Modulation of miR-21 signaling by MPS1 in human glioblastoma

The intra-tumoral heterogeneity in glioblastoma - a limitation for prognostic value of epigenetic markers?

OBJECTIVE

Epigenetic tumor features are getting into focus as prognostic markers in glioblastoma. Whether intra-tumoral heterogeneity in these epigenetic characteristics may influence prognostic value remains unclear.

METHODS

Of 154 patients suffering from glioblastoma, 120 patients served as reference collective, while 34 patients were compiled as test collective. MGMT, p15, and p16 promoter methylation and miRNA expression levels (miRNA-21, miRNA-24, miRNA-26a, and miRNA-181d) were measured in each tumor specimen. Serving as a statistical baseline, epigenetic heterogeneity between tumors (inter-tumoral) was estimated within a triplet of three tumor specimens from three different reference patients. For estimation of epigenetic heterogeneity within a tumor (intra-tumoral), previous results were compared to three tumor specimens within one glioblastoma of patients of the test collective. Resulting levels of heterogeneity were then correlated with survival and validated by an external TCGA data set.

RESULTS

Heterogeneity in MGMT promoter methylation occurred less likely in the test group compared to the reference group. No difference in heterogeneity was observed between test and reference group regarding p15 and p16 methylation. Intra-tumoral heterogeneity within the test group regarding miRNA-21, miRNA-24, miRNA-26a, and miRNA-181d expression was not distinguishable from inter-tumoral heterogeneity. A homogenously increased miRNA-21 expression was associated with reduced overall survival in the test collective. The findings could be validated by comparison with TCGA datasets.

CONCLUSION

Heterogeneity of epigenetic characteristics in one glioblastoma may be of the same magnitude as heterogeneity between different patients. Not only the extent of epigenetic characteristics but also the extent of intra-tumoral heterogeneity may influence survival in glioblastoma.

Downregulation of miR-21 as a promising strategy to overcome drug resistance in cancer

Despite tremendous achievements in the field of targeted cancer therapy, chemotherapy is still the main treatment option, which is challenged by acquired drug resistance. Various microRNAs are involved in developing drug-resistant cells. miR-21 is one of the first identified miRNAs involved in this process. Here, we conducted a literature review to categorize different mechanisms employed by miR-21 to drive drug resistance. miR-21 targets various genes involved in many pathways that can justify chemoresistance. It alters cancer cell metabolism and facilitates adaptation to the new environment. It also enhances drug detoxification in cancerous cells and increases genomic instability. We also summarized various strategies applied for the inhibition of miR-21 in order to reverse cancer drug resistance. These strategies include the delivery of antagomiRs, miRZip knockdown vectors, inhibitory small molecules, CRISPR-Cas9 technology, catalytic nucleic acids, artificial DNA and RNA sponges, and nanostructures like mesoporous silica nanoparticles, dendrimers, and exosomes. Furthermore, current challenges and limitations in targeting miR-21 are discussed in this article. Although huge progress has been made in the downregulation of miR-21 in drug-resistant cancer cells, there are still many challenges to be resolved. More research is still required to find the best strategy and timeline for the downregulation of miR-21 and also the most feasible approach for the delivery of this system into the tumor cells. In conclusion, downregulation of miR-21 would be a promising strategy to reverse chemoresistance, but still, more studies are required to clarify the aforementioned issues.

Hsp90 regulates the tumorigenic function of tyrosine protein kinase in osteosarcoma

Despite recent advances in diagnosis and treatment, osteosarcoma remains as the most common bone cancer in children and is associated with poor prognosis. Growing evidence has supported dysregulation of threonine and tyrosine protein kinase (TTK) expression as a hallmark of multiple cancers, however, its function in osteosarcoma remains to be elucidated. In the present study, we found that TTK was frequently overexpressed in osteosarcoma and associated with increased tumour growth and progression. Moreover, using both in vitro and in vivo assays, we provided evidence that TTK level was regulated by a molecular chaperone, heat shock protein 90 (Hsp90). Hsp90 directly interacted with TTK and prevents proteasome-dependent TTK degradation, leading to the accumulation of TTK in osteosarcoma cells. Elevated TTK promoted cancer cell proliferation and survival by activating cell-cycle progression and inhibiting apoptosis. Consistently, depletion of TTK by Hsp90 inhibition induced cell-cycle arrest, generated aneuploidy and eventually resulted in apoptotic cancer cell death. Together, our study revealed an important Hsp90-TTK regulatory axis in osteosarcoma cells to promote cancer cell growth and survival. These findings expand our knowledge on osteosarcoma pathogenesis and offer novel therapeutic options for clinical practice.

miRNA signature in glioblastoma: Potential biomarkers and therapeutic targets

MicroRNAs (miRNAs) are transcripts with sizes of about 22 nucleotides, which are produced through a multistep process in the nucleus and cytoplasm. These transcripts modulate the expression of their target genes through binding with certain target regions, particularly 3' suntranslated regions. They are involved in the pathogenesis of several kinds of cancers, such as glioblastoma. Several miRNAs, including miR-10b, miR-21, miR-17-92-cluster, and miR-93, have been up-regulated in glioblastoma cell lines and clinical samples. On the other hand, expression of miR-7, miR-29b, miR-32, miR-34, miR-181 family members, and a number of other miRNAs have been decreased in this type of cancer. In the current review, we explain the role of miRNAs in the pathogenesis of glioblastoma through providing a summary of studies that reported dysregulation of these epigenetic effectors in this kind of brain cancer.

Monopolar Spindle 1 Kinase (MPS1/TTK) mRNA Expression is Associated with Earlier Development of Clinical Symptoms, Tumor Aggressiveness and Survival of Glioma Patients

Inhibition of the protein kinase MPS1, a mitotic spindle-checkpoint regulator, reinforces the effects of multiple therapies against glioblastoma multiforme (GBM) in experimental settings. We analyzed MPS1 mRNA-expression in gliomas WHO grade II, III and in clinical subgroups of GBM. Data were obtained by qPCR analysis of tumor and healthy brain specimens and correlated with the patients’ clinical data. MPS1 was overexpressed in all gliomas on an mRNA level (ANOVA, p < 0.01) and correlated with tumor aggressiveness. We explain previously published conflicting results on survival: high MPS1 was associated with poorer long term survival when all gliomas were analyzed combined in one group (Cox regression: t < 24 months, p = 0.009, Hazard ratio: 8.0, 95% CI: 1.7–38.4), with poorer survival solely in low-grade gliomas (LogRank: p = 0.02, Cox regression: p = 0.06, Hazard-Ratio: 8.0, 95% CI: 0.9–66.7), but not in GBM (LogRank: p > 0.05). This might be due to their lower tumor volume at the therapy start. GBM patients with high MPS1 mRNA-expression developed clinical symptoms at an earlier stage. This, however, did not benefit their overall survival, most likely due to the more aggressive tumor growth. Since MPS1 mRNA-expression in gliomas was enhanced with increasing tumor aggressiveness, patients with the worst outcome might benefit best from a treatment directed against MPS1.

Circular RNA circ_0001946 acts as a competing endogenous RNA to inhibit glioblastoma progression by modulating miR-671-5p and CDR1

OBJECTIVES

In many malignant tumors, circRNAs play an important role. However, the biological role and clinical significance of circRNAs remain unclear. In this study, we investigated the effects of circ_0001946 on the progression of glioblastoma (GBM) and the molecular mechanism of circ_0001946.

METHODS

Microarrays were applied to test the expression profiles of circRNAs and messenger RNAs (mRNAs). Coexpressed genes were identified by constructing differentially expressed circRNA-mRNA networks. The expression of circ_0001946, miR-671-5p, and cerebellar degeneration-related autoantigen 1 (CDR1) was detected by real-time quantitative PCR, and the protein expression of CDR1 was determined by western blotting. A dual-luciferase reporter assay was used to evaluate potential miR-671-5p target sites on circ_0001946 and CDR1. The proliferation, apoptosis, migration, and invasion of GBM cells were assessed by a colony formation assay, flow cytometry assay, transwell migration assay, and transwell invasion assay. Xenograft mouse models were used to determine the role of circ_0001946 in vivo.

RESULTS

The expression of circ_0001946 and CDR1 was low and that of miR-671-5p was high in GBM cells. Circ_0001946 suppressed the expression of miR-671-5p, thus upregulating the expression of CDR1, the gene downstream of miR-671-5p. Circ_0001946 and CDR1 reduced proliferation, migration, and invasion and increased apoptosis in GBM cells, whereas miR-671-5p had an opposite effect. The xenograft mouse model and immunohistochemistry results indicated that circ_0001946 inhibited GBM growth as well as the expression of Ki67 in GBM cells.

CONCLUSION

Our study confirmed that the circ_0001946/miR-671-5p/ CDR1 pathway modulates the development of GBM, and this pathway might be a promising target for the development of therapeutics for GBM.

Overview upon miR-21 in lung cancer: focus on NSCLC

Considering the high mortality rate encountered in lung cancer, there is a strong need to explore new biomarkers for early diagnosis and also improved therapeutic targets to overcome this issue. The implementation of microRNAs as important regulators in cancer and other pathologies expanded the possibilities of lung cancer management and not only. MiR-21 represents an intensively studied microRNA in many types of cancer, including non-small cell lung cancer (NSCLC). Its role as an oncogene is underlined in multiple studies reporting the upregulated expression of this sequence in patients diagnosed with this malignancy; moreover, several studies associated this increased expression of miR-21 with a worse outcome within NSCLC patients. The same pattern is supported by the data existent in the Cancer Genome Atlas (TCGA). The carcinogenic advantage generated by miR-21 in NSCLC resides in the target genes involved in multiple pathways such as cell growth and proliferation, angiogenesis, invasion and metastasis, but also chemo- and radioresistance. Therapeutic modulation of miR-21 by use of antisense sequences entrapped in different delivery systems has shown promising results in impairment of NSCLC. Hereby, we review the mechanisms of action of miR-21 in cancer and the associated changes upon tumor cells together a focused perspective on NSCLC signaling, prognosis and therapy.

TTK promotes mesenchymal signaling via multiple mechanisms in triple negative breast cancer

Abnormal expression of TTK kinase has been associated with the initiation, progression, and therapeutic resistance of breast and other cancers, but its roles remain to be clarified. In this study, we examined the role of TTK in triple negative breast cancer (TNBC), and found that higher TTK expression correlated with mesenchymal and proliferative phenotypes in TNBC cells. Pharmacologic inhibition and genomic silencing of TTK not only reversed the epithelial-to-mesenchymal transition (EMT) in TNBC cells, but also increased the expression of KLF5, an effector of TGF-β signaling and inhibitor of EMT. In addition, TTK inhibition decreased the expression of EMT-associated micro-RNA miR-21 but increased the expression of miR-200 family members and suppressed TGF-β signaling. To test if upregulation of KLF5 plays a role in TTK-induced EMT, TTK and KLF5 were silenced simultaneously, which reversed the decreased EMT caused by loss of TTK. Consistently, the decrease in miR-21 expression and increase in miR-200 expression caused by TTK silencing were rescued by loss of KLF5. Altogether, this study highlights a novel role and signaling pathway for TTK in regulating EMT of TN breast cancer cells through TGF-β and KLF5 signaling, highlighting targetable signaling pathways for TTK inhibitors in aggressive breast cancer.

MicroRNA-21 in the Pathogenesis of Traumatic Brain Injury

MicroRNAs (miRNAs), an abundant class of small noncoding RNA molecules, which regulate gene expression by functioning as post-transcriptional regulatory factors, have been identified as key components of traumatic brain injury (TBI) progression. MicroRNA-21 (miR-21) is a recently identified typical miRNA that is involved in the signaling pathways of inflammation, neuronal apoptosis, reactive gliosis, disruption of blood brain barrier, angiogenesis and recovery process induced by physical exercises in TBI. Hence, miR-21 is now considered as a potential therapeutic target of TBI. We review the correlative literature and research progress regarding the roles of miR-21 in TBI in this article.

G2/M inhibitors as pharmacotherapeutic opportunities for glioblastoma: the old, the new, and the future

Glioblastoma (GBM) is one of the deadliest tumors and has a median survival of 3 months if left untreated. Despite advances in rationally targeted pharmacological approaches, the clinical care of GBM remains palliative in intent. Since the majority of altered signaling cascades involved in cancer establishment and progression eventually affect cell cycle progression, an alternative approach for cancer therapy is to develop innovative compounds that block the activity of crucial molecules needed by tumor cells to complete cell division. In this context, we review promising ongoing and future strategies for GBM therapeutics aimed towards G2/M inhibition such as anti-microtubule agents and targeted therapy against G2/M regulators like cyclin-dependent kinases, Aurora inhibitors, PLK1, BUB, 1, and BUBR1, and survivin. Moreover, we also include investigational agents in the preclinical and early clinical settings. Although several drugs were shown to be gliotoxic, most of them have not yet entered therapeutic trials. The use of either single exposure or a combination with novel compounds may lead to treatment alternatives for GBM patients in the near future.

MiR-21: A key player in glioblastoma pathogenesis

Glioblastoma multiform (GBM) is one of common cancers worldwide which has high rate among various populations. Despite serious efforts worldwide, GBM remains a deadly disease which is associated with poor prognosis. Multiple lines evidence indicated that deregulation of a variety of cellular and molecular pathways are related with GBM pathogenesis. Among of various targets involved in GBM pathogenesis, microRNAs (miRNAs) have been emerged as targets which deregulation of them are related with various stages of GBM. These molecules are small non-coding RNAs which could affect on a variety of cellular and molecular pathways involved in GBM. It has been showed that deregulation of them are associated with initiation and progression of GBM. MiR-21 is one of important miRNAs involved in GBM pathogenesis. A large number studies indicated that this miRNA could affect on a variety of cellular and molecular pathways such as insulin-like growth factor (IGF)-binding protein-3 (IGFBP3), RECK, and TIMP3. Exosomes are one of important players in GBM pathogenesis. Among of various exosomes, exosomal miR-21 may has key roles in GBM pathogenesis. These findings indicated that miR-21 has critical roles in GBM pathogenesis and could be used as diagnostic and therapeutic biomarkers for GBM patients. Here, we summarized the roles of miR-21 and exosomal miR-21 in GBM pathogenesis. Moreover, we highlighted utilization of miR-21 as diagnostic and therapeutic biomarker for GBM patients.

Integrative analysis of novel hypomethylation and gene expression signatures in glioblastomas

Molecular and clinical heterogeneity critically hinders better treatment outcome for glioblastomas (GBMs); integrative analysis of genomic and epigenomic data may provide useful information for improving personalized medicine. By applying training-validation approach, we identified a novel hypomethylation signature comprising of three CpGs at non-CpG island (CGI) open sea regions for GBMs. The hypomethylation signature consistently predicted poor prognosis of GBMs in a series of discovery and validation datasets. It was demonstrated as an independent prognostic indicator, and showed interrelationships with known molecular marks such as MGMT promoter methylation status, and glioma CpG island methylator phenotype (G-CIMP) or IDH1 mutations. Bioinformatic analysis found that the hypomethylation signature was closely associated with the transcriptional status of an EGFR/VEGFA/ANXA1-centered gene network. The integrative molecular analysis finally revealed that the gene network defined two distinct clinically relevant molecular subtypes reminiscent of different immature neuroglial lineages in GBMs. The novel hypomethylation signature and relevant gene network may provide new insights into prognostic classification, molecular characterization, and treatment development for GBMs.

Prognostic role of microRNA-21 expression in gliomas: a meta-analysis

MicroRNA-21 (miRNA-21) has recently been shown to be a promising prognostic tumor biomarker. However, few studies have not supported this idea and have shown inconsistent data. Thus, we conducted a meta-analysis to elucidate the predictive value of miRNA-21 in gliomas. The relevant studies were identified by performing online search in PubMed, EMBASE and Web of Science databases up to Apr 2016. This meta-analysis study included seven eligible studies, consisting of 1121 gliomas and 533 glioblastoma multiforme (GBM) patients. Heterogeneity between studies was assessed using Egger's and Begg's test. Hazard ratios (HRs) with 95 % confidence intervals (CIs) for overall survival (OS), which compared the expression levels of miRNA-21 in patients with gliomas, were extracted and estimated. Our analysis revealed that the high expression of miRNA-21 is associated with the worse OS in gliomas. Further subgroup analysis indicated that increased expression of miRNA-21 was also associated with OS in GBM patients. Moreover, we observed a correlation between miRNA-21 expression and the World Health Organization defined gliomas grading system (WHO grade). Besides, high miRNA-21 expression was significantly correlated with lowered OS both in the Asian group and non-Asian group. In the cut-off subgroup analysis, both mean cut off value and median cut off value were significantly associated with OS. The expression level of miRNA-21 was not high in low KPS (Karnofsky score) group. miRNA-21 appears to be a promising biomarker for predicting the progression of patients with gliomas or GBM. However, due to the limited sample size, further prospective or retrospective multi-center well designed studies with adequate sample size should be conducted to verify its definite prognostic value.

Exosomal levels of miRNA-21 from cerebrospinal fluids associated with poor prognosis and tumor recurrence of glioma patients

Glioma is a most common type of primary brain tumors. Extracellular vesicles, in the form of exosomes, are known to mediate cell–cell communication by transporting cell-derived proteins and nucleic acids, including various microRNAs (miRNAs). Here we examined the cerebrospinal fluid (CSF) from patients with recurrent glioma for the levels of cancer-related miRNAs, and evaluated the values for prognosis by comparing the measures of CSF-, serum-, and exosome-contained miR-21 levels. Samples from seventy glioma patients following surgery were compared with those from brain trauma patients as a non-tumor control group. Exosomal miR-21 levels in the CSF of glioma patients were found significantly higher than in the controls; whereas no difference was detected in serum-derived exosomal miR-21 expression. The CSF-derived exosomal miR-21 levels correlated with tumor spinal/ventricle metastasis and the recurrence with anatomical site preference. From additional 198 glioma tissue samples, we verified that miR-21 levels associated with tumor grade of diagnosis and negatively correlated with the median values of patient overall survival time. We further used a lentiviral inhibitor to suppress miR-21 expression in U251 cells. The results showed that the levels of miR-21 target genes of PTEN, RECK and PDCD4 were up-regulated at protein levels. Therefore, we concluded that the exosomal miR-21 levels could be demonstrated as a promising indicator for glioma diagnosis and prognosis, particularly with values to predict tumor recurrence or metastasis.

Comprehensive molecular tumor profiling in radiation oncology: How it could be used for precision medicine

New technologies enabling the analysis of various molecules, including DNA, RNA, proteins and small metabolites, can aid in understanding the complex molecular processes in cancer cells. In particular, for the use of novel targeted therapeutics, elucidation of the mechanisms leading to cell death or survival is crucial to eliminate tumor resistance and optimize therapeutic efficacy. While some techniques, such as genomic analysis for identifying specific gene mutations or epigenetic testing of promoter methylation, are already in clinical use, other "omics-based" assays are still evolving. Here, we provide an overview of the current status of molecular profiling methods, including promising research strategies, as well as possible challenges, and their emerging role in radiation oncology.

Expression and Clinical Pathological Significance of miR-200a in Concurrent Cholangiocarcinoma Associated with Hepatolithiasis

Background

Approximately 2–10% of the patients with hepatolithiasis may develop cholangiocarcinoma (CCA). Despite recent advances in the treatment of cancers, the 5-year survival rate for CCA patients currently remains poor, primarily due to early local invasion and distant metastasis of the cancer. This study aimed to investigate miR-200a expression in combined hepatolithiasis and CCA as well as its correlation with the clinical features of CCA.

Material/Methods

miR-200a expression in combined hepatolithiasis and CCA was detected by real-time reverse transcription PCR (qRT-PCR). Its correlation with the clinicopathology of CCA was analyzed by t-tests. The effect of miR-200a on the proliferation CCA cells was determined by MTT assay. The effect of miR-200a on the invasive ability of CCA cells was assessed by Boyden chamber test.

Results

The expression level of MiR-200a in patients with combined hepatolithiasis and CCA was significantly decreased compared with patients with only hepatolithiasis (P<0.01). Furthermore, miR-200a expression in hepatic duct cancer RBE cells was substantially reduced compared with hepatolithiasis group (P<0.01). Correlation analysis showed that abnormal expression of miR-200a was only associated with the differentiation degree and metastasis of CCA. MiR-200a transfection significantly inhibited the proliferation and invasion of REB cells (P<0.01).

Conclusions

MiR-200a may suppress the proliferative and invasive ability of REB cells. The reduced miR-200a expression might be correlated with the development and progression of CCA.

miR-125b suppresses the proliferation of hepatocellular carcinoma cells by targeting Sirtuin7

Previous studies have shown that microRNAs are involved in many human cancers. However, the role of miR-125b in hepatocellular carcinoma (HCC) has not been fully understood. In our study, we detected the expression of miR-125b using Real-time quantitative-polymerase chain reaction (RT-PCR) and found that the expressions of miR-125b were significantly inhibited in HCC tissues and cell lines. The levels of miR-125b were associated with the degree of HCC malignancy. Otherwise, MTT assay showed that the proliferation was significantly decreased after transfection of miR-125b mimics into HepG2 cells; while the proliferation was significantly increased in HepG2 cells transfected with miR-125b inhibitors. Furthermore, TargetScan was conducted to predict the target gene of miR-125b and Sirtuin7 (SIRT7) was chosen to a potential target gene. And then we used luciferase reporter assay and western blot to confirm that SIRT7 is a direct target gene. Western blot indicated that transfection of miR-125b mimics could significantly inhibit the expression of SIRT7 in HepG2 cells, whereas, transfection of miR-125b inhibitor could significantly increase the expression of SIRT7 in HepG2 cells. These results suggest that miR-125b can inhibit the proliferation of HCC by adjusting the expression of SIRT7 and may be a key element of HCC progression.

Degradation of miR-21 induces apoptosis and inhibits cell proliferation in human hepatocellular carcinoma

MicroRNAs (miRNAs) are small non-coding RNAs, 18-25 nucleotides long and have an important role in post-transcriptional regulation of gene. Several aspects of cellular activities such as cell growth, proliferation and differentiation are regulated by miRNAs. In many cancers and malignancies, up- or downregulation of different miRNAs has been reported. In human hepatocellular carcinoma (HCC), upregulation of miR-21 has been reported in human in vitro studies. Here, we made an assessment of the effect of miR-21 degradation on viability and apoptosis of HCC cell line (HepG2) using locked nucleic acid (LNA). At different time points (24, 48, 72 h) after LNA-anti-miR-21 transfection, 3-[4,5-dimethylthiazol-2-yl]-2, 5-diphenyl tetrazolium bromide assay and Annexin/propidium iodide staining were performed. The results show that miR-21 degradation can decrease the viability of cells, mainly by induction of apoptosis and necrosis. These findings suggest that degradation of miR-21 could be used as a novel approach in treatment of HCC.