Overexpression of RKIP inhibits cell invasion in glioma cell lines through upregulation of miR-98

LIN28B and Let-7 in Diffuse Midline Glioma: A Review

Diffuse midline glioma (DMG) is the most lethal of all childhood cancers. DMGs are driven by histone-tail-mutation-mediated epigenetic dysregulation and partner mutations in genes controlling proliferation and migration. One result of this epigenetic and genetic landscape is the overexpression of LIN28B RNA binding protein. In other systems, LIN28B has been shown to prevent let-7 microRNA biogenesis; however, let-7, when available, faithfully suppresses tumorigenic pathways and induces cellular maturation by preventing the translation of numerous oncogenes. Here, we review the current literature on LIN28A/B and the let-7 family and describe their role in gliomagenesis. Future research is then recommended, with a focus on the mechanisms of LIN28B overexpression and localization in DMG.

Non-coding RNAs and glioblastoma: Insight into their roles in metastasis

Glioma, also known as glioblastoma multiforme (GBM), is the most prevalent and most lethal primary brain tumor in adults. Gliomas are highly invasive tumors with the highest death rate among all primary brain malignancies. Metastasis occurs as the tumor cells spread from the site of origin to another site in the brain. Metastasis is a multifactorial process, which depends on alterations in metabolism, genetic mutations, and the cancer microenvironment. During recent years, the scientific study of non-coding RNAs (ncRNAs) has led to new insight into the molecular mechanisms involved in glioma. Many studies have reported that ncRNAs play major roles in many biological procedures connected with the development and progression of glioma. Long ncRNAs (lncRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs) are all types of ncRNAs, which are commonly dysregulated in GBM. Dysregulation of ncRNAs can facilitate the invasion and metastasis of glioma. The present review highlights some ncRNAs that have been associated with metastasis in GBM. miRNAs, circRNAs, and lncRNAs are discussed in detail with respect to their relevant signaling pathways involved in metastasis.

HMGA2 as a Critical Regulator in Cancer Development

The high mobility group protein 2 (HMGA2) regulates gene expression by binding to AT-rich regions of DNA. Akin to other DNA architectural proteins, HMGA2 is highly expressed in embryonic stem cells during embryogenesis, while its expression is more limited at later stages of development and in adulthood. Importantly, HMGA2 is re-expressed in nearly all human malignancies, where it promotes tumorigenesis by multiple mechanisms. HMGA2 increases cancer cell proliferation by promoting cell cycle entry and inhibition of apoptosis. In addition, HMGA2 influences different DNA repair mechanisms and promotes epithelial-to-mesenchymal transition by activating signaling via the MAPK/ERK, TGFβ/Smad, PI3K/AKT/mTOR, NFkB, and STAT3 pathways. Moreover, HMGA2 supports a cancer stem cell phenotype and renders cancer cells resistant to chemotherapeutic agents. In this review, we discuss these oncogenic roles of HMGA2 in different types of cancers and propose that HMGA2 may be used for cancer diagnostic, prognostic, and therapeutic purposes.

Downregulation of RKIP promotes radioresistance of nasopharyngeal carcinoma by activating NRF2/NQO1 axis via downregulating miR-450b-5p

Dysregulation of RKIP and NRF2 has been widely involved in the therapy resistance of multiple malignances, however, their relation and the corresponding mechanisms, especially in radiation response, have not been elucidated. In this study, we revealed that RKIP could negatively regulate the expression of NRF2 in nasopharyngeal carcinoma (NPC) cells. Depletion or ectopic expression of NRF2 countered the pro- or anti- radioresistant effects of RKIP knockdown or overexpression on NPC cells, respectively, both in vitro and in vivo. Furthermore, our results indicated that NQO1 was positively regulated by NRF2 and served as the downstream effector of RKIP/NRF2 axis in regulation of NPC radioresistance. Mechanistically, miR-450b-5p, being positively regulated by RKIP in NPC cells, could sensitize NPC cells to irradiation by directly targeting and suppressing the level of NRF2. Besides, we analyzed the level of aforementioned molecules in NPC tissues. The results indicated that RKIP was significantly downregulated, NRF2 and NQO1 were notably upregulated in NPC tissues compared with in normal nasopharyngeal mucosa (NNM) tissues. Furthermore, RKIP and miR-450b-5p were remarkably lower, yet NRF2 and NQO1 were notably higher, in radioresistant NPC tissues relative to in radiosensitive NPC tissues. Consistent with the pattern in NPC cells, the RKIP/miR-450b-5p/NRF2/NQO1 axis was significantly correlated in NPC tissues. Downregulation of RKIP and miR-450b-5p, and upregulation of NRF2 and NQO1, positively correlated to malignant pathological parameters such as primary T stage, Lymph node (N) metastasis, and TNM stage. Finally, RKIP and miR-450b-5p served as favorable prognostic indicators, and NRF2 and NQO1 acted as unfavorable prognostic biomarkers in patients with NPC. Collectively, our outcomes reveal that RKIP downregulation promotes radioresistance of NPC by downregulating miR-450b-5p and subsequently upregulating and activating NRF2 and NQO1, highlighting RKIP/miR-450b-5p/NRF2/NQO1 axis as a potential therapeutic target for improving the radiosensitivity of NPC.

High Mobility Group A (HMGA): Chromatin Nodes Controlled by a Knotty miRNA Network

High mobility group A (HMGA) proteins are oncofoetal chromatin architectural factors that are widely involved in regulating gene expression. These proteins are unique, because they are highly expressed in embryonic and cancer cells, where they play a relevant role in cell proliferation, stemness, and the acquisition of aggressive tumour traits, i.e., motility, invasiveness, and metastatic properties. The HMGA protein expression levels and activities are controlled by a connected set of events at the transcriptional, post-transcriptional, and post-translational levels. In fact, microRNA (miRNA)-mediated RNA stability is the most-studied mechanism of HMGA protein expression modulation. In this review, we contribute to a comprehensive overview of HMGA-targeting miRNAs; we provide detailed information regarding HMGA gene structural organization and a comprehensive evaluation and description of HMGA-targeting miRNAs, while focusing on those that are widely involved in HMGA regulation; and, we aim to offer insights into HMGA-miRNA mutual cross-talk from a functional and cancer-related perspective, highlighting possible clinical implications.

Silencing lncRNA FOXD2-AS1 inhibits proliferation, migration, invasion and drug resistance of drug-resistant glioma cells and promotes their apoptosis via microRNA-98-5p/CPEB4 axis

OBJECTIVE

This study was conducted to elucidate the long non-coding RNA FOXD2-AS1 (lncRNA FOXD2-AS1) expression in glioma and its mechanism on the biological features of glioma cells and the drug resistance of temozolomide (TMZ).

RESULTS

Highly expressed FOXD2-AS1 was found in glioma. There was more powerful chemotherapeutic resistance of TMZ resistant cell lines than that of the parent cell lines. Silence of FOXD2-AS1 suppressed proliferation and drug resistance and promoted apoptosis of drug-resistant glioma cells. Overexpressed FOXD2-AS1 presented an opposite trend. FOXD2-AS1 could be used as a competing endogenous RNA to adsorb miR-98-5p, thereby up-regulating CPEB4.

CONCLUSION

Our study suggests that down-regulated FOXD2-AS1 repressed invasion, proliferation, migration and drug resistance of drug-resistant glioma cells while stimulating their apoptosis via increasing miR-98-5p and inhibiting CPEB4 expression.

METHODS

FOXD2-AS1, microRNA-98-5p (miR-98-5p) and cytoplasmic polyadenylation element binding (CPEB4) expression in glioma tissues were tested. Expression of E-cadherin, N-cadherin and Vimentin in glioma cells were explored. A series of assays were conducted to detect the function of FOXD2-AS1 in migration, proliferation, apoptosis, and invasion of glioma cells. Changes in drug-resistance of cells under TMZ treatment were examined, and tumor formation in nude mice was performed to test the changes of drug resistance in vivo.

Oleuropein modulates glioblastoma miRNA pattern different from Olea europaea leaf extract

Glioblastoma (GBM) is the most prevalent and deadliest subtype of glioma. Despite current innovations in existing therapeutic modalities, GBM remains incurable, and alternative therapies are required. Previously, we demonstrated that Olea europaea leaf extract (OLE) kills GBM cells by modulating miR-181b, miR-137, miR-153 and Let-7d expression. However, although oleuropein (OL) is the main compound in OLE, its role in the antitumour effect of OLE remains unknown. This study determined the effect of OL on GBM cell line T98G and compared the results with our previous findings regarding the effect of OLE on the same cell line. The antiproliferative activity of OL and its effect on temozolomide (TMZ) response were tested inT98G cells using WST-1 assay. OL inhibition was evaluated using one-way analysis of variance with Tukey's post hoc test. The effect of OL on miR-181b, miR-137, miR-153 and Let-7d expression was assessed using quantitative reverse transcription polymerase chain reaction. Fold differences in expression between untreated, OL or OL + TMZ-treated samples were calculated using 2^-ΔCt method. Significance was evaluated using an independent sample t-test. Treatment with 277.5 and 555 µM OL resulted in 39.51% and 75.40% reductions in T98G cells within 24 h. Coadministration of 325 µM TMZ and 277.5 or 555 µM, OL caused 2.08- and 2.83-fold increases, respectively, in the therapeutic effect of TMZ. OL + TMZ significantly increased microRNA expression, particularly Let-7d, than OLE. In conclusion, OL has an antitumour effect on GBM cells mainly via regulation of Let-7d expression. The present results also indicate other minor compounds in OLE play important anticancer roles.

The Transient Receptor Potential Vanilloid Type-2(TRPV2) Ion Channels in Neurogenesis andGliomagenesis: Cross-Talk between TranscriptionFactors and Signaling Molecules

Recently, the finding of cancer stem cells in brain tumors has increased the possibilities for advancing new therapeutic approaches with the aim to overcome the limits of current available treatments. In addition, a role for ion channels, particularly of TRP channels, in developing neurons as well as in brain cancer development and progression have been demonstrated. Herein, we focus on the latest advancements in understanding the role of TRPV2, a Ca²⁺ permeable channel belonging to the TRPV subfamily in neurogenesis and gliomagenesis. TRPV2 has been found to be expressed in both neural progenitor cells and glioblastoma stem/progenitor-like cells (GSCs). In developing neurons, post-translational modifications of TRPV2 (e.g., phosphorylation by ERK2) are required to stimulate Ca²⁺ signaling and nerve growth factor-mediated neurite outgrowth. TRPV2 overexpression also promotes GSC differentiation and reduces gliomagenesis in vitro and in vivo. In glioblastoma, TRPV2 inhibits survival and proliferation, and induces Fas/CD95-dependent apoptosis. Furthermore, by proteomic analysis, the identification of a TRPV2 interactome-based signature and its relation to glioblastoma progression/recurrence, high or low overall survival and drug resistance strongly suggest an important role of the TRPV2 channel as a potential biomarker in glioblastoma prognosis and therapy.

Assessment of miR-98-5p, miR-152-3p, miR-326 and miR-4289 Expression as Biomarker for Prostate Cancer Diagnosis

Prostate cancer (PCa) is one of the most commonly diagnosed cancers worldwide, accounting for almost 1 in 5 new cancer diagnoses in the US alone. The current non-invasive biomarker prostate specific antigen (PSA) has lately been presented with many limitations, such as low specificity and often associated with over-diagnosis. The dysregulation of miRNAs in cancer has been widely reported and it has often been shown to be specific, sensitive and stable, suggesting miRNAs could be a potential specific biomarker for the disease. Previously, we identified four miRNAs that are significantly upregulated in plasma from PCa patients when compared to healthy controls: miR-98-5p, miR-152-3p, miR-326 and miR-4289. This panel showed high specificity and sensitivity in detecting PCa (area under the curve (AUC) = 0.88). To investigate the specificity of these miRNAs as biomarkers for PCa, we undertook an in depth analysis on these miRNAs in cancer from the existing literature and data. Additionally, we explored their prognostic value found in the literature when available. Most studies showed these miRNAs are downregulated in cancer and this is often associated with cancer progression and poorer overall survival rate. These results suggest our four miRNA signatures could potentially become a specific PCa diagnostic tool of which prognostic potential should also be explored.

MicroRNA-34a-5p suppresses tumorigenesis and progression of glioma and potentiates Temozolomide-induced cytotoxicity for glioma cells by targeting HMGA2

Glioma is a frequently diagnosed brain tumors and Temozolomide (TMZ) is a common chemotherapeutic drug for glioma. High mobility group AT-hook 2 (HMGA2) was reported to be linked with glioma pathogenesis and Temozolomide (TMZ)-induced cytotoxicity. Our present study aimed to further search for the upstream regulatory microRNAs (miRNAs) of HMGA2 in glioma. RT-qPCR assay was conducted to measure the expression of HMGA2 mRNA and microRNA-34a-5p (miR-34a-5p). HMGA2 protein expression was examined by western blot assay. Cell proliferative ability and cell viability was assessed by CCK-8 assay. Cell migratory and invasive capacities were estimated by Transwell migration and invasion assay. Bioinformatics analysis and luciferase reporter assay was conducted to investigate the potential interaction between miR-34a-5p and HMGA2. Mouse xenograft experiments were performed to further test the roles of TMZ, miR-34a-5p and HMGA2, alone or in combination, in glioma tumorigenesis in vivo. We found HMGA2 expression was notably upregulated in glioma tissues and cells, and associated with glioma grade and poor prognosis. HMGA2 knockdown or miR-34a-5p overexpression inhibited migration, invasion, proliferation and enhanced TMZ-induced cytotoxicity in glioma cells. Moreover, HMGA2 was a target of miR-34a-5p. And, miR-34a-5p expression was remarkably reduced in glioma tissues and cells. MiR-34a-5p exerted its function through targeting HMGA2 in glioma cells. HMGA2 knockdown or miR-34a-5p overexpression inhibited tumor growth and enhanced TMZ-mediated anti-tumor effect in glioma xenograft models. We concluded MiR-34a-5p suppressed tumorigenesis and progression of glioma and potentiated TMZ-induced cytotoxicity for glioma cells by targeting HMGA2, deepening our understanding on molecular basis of HMGA2 in glioma.

NEAT1/hsa-mir-98-5p/MAPK6 axis is involved in non-small-cell lung cancer development

Long noncoding RNAs (lncRNAs) or microRNAs belong to the two most important noncoding RNAs and they are involved in a lot of cancers, including non-small-cell lung cancer (NSCLC). Therefore, currently, we focused on the biological and clinical significance of lncRNA nuclear enriched abundant transcript 1 (NEAT1) and hsa-mir-98-5p in NSCLC. It was observed that NEAT1 was upregulated while hsa-mir-98-5p was downregulated respectively in NSCLC cell lines compared to human normal lung epithelial BES-2B cells. Inhibition of NEAT1 can suppress the progression of NSCLC cells and hsa-mir-98-5p can reverse this phenomenon. Bioinformatics search was used to elucidate the correlation between NEAT1 and hsa-mir-98-5p. Additionally, a novel messenger RNA target of hsa-mir-98-5p, mitogen-activated protein kinase 6 (MAPK6), was predicted. Overexpression and knockdown studies were conducted to verify whether NEAT1 exhibits its biological functions through regulating hsa-mir-98-5p and MAPK6 in vitro. NEAT1 was able to increase MAPK6 expression and hsa-mir-98-5p mimics can inhibit MAPK6 via downregulating NEAT1 levels. We speculated that NEAT1 may act as a competing endogenous lncRNA to upregulate MAPK6 by attaching hsa-mir-98-5p in lung cancers. Taken these together, NEAT1/hsa-mir-98-5p/MAPK6 is involved in the development and progress in NSCLC. NEAT1 could be recommended as a prognostic biomarker and therapeutic indicator in NSCLC diagnosis and treatment.

Dynamic expression of 11 miRNAs in 83 consecutive primary and corresponding recurrent glioblastoma: correlation to treatment, time to recurrence, overall survival and MGMT methylation status

Background

Glioblastoma (GBM) is the most common and the most malignant glioma subtype. Among numerous genetic alterations, miRNAs contribute to pathogenesis of GBM and it is suggested that also to GBM recurrence and resistance to therapy. Based on publications, we have selected 11 miRNAs and analyzed their expression in GBM. We hypothesized that selected miRNAs are differentially expressed and involved in primary as well as in recurrent GBM, that show significant expressional differences when different treatment options are in question, and that are related to certain patients and tumor characteristics.

Patients and methods

Paraffin embedded tissues, obtained from primary and corresponding recurrent tumor from 83 patients with primary GBM were used. Eleven miRNAs (miR-7, miR-9, miR-15b, miR-21, miR-26b, miR-124a, miR-199a, let-7a, let-7b, let-7d, and let-7f) were selected for qPCR expression analysis. For patients who received temozolamide (TMZ) as chemotherapeutic drug, O6-methylguanine-DNA methyltransferase (MGMT) methylation status was defined using the methyl-specific PCR.

Results

There was a significant change in expression of miR-7, miR-9, miR-21, miR-26b, mirR-124a, miR-199a and let-7f in recurrent tumor compared to the primary. In recurrent tumor, miR-15b, let-7d and let-7f significantly changed comparing both treatment options. We also observed difference in progression free survival between patients that received radiotherapy and patients that received radiotherapy and chemotherapy, and longer survival for patients who received chemotherapy after second surgery compared to not treated patients. miR-26b showed correlation to progression free survival and let-7f to overall survival. We did not find any expression difference between the tumors with and without methylated MGMT.

Conclusions

Our data suggest that analyzed miRNAs may not only contribute to pathogenesis of primary GBM, but also to tumor progression and its recurrence. Moreover, expression of certain miRNAs appears to be therapy-dependent and as such they might serve as additional biomarker for recurrence prediction and potentially predict a therapy-resistance.

microRNA-98 inhibits the proliferation, invasion, migration and promotes apoptosis of breast cancer cells by binding to HMGA2

Breast cancer is a major contributor leading to cancer death in females worldwide. The aim of the present study was to investigate the effects of microRNA-98 (miR-98) on the processes of cell proliferation, invasion, migration and apoptosis by binding to high-mobility group AT-hook 2 (HMGA2) in breast cancer. Breast cancer tissues and adjacent normal tissues were collected from 112 patients suffering from breast cancer. The target relationship between miR-98 and HMGA2 was verified by in connection with the bioinformatics website as well as a dual-luciferase reporter assay, both of which provided evidence indicating that HMGA2 was a target gene of miR-98. Human breast cancer MDA-MB-231 cells were treated with miR-98 mimics, miR-98 inhibitors, siRNA-HMGA2 or miR-98 inhibitors + siRNA-HMGA2. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and flow cytometry methods were performed to determine cell proliferation, cell cycle and apoptosis, respectively, while a Transwell assay was employed to detect cell migration and invasion. Breast cancer tissues exhibited decreased miR-98 expression, while increased expression levels of HMGA2 were recorded. The mRNA and protein expressions of HMGA2, cell proliferation, cells at the S phase, cell migration, invasion, expressions of matrix metalloproteinase (MMP)2 as well as MMP9 were all reduced in response to miR-98 mimics or siRNA-HMGA2, while a contradictory trend was observed in the miR-98 inhibitors group. In conclusion, the results of the study demonstrate that miR-98 inhibits cell proliferation, migration and invasion, while acting to promote apoptosis by negatively regulating HMGA2 in breast cancer.

RKIP: A Key Regulator in Tumor Metastasis Initiation and Resistance to Apoptosis: Therapeutic Targeting and Impact

RAF-kinase inhibitor protein (RKIP) is a well-established tumor suppressor that is frequently downregulated in a plethora of solid and hematological malignancies. RKIP exerts antimetastatic and pro-apoptotic properties in cancer cells, via modulation of signaling pathways and gene products involved in tumor survival and spread. Here we review the contribution of RKIP in the regulation of early metastatic steps such as epithelial–mesenchymal transition (EMT), migration, and invasion, as well as in tumor sensitivity to conventional therapeutics and immuno-mediated cytotoxicity. We further provide updated justification for targeting RKIP as a strategy to overcome tumor chemo/immuno-resistance and suppress metastasis, through the use of agents able to modulate RKIP expression in cancer cells.

Methylation-induced downregulation and tumor-suppressive role of microRNA-98 in glioma through targeting Sal-like protein 4

MicroRNAs (miRs) have been found to play key roles in various human cancers, but the detailed regulatory mechanism of miR-98 in glioma remains largely unknown. The findings of the present study demonstrated that miR-98 was frequently downregulated in glioma tissues and cell lines (U87, U251, U373 and SHG44), and the decreased miR-98 levels were associated with DNA methylation. Treatment with 5-Aza-20-deoxycytidine, a DNA methyltransferase inhibitor, significantly increased the expression of miR-98 in glioma cells. Moreover, both miR-98 downregulation and methylation were significantly associated with a more aggressive tumor phenotype in glioma, as well as shorter survival time of glioma patients. Restoration of miR-98 expression caused a marked decrease in the migration and invasion of U87 cells, but did not affect cell proliferation. Sal-like protein 4 (SALL4) was further identified as a novel target gene of miR-98, and its protein expression was negatively regulated by miR-98 in U87 cells. Restoration of SALL4 expression reversed the suppressive effects of miR-98 on the migration and invasion of U87 cells. Furthermore, SALL4 was significantly upregulated in glioma tissues and cell lines, and an inverse correlation between miR-98 and SALL4 expression in glioma tissues was identified. In addition, the increased expression of SALL4 was significantly associated with glioma progression. Taken together, these data demonstrated that downregulation of miR-98, induced by methylation, promotes glioma cell migration and invasion via targeting SALL4. Therefore, miR-98 may become a potential therapeutic candidate for glioma.

MiR-98 Promotes Apoptosis of Glioma Cells via Suppressing IKBKE/NF-κB Pathway

The inhibitor of kappa B kinase epsilon is overexpressed in glioma and plays antiapoptotic role via activating nuclear factor-kappa B. microRNA-98 can suppress glioma, modulate the activities of nuclear factor-kappa B, and bind to the 3′-untranslated region of inhibitor of kappa B kinase epsilon messenger RNA. This study was aimed to investigate the modulation of inhibitor of kappa B kinase epsilon/nuclear factor-kappa B by microRNA-98 in glioma. The results indicated that microRNA-98 was downregulated in glioma cell lines and human glioma tissues. Overexpression of microRNA-98 in U87MG and T98G glioma cells significantly increased the apoptosis induced by ultraviolet irradiation and suppressed nuclear factor-kappa B luciferase activity, nuclear factor-kappa B p50 subunit expression, and B-cell lymphoma-2 (Bcl-2) expression in glioma cells. Silencing inhibitor of kappa B kinase epsilon decreased the expression of nuclear factor-kappa B p50 subunit and the luciferase activity of nuclear factor-kappa B, while the nuclear factor-kappa B activity could be significantly retrieved when inhibitor of kappa B kinase epsilon was expressed in microRNA-98-transfected cells. These findings indicated that microRNA-98 could promote apoptosis of glioma cells via inhibiting inhibitor of kappa B kinase epsilon/nuclear factor-kappa B signaling and presented a novel regulatory pathway of microRNA-98 by direct suppression of inhibitor of kappa B kinase epsilon/nuclear factor-kappa B expression in glioma cells.

MicroRNA-98 Attenuates Cell Migration and Invasion in Glioma by Directly Targeting Pre-B Cell Leukemia Homeobox 3

Glioblastoma multiforme (GBM) is the most common primary brain tumor in adults. The extraordinary invasion of human GBM into adjacent normal brain tissues contributes to treatment failure. However, the mechanisms that control this process remain poorly understood. Increasing evidence has demonstrated that microRNAs are strongly implicated in the migration and invasion of GBM. In this study, we found that microRNA-98 (miR-98) was markedly downregulated in human glioma tissues and cell lines. Functional experiments indicated that restored expression of miR-98 attenuated glioma cell invasion and migration, whereas depletion of miR-98 promoted glioma cell invasion and migration. Subsequent investigation showed that pre-B-cell leukemia homeobox 3 (PBX3), an important transcription factor that controls tumor invasion, was a direct and functional target of miR-98 in GBM cells. Consistently, an orthotopic mouse model also demonstrated the suppressive effects of miR-98 overexpression on tumor invasion and PBX3 expression. Silencing of PBX3 using small interfering RNA inhibited the migratory and invasive capacities of glioma cells, whereas reintroduction of PBX3 into glioma cells reversed the anti-invasive function of miR-98. Furthermore, depletion of PBX3 phenocopied the effects of miR-98 overexpression in vivo. Finally, quantitative real-time polymerase chain reaction results showed that miR-98 was negatively correlated with PBX3 expression in 24 glioma tissues. Thus, we propose that PBX3 modulation by miR-98 has an important role in regulating GBM invasion and may serve as therapeutic target for GBM.

miR-98 inhibits expression of TWIST to prevent progression of non-small cell lung cancers

Evidence is mounting that micro RNAs (miRNAs) play a critical role in tumor development. However, the role of miRNAs in lung cancer progression remains largely unknown. Herein, we found that miR-98 significantly impaired in patients with non-small cell lung cancers (NSCLC) and was a novel regulator of NSCLC progression. Patients with high miR-98 expression had a longer overall survival than with low miR-98 expression (p=0.0495). miR-98 expression level inversely correlated with TWIST mRNA level in 71 clinical tissue specimens of NSCLC (p<0.01). Luciferase assay demonstrated that miR-98 interacted binding sites in the TWIST 3'-UTR and reduced expression of TWIST, resulting in repression of cell migration and invasion via impeding TWIST-mediated EMT. Furthermore, introduction of synthetic miR-98 caused growth arrest by inactivating TWIST-Akt-CDK4/CDK6. Meanwhile, miR-98 mimic induced apoptosis by targeting TWIST-Akt axis. In a conclusion, these observations imply that miR-98 may act as a tumor suppressor in NSCLC to decelerate NSCLC aggressiveness by inhibiting TWIST expression.

Understanding perspectives of signalling mechanisms regulating PEBP1 function

Phosphatidylethanolamine-binding protein 1 (PEBP1), also known as Raf kinase inhibitor protein, belongs to PEBP family of proteins. It is known to interact with many proteins that are mainly involved in pathways that monitor cell proliferation and differentiation. PEBP1 in many cells interacts with several pathways, namely MAPK, GRK2, NF-кB, etc. that keeps the cell proliferation and differentiation in check. This protein is expressed by many cells in humans, including neurons where it is predominantly involved in production of choline acetyltransferase. Deregulated PEBP1 is known to cause cancer, diabetic nephropathy and neurodegenerative diseases like Alzheimer's and dementia. Recent research led to the discovery of many drugs that mainly target the interaction of PEBP1 with its partners. These compounds are known to bind PEBP1 in its conserved domain which abrogate its association with interacting partners in several different pathways. We outline here the latest developments in understanding of PEBP1 function in maintaining cell integrity. Copyright © 2016 John Wiley & Sons, Ltd.

SIGNIFICANCE OF THE STUDY

Phosphatidylethanolamine-binding protein is crucial in regulation of MAPK and PKC pathways. Its diverse roles, including regulating these pathways keep cell differentiation and proliferation in check. This review outlines some latest findings which greatly add to our current knowledge of phosphatidylethanolamine-binding protein.

Increased Expression of miR-23a Mediates a Loss of Expression in the RAF Kinase Inhibitor Protein RKIP

RAF kinase inhibitor protein (RKIP) is a seminal regulator of intracellular signaling and exhibits both antimetastatic and antitumorigenic properties. Decreased expression of RKIP has been described in several human malignancies, including acute myelogenous leukemia (AML). As the mechanisms leading to RKIP loss in AML are still unclear, we aimed to analyze the potential involvement of miRNAs within this study. miRNA microarray and qPCR data of more than 400 AML patient specimens revealed correlation between decreased expression of RKIP and increased expression of miR-23a, a member of the miR-23a/27a/24-2 cluster. In functional experiments, overexpression of miR-23a decreased RKIP mRNA and protein expression, whereas miR-23a inhibition caused the opposite effect. By using an RKIP 3'-untranslated region luciferase reporter construct with and without mutation or deletion of the putative miR-23a-binding site, we could show that RKIP modulation by miR-23a is mediated via direct binding to this region. Importantly, miR-23a overexpression induced a significant increase of proliferation in hematopoietic cells. Simultaneous transfection of an RKIP expression construct lacking the miR-23a-binding sites reversed this phenotype, indicating that this effect is truly mediated via downregulation of RKIP. Finally, by analyzing more than 4,300 primary patient specimens via database retrieval from The Cancer Genome Atlas, we could highlight the importance of the miR-23a/RKIP axis in a broad range of human cancer entities. In conclusion, we have identified miR-23a as a negative regulator of RKIP expression in AML and have provided data that suggest the importance of our observation beyond this tumor entity. Cancer Res; 76(12); 3644-54. ©2016 AACR.

MicroRNA-98 suppresses cell proliferation, migration and invasion by targeting collagen triple helix repeat containing 1 in hepatocellular carcinoma

MicroRNAs (miRNAs) are emerging as critical regulators in carcinogenesis and tumor progression. miR-98 has previously been verified to be important in tumor progression, however, its function in hepatocellular carcinoma (HCC) remains to be elucidated. The expression levels of miR-98 in HCC tissues and cell lines were determined by reverse transcription quantitative polymerase chain reaction. Subsequently, the effect of miR‑98 on cell proliferation, migration and invasion was evaluated by MTT assay, transwell migration assay and transwell invasion assay. Furthermore, a luciferase reporter assay was conducted to confirm the action of miR‑98 on downstream target genes, including collagen triple helix repeat containing 1 (CTHRC1). In the present study, it was confirmed that miR‑98 was significantly downregulated in HCC tissues and cell lines. Overexpression of miR‑98 inhibited HCC cell proliferation, migration and invasion in vitro. In addition, at the molecular level, the tumor oncogene CTHRC1 was identified to be the direct target of miR-98. Our findings suggested that miR‑98 was significantly downregulated in HCC and suppressed HCC cell proliferation, migration and invasion partially via the downregulation of CTHRC1. Thus, these data demonstrated that miR-98 could be a potential therapeutic target in HCC.

RKIP suppresses the proliferation and invasion ofchoriocarcinoma cells through inhibiting the MAPK signaling pathway

Raf kinase inhibitor protein (RKIP), an inhibitor of Raf-mediated activation of mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK), has been identified as a metastasis suppressor gene. However, the role of RKIP in human choriocarcinoma remains undetermined. Therefore, in the present study, we investigated the expression of RKIP in human choriocarcinoma cells and evaluated the effects of RKIP on choriocarcinoma cell proliferation and invasion. Our results indicated that RKIP was lowly expressed in human choriocarcinoma cells. Overexpression of RKIP inhibits choriocarcinoma cell proliferation, migration and invasion, promotes the apoptosis of choriocarcinoma cells. Furthermore, overexpression of RKIP significantly inhibited the expression of MEK and ERK phosphorylation in choriocarcinoma cells. Taken together, these data suggest that RKIP suppresses cell proliferation and invasion in choriocarcinoma cells through inhibiting the MAPK signaling pathway, implying that RKIP may serve as a potential molecular target for the treatment of human choriocarcinoma.

Raf kinase inhibitor protein (RKIP) inhibits the cell migration and invasion in human glioma cell lines in vitro

OBJECTIVE

To investigate the effects and the potential mechanisms of RKIP on cell migration, invasion and proliferation in human glioma cell lines in vitro.

METHODS

The RKIP over-expressing and RKIP knockdown human U87 glioma cells were used to reveal the effects of RKIP on human glioma cells migration, invasion and proliferation. After the recombinant plasmid pcDNA3.0-RKIP or RKIP-shRNA was transfected into the cell lines U87 by the means of liposome assay, the cells migration, invasion and proliferation were detected by wound healing, Transwell and MTT assay. Then, the levels of RKIP, MMP-3, MMP-9 and HMGA2 mRNA transcription were measured by means of RT-qPCR and levels of proteins expressions were determined using Western blot.

RESULTS

The results of MTT assay suggested that the PKIP have little inhibitive effects on glioma cells proliferation (P>0.05). The present paper showed that the migration distances in the group of RKIP-shRNA were markedly increased compared to the pcDNA3.0-RKIP and control. Similarly, the results showed that the numbers of invasion cells in RKIP-shRNA were remarkably increased than the pcDNA3.0-RKIP group and control group. Western blot and RT-qPCR suggested that over-expressions of RKIP lessened the MMP-2, MMP-9 and HMGA2 expression, however, turning down the RKIP expression showed the inverse effects.

CONCLUSION

RKIP inhibits the cells migrations and invasions. Meanwhile, RKIP might inhibit the glioma cells through inhibiting MMPs and HMAG2 expression. Therefore, we demonstrated that RKIP is an underlying target for the treatment of glioma.

miR-98 suppresses tumor cell growth and metastasis by targeting IGF1R in oral squamous cell carcinoma

Increasing evidences indicate that dysregulation of miRNAs contributes to the pathogenesis of oral squamous cell carcinoma (OSCC). However, little is known about the potential role of miR-98 in OSCC. Here, we found that miR-98 was downregulated in OSCC tissues and cell lines. Overexpression of miR-98 inhibited proliferation, colony formation, migration, and invasion of OSCC cells. IGF1R was identified as the potential target of miR-98 using dual luciferase assay, qRT-PCR and western blot. Furthermore, restoration of IGF1R remarkably reversed the tumor-suppressive effects of miR-98 on OSCC cells. Moreover, miR-98 expression was inversely correlated with IGF1R expression in 19 cases of OSCC. These findings suggest that miR-98 inhibits cancer cell growth and metastasis by direct targeting IGF1R, implicating miR-98 as a novel potential therapeutic target for OSCC.

The biological complexity of RKIP signaling in human cancers

The Raf kinase inhibitory protein (RKIP) has been demonstrated to modulate different intracellular signaling pathways in cancers. Studies have shown that RKIP is frequently downregulated in cancers; therefore, attempts have been made to upregulate the expression of RKIP using natural and synthetic agents for the treatment of human malignancies. Moreover, various regulators such as specific proteins and microRNAs (miRNAs) that are involved in the regulation of RKIP expression have also been identified. RKIP mechanistically modulates the apoptotic regulators of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) signaling. Because of its critical role in human cancers, RKIP has drawn much research attention, and our understanding is expanding rapidly. Here, we summarize some of the biological complexities of RKIP regulation. However, we restrict our discussion to selected tumors by focusing on TRAIL, miRNAs and natural agents. Emerging evidence suggests a role for natural agents in RKIP regulation in cancer cells; therefore, naturally occurring agents may serve as cancer-targeting agents for cancer treatment. Although the literature suggests some advancement in our knowledge of RKIP biology, it is incomplete with regard to its preclinical and clinical efficacy; thus, further research is warranted. Furthermore, the mechanism by which chemotherapeutic drugs and novel compounds modulate RKIP and how nanotechnologically delivered RKIP can be therapeutically exploited remain to be determined.

Ficus carica latex prevents invasion through induction of let-7d expression in GBM cell lines

Glioblastoma multiforme (GBM) is one of the deadliest human malignancies. A cure for GBM remains elusive, and the overall survival time is less than 1 year. Thus, the development of more efficient therapeutic approaches for the treatment of these patients is required. Induction of tumor cell death by certain phytochemicals derived from medicinal herbs and dietary plants has become a new frontier for cancer therapy research. Although the cancer suppressive effect of Ficus carica (fig) latex (FCL) has been determined in a few cancer types, the effect of this latex on GBM tumors has not been investigated. Therefore, in the current study, the anti-proliferative activity of FCL and the effect of the FCL-temozolomide (TMZ) combination were tested in the T98G, U-138 MG, and U-87 MG GBM cell lines using the WST-1 assay. The mechanism of cell death was analyzed using Annexin-V/FITC and TUNEL assays, and the effect of FCL on invasion was tested using the chick chorioallantoic membrane assay. To determine the effect of FCL on GBM progression, the expression levels of 40 GBM associated miRNAs were analyzed in T98G cells using RT-qPCR. According to the obtained data, FCL causes cell death in GBM cells with different responses to TMZ, and this effect is synergistically increased in combination with TMZ. In addition, the current study is the first to demonstrate the effect of FCL on modulation of let-7d expression, which may be an important underlying mechanism of the anti-invasive effect of this extract.

Raf kinase inhibitory protein (RKIP): functional pleiotropy in the mammalian brain

In 1984, a cytosolic protein was isolated from bovine brain and coined phosphatidylethanolamine binding protein (PEBP) to describe its phospholipid-binding potential. Its cellular function remained elusive for more than a decade until it was discovered that PEBP had the ability to suppress the Raf1-mitogen activated protein kinase (MAPK) pathway, earning it the new name of Raf1 kinase inhibitory protein (RKIP). This milestone discovery has paved the way for numerous studies that have now extended the reach of RKIP's function to other signaling cascades, within the context of various physiological and pathophysiological systems. This review will summarize our current knowledge of the neurophysiological roles of RKIP in the mammalian brain, including its function in the circadian clock and synaptic plasticity. It will also discuss evidence for an involvement of RKIP and its derived neuropeptide, hippocampal cholinergic neurostimulating peptide (HCNP), in neural development and differentiation. Implications in certain pathologies such as Alzheimer's disease and brain cancer will be highlighted. By chronicling the diverse functions of RKIP in the brain, we hope that this review will serve as a timely resource that ignites future studies on this versatile, multifaceted protein in the nervous system.

miRNA expression in anaplastic thyroid carcinomas

Anaplastic thyroid carcinoma (ATC) is the most lethal form of thyroid neoplasia and represents an end stage of thyroid tumor progression. No effective treatment exists so far. In this study, we analyzed the miRNA expression profiles of 11 ATC by microarrays and their relationship with the mRNA expression profiles of the same 11 ATC samples. ATC show distinct miRNA expression profiles compared to other less aggressive thyroid tumor types. ATC show 18 commonly deregulated miRNA compared to normal thyroid tissue (17 downregulated and 1 upregulated miRNA). First, the analysis of a combined approach of the mRNA gene expression and of the bioinformatically predicted mRNA targets of the deregulated miRNA suggested a role for these regulations in the epithelial to mesenchymal transition (EMT) process in ATC. Second, the direct interaction between one of the upregulated mRNA target, the LOX gene which is an EMT key player, and a downregulated miRNA, the miR-29a, was experimentally validated by a luciferase assay in HEK cell. Third, we confirmed that the ATC tissue is composed of about 50% of tumor associated macrophages (TAM) and suggested, by taking into account our data and published data, their most likely direct or paracrine intercommunication between them and the thyroid tumor cells, amplifying the tumor aggressiveness. Finally, we demonstrated by in situ hybridization a specific thyrocyte localization of 3 of the deregulated miRNA: let-7g, miR-29a and miR-30e and we pointed out the importance of identifying the cell type localization before drawing any conclusion on the physiopathological role of a given gene.