In human glioblastomas transcript elongation by alternative polyadenylation and miRNA targeting is a potent mechanism of MGMT silencing

Unraveling the role of miR-767 in tumor progression: Mechanisms and clinical implications

MicroRNAs (miRNAs), a distinctive class of small single-stranded non-coding RNA molecules typically spanning between 21 and 23 nucleotides, hold a pivotal position within the intricate regulatory network governing gene expression. Notably, miR-767, located on chromosome Xq28, has emerged as a significant player in tumor development, with its two mature products, miR-767-3p and miR-767-5p, garnering considerable attention in scientific inquiry. Extensive investigations reveal aberrant expression patterns of miR-767 across a spectrum of cancers affecting neurological, digestive, reproductive, urinary, and respiratory systems. Remarkably, miR-767 exhibits substantial upregulation in 13 distinct cancer types and demonstrates precise targeting of at least 14 pivotal protein-coding genes (PCGs) crucial for regulating cellular processes including the cell cycle, proliferation, epithelial-mesenchymal transition (EMT), invasion, and migration. Moreover, the expression level of miR-767 bears significant implications for cancer patient diagnosis, prognosis, and drug sensitivity, thus offering novel insights for clinical tumor management. At the mechanistic level, miR-767-5p and miR-767-3p intricately participate in the regulation of key signaling pathways, with miR-767-5p influencing JAK/STAT, EPK1/2, and PI3K/Akt pathways, while miR-767-3p predominantly affects TGF-β and PI3K/Akt pathways. Notably, both miRNAs converge on the PI3K/Akt pathway, underscoring its pivotal role in their joint regulation. This review provides a comprehensive analysis of the intricate mechanisms underlying miR-767-mediated tumor progression through the modulation of diverse target genes, and explores the potential correlation between host gene GABRA3 transcription and the expression of these miRNAs. Furthermore, the review systematically delineates the binding sites of miR-767-5p and miR-767-3p with circRNA and target genes, alongside the PCGs regulated by miR-767, offering profound insights into their multifaceted roles in tumor development. In essence, this review not only comprehensively elucidates the pivotal role of miR-767 in tumor progression but also provides valuable cues and avenues for future research, thereby fostering deeper scientific inquiry within the realm of cancer research.

The Clinical Role of miRNAs in the Development and Treatment of Glioblastoma

Glioblastoma multiforme (GBM) is the most common brain tumor and one of the most aggressive, with a median overall survival (OS) of only 15-18 months. These characteristics make it necessary to identify new targets for the improvement of prognosis and better prediction of response to therapies currently available for GBM patients. One possible candidate target could be the evaluation of miRNAs. miRNAs are small non-coding RNAs that play important roles in post-transcriptional gene regulation. Due to their functions, miRNAs also control biological processes underlying the development of GBM and may be considered possible targets with a clinical role. This narrative review introduces the concept of miRNAs in GBM from a clinical and a molecular perspective and then addresses the specific miRNAs that are most described in the literature as relevant for the development, the prognosis, and the response to therapies for patients affected by GBM.

Unraveling the mysteries of MGMT: Implications for neuroendocrine tumors

Neuroendocrine tumors (NETs) are a diverse group of tumors that arise from neuroendocrine cells and are commonly found in various organs. A considerable proportion of NET patients were diagnosed at an advanced or metastatic stage. Alkylating agents are the primary treatment for NET, and O6-methylguanine methyltransferase (MGMT) remains the first-line of defense against DNA damage caused by these agents. Clinical trials have indicated that MGMT promoter methylation or its low/lacked expression can predict a favorable outcome with Temozolomide in NETs. Its status could help select NET patients who can benefit from alkylating agents. Therefore, MGMT status serves as a biomarker to guide decisions on the efficacy of Temozolomide as a personalized treatment option. Additionally, delving into the regulatory mechanisms of MGMT status can lead to the development of MGMT-targeted therapies, benefiting individuals with high levels of MGMT expression. This review aims to explore the polymorphism of MGMT regulation and summarize its clinical implications in NETs, which would help establish the role of MGMT as a biomarker and its potential as a therapeutic target in NETs. Additionally, we explore the benefits of combining Temozolomide and immunotherapy in MGMT hypermethylated subgroups. Future studies can focus on optimizing Temozolomide administration to induce specific immunomodulatory changes.

MGMT in TMZ-based glioma therapy: Multifaceted insights and clinical trial perspectives

Temozolomide (TMZ) is the most preferred and approved chemotherapeutic drug for either first- or second-line chemotherapy for glioma patients across the globe. In glioma patients, resistance to treatment with alkylating drugs like TMZ is known to be conferred by exalted levels of MGMT gene expression. On the contrary, epigenetic silencing through MGMT gene promoter methylation leading to subsequent reduction in MGMT transcription and protein expression, is predicted to have a response favoring TMZ treatment. Thus, MGMT protein level in cancer cells is a crucial determining factor in indicating and predicting the choice of alkylating agents in chemotherapy or choosing glioma patients directly for a second line of treatment. Thus, in-depth research is necessary to achieve insights into MGMT gene regulation that has recently enticed a fascinating interest in epigenetic, transcriptional, post-transcriptional, and post-translational levels. Furthermore, MGMT promoter methylation, stability of MGMT protein, and related subsequent adaptive responses are also important contributors to strategic developments in glioma therapy. With applications to its identification as a prognostic biomarker, thus predicting response to advanced glioma therapy, this review aims to concentrate on the mechanistic role and regulation of MGMT gene expression at epigenetic, transcriptional, post-transcriptional, and post-translational levels functioning under the control of multiple signaling dynamics.

Clinical Relevance and Interplay between miRNAs in Influencing Glioblastoma Multiforme Prognosis

Glioblastoma multiforme (GBM) is usually treated with surgery followed by adjuvant partial radiotherapy combined with temozolomide (TMZ) chemotherapy. Recent studies demonstrated a better survival and good response to TMZ in methylguanine-DNA methyltransferase (MGMT)-methylated GBM cases. However, approximately 20% of patients with MGMT-unmethylated GBM display an unexpectedly favorable outcome. Therefore, additional mechanisms related to the TMZ response need to be investigated. As such, we decided to investigate the clinical relevance of six miRNAs involved in brain tumorigenesis (miR-181c, miR-181d, miR-21, miR-195, miR-196b, miR-648) as additional markers of response and survival in patients receiving TMZ for GBM. We evaluated miRNA expression and the interplay between miRNAs in 112 IDH wt GBMs by applying commercial assays. Then, we correlated the miRNA expression with patients' clinical outcomes. Upon bivariate analyses, we found a significant association between the expression levels of the miRNAs analyzed, but, more interestingly, the OS curves show that the combination of low miR-648 and miR-181c or miR-181d expressions is associated with a worse prognosis than cases with other low-expression miRNA pairs. To conclude, we found how specific miRNA pairs can influence survival in GBM cases treated with TMZ.

Modulating MGMT expression through interfering with cell signaling pathways

Guanine O6-alkylating agents are widely used as first-line chemotherapeutic drugs due to their ability to induce cytotoxic DNA damage. However, a major hurdle in their effectiveness is the emergence of chemoresistance, largely attributed to the DNA repair pathway mediated by O6-methylguanine-DNA methyltransferase (MGMT). MGMT plays an important role in removing the alkyl groups from lethal O6-alkylguanine (O6-AlkylG) adducts formed by chemotherapeutic alkylating agents. By doing so, MGMT enables tumor cells to evade apoptosis and develop drug resistance toward DNA alkylating agents. Although covalent inhibitors of MGMT, such as O6-benzylguanine (O6-BG) and O6-(4-bromothenyl)guanine (O6-4-BTG or lomeguatrib), have been explored in clinical settings, their utility is limited due to severe delayed hematological toxicity observed in most patients when combined with alkylating agents. Therefore, there is an urgent need to identify new targets and unravel the underlying molecular mechanisms and to develop alternative therapeutic strategies that can overcome MGMT-mediated tumor resistance. In this context, the regulation of MGMT expression via interfering the specific cell signaling pathways (e.g., Wnt/β-catenin, NF-κB, Hedgehog, PI3K/AKT/mTOR, JAK/STAT) emerges as a promising strategy for overcoming tumor resistance, and ultimately enhancing the efficacy of DNA alkylating agents in chemotherapy.

Identification of MGMT Downregulation Induced by miRNA in Glioblastoma and Possible Effect on Temozolomide Sensitivity

Glioblastoma multiforme (GBM) remains one of the tumors with the worst prognosis. In recent years, a better overall survival (OS) has been described in cases subjected to Gross Total Resection (GTR) that were presenting hypermethylation of Methylguanine-DNA methyltransferase (MGMT) promoter. Recently, also the expression of specific miRNAs involved in MGMT silencing has been related to survival. In this study, we evaluate MGMT expression by immunohistochemistry (IHC), MGMT promoter methylation and miRNA expression in 112 GBMs and correlate the data to patients' clinical outcomes. Statistical analyses demonstrate a significant association between positive MGMT IHC and the expression of miR-181c, miR-195, miR-648 and miR-767.3p between unmethylated cases and the low expression of miR-181d and miR-648 and between methylated cases and the low expression of miR-196b. Addressing the concerns of clinical associations, a better OS has been described in presence of negative MGMT IHC, in methylated patients and in the cases with miR-21, miR-196b overexpression or miR-767.3 downregulation. In addition, a better progression-free survival (PFS) is associated with MGMT methylation and GTR but not with MGMT IHC and miRNA expression. In conclusion, our data reinforce the clinical relevance of miRNA expression as an additional marker to predict efficacy of chemoradiation in GBM.

The dual role of DNA repair protein MGMT in cancer prevention and treatment

Alkylating agents are genotoxic chemicals that can induce and treat various types of cancer. This occurs through covalent bonding with cellular macromolecules, in particular DNA, leading to the loss of functional integrity under the persistence of modifications upon replication. O6-alkylguanine (O6-AlkylG) adducts are proposed to be the most potent DNA lesions induced by alkylating agents. If not repaired correctly, these adducts can result, at the molecular level, in DNA point mutations, chromosome aberrations, recombination, crosslinking, and single- and double-strand breaks (SSB/DSBs). At the cellular level, these lesions can result in malignant transformation, senescence, or cell death. O6-methylguanine-DNA methyltransferase (MGMT) is a DNA repair protein capable of removing the alkyl groups from O6-AlkylG adducts in a damage reversal process that can prevent the adverse biological effects of DNA damage caused by guanine O6-alkylation. MGMT can thereby defend normal cells against tumor initiation, however it can also protect tumor cells against the beneficial effects of chemotherapy. Hence, MGMT can play an important role in both the prevention and treatment of cancer; thus, it can be considered as a double-edged sword. From a clinical perspective, MGMT is a therapeutic target, and it is important to explore the rational development of its clinical exploitation.

Restoration of miR-648 overcomes 5-FU-resistance through targeting ET-1 in gastric cancer cells in-vitro

BACKGROUND

Endothelin-1 (ET-1) is a peptide overexpressed in gastric cancer (GC) and linked to carcinogenesis and resistance to chemotherapy. Applying microRNAs (miRNAs/miRs) to downregulate ET-1 and reverse resistance to commonly used chemotherapy drugs such as 5-fluorouracil (5-FU) is practical.

METHODS

The current study sought to evaluate the miR-648 expression in GC and any plausibility of its replacement, either with or without the combination of chemo agents to downregulate ET-1 expression through interaction with its target gene. To this end, miR-648 and ET-1 expression levels were assessed in GC tissues and adjacent non-tumor tissues driven from 65 patients who had already undergone surgery, fifteen of which had received 5-FU before surgery. The impact of miR-648 and chemo agents on ET-1 expression was measured using qPCR and Western blotting. Further, an MTT assay was conducted to assess its association with cell viability. Ultimately, the association of miR-648 and ET-1 with clinicopathological characteristics was evaluated.

RESULTS

The current study revealed that miR-648 was considerably down-regulated, while ET-1 was substantially up-regulated in patients with GC. The 5-FU caused a significant increase in miR-648 and reduced ET-1 expression. It was also determined that overexpression of miR-648 suppressed ET-1 production, notably when combined with 5-FU, leading to survival reduction. These results further showed that miR-648 replacement could sensitize chemoresistant GC cells. Besides, a significant association between ET-1 and miR-648 with clinicopathological features was discovered CONCLUSIONS: miR-648 replacement may serve as a potential oncosuppressive therapeutic approach that warrants further investigation to translate into an effective GC treatment.

miR-767-3p suppresses melanoma progression by inhibiting ASF1B expression

BACKGROUND

Melanoma, the type of skin cancer considered as most malignant, and known to be linked with a high incidence as well as high mortality rate. Although the dysregulation of ASF1B and miR-767-3p expression is involved in the progression of various cancers, their biological function in melanoma remains unclear.

METHODS

Real-time qPCR was the primary source for determining the levels of ASF1B and miR-767-3p in melanoma. For the validation of association among miR-767-3p and ASF1B, luciferase activity assay was used. Quantification of cell apoptosis, proliferation, migration and viability in melanoma cells were carried out by flow cytometry, BrdU, transwell assays, and CCK-8, respectively. Further evaluation of tumor growth was achieved by xenograft in vivo.

RESULTS

Results showed an increased expression of ASF1B while declined expression of miR-767-3p in melanoma. ASF1B knockdown repressed cell migration, viability, proliferation, and tumor growth whereas boosted apoptosis in A375 as well as in A875 melanoma cells. Moreover, miR-767-3p attenuated the migration and proliferation of melanoma cells and encouraged cell apoptosis by reducing ASF1B levels.

CONCLUSION

In this study, miR-767-3p was shown to inhibit ASF1B which will attenuate melanoma tumorigenesis, and by this it can be a potential new effective biomarker for the treatment of melanoma.

Alternative polyadenylation: An enigma of transcript length variation in health and disease

Alternative polyadenylation (APA) is a molecular mechanism during a pre-mRNA processing that involves usage of more than one polyadenylation site (PA-site) generating transcripts of varying length from a single gene. The location of a PA-site affects transcript length and coding potential of an mRNA contributing to both mRNA and protein diversification. This variation in the transcript length affects mRNA stability and translation, mRNA subcellular and tissue localization, and protein function. APA is now considered as an important regulatory mechanism in the pathophysiology of human diseases. An important consequence of the changes in the length of 3'-untranslated region (UTR) from disease-induced APA is altered protein expression. Yet, the relationship between 3'-UTR length and protein expression remains a paradox in a majority of diseases. Here, we review occurrence of APA, mechanism of PA-site selection, and consequences of transcript length variation in different diseases. Emerging evidence reveals coordinated involvement of core RNA processing factors including poly(A) polymerases in the PA-site selection in diseases-associated APAs. Targeting such APA regulators will be therapeutically significant in combating drug resistance in cancer and other complex diseases. This article is categorized under: RNA Processing > 3' End Processing RNA in Disease and Development > RNA in Disease Translation > Regulation.

Identification of a circRNA-miRNA-mRNA regulatory network for exploring novel therapeutic options for glioma

Background

Glioma is the most common brain neoplasm with a poor prognosis. Circular RNA (circRNA) and their associated competing endogenous RNA (ceRNA) network play critical roles in the pathogenesis of glioma. However, the alteration of the circRNA-miRNA-mRNA regulatory network and its correlation with glioma therapy haven't been systematically analyzed.

Methods

With GEO, GEPIA2, circBank, CSCD, CircInteractome, mirWalk 2.0, and mirDIP 4.1, we constructed a circRNA-miRNA-mRNA network in glioma. LASSO regression and multivariate Cox regression analysis established a hub mRNA signature to assess the prognosis. GSVA was used to estimate the immune infiltration level. Potential anti-glioma drugs were forecasted using the cMap database and evaluated with GSEA using GEO data.

Results

A ceRNA network of seven circRNAs (hsa_circ_0030788/0034182/0000227/ 0018086/0000229/0036592/0002765), 15 miRNAs(hsa-miR-1200/1205/1248/ 1303/3925-5p/5693/581/586/599/607/640/647/6867-5p/767-3p/935), and 46 mRNAs (including 11 hub genes of ARHGAP11A, DRP2, HNRNPA3, IGFBP5, IP6K2, KLF10, KPNA4, NRP2, PAIP1, RCN1, and SEMA5A) was constructed. Functional enrichment showed they influenced majority of the hallmarks of tumors. Eleven hub genes were proven to be decent prognostic signatures for glioma in both TCGA and CGGA datasets. Forty-six LASSO regression significant genes were closely related to immune infiltration. Finally, five compounds (fulvestrant, tanespimycin, mifepristone, tretinoin, and harman) were predicted as potential treatments for glioma. Among them, mifepristone and tretinoin were proven to inhibit the cell cycle and DNA repair in glioma.

Conclusion

This study highlights the potential pathogenesis of the circRNA-miRNA-mRNA regulatory network and identifies novel therapeutic options for glioma.

Mechanisms of temozolomide resistance in glioblastoma - a comprehensive review

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults and has an exceedingly low median overall survival of only 15 months. Current standard-of-care for GBM consists of gross total surgical resection followed by radiation with concurrent and adjuvant chemotherapy. Temozolomide (TMZ) is the first-choice chemotherapeutic agent in GBM; however, the development of resistance to TMZ often becomes the limiting factor in effective treatment. While O6-methylguanine-DNA methyltransferase repair activity and uniquely resistant populations of glioma stem cells are the most well-known contributors to TMZ resistance, many other molecular mechanisms have come to light in recent years. Key emerging mechanisms include the involvement of other DNA repair systems, aberrant signaling pathways, autophagy, epigenetic modifications, microRNAs, and extracellular vesicle production. This review aims to provide a comprehensive overview of the clinically relevant molecular mechanisms and their extensive interconnections to better inform efforts to combat TMZ resistance.

The regulation of protein translation and its implications for cancer

In addition to the deregulation of gene transcriptions and post-translational protein modifications, the aberrant translation from mRNAs to proteins plays an important role in the pathogenesis of various cancers. Targeting mRNA translation are expected to become potential approaches for anticancer treatments. Protein translation is affected by many factors including translation initiation factors and RNA-binding proteins. Recently, modifications of mRNAs mainly N6-methyladenine (m⁶A) modification and noncoding RNAs, such as microRNAs and long noncoding RNAs are involved. In this review, we generally summarized the recent advances on the regulation of protein translation by the interplay between mRNA modifications and ncRNAs. By doing so, we hope this review could offer some hints for the development of novel approaches in precision therapy of human cancers.

Non-Coding RNAs as Mediators of Epigenetic Changes in Malignancies

Non-coding RNAs (ncRNAs) are untranslated RNA molecules that regulate gene expressions. NcRNAs include small nuclear RNAs (snRNAs), small nucleolar RNAs (snoRNAs), ribosomal RNAs (rRNAs), transfer RNAs (tRNAs), circular RNAs (cRNAs) and piwi-interacting RNAs (piRNAs). This review focuses on two types of ncRNAs: microRNAs (miRNAs) or short interfering RNAs (siRNAs) and long non-coding RNAs (lncRNAs). We highlight the mechanisms by which miRNAs and lncRNAs impact the epigenome in the context of cancer. Both miRNAs and lncRNAs have the ability to interact with numerous epigenetic modifiers and transcription factors to influence gene expression. The aberrant expression of these ncRNAs is associated with the development and progression of tumors. The primary reason for their deregulated expression can be attributed to epigenetic alterations. Epigenetic alterations can cause the misregulation of ncRNAs. The experimental evidence indicated that most abnormally expressed ncRNAs impact cellular proliferation and apoptotic pathways, and such changes are cancer-dependent. In vitro and in vivo experiments show that, depending on the cancer type, either the upregulation or downregulation of ncRNAs can prevent the proliferation and progression of cancer. Therefore, a better understanding on how ncRNAs impact tumorigenesis could serve to develop new therapeutic treatments. Here, we review the involvement of ncRNAs in cancer epigenetics and highlight their use in clinical therapy.

Long noncoding RNA RP11-909N17.2 promotes proliferation, invasion, and migration of hepatocellular carcinoma by regulating microRNA-767-3p

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related deaths worldwide, especially in developing countries. Although advances in surgical procedures and targeted medicine have improved the overall survival of patients with HCC, the prognosis is poor. Hence, there is a need to identify novel therapeutic targets for HCC. Here, we report that the expression of RP11-909N17.2, a novel, long, noncoding RNA (lncRNA), is dysregulated in patients with HCC and cell lines. Additionally, this study demonstrated that RP11-909N17.2 facilitates the proliferation and invasion of HCC cells by binding to miRNA-767-3p, a tumor-suppressive microRNA (miRNA). Small integral membrane protein 7 (SMIM7) was identified as the downstream target of miRNA-767-3p. The expression of SMIM7 was upregulated in HCC clinical samples and cell lines. Moreover, SMIM7 was involved in the proliferation and invasion of HCC cells. Furthermore, SMIM7 inhibited the apoptosis of HCC cells, which indicated the oncogenic role of SMIM7 in HCC. The findings of this study suggest that the lncRNA-miRNA-mRNA regulatory axis, which regulates the pathogenesis of HCC, can be a potential novel diagnostic and therapeutic target for HCC.

Emerging Roles of RNA 3'-end Cleavage and Polyadenylation in Pathogenesis, Diagnosis and Therapy of Human Disorders

A crucial feature of gene expression involves RNA processing to produce 3′ ends through a process termed 3′ end cleavage and polyadenylation (CPA). This ensures the nascent RNA molecule can exit the nucleus and be translated to ultimately give rise to a protein which can execute a function. Further, alternative polyadenylation (APA) can produce distinct transcript isoforms, profoundly expanding the complexity of the transcriptome. CPA is carried out by multi-component protein complexes interacting with multiple RNA motifs and is tightly coupled to transcription, other steps of RNA processing, and even epigenetic modifications. CPA and APA contribute to the maintenance of a multitude of diverse physiological processes. It is therefore not surprising that disruptions of CPA and APA can lead to devastating disorders. Here, we review potential CPA and APA mechanisms involving both loss and gain of function that can have tremendous impacts on health and disease. Ultimately we highlight the emerging diagnostic and therapeutic potential CPA and APA offer.

Wide-ranging transcriptome remodelling mediated by alternative polyadenylation in response to abiotic stresses in Sorghum

Alternative polyadenylation (APA) regulates diverse developmental and physiological processes through its effects on gene expression, mRNA stability, translatability, and transport. Sorghum is a major cereal crop in the world and, despite its importance, not much is known about the role of post-transcriptional regulation in mediating responses to abiotic stresses in Sorghum. A genome-wide APA analysis unveiled widespread occurrence of APA in Sorghum in response to drought, heat, and salt stress. Abiotic stress treatments incited changes in poly(A) site choice in a large number of genes. Interestingly, abiotic stresses led to the re-directing of transcriptional output into non-productive pathways defined by the class of poly(A) site utilized. This result revealed APA to be part of a larger global response of Sorghum to abiotic stresses that involves the re-direction of transcriptional output into non-productive transcriptional and translational pathways. Large numbers of stress-inducible poly(A) sites could not be linked with known, annotated genes, suggestive of the existence of numerous unidentified genes whose expression is strongly regulated by abiotic stresses. Furthermore, we uncovered a novel stress-specific cis-element in intronic poly(A) sites used in drought- and heat-stressed plants that might play an important role in non-canonical poly(A) site choice in response to abiotic stresses.

RNA modifications in brain tumorigenesis

RNA modifications are emerging as critical regulators in cancer biology, thanks to their ability to influence gene expression and the predominant protein isoforms expressed during cell proliferation, migration, and other pro-oncogenic properties. The reversibility and dynamic nature of post-transcriptional RNA modifications allow cells to quickly adapt to microenvironmental changes. Recent literature has revealed that the deregulation of RNA modifications can promote a plethora of developmental diseases, including tumorigenesis. In this review, we will focus on four key post-transcriptional RNA modifications which have been identified as contributors to the pathogenesis of brain tumors: m6A, alternative polyadenylation, alternative splicing and adenosine to inosine modifications. In addition to the role of RNA modifications in brain tumor progression, we will also discuss potential opportunities to target these processes to improve the dismal prognosis for brain tumors.

The Role of miRNA for the Treatment of MGMT Unmethylated Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is the most common high-grade intracranial tumor in adults. It is characterized by uncontrolled proliferation, diffuse infiltration due to high invasive and migratory capacities, as well as intense resistance to chemo- and radiotherapy. With a five-year survival of less than 3% and an average survival rate of 12 months after diagnosis, GBM has become a focus of current research to urgently develop new therapeutic approaches in order to prolong survival of GBM patients. The methylation status of the promoter region of the O⁶-methylguanine–DNA methyltransferase (MGMT) is nowadays routinely analyzed since a methylated promoter region is beneficial for an effective response to temozolomide-based chemotherapy. Furthermore, several miRNAs were identified regulating MGMT expression, apart from promoter methylation, by degrading MGMT mRNA before protein translation. These miRNAs could be a promising innovative treatment approach to enhance Temozolomide (TMZ) sensitivity in MGMT unmethylated patients and to increase progression-free survival as well as long-term survival. In this review, the relevant miRNAs are systematically reviewed.

Screening of potential miRNA therapeutics for the prevention of multi-drug resistance in cancer cells

Chemotherapy, a major cancer treatment approach, suffers seriously from multidrug resistance (MDR), generally caused by innate DNA repair proteins that reverse the DNA modification by anti-cancer therapeutics or trans-membrane efflux proteins that pump anti-cancer therapeutics out of the cytosol. This project focused on finding microRNAs that can regulate MDR proteins by managing corresponding mRNA levels through post-transcriptional regulation based on nucleotide sequence matching. Screening was done with bioinformatics databases for unpublished/unexplored microRNAs with high nucleotide sequence correspondence to two representative MDR proteins, MGMT (a DNA repair protein) and ABCB1 (an efflux protein), revealing microRNA-4539 and microRNA-4261 respectively. To investigate the enhancement of chemotherapeutics in cancer cells, high MGMT expressing glioblastoma (T98G) and a high ABCB1 expressing triple-negative breast cancer cell line (MDA-MB-231-luc) were treated with varying concentrations of chemotherapeutics and corresponding miRNAs. Newly identified MDR-related miRNAs (MDRmiRs) enhanced the response to anti-cancer therapeutics and resulted in effective cell death. In this study, we demonstrated that therapeutic miRNAs could be identified based on the nucleotide sequence matching of miRNAs to targeted mRNA and the same approach could be employed for the screening of therapeutic candidates to regulate specific target proteins in diverse diseases.

The Impact of Surgery in IDH 1 Wild Type Glioblastoma in Relation With the MGMT Deregulation

Object: The treatment of choice in glioblastoma (GBM) is the maximal surgical extent of resection (EOR) followed by adjuvant chemo-radiotherapy. Furthermore, methylguanine-DNA methyltransferase (MGMT) promoter methylation is associated with prolonged overall survival (OS) and progression free survival (PFS). The objective of the present study is correlate the biomolecular aspects in relation with EOR.

Materials and methods: We analyzed a series of 116 patients with IDH-1 wild type GBM and different EOR (Gross Total Resection—GTR-, Partial Resection—PR- and Biopsy), treated with adjuvant chemo-radiotherapy. The MGMT status was analyzed in terms of promoter methylation and protein expression.

Results: When GTR was possible, OS and PFS were significantly better compared to the other two groups (p = 0.001 and p = 0.035, respectively). MGMT methylation was significantly associated with better OS in the biopsy group (p = 0.022) and better OS and PFS in PR (p = 0.02 and p = 0.012, respectively), but not in the GTR group (p = 0.252 for OS, p = 0.256 for PFS) nor the PFS in the biopsy group (p = 0.259). MGMT protein expression levels do not show any association with OS and PFS, regardless of the type of surgery.

Conclusions: Our study confirms the positive association of a safe maximal EOR with better OS and PFS, and indicates a positive prognostic value of MGMT methylation status only in case of the presence of residual tumor tissue. MGMT protein expression seems not to play a clinical role in relation with the type of surgery.

Comprehensive Analysis of Aberrantly Expressed Profiles of lncRNAs and miRNAs with Associated ceRNA Network in Lung Adenocarcinoma and Lung Squamous Cell Carcinoma

Lung cancer (LC) continues to be the leading cause of cancer-related deaths worldwide and the prognosis remains poor worldwide. At present, the long non-coding RNAs (lncRNAs) was considered as a part of competing endogenous RNA (ceRNA) network act as natural microRNA (miRNA) sponges to regulate protein-coding gene expression. However, functional roles of lncRNA-mediated ceRNAs in LC are insufficiently understood. To classify the specific mechanism of lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC), we comprehensively compared the expression profiles of mRNAs, lncRNAs and miRNAs obtained from 509 LUAD, 473 LUSC tissues and 49 adjacent non-cancerous lung tissues, based on The Cancer Genome Atlas (TCGA). After screening for differently expressed (DE) mRNAs, DEmiRNAs, DElncRNAs and weighted gene co-expression network analysis (WGCNA) (|log2FC| > 2.0 and an adjusted p value <0.05), a total of 4478 DEmRNAs, 526 DElncRNAs and 75 DEmiRNAs in LUAD, while 6237 DEmRNAs, 843 DElncRNAs and 117 DEmiRNAs in LUSC were discovered. Interaction (PPI) network analysis was performed to identify 656 nodes and 2987 edges (minimum required interaction score > 0.9), as well as 8 different protein-protein interactions. Gene ontology (GO) analysis mainly associated with cell proliferation. KEGG pathway enrichment analyses most partly associated with metabolism pathway and cytokine-cytokine receptor interaction. Finally, the dysregulated lncRNA-miRNA-ceRNA network was constructed based on correlation analyses and a total of 62 dysregulated lncRNAs, 28 DEmRNAs and 18 DEmiRNAs were involved. The most significant lncRNAs included DElncRNAs, LINC00641 and AC004947.2, miRNAs included miR-6860, miR-1285-3p, miR-767-3p and miR-7974, mRNAs included MAP3K3, FGD3 and ATP1B2. Then we analyzed and described the potential characteristics of biological function and pathological roles of the LUAD and LUSC ceRNA co-regulatory network. Our findings revealed ceRNA network will be beneficial for promoting the understanding of lncRNA-mediated ceRNA regulatory mechanisms in the pathogenesis of LUAD and LUSC.

Lnc-TALC promotes O6-methylguanine-DNA methyltransferase expression via regulating the c-Met pathway by competitively binding with miR-20b-3p

Long noncoding RNAs (lncRNAs) have emerged as new regulatory molecules implicated in diverse biological processes, including therapeutic resistance. However, the mechanisms underlying lncRNA-mediated temozolomide (TMZ) resistance in glioblastoma (GBM) remain largely unknown. To illustrate the role of lncRNA in TMZ resistance, we induce TMZ-resistant GBM cells, perform a lncRNA microarray of the parental and TMZ-resistant cells, and find an unreported lncRNA in GBM, lnc-TALC (temozolomide-associated lncRNA in glioblastoma recurrence), correlated with TMZ resistance via competitively binding miR-20b-3p to facilitate c-Met expression. A phosphorylated AKT/FOXO3 axis regulated lnc-TALC expression in TMZ-resistant GBM cells. Furthermore, lnc-TALC increased MGMT expression by mediating the acetylation of H3K9, H3K27 and H3K36 in MGMT promoter regions through the c-Met/Stat3/p300 axis. In clinical patients, lnc-TALC is required for TMZ resistance and GBM recurrence. Our results reveal that lnc-TALC in GBM could serve as a therapeutic target to overcome TMZ resistance, enhancing the clinical benefits of TMZ chemotherapy.

Temozolomide resistance in glioblastoma is associated with MGMT overexpression. Here, the authors identify a lncRNA that is a competitive endogenous RNA for miR-20b-3p, which causes c-Met activation to modulate acetylation of histone H3 on MGMT promoter through Stat3/p300 complex to increase MGMT expression and temozolomide resistance.

The Untranslated Regions of mRNAs in Cancer

The 5' and 3' untranslated regions (UTRs) regulate crucial aspects of post-transcriptional gene regulation that are necessary for the maintenance of cellular homeostasis. When these processes go awry through mutation or misexpression of certain regulatory elements, the subsequent deregulation of oncogenic gene expression can drive or enhance cancer pathogenesis. Although the number of known cancer-related mutations in UTR regulatory elements has recently increased markedly as a result of advances in whole-genome sequencing, little is known about how the majority of these genetic aberrations contribute functionally to disease. In this review we explore the regulatory functions of UTRs, how they are co-opted in cancer, new technologies to interrogate cancerous UTRs, and potential therapeutic opportunities stemming from these regions.

Alkylating anticancer agents and their relations to microRNAs

Alkylating agents represent an important class of anticancer drugs. The occurrence and emergence of tumor resistance to the treatment with alkylating agents denotes a severe problem in the clinics. A detailed understanding of the mechanisms of activity of alkylating drugs is essential in order to overcome drug resistance. In particular, the role of non-coding microRNAs concerning alkylating drug activity and resistance in various cancers is highlighted in this review. Both synthetic and natural alkylating agents, which are approved for cancer therapy, are discussed concerning their interplay with microRNAs.

MiR-21, miR-34a, miR-125b, miR-181d and miR-648 levels inversely correlate with MGMT and TP53 expression in primary glioblastoma patients

INTRODUCTION

TP53 and MGMT alterations play a crucial role in glioblastoma (GB) pathogenesis. TP53 and MGMT function is affected by several pathologic mechanisms, such as point mutations or promoter methylation, which are well characterized. Expression of both genes can be regulated by other mechanisms as well, e.g., microRNAs (miRNAs). Moreover, cross-talk among various pathologic processes may occur, further affecting MGMT and TP53 functionality.

MATERIAL AND METHODS

In 49 GB patients, we analyzed the possible associations between TP53 and its miRNA regulators miR-125b, miR-21, and miR-34a, as well as MGMT and its miRNA regulators miR-181d and miR-648. We evaluated the possible influence of mutational and methylation status on the pre-identified associations.

RESULTS

In patients with immunohistochemistry-detected TP53 overexpression, expression levels of miR-34a and TP53 were negatively correlated (r = -0.56, p = 0.0195), and in patients with TP53 mutations, expression levels of TP53 and miR-21 were negatively correlated (r = -0.67, p = 0.0330). In patients with MGMT methylation, expression levels of MGMT were negatively correlated with miR-648 and miR-125b expression levels (r = -0.61, p = 0.0269 and r = -0.34, p = 0.0727, respectively).

CONCLUSIONS

Our findings demonstrate that selected miRNAs are significantly correlated with MGMT and TP53 levels, but the extent of this correlation differs regarding the TP53 and MGMT mutational and promoter methylation status.

The surgical perspective in precision treatment of diffuse gliomas

Over the last decade, advances in molecular and imaging-based biomarkers have induced a more versatile diagnostic classification and prognostic evaluation of glioma patients. This, in combination with a growing therapeutic armamentarium, enables increasingly individualized, risk-benefit-optimized treatment strategies. This path to precision medicine in glioma patients requires surgical procedures to be reassessed within multidimensional management considerations. This article attempts to integrate the surgical intervention into a dynamic network of versatile diagnostic characterization, prognostic assessment, and multimodal treatment options in the light of the latest 2016 World Health Organization (WHO) classification of diffuse brain tumors, WHO grade II, III, and IV. Special focus is set on surgical aspects such as resectability, extent of resection, and targeted surgical strategies including minimal invasive stereotactic biopsy procedures, convection enhanced delivery, and photodynamic therapy. Moreover, the influence of recent advances in radiomics/radiogenimics on the process of surgical decision-making will be touched.

DNA damage repair alterations modulate M2 polarization of microglia to remodel the tumor microenvironment via the p53-mediated MDK expression in glioma

Background

DNA damage repair (DDR) alterations are important events in cancer initiation, progression, and therapeutic resistance. However, the involvement of DDR alterations in glioma malignancy needs further investigation. This study aims to characterize the clinical and molecular features of gliomas with DDR alterations and elucidate the biological process of DDR alterations that regulate the cross talk between gliomas and the tumor microenvironment.

Methods

Integrated transcriptomic and genomic analyses were undertaken to conduct a comprehensive investigation of the role of DDR alterations in glioma. The prognostic DDR-related cytokines were identified from multiple datasets. In vivo and in vitro experiments validated the role of p53, the key molecule of DDR, regulating M2 polarization of microglia in glioma.

Findings

DDR alterations are associated with clinical and molecular characteristics of glioma. Gliomas with DDR alterations exhibit distinct immune phenotypes, and immune cell types and cytokine processes. DDR-related cytokines have an unfavorable prognostic implication for GBM patients and are synergistic with DDR alterations. Overexpression of MDK mediated by p53, the key transcriptional factor in DDR pathways, remodels the GBM immunosuppressive microenvironment by promoting M2 polarization of microglia, suggesting a potential role of DDR in regulating the glioma microenvironment.

Interpretation

Our work suggests that DDR alterations significantly contribute to remodeling the glioma microenvironment via regulating the immune response and cytokine pathways.

Fund

This study was supported by: 1. The National Key Research and Development Plan (No. 2016YFC0902500); 2. National Natural Science Foundation of China (No. 81702972, No. 81874204, No. 81572701, No. 81772666); 3. China Postdoctoral Science Foundation (2018M640305); 4. Special Fund Project of Translational Medicine in the Chinese-Russian Medical Research Center (No. CR201812); 5. The Research Project of the Chinese Society of Neuro-oncology, CACA (CSNO-2016-MSD12); 6. The Research Project of the Health and Family Planning Commission of Heilongjiang Province (2017–201); and 7. Harbin Medical University Innovation Fund (2017LCZX37, 2017RWZX03).

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Gliomas with DNA damage repair alterations had distinct genomic variation spectrum.

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DDR alterations exhibit distinct immune phenotypes, cytokine processes and immune cell types in glioma.

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DDR-related cytokines in GME have an unfavorable prognostic implication for GBM patients.

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P53-mediated midkine expression derived from glioma cells promotes M2 polarization of microglia.

MiR-145-modulated SOX9-mediated hypospadias through acting on mitogen-activated protein kinase signaling pathway

This study primarily explored how miR-145, mitogen-activated protein kinase (MAPK) signaling and a downstream transcription factor (i.e., SOX9) mediated development of hypospadias. The hypospadias tissues and preputial tissues were isolated from pediatric inpatients postoperatively. Simultaneously, the rat models of hypospadias were established, and spermatogonial stem cells were separated. The expressions of proteins that symbolized cell apoptosis and oxidative stress were quantified via western blot analysis. Furthermore, the apoptosis, proliferation, and viability of cells were evaluated by means of flow cytometry, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and colony formation assays. The results of microarray indicated miR-145 as a differentially expressed biomarker between hypospadias tissues and normal tissues (p < 0.05). Moreover, rat models of hypospadias were observed with markedly lower vitamins A and E levels, reduced expressions of proteins relevant to oxidative stress (i.e., Nrf2, HO-1, Gpx, and SOD-1), as well as enhanced Bax and cleaved caspase-3 expressions ( p < 0.05). Furthermore, SOX9 was found to be targeted by miR-145, and it was also modified by phosphorylated extracellular-regulated kinase (p-ERK), a portion of MAPK signaling ( p < 0.05). The p-ERK was significantly regulated after altering the expression of miR-145 ( p < 0.05). Moreover, activation of p-ERK and transfection of pcDNA-SOX9 could cause higher expression of apoptins and larger apoptotic proportion of cells ( p < 0.05), yet transfection of miR-145 mimic led to improved cell apoptosis and depressed cell viability ( p < 0.05). In conclusion, SOX9, which was regulated by both miR-145 and miR-145/MAPK signaling, could be involved in the pathogenesis of hypospadias.

Alternative polyadenylation factors link cell cycle to migration

BACKGROUND

In response to a wound, fibroblasts are activated to migrate toward the wound, to proliferate and to contribute to the wound healing process. We hypothesize that changes in pre-mRNA processing occurring as fibroblasts enter the proliferative cell cycle are also important for promoting their migration.

RESULTS

RNA sequencing of fibroblasts induced into quiescence by contact inhibition reveals downregulation of genes involved in mRNA processing, including splicing and cleavage and polyadenylation factors. These genes also show differential exon use, especially increased intron retention in quiescent fibroblasts compared to proliferating fibroblasts. Mapping the 3' ends of transcripts reveals that longer transcripts from distal polyadenylation sites are more prevalent in quiescent fibroblasts and are associated with increased expression and transcript stabilization based on genome-wide transcript decay analysis. Analysis of dermal excisional wounds in mice reveals that proliferating cells adjacent to wounds express higher levels of cleavage and polyadenylation factors than quiescent fibroblasts in unwounded skin. Quiescent fibroblasts contain reduced levels of the cleavage and polyadenylation factor CstF-64. CstF-64 knockdown recapitulates changes in isoform selection and gene expression associated with quiescence, and results in slower migration.

CONCLUSIONS

Our findings support cleavage and polyadenylation factors as a link between cellular proliferation state and migration.

MiRNAs: dynamic regulators of immune cell functions in inflammation and cancer

MicroRNAs (miRNAs), small noncoding RNA molecules, have emerged as important regulators of almost all cellular processes. By binding to specific sequence motifs within the 3'- untranslated region of their target mRNAs, they induce either mRNA degradation or translational repression. In the human immune system, potent miRNAs and miRNA-clusters have been discovered, that exert pivotal roles in the regulation of gene expression. By targeting cellular signaling hubs, these so-called immuno-miRs have fundamental regulative impact on both innate and adaptive immune cells in health and disease. Importantly, they also act as mediators of tumor immune escape. Secreted by cancer cells and consecutively taken up by immune cells, immuno-miRs are capable to influence immune functions towards a blunted anti-tumor response, thus shaping a permissive tumor environment. This review provides an overview of immuno-miRs and their functional impact on individual immune cell entities. Further, implications of immuno-miRs in the amelioration of tumor surveillance are discussed.

Upregulation of miR-125b, miR-181d, and miR-221 Predicts Poor Prognosis in MGMT Promoter-Unmethylated Glioblastoma Patients

OBJECTIVES

To evaluate the prognostic values of microRNAs (miRNAs) in glioblastoma, and to see if there is an association between miRNAs and MGMT promoter methylation status.

METHODS

We collected paraffin blocks from resection specimens from 114 glioblastoma patients who had received temozolomide treatment and radiotherapy. Real-time quantitative PCR was performed to determine the expression levels of five miRNAs.

RESULTS

Upregulation of miR 125b-5p, miR 181d-3p, miR 221-3p, miR-222-3p, and miR 224-5p was observed in 13.2%, 5.3%, 12.3%, 32.5%, and 78.9% of the cases, respectively. The expression level of miRNAs was not significantly different in tumors with MGMT promoter methylation vs tumors without such methylation. Upregulation of miR 125b-5p, miR 181d-3p, or miR 221-3p was significantly associated with shorter survival in MGMT-unmethylated glioblastoma patients.

CONCLUSIONS

miR 125b-5p, miR 181d-3p, and miR 221-3p are useful in predicting poor prognosis in patients with MGMT-unmethylated glioblastomas.

Repair gene O6 -methylguanine-DNA methyltransferase is controlled by SP1 and up-regulated by glucocorticoids, but not by temozolomide and radiation

Therapy of malignant glioma relies on treatment with the O⁶ -methylating agent temozolomide (TMZ) concomitant with ionizing radiation followed by adjuvant TMZ. For the treatment of recurrences, DNA chloroethylating drugs are also used. The main killing lesion induced by these drugs is O⁶ -alkylguanine. Since this damage is repaired by O⁶ -methylguanine-DNA methyltransferase (MGMT), the repair enzyme represents a most important factor of drug resistance, limiting the therapy of malignant high-grade gliomas. Although MGMT has been shown to be transcriptionally up-regulated in rodents following genotoxic stress, it is still unclear whether human MGMT is subject to up-regulation. Here, we addressed the question whether MGMT in glioma cells is enhanced following alkylating drugs or ionizing radiation, using promoter assays. We also checked the response of glioma cell lines to dexamethasone. In a series of experiments, we found no evidence that the human MGMT promoter is significantly up-regulated following treatment with TMZ, the chloroethylating agent nimustine or radiation. It was activated, however, by dexamethasone. Using deletion constructs, we further show that the basal level of MGMT is mainly determined by the transcription factor SP1. The high amount of SP1 sites in the MGMT promoter likely prevents transcriptional up-regulation following genotoxic stress by neutralizing inducible signals. The regulation of MGMT by miRNAs plays only a minor role, as shown by DICER knockdown experiments. Since high dose dexamethasone concomitant with temozolomide is frequently used in glioblastoma therapy, induction of the MGMT gene through glucocorticoids in MGMT promoter unmethylated cases might cause further elevation of drug resistance, while radiation and alkylating drugs seem not to induce MGMT at transcriptional level.

The MGMT promoter single-nucleotide polymorphism rs1625649 had prognostic impact on patients with MGMT methylated glioblastoma

Promoter methylation is the most significant mechanism to regulate O6-methylguanine-DNA-methyltransferase (MGMT) expression. Single-nucleotide polymorphisms (SNPs) in the MGMT promoter region may also play a role. The aim of this study was to evaluate the clinical significance of SNPs in the MGMT promoter region of glioblastoma. Genomic DNAs from 118 glioblastomas were collected for polymerase chain reaction (PCR) amplification. Sanger sequencing was used to sequence the MGMT promoter region to detect SNPs. The results were correlated with MGMT status and patient survival. Rs1625649 was the only polymorphic SNP located at the MGMT promoter region in 37.5% of glioblastomas. Homozygous rs1625649 (AA genotype) was correlated with a higher MGMT methylation level and a lower protein expression, but the result was not statistically significant. In patients with MGMT methylated glioblastoma, cases with homozygous rs1625649 (AA genotype) were significantly associated with a lack of MGMT protein expression and a better progression-free survival (PFS) than the cases with wild type rs1625649 (CC genotype) or heterozygous rs1625649 (CA genotype). The survival impact was significant in multivariate analyses. In conclusion, the MGMT promoter homozygous rs1625649 (AA genotype) was found to correlate with a better PFS in patients with MGMT methylated glioblastoma.

Biomarkers and therapeutic advances in glioblastoma multiforme

Glioblastoma multiforme (GBM) is a malignant tumor within the brain. Generally classified as primary and secondary with several different subtypes, ample molecular biomarkers have risen throughout the years which have garnered the attention of researchers. The advancements in genomics and proteomics have allowed researchers to gather prominent molecular biomarkers. All these biomarkers are gathered by means of biopsy or bodily fluid sample collection and are quantitatively analyzed by polymerase chain reaction coupled with other computational technologies. This review highlights the significance, regulation and prevalence of molecular biomarkers such as O⁶ -methylguanine-DNA methyltransferase, epidermal growth factor receptor vIII, isocitrate dehydrogenase mutation and several others which expressed differently in different types and molecular subtypes of GBM. The discoveries and roles of GBM-specific microRNAs including miR-21 and miR-10b as biomarkers with promising prognostic values were also delineated. The role and mechanism of biomarkers in GBM tumorigenesis are essential in the development of therapy for patients suffering from the disease itself. Thus, this review also discusses the mechanisms, effects and limitations of therapy such as temozolomide, viral gene transfer, biomarker-based vaccines or even engineered T cells for more specific responses. Biomarkers have displayed a high value and could eventually be utilized as drug targets. It is hoped that by combining different aspects of the disease which present with different biomarkers could lead to the development of a robust, effective and innovative take on GBM therapy.

Cleavage and polyadenylation: Ending the message expands gene regulation

Cleavage and polyadenylation (pA) is a fundamental step that is required for the maturation of primary protein encoding transcripts into functional mRNAs that can be exported from the nucleus and translated in the cytoplasm. 3'end processing is dependent on the assembly of a multiprotein processing complex on the pA signals that reside in the pre-mRNAs. Most eukaryotic genes have multiple pA signals, resulting in alternative cleavage and polyadenylation (APA), a widespread phenomenon that is important to establish cell state and cell type specific transcriptomes. Here, we review how pA sites are recognized and comprehensively summarize how APA is regulated and creates mRNA isoform profiles that are characteristic for cell types, tissues, cellular states and disease.

RNA processing as an alternative route to attack glioblastoma

Genomic analyses have become an important tool to identify new avenues for therapy. This is especially true for cancer types with extremely poor outcomes, since our lack of effective therapies offers no tangible clinical starting point to build upon. The highly malignant brain tumor glioblastoma (GBM) exemplifies such a refractory cancer, with only 15 month average patient survival. Analyses of several hundred GBM samples compiled by the TCGA (The Cancer Genome Atlas) have produced an extensive transcriptomic map, identified prevalent chromosomal alterations, and defined important driver mutations. Unfortunately, clinical trials based on these results have not yet delivered an improvement on outcome. It is, therefore, necessary to characterize other regulatory routes known for playing a role in tumor relapse and response to treatment. Alternative splicing affects more than 90% of the human coding genes and it is an important source for transcript variation and gene regulation. Mutations and alterations in splicing factors are highly prevalent in multiple cancers, demonstrating the potential for splicing to act as a tumor driver. As a result, numerous genes are expressed as cancer-specific splicing isoforms that are functionally distinct from the canonical isoforms found in normal tissue. These include genes that regulate cancer-critical pathways such as apoptosis, DNA repair, cell proliferation, and migration. Splicing defects can even induce genomic instability, a common characteristic of cancer, and a driver of tumor evolution. Importantly, components of the splicing machinery are targetable; multiple drugs can inhibit splicing factors or promote changes in splicing which could be exploited to begin improving clinical outcomes. Here, we review the current literature and present a case for exploring RNA processing as therapeutic route for the treatment of GBM.

Intronic miRNA-641 controls its host Gene's pathway PI3K/AKT and this relationship is dysfunctional in glioblastoma multiforme

MicroRNAs have established their role as important regulators of the epigenome. A considerable number of human miRNA genes are found in intronic regions of protein-coding host genes, in many cases adopting their regulatory circuitry. However, emerging evidence foreshadows an unprecedented importance for this relationship: Intronic miRNAs may protect the cell from overactivation of the respective host pathway, a setting that may trigger tumor development. AKT2 is a well-known proto-oncogene central to the PI3K/AKT pathway. This pathway is known to promote tumor growth and survival, especially in glioblastoma. Its intronic miRNA, hsa-miR-641, is scarcely investigated, however. We hypothesized that miR-641 regulates its host AKT2 and that this regulation may become dysfunctional in glioblastoma. We found that indeed miR-641 expression differs significantly between GBM tissue and normal brain samples, and that transfection of glioma cells with miR-641 antagonizes the PI3K/AKT pathway. Combining clinical samples, cell cultures, and biomolecular methods, we could show that miR-641 doesn't affect AKT2's expression levels, but down-regulates kinases that are necessary for AKT2-activation, thereby affecting its functional state. We also identified NFAT5 as a miR-641 regulated central factor to trigger the expression of these kinases and subsequently activate AKT2. In summary, our study is the first that draws a connecting line between the proto-oncogene AKT2 and its intronic miRNA miR-641 with implication for glioblastoma development.

Expression of miR-944 in esophageal squamous cell carcinoma and its role in cell proliferation and invasion in human esophageal carcinoma cell line Eca109

AIM

To detect the expression of miRNA-944 in esophageal squamous cell carcinoma (ESCC), and to explore its role in cell proliferation and migration in human esophageal cancer cell line Eca109.

METHODS

ESCC and matched tumor adjacent noncancerous tissue samples were obtained from 36 patients who underwent surgical treatment and were pathologically diagnosed with ESCC. Real-time quantitative PCR (qRT-PCR) was used to detect the expression levels of miRNA-944, and the relationship between miRNA-944 and clinical and pathological parameters were then analyzed. Eca109 cells were transfected with miR-944 mimic, inhibitor and negative control using LipofectamineTM2000, and then the expression level of miR-944 was detected by qRT-PCR. Cell proliferation and invasion were assessed by MTT assay and transwell assay, respectively.

RESULTS

The expression level of miR-944 in ESCC tissues was significantly higher than that in tumor adjacent non-cancerous tissues (P < 0.01).The up-regulation of miR-944 expression in ESCC was correlated with advanced TNM stage (P < 0.01) and lymph node metastasis (P < 0.01). Compared to control cells, transfection of miR-944 mimic and inhibitor up- and down-regulated miR-944 expression in Eca109 cells, respectively (P < 0.01). Furthermore, transfection of miR-944 mimic enhanced cell proliferation and invasion, while transfection of miR-944 inhibitor inhibited cell proliferation and invasion (P < 0.01).

CONCLUSION

The expression of miR-944 is up-regulated in ESCC and associated with TNM stage and lymph node metastasis, indicating that miR-944 may facilitate ESCC occurrence possibly by promoting the proliferation and invasion of ESCC cells.

Inhibiting MicroRNA-503 and MicroRNA-181d with Losartan Ameliorates Diabetic Nephropathy in KKAy Mice

BACKGROUND Diabetic nephropathy (DN) is the most lethal diabetic microvascular complication; it is a major cause of renal failure, and an increasingly globally prominent healthcare problem. MATERIAL AND METHODS To identify susceptible microRNAs for the pathogenesis of DN and the targets of losartan treatment, microRNA arrays were employed to survey the glomerular microRNA expression profiles of KKAy mice treated with or without losartan. KKAy mice were assigned to either a losartan-treated group or a non-treatment group, with C57BL/6 mice used as a normal control. Twelve weeks after treatment, glomeruli from the mice were isolated. MicroRNA expression profiles were analyzed using microRNA arrays. Real-time PCR was used to confirm the results. RESULTS Losartan treatment improved albuminuria and the pathological lesions of KKAy mice. The expression of 10 microRNAs was higher, and the expression of 12 microRNAs was lower in the glomeruli of the KKAy untreated mice than that of the CL57BL/6 mice. The expression of 4 microRNAs was down-regulated in the glomeruli of the KKAy losartan-treated mice compared to that of the untreated mice. The expression of miRNA-503 and miRNA-181d was apparently higher in the glomeruli of the KKAy untreated mice, and was inhibited by losartan treatment. CONCLUSIONS The over-expression of miR-503 and miR-181d in glomeruli of KKAy mice may be responsible for the pathogenesis of DN and are potential therapeutic targets for DN.

Extensive miRNA expression analysis in craniopharyngiomas

PURPOSE

Craniopharyngiomas are benign tumors of the sellar or parasellar regions. They arise from the remnants of Rathke's pouch and are considered a "developmental disease." microRNAs are short non-coding RNAs that play a key regulatory role in the control of expression of entire gene networks. We performed an extensive analysis of miRNAs in craniopharyngiomas aiming to identify a miRNA expression signature that might aid in the prognosis of disease progression and outcome.

METHODS

Thirty-seven craniopharyngioma samples from twenty-three patients, ten age-matched controls from autopsy, and ten infant controls from the developing pituitary from autopsy were evaluated for the expression of 754 miRNAs using TaqMan® Low Density Arrays (TLDAs) v2.0 (Applied Biosystems, Foster City, CA).

RESULTS

Among the most differentially expressed miRNAs, downregulation of miR-132 appears to be a marker of aggressiveness and also plays a role in epithelial-mesenchymal transition.

CONCLUSIONS

This is the first time that an extensive study of miRNA expression has been performed in craniopharyngiomas. Further research needs to be performed to investigate the potential role of miR-132 in the development and progression of craniopharyngiomas, and its value as a prognostic marker of aggressiveness.

MGMT expression predicts response to temozolomide in pancreatic neuroendocrine tumors

Temozolomide (TEM) showed encouraging results in well-differentiated pancreatic neuroendocrine tumors (WDPNETs). Low O(6)-methylguanine-DNA methyltransferase (MGMT) expression and MGMT promoter methylation within tumors correlate with a better outcome under TEM-based chemotherapy in glioblastoma. We aimed to assess whether MGMT expression and MGMT promoter methylation could help predict the efficacy of TEM-based chemotherapy in patients with WDPNET. Consecutive patients with progressive WDPNET and/or liver involvement over 50% who received TEM between 2006 and 2012 were retrospectively studied. Tumor response was assessed according to Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 guidelines. Nuclear expression of MGMT was assessed by immunochemistry (H-score, 0-300) and MGMT promoter methylation by pyrosequencing. Forty-three patients (21 men, 58years (27-84)) with grade 1 WDPNET (n=6) or 2 (n=36) were analyzed. Objective response, stable disease, and progression rates were seen in 17 patients (39.5%), 18 patients (41.9%), and 8 patients (18.6%), respectively. Low MGMT expression (≤50) was associated with radiological objective response (P=0.04) and better progression-free survival (PFS) (HR=0.35 (0.15-0.81), P=0.01). Disease control rate at 18months of treatment remained satisfying with an MGMT score up to 100 (74%) but dropped with a higher expression. High MGMT promoter methylation was associated with a low MGMT expression and longer PFS (HR=0.37 (0.29-1.08), P=0.05). Low MGMT score (≤50) appears to predict an objective tumor response, whereas an intermediate MGMT score (50-100) seems to be associated with prolonged stable disease.

DNA repair mechanisms and their clinical impact in glioblastoma

Despite surgical resection and genotoxic treatment with ionizing radiation and the DNA alkylating agent temozolomide, glioblastoma remains one of the most lethal cancers, due in great part to the action of DNA repair mechanisms that drive resistance and tumor relapse. Understanding the molecular details of these mechanisms and identifying potential pharmacological targets have emerged as vital tasks to improve treatment. In this review, we introduce the various cellular systems and animal models that are used in studies of DNA repair in glioblastoma. We summarize recent progress in our knowledge of the pathways and factors involved in the removal of DNA lesions induced by ionizing radiation and temozolomide. We introduce the therapeutic strategies relying on DNA repair inhibitors that are currently being tested in vitro or in clinical trials, and present the challenges raised by drug delivery across the blood brain barrier as well as new opportunities in this field. Finally, we review the genetic and epigenetic alterations that help shape the DNA repair makeup of glioblastoma cells, and discuss their potential therapeutic impact and implications for personalized therapy.

miRNA array screening reveals cooperative MGMT-regulation between miR-181d-5p and miR-409-3p in glioblastoma

The levels of expression of O6-methylguanine-DNA methyltransferase (MGMT) are relevant in predicting the response to the alkylating chemotherapy in patients affected by glioblastoma. MGMT promoter methylation and the published MGMT regulating microRNAs (miRNAs) do not completely explain the expression pattern of MGMT in clinical glioblastoma specimens. Here we used a genome-wide microarray-based approach to identify MGMT regulating miRNAs. Our screen unveiled three novel MGMT regulating miRNAs, miR-127-3p, miR-409-3p, and miR-124-3p, in addition to the previously identified miR-181d-5p. Transfection of these three novel miRNAs into the T98G glioblastoma cell line suppressed MGMT mRNA and protein expression. However, their MGMT- suppressive effects are 30-50% relative that seen with miR-181d-5p transfection. In silico analyses of The Cancer Genome Atlas (TCGA) and Chinese Glioma Genome Atlas (CGGA) revealed that miR-181d-5p is the only miRNA that consistently exhibited inverse correlation with MGMT mRNA expression. However, statistical models incorporating both miR-181d-5p and miR-409-3p expression better predict MGMT expression relative to models involving either miRNA alone. Our results confirmed miR-181d-5p as the key MGMT-regulating miRNA. Other MGMT regulating miRNAs, including the miR-409-3p identified in this report, modify the effect of miR-181d-5p on MGMT expression. MGMT expression is, thus, regulated by cooperative interaction between key MGMT-regulating miRNAs.