma

Background

Chordoma pathogenesis remains poorly understood. In this study, we aimed to evaluate the relationships between microRNA-155 (miR-155) expression and the clinicopathological features of chordoma patients, and to evaluate the functional role of miR-155 in chordoma.

Methods

The miRNA expression profiles were analyzed using miRNA microarray assays. Regulatory activity of miR-155 was assessed using bioinformatic tools. miR-155 expression levels were validated by reverse transcription-polymerase chain reaction. The relationships between miR-155 expression and the clinicopathological features of chordoma patients were analyzed. Proliferative, migratory and invasive activities were assessed by MTT, wound healing, and Matrigel invasion assays, respectively.

Results

The miRNA microarray assay revealed miR-155 to be highly expressed and biologically active in chordoma. miR-155 expression in chordoma tissues was significantly elevated, and this expression correlated significantly with disease stage (p = 0.036) and the presence of metastasis (p = 0.035). miR-155 expression also correlated significantly with poor outcomes for chordoma patients (hazard ratio, 5.32; p = 0.045). Inhibition of miR-155 expression suppressed proliferation, and the migratory and invasive activities of chordoma cells.

Conclusions

We have shown miR-155 expression to independently affect prognosis in chordoma. These results collectively indicate that miR-155 expression may serve not only as a prognostic marker, but also as a potential therapeutic target in chordoma.

Dysregulated miRNA in progression of hepatocellular carcinoma: A systematic review

Hepatocellular carcinoma (HCC) is the fifth most frequent cancer and the third cause of cancer-related mortality worldwide. The primary risk factor for HCC is liver cirrhosis secondary to persistent infection with hepatitis B virus or hepatitis C virus. Although a number of cellular phenomena and molecular events have been reported to facilitate tumor initiation, progression and metastasis, the exact etiology of HCC has not yet been fully uncovered. miRNA, a class of non-coding RNA, negatively regulate post-transcriptional processes that participate in crucial biological processes, including development, differentiation, apoptosis and proliferation. In the liver, specific miRNA can be negative regulators of gene expression. Recent studies have uncovered the contribution of miRNA to cancer pathogenesis as they can function as oncogenes or tumor suppressor genes. In addition, other studies have demonstrated their potential value in the clinical management of patients with HCC as some miRNA may be used as prognostic or diagnostic markers. In this review, we summarize the current knowledge about the roles of miRNA in the carcinogenesis and progression of HCC.

The role of microRNAs in osteoclasts and osteoporosis

Osteoclasts are the exclusive cells of bone resorption. Abnormally activating osteoclasts can lead to low bone mineral density, which will cause osteopenia, osteoporosis, and other bone disorders. To date, the mechanism of how osteoclast precursors differentiate into mature osteoclasts remains elusive. MicroRNAs (miRNAs) are novel regulatory factors that play an important role in numerous cellular processes, including cell differentiation and apoptosis, by post-transcriptional regulation of genes. Recently, a number of studies have revealed that miRNAs participate in bone homeostasis, including osteoclastic bone resorption, which sheds light on the mechanisms underlying osteoclast differentiation. In this review, we highlight the miRNAs involved in regulating osteoclast differentiation and bone resorption, and their roles in osteoporosis.

The candidate oncogene (MCRS1) promotes the growth of human lung cancer cells via the miR-155-Rb1 pathway

Background

Microspherule protein 1 (MCRS1) is a candidate oncogene and participates in various cellular processes, including growth, migration, senescence and transformation. MCRS1 is overexpressed in non-small cell lung cancer (NSCLC) and promotes the growth of cancer cells. However, the mechanisms driving these processes are not fully understood.

Methods

Retrovirus-mediated RNA interference was employed to knockdown MCRS1 expression in cell lines. Cell proliferation assays and animal experiments were respectively performed to evaluate the growth of NSCLC cells in vitro and in vivo. Microarray analysis was carried out for mRNA profiling. Luciferase reporter assay and microRNA (miRNA) transfection were used to investigate the interaction between miRNA and gene.

Results

Stably knocking down MCRS1 expression inhibited the proliferation of NSCLC cells in vitro and in vivo. By comparing the mRNA expression profiles of NSCLC cells with or without MCRS1 silencing, we found that MCRS1 regulated expressions of various genes related to cell proliferation, including Rb1, TP53, cell cycle-related genes, MYC, E2F2, PCNA, and Ki67. However, MCRS1 did not directly bind to these differentially expressed genes. Here, we confirmed that Rb1, an important tumor suppression gene (TSG), is a direct target of miR-155 which is directly up-regulated by MCRS1. Furthermore, the level of Rb1 expression in NSCLC tissues was inversely correlated with those of miR-155 and MCRS1, and MCRS1 regulated expression of Rb1 via miR-155. Additionally, we found that the DNA copy number of the MCRS1 gene played a role in MCRS1 overexpression in NSCLCs.

Conclusion

MCRS1 overexpression induced NSCLC proliferation through the miR-155–Rb1 pathway and DNA copy-number amplification is one of the mechanisms underlying MCRS1 overexpression in NSCLC. Moreover, we put forward the hypothesis that there are regulatory relationships between oncogenes and TSGs apart from the functional synergy of both; the oncogene-miRNA-TSG networks are one of mechanisms among the regulatory relationships; the regulatory relationships and the networks might play active roles in the development and progression of cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-015-0235-5) contains supplementary material, which is available to authorized users.

Does miRNA-155 Promote Cyclooxygenase-2 Expression in Cancer?

Preclinical Research MicroRNA (miR)-155 and cyclooxygenase (COX)-2 are both elevated in numerous cancers including colorectal cancer. MiR-155 enhances COX-2 expression and is an established regulator of epithelial-mesenchymal transition and inflammation. Inhibition of miR-155 or COX-2 exhibit similar negative effects on tumorigenicity. Thus, it is hypothesized that miR-155 may be a promising target for antagonizing COX-2 expression in colorectal and other cancers.

The Emerging Role of miRNAs in HTLV-1 Infection and ATLL Pathogenesis

Human T-cell leukemia virus (HTLV)-1 is a human retrovirus and the etiological agent of adult T-cell leukemia/lymphoma (ATLL), a fatal malignancy of CD4/CD25+ T lymphocytes. In recent years, cellular as well as virus-encoded microRNA (miRNA) have been shown to deregulate signaling pathways to favor virus life cycle. HTLV-1 does not encode miRNA, but several studies have demonstrated that cellular miRNA expression is affected in infected cells. Distinct mechanisms such as transcriptional, epigenetic or interference with miRNA processing machinery have been involved. This article reviews the current knowledge of the role of cellular microRNAs in virus infection, replication, immune escape and pathogenesis of HTLV-1.

MicroRNA-155 hallmarks promising accuracy for the diagnosis of various carcinomas: results from a meta-analysis

Background. Recent studies have shown that microRNAs (miRNAs) have diagnostic values in various cancers. This meta-analysis seeks to summarize the global diagnostic role of miR-155 in patients with a variety of carcinomas. Methods. Eligible studies were retrieved by searching the online databases, and the bivariate meta-analysis model was employed to generate the summary receiver operator characteristic (SROC) curve. Results. A total of 17 studies dealing with various carcinomas were finally included. The results showed that single miR-155 testing allowed for the discrimination between cancer patients and healthy donors with a sensitivity of 0.82 (95% CI: 0.73–0.88) and specificity of 0.77 (95% CI: 0.70–0.83), corresponding to an area under curve (AUC) of 0.85, while a panel comprising expressions of miR-155 yielded a sensitivity of 0.76 (95% CI: 0.68–0.82) and specificity of 0.82 (95% CI: 0.77–0.86) in diagnosing cancers. The subgroup analysis displayed that serum miR-155 test harvested higher accuracy than plasma-based assay (the AUC, sensitivity, and specificity were, resp., 0.87 versus 0.73, 0.78 versus 0.74, and 0.77 versus 0.70). Conclusions. Our data suggest that single miR-155 profiling has a potential to be used as a screening test for various carcinomas, and parallel testing of miR-155 confers an improved specificity compared to single miR-155 analysis.

MicroRNAs are differentially deregulated in mammary malignant phyllodes tumour

AIMS

MicroRNAs (miRs) have been shown to play important roles in tumour progression. Their expression pattern can be useful for cancer classification. However, little is known about miRs in mammary phyllodes tumours (PT).

METHODS AND RESULTS

In this study, polymerase chain reaction (PCR)-based miR profiling was performed in a small PT cohort to identify deregulated miRs in malignant PT. The purported roles and targets of these miRs were further validated. Unsupervised clustering of miR expression profiling segregated PT into different grades, implicating the miR profile in PT classification. Among the deregulated miRs, miR-21, miR-335 and miR-155 were validated to be higher in malignant than in lower-grade PT in the independent cohort by quantitative PCR (qPCR) (P ≤ 0.032). Their expression correlated with some of the malignant histological features, including high stromal cellularity, nuclear pleomorphism and mitosis. Subsequent analysis of their downstream proteins, namely PTEN for miR-21/miR-155 and Rb for miR-335, also showed an independent significant negative association between miR and protein expression.

CONCLUSIONS

Differential expression of miRs in PT could be useful in diagnosis and grading of PT. Their deregulated expression, together with the altered downstream targets, implicated their active involvement in PT malignant transformation.

miR-155 contributes to the progression of glioma by enhancing Wnt/β-catenin pathway

As the most common brain tumor, glioma is featured with poor prognosis due to its resistance to current therapeutic strategies. The elucidation of etiology is believed to facilitate the development of novel effective anti-glioma treatment modalities. As a confirmed oncogenic microRNA (miRNA) in many other types of cancers, the role of miR-155 in glioma is still unknown. This study is aimed to study the role of miR-155 in the progression of glioma. Our results revealed that miR-155 was overexpressed in the collected glioma specimen, compared with noncancerous brain tissues. The suppression of miR-155 attenuated the proliferation of glioma cells and the activation of Wnt pathway. Silencing miR-155 was also able to suppress the growth of U-87 MG glioma xenografts in mice. Pearson analysis indicated that miR-155 level was inversely correlated with the abundance of HMG-box transcription factor 1 (HBP1), a strong Wnt pathway inhibitor, in glioma samples. Further experiments confirmed that miR-155 suppressed the expression of HBP1 by targeting the putative miRNA recognition elements (MREs) within its messenger RNA (mRNA) 3' untranslated region (UTR). Furthermore, HBP1 small interfering RNA (siRNA) abolished the effect of miR-155 suppression on the proliferation of glioma and the activation of Wnt pathway. Taken together, miR-155 promoted the progression of glioma by enhancing the activation of Wnt pathway. Thus, targeting miR-155 may be an effective strategy for glioma treatment.

MicroRNA modulators of epigenetic regulation, the tumor microenvironment and the immune system in lung cancer

Cancer is an exceedingly complex disease that is orchestrated and driven by a combination of multiple aberrantly regulated processes. The nature and depth of involvement of individual events vary between cancer types, and in lung cancer, the deregulation of the epigenetic machinery, the tumor microenvironment and the immune system appear to be especially relevant. The contribution of microRNAs to carcinogenesis and cancer progression is well established with many reports and investigations describing the involvement of microRNAs in lung cancer, however most of these studies have concentrated on single microRNA-target relations and have not adequately addressed the complexity of their interactions. In this review, we focus, in part, on the role of microRNAs in the epigenetic regulation of lung cancer where they act as active molecules modulating enzymes that take part in methylation-mediated silencing and chromatin remodeling. Additionally, we highlight their contribution in controlling and modulating the tumor microenvironment and finally, we describe their role in the critical alteration of essential molecules that influence the immune system in lung cancer development and progression.

Possible role of tocopherols in the modulation of host microRNA with potential antiviral activity in patients with hepatitis B virus-related persistent infection: a systematic review

Hepatitis B virus (HBV) infection represents a serious global health problem and persistent HBV infection is associated with an increased risk of cirrhosis, hepatocellular carcinoma and liver failure. Recently, the study of the role of microRNA (miRNA) in the pathogenesis of HBV has gained considerable interest as well as new treatments against this pathogen have been approved. A few studies have investigated the antiviral activity of vitamin E (VE) in chronic HBV carriers. Herein, we review the possible role of tocopherols in the modulation of host miRNA with potential anti-HBV activity. A systematic research of the scientific literature was performed by searching the MEDLINE, Cochrane Library and EMBASE databases. The keywords used were 'HBV therapy', 'HBV treatment', 'VE antiviral effects', 'tocopherol antiviral activity', 'miRNA antiviral activity' and 'VE microRNA'. Reports describing the role of miRNA in the regulation of HBV life cycle, in vitro and in vivo available studies reporting the effects of VE on miRNA expression profiles and epigenetic networks, and clinical trials reporting the use of VE in patients with HBV-related chronic hepatitis were identified and examined. Based on the clinical results obtained in VE-treated chronic HBV carriers, we provide a reliable hypothesis for the possible role of this vitamin in the modulation of host miRNA profiles perturbed by this viral pathogen and in the regulation of some cellular miRNA with a suggested potential anti-HBV activity. This approach may contribute to the improvement of our understanding of pathogenetic mechanisms involved in HBV infection and increase the possibility of its management and treatment.

Host miR155 promotes tumor growth through a myeloid-derived suppressor cell-dependent mechanism

miR155 is a regulator of immune cell development and function that is generally thought to be immunostimulatory. However, we report here that genetic ablation of miR155 renders mice resistant to chemical carcinogenesis and the growth of several transplanted tumors, suggesting that miR155 functions in immunosuppression and tumor promotion. Host miR155 deficiency promoted overall antitumor immunity despite the finding of defective responses of miR155-deficient dendritic cells and antitumor T cells. Further analysis of immune cell compartments revealed that miR155 regulated the accumulation of functional myeloid-derived suppressive cells (MDSC) in the tumor microenvironment. Specifically, miR155 mediated MDSC suppressor activity through at least two mechanisms, including SOCS1 repression and a reduced ability to license the generation of CD4(+)Foxp3(+) regulatory T cells. Importantly, we demonstrated that miR155 expression was required for MDSC to facilitate tumor growth. Thus, our results revealed a contextual function for miR155 in antitumor immunity, with a role in MDSC support that appears to dominate in tumor-bearing hosts. Overall, the balance of these cellular effects appears to be a root determinant of whether miR155 promotes or inhibits tumor growth.

Bioinformatic and metabolomic analysis reveals miR-155 regulates thiamine level in breast cancer

microRNA-155 (miR-155) is one of the well-known oncogenic miRNA implicated in various types of tumors. Thiamine, commonly known as vitamin B1, is one of critical cofactors for energy metabolic enzymes including pyruvate dehydrogenase, alpha ketoglutarate dehydrogenase, and transketolase. Here we report a novel role of miR-155 in cancer metabolism through the up-regulation of thiamine in breast cancer cells. A bioinformatic analysis of miRNA array and metabolite-profiling data from NCI-60 cancer cell panel revealed thiamine as a metabolite positively correlated with the miR-155 expression level. We confirmed it in MCF7, MDA-MB-436 and two human primary breast cancer cells by showing reduced thiamine levels upon a knock-down of miR-155. To understand how the miR-155 controls thiamine level, a set of key molecules for thiamine homeostasis were further analyzed after the knockdown of miR-155. The results showed the expression of two thiamine transporter genes (SLC19A2, SLC25A19) as well as thiamine pyrophosphokinase-1 (TPK1) were decreased in both RNA and protein level in miR-155 dependent manner. Finally, we confirm the finding by showing a positive correlation between miR-155 and thiamine level in 71 triple negative breast tumors. Taken altogether, our study demonstrates a role of miR-155 in thiamine homeostasis and suggests a function of this oncogenic miRNA on breast cancer metabolism.

A 3-microRNA scoring system for prognostication in de novo acute myeloid leukemia patients

As a highly heterogeneous disease, acute myeloid leukemia (AML) needs fine risk stratification to get an optimal outcome of patients. MicroRNAs have florid biological functions and have critical roles in the pathogenesis and prognosis in AML. Expression levels of some single microRNAs are influential for prognosis, but a system integrating several together and considering the weight of each should be more powerful. We thus analyzed the clinical, genetic and microRNA profiling data of 138 de novo AML patients of our institute. By multivariate analysis, we identified that high expression of hsa-miR-9-5p and hsa-miR-155-5p were independent poor prognostic factors, whereas that of hsa-miR-203 had a trend to be a favorable factor. We constructed a scoring system from expression of these three microRNAs by considering the weight of each. The scores correlated with distinct clinical and biological features and outperformed single microRNA expression in prognostication. In both ours and another validation cohort, higher scores were associated with shorter overall survival, independent of other well-known prognostic factors. By analyzing the mRNA expression profiles, we sorted out several cancer-related pathways highly correlated with the microRNA prognostic signature. We conclude that this 3-microRNA scoring system is simple and powerful for risk stratification of de novo AML patients.

The oncogenic MicroRNA Hsa-miR-155-5p targets the transcription factor ELK3 and links it to the hypoxia response

The molecular response to hypoxia is a critical cellular process implicated in cancer, and a target for drug development. The activity of the major player, HIF1α, is regulated at different levels by various factors, including the transcription factor ELK3. The molecular mechanisms of this intimate connection remain largely unknown. Whilst investigating global ELK3-chromatin interactions, we uncovered an unexpected connection that involves the microRNA hsa-miR-155-5p, a hypoxia-inducible oncomir that targets HIF1α. One of the ELK3 chromatin binding sites, detected by Chromatin Immuno-Precipitation Sequencing (ChIP-seq) of normal Human Umbilical Vein Endothelial Cells (HUVEC), is located at the transcription start site of the MIR155HG genes that expresses hsa-miR-155-5p. We confirmed that ELK3 binds to this promoter by ChIP and quantitative polymerase chain reaction (QPCR). We showed that ELK3 and hsa-miR-155-5p form a double-negative regulatory loop, in that ELK3 depletion induced hsa-miR-155-5p expression and hsa-miR-155-5p expression decreased ELK3 expression at the RNA level through a conserved target sequence in its 3'-UTR. We further showed that the activities of hsa-miR-155-5p and ELK3 are functionally linked. Pathway analysis indicates that both factors are implicated in related processes, including cancer and angiogenesis. Hsa-miR-155-5p expression and ELK3 depletion have similar effects on expression of known ELK3 target genes, and on in-vitro angiogenesis and wound closure. Bioinformatic analysis of cancer RNA-seq data shows that hsa-miR-155-5p and ELK3 expression are significantly anti-correlated, as would be expected from hsa-miR-155-5p targeting ELK3 RNA. Finally, hypoxia (0% oxygen) down-regulates ELK3 mRNA in a microRNA and hsa-miR-155-5p dependent manner. These results tie ELK3 into the hypoxia response pathway through an oncogenic microRNA and into a circuit implicated in the dynamics of the hypoxic response. This crosstalk could be important for the development of new treatments for a range of pathologies.

Inhibition of transforming growth factor beta/SMAD signal by MiR-155 is involved in arsenic trioxide-induced anti-angiogenesis in prostate cancer

Prostate cancer is the most common cause of cancer-related deaths in men. Current practices for treatment of prostate cancer are less than satisfactory because of metastasis and recurrence, which are primarily attributed to angiogenesis. Hence, anti-angiogenesis treatment is becoming a promising new approach for prostate cancer therapy. In addition to treating acute promyelocytic leukemia, arsenic trioxide (As₂O₃) suppresses other solid tumors, including prostate cancer. However, the effects of As₂O₃ on angiogenesis in prostate cancer cells, and the underlying molecular mechanisms remain unclear. In the present study, As₂O₃ attenuated angiogenic ability through microRNA-155 (miR-155)-mediated inhibition of transforming growth factor beta (TGF-β)/SMAD signal pathway in human prostate cancer PC-3 and LNCaP cells in vitro and in vivo. Briefly, As₂O₃ inhibited the activations/expressions of both TGFβ-induced and endogenous SMAD2/3. Furthermore, As₂O₃ improved the expression of miR-155 via DNA-demethylation. MiR-155, which targeted the SMAD2-3′UTR, decreased the expression and function of SMAD2. Knockdown of miR-155 abolished the As₂O₃-induced inhibitions of the TGF-β/SMAD2 signaling, the vascular endothelial growth factor secretion and angiogenesis. Through understanding a novel mechanism whereby As₂O₃ inhibits angiogenic potential of prostate cancer cells, our study would help in the development of As₂O₃ as a potential chemopreventive agent when used alone or in combination with other current anticancer drugs.

Caught in the cross fire: p53 in inflammation

The p53 transcription factor is a major tumor suppressor, whose diverse activities serve to ensure genome stability and inhibit neoplastic processes. In recent years, it is becoming increasingly clear that p53 also plays a broader role in maintaining cellular homeostasis, as well as contributing to tissue homeostasis in a non-cell-autonomous fashion. Chronic inflammation is a potential cancer-promoting condition, and as such is also within the radar of p53, which mounts a multifaceted attempt to prevent the escalation of chronic tissue imbalance into neoplasia. Recent understanding of the p53 pathway and other family members reveals a broad interaction with inflammatory elements such as reactive oxygen and nitrogen species, cytokines, infectious agents and major immune-regulatory pathways like nuclear factor-kappaB. This complex cross talk is highly dependent on p53 status, as different p53 isoforms and p53 mutants can mediate different responses and even promote chronic inflammation and associated cancer, acting in the tumor cells as well as in the stromal and immune compartments.

Overexpression of microRNA-155 predicts poor prognosis in glioma patients

MicroRNA-155 is highly expressed in many malignant tumors with poor prognosis, which regulates cell apoptosis, proliferation, invasion, metastasis, tumor angiogenesis, and metabolism. This study aims at investigating the clinical significance of miR-155 expression in human gliomas. Real-time quantitative PCR was used to detect the expression levels of miR-155 in 131 glioma and 16 normal brain tissues. The association of miR-155 expression with clinicopathological factors and prognosis of glioma patients were analyzed. The expression levels of miR-155 were significantly higher in glioma tissues than that in normal brain tissues (P < 0.001), which was associated with high pathological grade (P < 0.001) and low Karnofsky Performance Status score (P = 0.022). As a result of Kaplan-Meier survival and Cox regression analyses, overall survival (OS) rates and progression-free survival were significantly poorer in high-expression group relative to low-expression group (both P < 0.001). Furthermore, miR-155 expression was significantly associated with poor OS (P < 0.001) and PFS (P = 0.001) in glioma patients who had high pathological grades (III-IV) as calculated by subgroup analyses. These findings reveal that miR-155 expression might be an independent prognostic factor and a therapeutic target for human glioma.