MiRNA expression patterns predict survival in glioblastoma

miRNAs and related genetic biomarkers according to the WHO glioma classification: From diagnosis to future therapeutic targets

In the 2021 WHO classification of Tumors of the Central Nervous System, additional molecular characteristics have been included, defining the following adult-type diffuse glioma entities: Astrocytoma IDH-mutant, Oligodendroglioma IDH-mutant and 1p/19q-codeleted, and Glioblastoma IDH-wildtype. Despite advances in genetic analysis, precision oncology, and targeted therapy, malignant adult-type diffuse gliomas remain "hard-to-treat tumors", indicating an urgent need for better diagnostic and therapeutic strategies. In the last decades, miRNA analysis has been a hotspot for researching and developing diagnostic, prognostic, and predictive biomarkers for various disorders, including brain cancer. Scientific interest has recently been directed towards therapeutic applications of miRNAs, with encouraging results. Databases such as NCBI, PubMed, and Medline were searched for a selection of articles reporting the relationship between deregulated miRNAs and genetic aberrations used in the latest WHO CNS classification. The current review discussed the recommended molecular biomarkers and genetic aberrations based on the 2021 WHO classification in adult-type diffuse gliomas, along with associated deregulated miRNAs. Additionally, the study highlights miRNA-based treatment advancements in adults with gliomas.

Recent insights into the microRNA-dependent modulation of gliomas from pathogenesis to diagnosis and treatment

Gliomas are the most lethal primary brain tumors in adults. These highly invasive tumors have poor 5-year survival for patients. Gliomas are principally characterized by rapid diffusion as well as high levels of cellular heterogeneity. However, to date, the exact pathogenic mechanisms, contributing to gliomas remain ambiguous. MicroRNAs (miRNAs), as small noncoding RNAs of about 20 nucleotides in length, are known as chief modulators of different biological processes at both transcriptional and posttranscriptional levels. More recently, it has been revealed that these noncoding RNA molecules have essential roles in tumorigenesis and progression of multiple cancers, including gliomas. Interestingly, miRNAs are able to modulate diverse cancer-related processes such as cell proliferation and apoptosis, invasion and migration, differentiation and stemness, angiogenesis, and drug resistance; thus, impaired miRNAs may result in deterioration of gliomas. Additionally, miRNAs can be secreted into cerebrospinal fluid (CSF), as well as the bloodstream, and transported between normal and tumor cells freely or by exosomes, converting them into potential diagnostic and/or prognostic biomarkers for gliomas. They would also be great therapeutic agents, especially if they could cross the blood–brain barrier (BBB). Accordingly, in the current review, the contribution of miRNAs to glioma pathogenesis is first discussed, then their glioma-related diagnostic/prognostic and therapeutic potential is highlighted briefly.

A 3-miRNA Signature Enables Risk Stratification in Glioblastoma Multiforme Patients with Different Clinical Outcomes

Malignant gliomas constitute a complex disease phenotype that demands optimum decision-making as they are highly heterogeneous. Such inter-individual variability also renders optimum patient stratification extremely difficult. microRNA (hsa-miR-20a, hsa-miR-21, hsa-miR-21) expression levels were determined by RT-qPCR, upon FFPE tissue sample collection of glioblastoma multiforme patients (n = 37). In silico validation was then performed through discriminant analysis. Immunohistochemistry images from biopsy material were utilized by a hybrid deep learning system to further cross validate the distinctive capability of patient risk groups. Our standard-of-care treated patient cohort demonstrates no age- or sex- dependence. The expression values of the 3-miRNA signature between the low- (OS > 12 months) and high-risk (OS < 12 months) groups yield a p-value of <0.0001, enabling risk stratification. Risk stratification is validated by a. our random forest model that efficiently classifies (AUC = 97%) patients into two risk groups (low- vs. high-risk) by learning their 3-miRNA expression values, and b. our deep learning scheme, which recognizes those patterns that differentiate the images in question. Molecular-clinical correlations were drawn to classify low- (OS > 12 months) vs. high-risk (OS < 12 months) glioblastoma multiforme patients. Our 3-microRNA signature (hsa-miR-20a, hsa-miR-21, hsa-miR-10a) may further empower glioblastoma multiforme prognostic evaluation in clinical practice and enrich drug repurposing pipelines.

Identifying the miRNA Signature Association with Aging-Related Senescence in Glioblastoma

Glioblastoma (GBM) is the most common malignant brain tumor and its malignant phenotypic characteristics are classified as grade IV tumors. Molecular interactions, such as protein–protein, protein–ncRNA, and protein–peptide interactions are crucial to transfer the signaling communications in cellular signaling pathways. Evidences suggest that signaling pathways of stem cells are also activated, which helps the propagation of GBM. Hence, it is important to identify a common signaling pathway that could be visible from multiple GBM gene expression data. microRNA signaling is considered important in GBM signaling, which needs further validation. We performed a high-throughput analysis using micro array expression profiles from 574 samples to explore the role of non-coding RNAs in the disease progression and unique signaling communication in GBM. A series of computational methods involving miRNA expression, gene ontology (GO) based gene enrichment, pathway mapping, and annotation from metabolic pathways databases, and network analysis were used for the analysis. Our study revealed the physiological roles of many known and novel miRNAs in cancer signaling, especially concerning signaling in cancer progression and proliferation. Overall, the results revealed a strong connection with stress induced senescence, significant miRNA targets for cell cycle arrest, and many common signaling pathways to GBM in the network.

Single-center versus multi-center data sets for molecular prognostic modeling: a simulation study

Background

Prognostic models based on high-dimensional omics data generated from clinical patient samples, such as tumor tissues or biopsies, are increasingly used for prognosis of radio-therapeutic success. The model development process requires two independent discovery and validation data sets. Each of them may contain samples collected in a single center or a collection of samples from multiple centers. Multi-center data tend to be more heterogeneous than single-center data but are less affected by potential site-specific biases. Optimal use of limited data resources for discovery and validation with respect to the expected success of a study requires dispassionate, objective decision-making. In this work, we addressed the impact of the choice of single-center and multi-center data as discovery and validation data sets, and assessed how this impact depends on the three data characteristics signal strength, number of informative features and sample size.

Methods

We set up a simulation study to quantify the predictive performance of a model trained and validated on different combinations of in silico single-center and multi-center data. The standard bioinformatical analysis workflow of batch correction, feature selection and parameter estimation was emulated. For the determination of model quality, four measures were used: false discovery rate, prediction error, chance of successful validation (significant correlation of predicted and true validation data outcome) and model calibration.

Results

In agreement with literature about generalizability of signatures, prognostic models fitted to multi-center data consistently outperformed their single-center counterparts when the prediction error was the quality criterion of interest. However, for low signal strengths and small sample sizes, single-center discovery sets showed superior performance with respect to false discovery rate and chance of successful validation.

Conclusions

With regard to decision making, this simulation study underlines the importance of study aims being defined precisely a priori. Minimization of the prediction error requires multi-center discovery data, whereas single-center data are preferable with respect to false discovery rate and chance of successful validation when the expected signal or sample size is low. In contrast, the choice of validation data solely affects the quality of the estimator of the prediction error, which was more precise on multi-center validation data.

Large miRNA survival analysis reveals a prognostic four-biomarker signature for triple negative breast cancer

Triple negative breast cancer (TNBC) is currently the only major breast tumor subtype without effective targeted therapy and, as a consequence, usually presents a poor outcome. Due to its more aggressive phenotype, there is an urgent clinical need to identify novel biomarkers that discriminate individuals with poor prognosis. We hypothesize that miRNAs can be used to this end because they are involved in the initiation and progression of tumors by altering the expression of their target genes. To identify a prognostic biomarker in TNBC, we analyzed the miRNA expression of a cohort composed of 185 patients diagnosed with TNBC using penalized Cox regression models. We identified a four-biomarker signature based on miR-221, miR-1305, miR-4708, and RMDN2 expression levels that allowed for the subdivision of TNBC into high- or low-risk groups (Hazard Ratio – HR = 0.32; 95% Confidence Interval - CI = 0.11–0.91; p = 0.03) and are also statistically associated with survival outcome in subgroups of postmenopausal status (HR = 0.19; 95% CI = 0.04–0.90; p= 0.016), node negative status (HR = 0.12; 95% CI = 0.01–1.04; p = 0.026), and tumors larger than 2cm (HR = 0.21; 95% CI = 0.05–0.81; p = 0.021). This four-biomarker signature was significantly associated with TNBC as an independent prognostic factor for survival.

miRNA-708 functions as a tumor suppressor in colorectal cancer by targeting ZEB1 through Akt/mTOR signaling pathway

BACKGROUND

Colon cancer, or colorectal cancer (CRC), is a type of cancer that develops from large bowel. Previous data has demonstrated that microRNAs (miRNAs) may be involved in the formation and progression of CRC. The deregulation of miR-708 has been identified in multiple types of cancer. However, to the best of our knowledge, there are no data concerning the expression and role of miR-708 in CRC.

METHODS

In this study, RT-PCR and Flow Cytometry were used to examine the expression and role of miR-708 and ZEB1 in proliferation and apoptosis. Transwell was used to examine the role of miR-708 and ZEB1 in invasion and migration. Western blot and qRT-PCR were conducted to determine the alteration of protein and miR-708 levels, respectively.

RESULTS

MiR-708 was significantly downregulated in CRC tissues and cell lines. The restoration of the expression of miR-708 suppressed cell proliferation, induced apoptosis, and reduced metastasis in CRC in vitro. Additionally, bioinformatics analysis predicted ZEB1 as a novel target gene of miR-708. Furthermore, ZEB1 was upregulated in CRC, which was negatively correlated with miR-708 expression. Further studies showed that the overexpression of miR-708 and silence of ZEB1 inhibited stage of CRC via inhibiting AKT/mTOR signaling pathway in CRC cells.

CONCLUSION

Taken together, these results indicate that miR-708 plays an important role in suppressing the development of CRC by directly targeting ZEB1 through AKT/mTOR signaling pathway, suggesting that miR-708 is a novel, effective therapeutic target for treating patients with CRC.

MiR-28-5p promotes human glioblastoma cell growth through inactivation of FOXO1

OBJECTIVE

Glioblastomais is one of the main universal, primary brain cancers, in adults, that has an extremely poor clinical prognosis and a median living period of 12-15 months, accounting for nearly 3-4% of all cancer-related deaths. MicroRNAs (miRNAs) play key roles in cancer pathogenesis by binding the specific and complementary sequences of the 3'UTR of target mRNAs to regulate protein synthesis. Therefore, recognizing functional miRNAs and the fundamental molecular mechanisms will offer novel evidences for the progress of targeted malignancy interferences. Our current study intended to explore the function of miR-28-5p in the promotion of the glioblastoma.

METHODS

Human glioblastoma tissues, paired nearby normal/non-tumor tissues were accumulated from our hospital. Human glioblastoma SNB19 cells were infected by miR-28-5p mimics or miR-28-5p siRNA by lentivirus. Tumor spheres formation was used to evaluate the growth ability. MTT examine was applied for measuring viability. BrdU cell proliferation assay was applied to uncover the proliferation ability of SNB19 glioblastoma cells. Real-time PCR was conducted to identify miRNA expression. Western blot analysis was employed to measure protein expression. Dual-luciferase FOXO1-3'UTR reporter was used to determine the ability of miR-28-5p to regulate FOXO1.

RESULTS

Expression of miR-28-5p was explored to be increased in both human glioblastoma tissues and cell lines. Up-regulated miR-28-5p expression promotes tumor spheres formation, cell viability, and proliferation ability of glioblastoma cells. FOXO1 was found to be the target of miR-28-5p and the activity of FOXO1 was down-regulated by miR-28-5p in glioblastoma cells.

CONCLUSIONS

MiR-28-5p is an oncogene and promotes the occurrence of glioblastoma by directly targeting the FOXO1.

Stepwise detection and evaluation reveal miR-10b and miR-222 as a remarkable prognostic pair for glioblastoma

Despite the existence of many clinical and molecular factors reported that contribute to survival in glioblastoma, prevailing studies fell into partial or local feature selection for survival analysis. We proposed a feature selection strategy including not only joint covariate detection but also its evaluations, and performed it on miRNA expression profiles with glioblastoma. MiR-10b and miR-222 were selected as the most significant two-dimensional feature. Crucially, we integrated in vitro experiments on GBM cells and in vivo studies on a mouse model of human glioma to elucidate the synergistic effects between miR-10b and miR-222. Inhibition of miR-10b and miR-222 strongly suppress GBM cells growth, invasion, and induce apoptosis by co-targeting PTEN and leading to activation of p53 ultimately. We also demonstrated that miR-10b and miR-222 co-target BIM to induce apoptosis independent of p53 status. The results define mir-10b and mir-222 important roles in gliomagenesis and provided a reliable survival analysis strategy.

Genetic secrets of long-term glioblastoma survivors

Glioblastomas are the most aggressive and lethal primary astrocytic tumors of the central nervous system. They account for 60% to 70% of all gliomas and the majority are diagnosed in Caucasian male patients at advanced age. Genetic analyses of glioblastoma show a great intra- and inter-tumor heterogeneity, which opens up a debate about its cellular origin. Different types of brain cells, including astrocytes, neural stem cells, oligodendrocyte precursor cells and glioblastoma stem cells are proposed to have a role in tumor initiation and spreading; however, data is still inconclusive. Due to short life expectancy, long-term glioblastoma survivors are defined as patients who live longer than two years post-diagnosis. Extreme survivors, living 10 years or more after diagnosis, comprise less than 1% of all patients. Molecular testing indicates genetic differences between short- and long-term survivors with glioblastoma. The most informative are IDH1/2 gene mutations and MGMT promoter methylation, which are associated with a better response to standard clinical care. Moreover, a decreased expression of the CHI3L1, FBLN4, EMP3, IGFBP2, IGFBP3, LGALS3, MAOB, PDPN, SERPING1 and TIMP1 genes has been associated with prolonged survival. In addition, emerging evidence suggests the role of different microRNAs in predicting patient survival. Other factors that may affect the survival of glioblastoma patients include clinical/demographic characteristics such as seizures at presentation, age at diagnosis, and the extent of surgical resection. Because of the small number of long-term survivors with glioblastoma, comparative studies on genetic differences between short- and long-term survivors are challenging. To improve patient management and clinical outcomes, a thorough "omics" approach is necessary for identifying differences between short- and long-term survivors with glioblastoma.

Locally dose-escalated radiotherapy may improve intracranial local control and overall survival among patients with glioblastoma

Background

The dismal overall survival (OS) prognosis of glioblastoma, even after trimodal therapy, can be attributed mainly to the frequent incidence of intracranial relapse (ICR), which tends to present as an in-field recurrence after a radiation dose of 60 Gray (Gy). In this study, molecular marker-based prognostic indices were used to compare the outcomes of radiation with a standard dose versus a moderate dose escalation.

Methods

This retrospective analysis included 156 patients treated between 2009 and 2016. All patients were medically fit for postoperative chemoradiotherapy. In the dose-escalation cohort a simultaneous integrated boost of up to 66 Gy (66 Gy RT) within small high-risk volumes was applied. All other patients received daily radiation to a total dose of 60 Gy or twice daily to a total dose of 59.2 Gy (60 Gy RT).

Results

A total of 133 patients received standard 60 Gy RT, while 23 received 66 Gy RT. Patients in the 66 Gy RT group were younger (p <  0.001), whereas concomitant temozolomide use was more frequent in the 60 Gy RT group (p <  0.001). Other intergroup differences in known prognostic factors were not observed. Notably, the median time to ICR was significantly prolonged in the 66 Gy RT arm versus the 60 Gy RT arm (12.2 versus 7.6 months, p = 0.011), and this translated to an improved OS (18.8 versus 15.3 months, p = 0.012). A multivariate analysis revealed a strong association of 66 Gy RT with a prolonged time to ICR (hazard ratio = 0.498, p = 0.01) and OS (hazard ratio = 0.451, p = 0.01). These differences remained significant after implementing molecular marker-based prognostic scores (ICR p = 0.008, OS p = 0.007) and propensity-scored matched pairing (ICR p = 0.099, OS p = 0.023).

Conclusion

Radiation dose escalation was found to correlate with an improved time to ICR and OS in this cohort of glioblastoma patients. However, further prospective validation of these results is warranted.

Electronic supplementary material

The online version of this article (10.1186/s13014-018-1194-8) contains supplementary material, which is available to authorized users.

Emerging biomarkers for the combination of radiotherapy and immune checkpoint blockers

Over the past few years, multiple immune checkpoint blockers (ICBs) have achieved unprecedented clinical success and have been approved by regulatory agencies for the treatment of an increasing number of malignancies. However, only a limited fraction of patients responds to ICBs employed as a standalone intervention, calling for the development of combinatorial regimens. Radiation therapy (RT) stands out as a very promising candidate for this purpose. Indeed, RT mediates antineoplastic effects not only by cytotoxic and cytostatic mechanisms, but also by modulating immunological functions, both locally (within the irradiated field) and systemically. As combinatorial regimens involving RT and ICBs are being developed and clinically tested at an accelerating pace, it is paramount to identify biomarkers that reliably predict the likelihood of individual patients to respond. Here, we discuss emerging biomarkers that may potentially predict the response of cancer patients to RT plus ICBs.

Relevance of MicroRNAs as Potential Diagnostic and Prognostic Markers in Colorectal Cancer

Colorectal cancer (CRC) is currently the third and the second most common cancer in men and in women, respectively. Every year, more than one million new CRC cases and more than half a million deaths are reported worldwide. The majority of new cases occur in developed countries. Current screening methods have significant limitations. Therefore, a lot of scientific effort is put into the development of new diagnostic biomarkers of CRC. Currently used prognostic markers are also limited in assessing the effectiveness of CRC therapy. MicroRNAs (miRNAs) are a promising subject of research especially since single miRNA can recognize a variety of different mRNA transcripts. MiRNAs have important roles in epigenetic regulation of basic cellular processes, such as proliferation, apoptosis, differentiation, and migration, and may serve as potential oncogenes or tumor suppressors during cancer development. Indeed, in a large variety of human tumors, including CRC, significant distortions in miRNA expression profiles have been observed. Thus, the use of miRNAs as diagnostic and prognostic biomarkers in cancer, particularly in CRC, appears to be an inevitable consequence of the advancement in oncology and gastroenterology. Here, we review the literature to discuss the potential usefulness of selected miRNAs as diagnostic and prognostic biomarkers in CRC.

A 4-miRNAs signature predicts survival in glioblastoma multiforme patients

BACKGROUND

Although O(6)-methylguanine DNA methyltransferase (MGMT) promoter methylation status is an important marker for glioblastoma multiforme (GBM), there is considerable variability in the clinical outcome of patients with similar methylation profles.

OBJECTIVE

We examined whether a MicroRNA (miRNA) signature can be identified for predicting clinical outcomes and helping in treatment decisions.

METHODS

The differentially expressed miRNAs were evaluated in 6 pairs of short- (⩽ 450 days) and long-term survivors (> 450 days) by using microarray. Real time quantitative PCR (qRT-PCR) was applied to further verify screened miRNAs with a greater number of samples (n= 48). Meanwhile, functional interpretation of miRNA profile was carried out based on miRNA-target databases. In addition, MGMT promoter methylation status was tested by means of pyrosequencing (PSQ) testing.

RESULTS

Six miRNAs were upregulated in the long-term survival group (fold change ⩾ 2.0, P< 0.05). The further verification by qRT-PCR indicated that the increase in let-7g-5p, miR-139-5p, miR-17-5p and miR-9-3p level in long-term survivors was statistically significant. Kaplan-Meier survival analysis showed that high expression of a prognostic 4-miRNA signature was significantly associated with good patient survival (p= 0.0012). The signature regulated signaling pathways including Calcium, MAPK, ErbB, mTOR and cell cycle involved in carcinogenesis from glial progenitor cell to primary GBM.

CONCLUSIONS

The 4-miRNA signature was identified as an independent prognostic biomarker that identified patients who have a favorable outcome.

The Clinical Significance of O6-Methylguanine-DNA Methyltransferase Promoter Methylation Status in Adult Patients With Glioblastoma: A Meta-analysis

Background and objective

Promoter status of O⁶-methylguanine-DNA methyltransferase (MGMT) has been widely established as a clinically relevant factor in glioblastoma (GBM) patients. However, in addition to varied therapy schedule, the prognosis of GBM patients is also affected by variations of age, race, primary or recurrent tumor. This study comprehensively investigated the association between MGMT promoter status and prognosis in overall GBM patients and in different GBM subtype including new diagnosed patients, recurrent patients and elderly patients.

Methods

A comprehensive search was performed using PubMed, EMBASE, Cochrane databases to identify literatures (published from January 1, 2005 to April 1, 2017) that evaluated the associations between MGMT promoter methylation and prognosis of GBM patients.

Results

Totally, 66 studies including 7,886 patients met the inclusion criteria. Overall GBM patients with a methylated status of MGMT receiving temozolomide (TMZ)-containing treatment had better overall survival (OS) and progression-free survival (PFS) [OS: hazard ratio (HR) = 0.46, 95% confidence interval (CI): 0.41–0.52, p < 0.001, Bon = 0.017; PFS: HR = 0.48, 95% CI 0.40–0.57, p < 0.001, Bon = 0.014], but no significant advantage on OS or PFS in GBM patients with TMZ-free treatment was observed (OS: HR = 0.97, 95% CI 0.91–1.03, p = 0.08, Bon = 1; PFS: HR = 0.76, 95% CI 0.57–1.02, p = 0.068, Bon = 0.748). These different impacts of MGMT status on OS were similar in newly diagnosed GBM patients, elderly GBM patients and recurrent GBM. Among patients receiving TMZ-free treatment, survival benefit in Asian patients was not observed anymore after Bonferroni correction (Asian OS: HR = 0.78, 95% CI 0.64–0.95, p = 0.02, Bon = 0.24, I² = 0%; PFS: HR = 0.69, 95% CI 0.50–0.94, p = 0.02, Bon = 0.24). No benefit was observed in Caucasian receiving TMZ-free therapy regardless of Bonferroni adjustment.

Conclusion

The meta-analysis highlights the universal predictive value of MGMT methylation in newly diagnosed GBM patients, elderly GBM patients and recurrent GBM patients. For elderly methylated GBM patients, TMZ alone therapy might be a more suitable option than radiotherapy alone therapy. Future clinical trials should be designed in order to optimize therapeutics in different GBM subpopulation.

A 4-miRNA signature predicts the therapeutic outcome of glioblastoma

Multimodal therapy of glioblastoma (GBM) reveals inter-individual variability in terms of treatment outcome. Here, we examined whether a miRNA signature can be defined for the a priori identification of patients with particularly poor prognosis.

FFPE sections from 36 GBM patients along with overall survival follow-up were collected retrospectively and subjected to miRNA signature identification from microarray data. A risk score based on the expression of the signature miRNAs and cox-proportional hazard coefficients was calculated for each patient followed by validation in a matched GBM subset of TCGA. Genes potentially regulated by the signature miRNAs were identified by a correlation approach followed by pathway analysis.

A prognostic 4-miRNA signature, independent of MGMT promoter methylation, age, and sex, was identified and a risk score was assigned to each patient that allowed defining two groups significantly differing in prognosis (p-value: 0.0001, median survival: 10.6 months and 15.1 months, hazard ratio = 3.8). The signature was technically validated by qRT-PCR and independently validated in an age- and sex-matched subset of standard-of-care treated patients of the TCGA GBM cohort (n=58). Pathway analysis suggested tumorigenesis-associated processes such as immune response, extracellular matrix organization, axon guidance, signalling by NGF, GPCR and Wnt. Here, we describe the identification and independent validation of a 4-miRNA signature that allows stratification of GBM patients into different prognostic groups in combination with one defined threshold and set of coefficients that could be utilized as diagnostic tool to identify GBM patients for improved and/or alternative treatment approaches.

miR-340 predicts glioblastoma survival and modulates key cancer hallmarks through down-regulation of NRAS

Glioblastoma is the most common primary brain tumor in adults; with a survival rate of 12 months from diagnosis. However, a small subgroup of patients, termed long-term survivors (LTS), has a survival rate longer then 12–14 months. There is thus increasing interest in the identification of molecular signatures predicting glioblastoma prognosis and in how to improve the therapeutic approach. Here, we report miR-340 as prognostic tumor-suppressor microRNA for glioblastoma. We analyzed microRNA expression in > 500 glioblastoma patients and found that although miR-340 is strongly down-regulated in glioblastoma overall, it is up-regulated in LTS patients compared to short-term survivors (STS). Indeed, miR-340 expression predicted better prognosis in glioblastoma patients. Coherently, overexpression of miR-340 in glioblastoma cells was found to produce a tumor-suppressive activity. We identified NRAS mRNA as a critical, direct target of miR-340: in fact, miR-340 negatively influenced multiple aspects of glioblastoma tumorigenesis by down-regulating NRAS and downstream AKT and ERK pathways. Thus, we demonstrate that expression of miR-340 in glioblastoma is responsible for a strong tumor-suppressive effect in LTS patients by down-regulating NRAS. miR-340 may thus represent a novel marker for glioblastoma diagnosis and prognosis, and may be developed into a tool to improve treatment of glioblastoma.

A 4-miRNA signature to predict survival in glioblastomas

Glioblastomas are among the most lethal cancers; however, recent advances in survival have increased the need for better prognostic markers. microRNAs (miRNAs) hold great prognostic potential being deregulated in glioblastomas and highly stable in stored tissue specimens. Moreover, miRNAs control multiple genes representing an additional level of gene regulation possibly more prognostically powerful than a single gene. The aim of the study was to identify a novel miRNA signature with the ability to separate patients into prognostic subgroups. Samples from 40 glioblastoma patients were included retrospectively; patients were comparable on all clinical aspects except overall survival enabling patients to be categorized as short-term or long-term survivors based on median survival. A miRNome screening was employed, and a prognostic profile was developed using leave-one-out cross-validation. We found that expression patterns of miRNAs; particularly the four miRNAs: hsa-miR-107_st, hsa-miR-548x_st, hsa-miR-3125_st and hsa-miR-331-3p_st could determine short- and long-term survival with a predicted accuracy of 78%. Heatmap dendrograms dichotomized glioblastomas into prognostic subgroups with a significant association to survival in univariate (HR 8.50; 95% CI 3.06–23.62; p<0.001) and multivariate analysis (HR 9.84; 95% CI 2.93–33.06; p<0.001). Similar tendency was seen in The Cancer Genome Atlas (TCGA) using a 2-miRNA signature of miR-107 and miR-331 (miR sum score), which were the only miRNAs available in TCGA. In TCGA, patients with O6-methylguanine-DNA-methyltransferase (MGMT) unmethylated tumors and low miR sum score had the shortest survival. Adjusting for age and MGMT status, low miR sum score was associated with a poorer prognosis (HR 0.66; 95% CI 0.45–0.97; p = 0.033). A Kyoto Encyclopedia of Genes and Genomes analysis predicted the identified miRNAs to regulate genes involved in cell cycle regulation and survival. In conclusion, the biology of miRNAs is complex, but the identified 4-miRNA expression pattern could comprise promising biomarkers in glioblastoma stratifying patients into short- and long-term survivors.

The role of microRNAs in colorectal liver metastasis: Important participants and potential clinical significances

Colorectal cancer is one of the most common cancers in the world, and liver metastasis is the leading direct cause of cancer-related deaths in colorectal cancer. MicroRNA is involved in tumor metastasis in many aspects; mounting studies have shown that microRNAs play important roles in colorectal liver metastasis. Although lots of reviews about the association between microRNAs and colorectal cancer metastasis have been published, the reviews specifically focusing on microRNAs and colorectal liver metastasis are still lacking in the literature. To address this issue, here, we summarize the underlying mechanisms of microRNAs in colorectal liver metastasis and explore their potential clinical applications in this aspect.

The Role of miRNAs in Angiogenesis, Invasion and Metabolism and Their Therapeutic Implications in Gliomas

MicroRNAs (miRNAs) are small, non-coding, endogenous RNA molecules that function in gene silencing by post-transcriptional regulation of gene expression. The dysregulation of miRNA plays a pivotal role in cancer tumorigenesis, including the development and progression of gliomas. Their small size, stability and ability to target multiple oncogenes have simultaneously distinguished miRNAs as attractive candidates for biomarkers and novel therapeutic targets for glioma patients. In this review, we summarize the most frequently cited miRNAs known to contribute to gliomagenesis and progression by regulating the defining hallmarks of gliomas, including angiogenesis, invasion, and cell metabolism. We also discuss their promising potential as prognostic and predictive biomarkers and novel therapeutic targets, in addition to the challenges that must be overcome before their translation from bench to bedside.

miRNA-708 functions as a tumour suppressor in hepatocellular carcinoma by targeting SMAD3

Hepatocellular carcinoma (HCC) is the most frequent subtype of primary liver cancer and the third most common cause of cancer-associated mortality worldwide. Previous studies have reported that microRNAs (miRNAs) serve key roles in the carcinogenesis and progression of HCC by regulating gene expression. The present study investigated the expression patterns, biological roles and underlying mechanisms of miRNA-708 (miR-708) in HCC. The expression levels of miR-708 in HCC tissue samples and cell lines were examined. Cell proliferation, migration and invasion assays were used to evaluate the effect of miR-708 on HCC cells. In addition, bioinformatic and western blotting analyses, and dual luciferase reporter assays were performed to investigate the direct gene target of miR-708. The results of the present study demonstrated that miR-708 expression was significantly decreased in HCC tissue samples and cell lines. In addition, the expression level of miR-708 was associated with increased HCC tumour stage. Furthermore, ectopic expression of miR-708 suppressed HCC cell proliferation, migration and invasion. The results of the present study also indicated that miR-708 targets SMAD family member 3 directly in vitro. The results of the present study indicated that miR-708 may be a novel target for future HCC therapy.

Human tissue engineering allows the identification of active miRNA regulators of glioblastoma aggressiveness

Glioblastoma multiforme (GBM) is among the most aggressive cancers associated with massive infiltration of peritumoral parenchyma by migrating tumor cells. The infiltrative nature of GBM cells, the intratumoral heterogeneity concomitant with redundant signaling pathways likely underlie the inability of conventional and targeted therapies to achieve long-term remissions. In this respect, microRNAs (miRNAs), which are endogenous small non-coding RNAs that play a role in cancer aggressiveness, emerge as possible relevant prognostic biomarkers or therapeutic targets for treatment of malignant gliomas. We previously described a tissue model of GBM developing into a stem cell-derived human Engineered Neural Tissue (ENT) that allows the study of tumor/host tissue interaction. Combined with high throughput sequencing analysis, we took advantage of this human and integrated tissue model to understand miRNAs regulation. Three miRNAs (miR-340, -494 and -1293) active on cell proliferation, adhesion to extracellular matrix and tumor cell invasion were identified in GBM cells developing within ENT, and also confirmed in GBM biopsies. The components of miRNAs regulatory network at the transcriptional and the protein level have been also revealed by whole transcriptome analysis and Tandem Mass Tag in transfected GBM cells. Notably, miR-340 has a clinical relevance and modulates the expression of miR-494 and -1293, emphasizing its biological significance. Altogether, these findings demonstrate that human tissue engineering modeling GBM development in neural host tissue is a suitable tool to identify active miRNAs. Collectively, our study identified miR-340 as a strong modulator of GBM aggressiveness which may constitute a therapeutic target for treatment of malignant gliomas.

MiRNA expression profiling in human gliomas: upregulated miR-363 increases cell survival and proliferation

The role of microRNAs (miRNAs) in glioma biology is increasingly recognized. To investigate the regulatory mechanisms governing the malignant signature of gliomas with different grades of malignancy, we analyzed miRNA expression profiles in human grade I-IV tumor samples and primary glioma cell cultures. Multiplex real-time PCR was used to profile miRNA expression in a set of World Health Organization (WHO) grade I (pilocytic astrocytoma), II (diffuse fibrillary astrocytoma), and IV (glioblastoma multiforme) astrocytic tumors and primary glioma cell cultures. Primary glioma cell cultures were used to evaluate the effect of transfection of specific miRNAs and miRNA inhibitors. miRNA microarray showed that a set of miRNAs was consistently upregulated in all glioma samples. miR-363 was upregulated in all tumor specimens and cell lines, and its expression correlated with tumor grading. The transfection of glioma cells with the specific inhibitor of miR-363 increased the expression level of tumor suppressor growth-associated protein 43 (GAP-43). Transfection of miR-363 induced cell survival, while inhibition of miR-363 significantly reduced glioma cell viability. Furthermore, miRNA-363 inhibition induced the downregulation of AKT, cyclin-D1, matrix metalloproteinase (MMP)-2, MMP-9, and Bcl-2 and upregulation of caspase 3. Together, these data suggest that the upregulation of miR-363 may play a role in malignant glioma signature.

Molecular Predictors of Long-Term Survival in Glioblastoma Multiforme Patients

Glioblastoma multiforme (GBM) is the most common and aggressive adult primary brain cancer, with <10% of patients surviving for more than 3 years. Demographic and clinical factors (e.g. age) and individual molecular biomarkers have been associated with prolonged survival in GBM patients. However, comprehensive systems-level analyses of molecular profiles associated with long-term survival (LTS) in GBM patients are still lacking. We present an integrative study of molecular data and clinical variables in these long-term survivors (LTSs, patients surviving >3 years) to identify biomarkers associated with prolonged survival, and to assess the possible similarity of molecular characteristics between LGG and LTS GBM. We analyzed the relationship between multivariable molecular data and LTS in GBM patients from the Cancer Genome Atlas (TCGA), including germline and somatic point mutation, gene expression, DNA methylation, copy number variation (CNV) and microRNA (miRNA) expression using logistic regression models. The molecular relationship between GBM LTS and LGG tumors was examined through cluster analysis. We identified 13, 94, 43, 29, and 1 significant predictors of LTS using Lasso logistic regression from the somatic point mutation, gene expression, DNA methylation, CNV, and miRNA expression data sets, respectively. Individually, DNA methylation provided the best prediction performance (AUC = 0.84). Combining multiple classes of molecular data into joint regression models did not improve prediction accuracy, but did identify additional genes that were not significantly predictive in individual models. PCA and clustering analyses showed that GBM LTS typically had gene expression profiles similar to non-LTS GBM. Furthermore, cluster analysis did not identify a close affinity between LTS GBM and LGG, nor did we find a significant association between LTS and secondary GBM. The absence of unique LTS profiles and the lack of similarity between LTS GBM and LGG, indicates that there are multiple genetic and epigenetic pathways to LTS in GBM patients.

MicroRNAs as Regulator of Signaling Networks in Metastatic Colon Cancer

MicroRNAs (miRNAs) are a class of small, noncoding RNA molecules capable of regulating gene expression translationally and/or transcriptionally. A large number of evidence have demonstrated that miRNAs have a functional role in both physiological and pathological processes by regulating the expression of their target genes. Recently, the functionalities of miRNAs in the initiation, progression, angiogenesis, metastasis, and chemoresistance of tumors have gained increasing attentions. Particularly, the alteration of miRNA profiles has been correlated with the transformation and metastasis of various cancers, including colon cancer. This paper reports the latest findings on miRNAs involved in different signaling networks leading to colon cancer metastasis, mainly focusing on miRNA profiling and their roles in PTEN/PI3K, EGFR, TGFβ, and p53 signaling pathways of metastatic colon cancer. The potential of miRNAs used as biomarkers in the diagnosis, prognosis, and therapeutic targets in colon cancer is also discussed.

MicroRNA-377 suppresses cell proliferation and invasion by inhibiting TIAM1 expression in hepatocellular carcinoma

Increasing evidence has suggested that microRNAs (miRNAs) play an important role in the initiation and progression of hepatocellular carcinoma (HCC). Here, we identified a novel tumor suppressive miRNA, miR-377, and investigated its role in HCC. The expression of miR-377 in HCC tissues and cell lines was detected by real-time reverse-transcription PCR. The effects of miR-377 on HCC cell proliferation and invasion were also investigated. Western blot and luciferase reporter assay were used to identify the direct and functional target of miR-377. The expression of miR-377 was markedly downregulated in human HCC tissues and cell lines. MiR-377 can dramatically inhibit cell growth and invasion in HCC cells. Subsequent investigation revealed that T lymphoma invasion and metastasis 1 (TIAM1) was a direct and functional target of miR-377 in HCC cells. Overexpression of miR-377 impaired TIAM1-induced promotion of proliferation and invasion in HCC cells. Finally, miR-377 is inversely correlated with TIAM1 expression in human HCC tissues. These findings reveal that miR-377 functions as a tumor suppressor and inhibits the proliferation and invasion of HCC cells by targeting TIAM1, which may consequently serve as a therapeutic target for HCC patients.

Prediction of clinical outcome in glioblastoma using a biologically relevant nine-microRNA signature

BACKGROUND

Glioblastoma is the most aggressive primary brain tumor, and is associated with a very poor prognosis. In this study we investigated the potential of microRNA expression profiles to predict survival in this challenging disease.

METHODS

MicroRNA and mRNA expression data from glioblastoma (n = 475) and grade II and III glioma (n = 178) were accessed from The Cancer Genome Atlas. LASSO regression models were used to identify a prognostic microRNA signature. Functionally relevant targets of microRNAs were determined using microRNA target prediction, experimental validation and correlation of microRNA and mRNA expression data.

RESULTS

A 9-microRNA prognostic signature was identified which stratified patients into risk groups strongly associated with survival (p = 2.26e-09), significant in all glioblastoma subtypes except the non-G-CIMP proneural group. The statistical significance of the microRNA signature was higher than MGMT methylation in temozolomide treated tumors. The 9-microRNA risk score was validated in an independent dataset (p = 4.50e-02) and also stratified patients into high- and low-risk groups in lower grade glioma (p = 5.20e-03). The majority of the 9 microRNAs have been previously linked to glioblastoma biology or treatment response. Integration of the expression patterns of predicted microRNA targets revealed a number of relevant microRNA/target pairs, which were validated in cell lines.

CONCLUSIONS

We have identified a novel, biologically relevant microRNA signature that stratifies high- and low-risk patients in glioblastoma. MicroRNA/mRNA interactions identified within the signature point to novel regulatory networks. This is the first study to formulate a survival risk score for glioblastoma which consists of microRNAs associated with glioblastoma biology and/or treatment response, indicating a functionally relevant signature.

MicroRNAs in colorectal cancer: Role in metastasis and clinical perspectives

Colorectal cancer (CRC) is the third most common malignancy and the third leading cause of cancer related deaths in the United States. Almost 90% of the patients diagnosed with CRC die due to metastases. MicroRNAs (miRNAs) are evolutionarily conserved molecules that modulate the expression of their target genes post-transcriptionally, and they may participate in various physiological and pathological processes including CRC metastasis by influencing various factors in the human body. Recently, the role miRNAs play throughout the CRC metastatic cascade has gain attention. Many studies have been published to link them with CRC metastasis. In this review, we will briefly discuss metastatic steps in the light of miRNAs, along with their target genes. We will discuss how the aberration in the expression of miRNAs leads to the formation of CRC by effecting the regulation of their target genes. As miRNAs are being exploited for diagnosis, prognosis, and monitoring of cancer and other diseases, their high tissue specificity and critical role in oncogenesis make them new biomarkers for the diagnosis and classification of cancer as well as for predicting patients’ outcome. MiRNA signatures have been identified for many human tumors including CRC, and miRNA-based therapies to treat cancer have been emphasized lately. These will also be discussed in this review.

MicroRNA expression signatures determine prognosis and survival in glioblastoma multiforme--a systematic overview

Despite advances in our knowledge about glioblastoma multiforme (GBM) pathology, clinical challenges still lie ahead with respect to treatment in GBM due to high prevalence, poor prognosis, and frequent tumor relapse. The implication of microRNAs (miRNAs) in GBM is a rapidly expanding field of research with the aim to develop more targeted molecular therapies. This review aims to present a comprehensive overview of all the available literature, evaluating miRNA signatures as a function of prognosis and survival in GBM. The results are presented with a focus on studies derived from clinical data in databases and independent tissue cohorts where smaller samples sizes were investigated. Here, miRNA associated to longer survival (protective) and miRNA with shorter survival (risk-associated) have been identified and their signatures based on different prognostic attributes are described. Finally, miRNAs associated with disease progression or survival in several studies are identified and functionally described. These miRNAs may be valuable for future determination of patient prognosis and could possibly serve as targets for miRNA-based therapies, which hold a great potential in the treatment of this severe malignant disease.

Cancer Stem Cells: Dynamic Entities in an Ever-Evolving Paradigm

The cancer stem cell (CSC) hypothesis postulates that there is a hierarchy of cellular differentiation within cancers and that the bulk population of tumor cells is derived from a relatively small population of multi-potent neoplastic stem-like cells (CSCs). This tumor-initiating cell population plays an important role in maintaining tumor growth through their unlimited self-renewal, therapeutic resistance, and capacity to propagate tumors through asymmetric cell division. Recent findings from multiple laboratories show that cancer progenitor cells have the capacity to de-differentiate and acquire a stem-like phenotype in response to either genetic manipulation or environmental cues. These findings suggest that CSCs and relatively differentiated progenitors coexist in dynamic equilibrium and are subject to bidirectional conversion. In this review, we discuss emerging concepts regarding the stem-like phenotype, its acquisition by cancer progenitor cells, and the molecular mechanisms involved. Understanding the dynamic equilibrium between CSCs and cancer progenitor cells is critical for the development of novel therapeutic strategies that focus on depleting tumors of their tumor-propagating cell population.

Validation of the prognostic Heidelberg re-irradiation score in an independent mono-institutional patient cohort

Purpose

Re-irradiation has been shown to be a valid option with proven efficacy for recurrent high-grade glioma patients. Overall, up to now it is unclear which patients might be optimal candidates for a second course of irradiation. A recently reported prognostic score developed by Combs et al. may guide treatment decisions and thus, our mono-institutional cohort served as validation set to test its relevance for clinical practice.

Patients and methods

The prognostic score is built upon histology, age (< 50 vs. ≥ 50 years) and the time between initial radiotherapy and re-irradiation (≤ 12 vs. > 12 months). This score was initially introduced to distinguish patients with excellent (0 points), good (1 point), moderate (2 points) and poor (3–4 points) post-recurrence survival (PRS) after re-irradiation. Median prescribed radiation dose during re-treatment of recurrent malignant glioma was 36 Gy in 2 Gy single fractions. A substantial part of the patients was additionally treated with bevacizumab (10 mg/kg intravenously at d1 and d15 during re-irradiation).

Results

88 patients (initially 61 WHO IV, 20 WHO III, 7 WHO II) re-irradiated in a single institution were retrospectively analyzed. Median follow-up was 30 months and median PRS of the entire patient cohort 7 months. Seventy-one patients (80.7%) received bevacizumab. PRS was significantly increased in patients receiving bevacizumab (8 vs. 6 months, p = 0.027, log-rank test). KPS, age, MGMT methylation status, sex, WHO grade and the Heidelberg score showed no statistically significant influence on neither PR-PFS nor PRS.

Conclusion

In our cohort which was mainly treated with bevacizumab the usefulness of the Heidelberg score could not be confirmed probably due to treatment heterogeneity; it can be speculated that larger multicentric data collections are needed to derive a more reliable score.

Differential expression of miR200a-3p and miR21 in grade II-III and grade IV gliomas: evidence that miR200a-3p is regulated by O⁶-methylguanine methyltransferase and promotes temozolomide responsiveness

Glioblastoma multiforme (GBM) is the most common primary brain tumor and is among the deadliest of human cancers. Dysregulation of microRNAs (miRNAs) expression is an important step in tumor progression as miRNAs can act as tumor suppressors or oncogenes and may affect cell sensitivity to chemotherapy. Whereas the oncogenic miR21 has been shown to be overexpressed in gliomas, the expression and function of the tumor-supressor miR200a in GBMs remains unknown. In this study, we show that miR21 is upregulated in grade IV (GBMs) vs. grade II-III (LGs) gliomas, confirming that miR21 expression level is correlated with tumor grade, and that it may be considered as a marker of tumor progression. Conversely, miR200a is demonstrated for the first time to be downregulated in GBMs compared with LGs, and overexpression of miR200a in GBM cells is shown to promote TMZ-sensitivity. Interestingly, miR200a but not miR21 expression level is significantly higher in TMZ-responsive vs. -unresponsive tumoral glial cells in primary culture. Furthermore, miR200a appears negatively correlated with the expression of the DNA repair enzyme O (6)-methylguanine methyltransferase (MGMT), and the inhibition of MGMT activity results in an increase of miR200a expression in GBM cells. Taken together, these data strongly suggest that miR200a is likely to act as a crucial antitumoral factor regarding glioma progression. Interplay between miR200a and MGMT should be considered as potential mechanism involved in therapeutic response.

Expression of 19 microRNAs in glioblastoma and comparison with other brain neoplasia of grades I-III

Several biomarkers have been proposed as useful parameters to better specify the prognosis or to delineate new target therapy strategies for glioblastoma patients. MicroRNAs could represent putative target molecules, considering their role in tumorigenesis, cancer progression and their specific tissue expression. Although several studies have tried to identify microRNA signature for glioblastoma, a microRNA profile is still far from being well-defined. In this work the expression of 19 microRNAs (miR-7, miR-9, miR-9∗, miR-10a, miR-10b, miR-17, miR-20a, miR-21, miR-26a, miR-27a, miR-31, miR-34a, miR-101, miR-137, miR-182, miR-221, miR-222, miR-330, miR-519d) was evaluated in sixty formalin-fixed and paraffin-embedded glioblastoma samples using a locked nucleic acid real-time PCR. Moreover, a comparison of miRNA expressions was performed between primary brain neoplasias of different grades (grades IV-I). The analysis of 14 validated miRNA expression in the 60 glioblastomas, using three different non-neoplastic references as controls, revealed a putative miRNA signature: mir-10b and miR-21 were up-regulated, while miR-7, miR-31, miR-101, miR-137, miR-222 and miR-330 were down-regulated in glioblastomas. Comparing miRNA expression between glioblastoma group and gliomas of grades I-III, 3 miRNAs (miR-10b, mir-34a and miR-101) showed different regulation statuses between high-grade and low-grade tumors. miR-10b was up-regulated in high grade and significantly down-regulated in low-grade gliomas, suggesting that could be a candidate for a GBM target therapy. This study provides further data for the identification of a miRNA profile for glioblastoma and suggests that different-grade neoplasia could be characterized by different expression of specific miRNAs.

Re-irradiation and bevacizumab in recurrent high-grade glioma: an effective treatment option

Re-irradiation has been shown to be a meaningful option for recurrent high-grade glioma (HGG) patients. Furthermore, bevacizumab exerts certain activity in combination with chemotherapy/as monotherapy and was safely tested in combination with radiotherapy in several previous studies. To our knowledge, this is the largest cohort of patients treated with both re-irradiation and bevacizumab to date. After receiving standard radiotherapy (with or without TMZ) patients with recurrent HGG were treated with bevacizumab (10 mg/kg intravenously at d1 and d15) during re-irradiation. Median prescribed radiation dose during re-treatment was 36 Gy, conventionally fractionated. Datasets of 71 re-irradiated patients were retrospectively analyzed. Patients either received bevacizumab (N = 57) or not (N = 14; other substances (N = 4) and sole radiation (N = 10)). In patients receiving bevacizumab, both post-recurrence survival (PRS) (median 8.6 vs. 5.7 months; p = 0.003, log-rank test) and post-recurrence progression-free survival (PR-PFS, 5.6 vs. 2.5 months; p = 0.005, log-rank test; PFS-6 42.1 % for the bevacizumab group) were significantly increased which was confirmed by multivariate analysis. KPS, re-surgery, MGMT methylation status, sex, WHO grade, tumor volume and age were no significant predictors for neither PR-PFS nor PRS (univariate analysis). Re-irradiation with bevacizumab remains a feasible and highly effective treatment schedule. Studies on further salvage strategies and timing of sequential treatment options versus observation are warranted.

Integrative radiation systems biology

Maximisation of the ratio of normal tissue preservation and tumour cell reduction is the main concept of radiotherapy alone or combined with chemo-, immuno- or biologically targeted therapy. The foremost parameter influencing this ratio is radiation sensitivity and its modulation towards a more efficient killing of tumour cells and a better preservation of normal tissue at the same time is the overall aim of modern therapy schemas. Nevertheless, this requires a deep understanding of the molecular mechanisms of radiation sensitivity in order to identify its key players as potential therapeutic targets. Moreover, the success of conventional approaches that tried to statistically associate altered radiation sensitivity with any molecular phenotype such as gene expression proofed to be somewhat limited since the number of clinically used targets is rather sparse. However, currently a paradigm shift is taking place from pure frequentistic association analysis to the rather holistic systems biology approach that seeks to mathematically model the system to be investigated and to allow the prediction of an altered phenotype as the function of one single or a signature of biomarkers. Integrative systems biology also considers the data from different molecular levels such as the genome, transcriptome or proteome in order to partially or fully comprehend the causal chain of molecular mechanisms. An example for the application of this concept currently carried out at the Clinical Cooperation Group "Personalized Radiotherapy in Head and Neck Cancer" of the Helmholtz-Zentrum München and the LMU Munich is described. This review article strives for providing a compact overview on the state of the art of systems biology, its actual challenges, potential applications, chances and limitations in radiation oncology research working towards improved personalised therapy concepts using this relatively new methodology.

Changes in circulating microRNAs after radiochemotherapy in head and neck cancer patients

INTRODUCTION

Circulating microRNAs (miRNAs) are easily accessible and have already proven to be useful as prognostic markers in cancer patients. However, their origin and function in the circulation is still under discussion. In the present study we analyzed changes in the miRNAs in blood plasma of head and neck squamous cell carcinoma (HNSCC) patients in response to radiochemotherapy and compared them to the changes in a cell culture model of primary HNSCC cells undergoing simulated anti-cancer therapy.

MATERIALS AND METHODS

MiRNA-profiles were analyzed by qRT-PCR arrays in paired blood plasma samples of HNSCC patients before therapy and after two days of treatment. Candidate miRNAs were validated by single qRT-PCR assays. An in vitro radiochemotherapy model using primary HNSCC cell cultures was established to test the possible tumor origin of the circulating miRNAs. Microarray analysis was performed on primary HNSCC cell cultures followed by validation of deregulated miRNAs via qRT-PCR.

RESULTS

Unsupervised clustering of the expression profiles using the six most regulated miRNAs (miR-425-5p, miR-21-5p, miR-106b-5p, miR-590-5p, miR-574-3p, miR-885-3p) significantly (p = 0.012) separated plasma samples collected prior to treatment from plasma samples collected after two days of radiochemotherapy. MiRNA profiling of primary HNSCC cell cultures treated in vitro with radiochemotherapy revealed differentially expressed miRNAs that were also observed to be therapy-responsive in blood plasma of the patients (miR-425-5p, miR-21-5p, miR-106b-5p, miR-93-5p) and are therefore likely to stem from the tumor. Of these candidate marker miRNAs we were able to validate by qRT-PCR a deregulation of eight plasma miRNAs as well as miR-425-5p and miR-93-5p in primary HNSCC cultures after radiochemotherapy.

CONCLUSION

Changes in the abundance of circulating miRNAs during radiochemotherapy reflect the therapy response of primary HNSCC cells after an in vitro treatment. Therefore, the responsive miRNAs (miR-425-5p, miR-93-5p) may represent novel biomarkers for therapy monitoring. The prognostic value of this exciting observation requires confirmation using an independent patient cohort that includes clinical follow-up data.

MicroRNA biomarkers in glioblastoma

Recent research suggests that deregulation of microRNAs (miRNAs) is involved in initiation and progression of many cancers, including gliomas and that miRNAs hold great potential as future diagnostic and therapeutic tools in cancer. MiRNAs are a class of short non-coding RNA sequences (18-24 nucleotides), which base-pair to target messenger RNA (mRNA) and thereby cause translational repression or mRNA degradation based on the level of complementarity between strands. Profiling miRNAs in clinical glioblastoma samples has shown aberrant expression of numerous miRNAs when compared to normal brain tissues. Understanding these alterations is key to developing new biomarkers and intelligent treatment strategies. This review presents an overview of current knowledge about miRNA alterations in glioblastoma while focusing on the clinical future of miRNAs as biomarkers and discussing the strengths and weaknesses of various methods used in evaluating their expression.

Current progress for the use of miRNAs in glioblastoma treatment

Glioblastoma (GBM) is a highly aggressive brain cancer with the worst prognosis of any central nervous system disease despite intensive multimodal therapy. Inevitably, glioblastoma is fatal, with recurrence of treatment-resistant tumour growth at distal sites leading to an extremely low median survival rate of 12-15 months from the time of initial diagnosis. With the advent of microarray and gene profiling technology, researchers have investigated trends in genetic alterations and, in this regard, the role of dysregulated microRNAs (highly conserved endogenous small RNA molecules) in glioblastoma has been studied with a view to identifying novel mechanisms of acquired drug resistance and allow for development of microRNA (miRNA)-based therapeutics for GBM patients. Considering the development of miRNA research from initial association to GBM to commercial development of miR-based therapeutics in less than a decade, it is not beyond reasonable doubt to anticipate significant advancements in this field of study, hopefully with the ultimate conclusion of improved patient outcome. This review discusses the recent advancements in miRNA-based therapeutic development for use in glioblastoma treatment and the challenges faced with respect to in vivo and clinical application.

Circulating microRNAs in hematological diseases: principles, challenges, and perspectives

The complex microRNA (miRNA) network plays an important role in the regulation of cellular processes such as development, differentiation, and apoptosis. Recently, the presence of cell-free miRNAs that circulate in body fluids was discovered. The ability of these circulating miRNAs to mirror physiological and pathophysiological conditions as well as their high stability in stored patient samples underlines the potential of these molecules to serve as biomarkers for various diseases. In this review, we describe recent findings in miRNA-mediated cell-to-cell communication and the functions of circulating miRNAs in the field of hematology. Furthermore, we discuss current approaches to design biomarker studies with circulating miRNAs. This article critically reviews the novel field of circulating miRNAs and highlights their suitability for clinical and basic research in addition to their potential as a novel class of biomarkers.

The role of cancer stem cells and miRNAs in defining the complexities of brain metastasis

Researchers and clinicians have been challenged with the development of therapies for the treatment of cancer patients whose tumors metastasized to the brain. Among the most lethal weapons known today, current management of brain metastases involves multiple therapeutic modalities that provide little, if any, for improving the quality of life and overall survival. Recently the role of cancer stem cells (CSCs) in the development of cancer has been studied extensively, and thus its role in the prognosis, diagnosis, and treatment is now being investigated even in the realm of brain metastasis (BM). Recognizing the molecular make-up of CSCs as well as understanding the role of these cells in resistance to treatment modalities is expected to benefit cancer patients. Additionally, past decade has witnessed an increase in awareness and understanding of the role of microRNAs (miRNAs) in various cancer types, and the deregulation miRNAs are critically important for the regulation of genes during the development and progression of human malignancies. The role miRNAs in BM is being investigated, and has also shown tremendous promise for future research. In this review, we discuss the problem and lethality of brain metastases and the current state of management, and further provide insight into novel avenues that are worth considering including the biological complexities of CSCs and miRNAs for designing novel therapies.

A catalogue of glioblastoma and brain MicroRNAs identified by deep sequencing

Glioblastoma is the most common and aggressive primary brain tumor. MicroRNAs (miRNAs) are a set of noncoding RNA of about 20∼22 nt in length and they play regulatory roles such as regulating the expression of proteins. Altered miRNA expression is related to cancers, including glioblastoma. In this report, we used deep sequencing to explore the miRNA profiles of glioblastoma and normal brain tissues. We found 875 and 811 known miRNA and miRNA* in glioblastoma and normal brain tissue, respectively, representing the largest characterization of the miRNAs in GBM so far. 33 of them were upregulated in glioblastoma, including miR-21, which is well known as an oncomir, while 40 of them were downregulated. Using miR-10b, miR-124, miR-433, and miR-92b as examples, we verified the data by quantitative RT-PCR, suggesting that deep sequencing was able to capture the expression profiles of miRNAs. In addition, we found 18 novel miRNA and 16 new miRNA* in glioblastoma and normal brain tissues. This report provides a useful resource for future studies of the roles of miRNAs in the pathogenesis and early detection of glioblastoma.

MiR-328 expression is decreased in high-grade gliomas and is associated with worse survival in primary glioblastoma

MicroRNAs, a group of small endogenous, noncoding RNAs, are aberrantly expressed in many human cancers and can act as oncogene or anti-oncogene. Recent evidence suggests that some miRNAs have prognostic value for tumors. MiR-328 is known as a tumor suppressor; however, its relationship with the clinicopathological features of glioblastoma (GBM) and its prognostic value has yet not been investigated. We found that expression of miR-328 was significantly decreased both in anaplastic and GBM cohorts and that low miR-328 expression also conferred poor survival in primary GBM (PGBM) patients. MiR-328 might, therefore, serve as an independent prognostic marker. Furthermore, expression profiles of miR-328-associated mRNAs were established via microarrays for 60 GBM samples. The ontology of the miR-328-associated genes was then analyzed, which identified gene sets tightly related to cell mitosis. In addition, ectopic expression of miR-328 inhibited U87 cell proliferation and induced U87 cell cycle arrest. In conclusion, this is the first report showing that miR-328 is associated with patient’s survival time and that miR-328 might serve as an independent prognostic biomarker for GBM.