Role of microRNAs in gliomagenesis: targeting miRNAs in glioblastoma multiforme therapy

Introduction: Gliomas consist of a very heterogeneous group of malignant tumors, accounting for 50 - 60% of primary brain tumors. Despite all the efforts of cytoreductive surgery in combination with intense chemoradiotherapy, glioblastoma multiforme (GBM, glioma grade IV) still has a dismal prognosis. Current research is focused on molecular targeting to overcome resistance to conventional therapy. MicroRNAs (miRNAs), small non-coding RNAs, represent endogenous agents of RNA interference, dramatically changing expression of target proteins. Their role in brain physiology as well as GBM development has attracted intense research efforts pointing toward therapeutic potential and immediate targeting for sensitization of glioma cells to chemo and/or radiotherapy. Areas covered: This review is focused on the variable role of miRNAs in gliomagenesis and their possible clinical relevance in patient's survival and prognosis. It further addresses the potential application of selected miRNAs as therapeutic targets or agents in GMB, including data from clinical studies in other central nervous system tumors. Expert opinion: Although miRNA-targeted therapy is still in its initial stage and clinical trials with glioma/brain tumor patients are under recruitment or currently running, several miRNAs have been selected as promising tumor biomarkers, with increased potential to reduce disease progression in combination to conventional first-line therapy for gliomas.     

Targeting multiple kinases in glioblastoma multiforme

Glioblastoma multiforme (GBM), the most common primary malignant brain tumor in adults, is associated with high mortality. Current standard-of-care treatments, including surgery, radiation and chemotherapy, offer only palliation. Recent research in cancer therapy has shifted towards targeting the specific molecular aberrations that underlie the pathogenesis of cancers including GBM. Protein kinases are a family of enzymes that are key components in regulating cellular homeostasis. Protein kinases can be deregulated by several mechanisms, which contribute to cancer initiation and maintenance. Several protein kinases are important in gliomagenesis, thus representing new therapeutic targets in GBM. Low molecular weight inhibitors are the most commonly used agents to target protein kinases in the treatment of cancers. However, first-generation kinase inhibitors targeting only single kinases have demonstrated limited efficacy in unselected GBM patient populations. Several mechanisms of failure of monotherapy with single-targeted kinase inhibitors have been explained as new therapeutic strategies have emerged to overcome resistance. Simultaneous disruption of several kinases can be achieved by either multitargeted kinase inhibitors or combination of single-targeted kinase inhibitors with one another or with traditional cytotoxics. In this review, we will discuss the current clinical status of targeted therapy in GBM and recent approaches to target multiple kinases in this devastating cancer.     

Boron neutron capture therapy for glioblastoma multiforme

Aim: Glioblastoma multiforme (GBM) is an incurable disease that can only be managed in a palliative way. The GBM accounts for approximately half of all newly diagnosed primary brain tumors with an incidence of 2–3 cases per 100,000 people each year. Surgery and radiation are the standard options for palliation, and whether there is a place for chemotherapy is still discussed. Boron neutron capture therapy (BNCT) is a promising and possibly curative method of treating GBM. The purpose of this article is to provide an updated review on the current management and future possibilities of treating GBM with BNCT.Method: Use was made of computerized searches and of checking cross-references of articles and book chapters.Results: The principle of BNCT uses the high ability of ¹⁰B to capture thermal neutrons and to disintegrate immediately into a He nucleus (-particle) and a Li nucleus. To reach a sufficient concentration of ¹⁰B in the malignant cells compared to the surrounding healthy tissue, ¹⁰B-carriers must be highly tumor-selective. At present, the ¹⁰B carriers boronophenylalanine (BPA) and sodium borocaptate (BSH) are used in clinical trials to perform BNCT.Conclusion: The BNCT is a promising and possibly curative method of treating GBM, but at present this procedure is far from perfect. Because of the lack of selectivity of the boron carriers, it appears so far that radiation toxicity limits the radiation dose, so that tumor damage is modest. Current investigations and developments are aimed at targeting the boron carriers to the tumor, in order to limit the damage to the healthy, surrounding tissue.     

上皮样胶质母细胞瘤临床病理分析

目的 探讨上皮样胶质母细胞瘤(epithelioid glioblastoma,Ep-GBM)的临床病理特征、免疫表型及鉴别诊断.方法 收集2011年1月至2019年11月安徽医科大学附属巢湖医院及郑州市第一人民医院4例Ep-GBM临床病理及影像学资料、观察其病理学形态及免疫表型,并复习相关文献,探讨Ep-GBM的病理诊断和鉴别诊断要点.结果 4例Ep-GBM中,男3例,女1例.4例均发生于颞叶,临床表现为头痛伴恶心、呕吐,言语不清,感觉及语言障碍.影像学多提示囊实性肿物,可见出血、坏死及水肿.肿瘤切面灰白色、灰红色或灰黄色,无明显界限,质软或韧,可见囊性变及出血.镜检见肿瘤细胞以上皮样细胞及横纹肌样细胞为主,含有多少不等经典型胶质母细胞瘤成分.免疫组化:4例Vim与GFAP均(+),3例PCK(+)、INI-1(+);2例S-100、EGFR(+);1例Syn(弱+).随访4、8、9、13个月,4例均死亡.结论 Ep-GBM为罕见的高级别胶质瘤,容易沿脑脊膜播散,其确诊需结合临床病理特征进行综合分析.     

Targeting miR-21 in glioma: a small RNA with big potential

Importance of the field: Glioma therapies have produced relatively small improvements over the past decade, highlighting an important need to identify novel ways to target this disease. Targeted therapies against single activated protein kinases have proven effective in some cancers including gastrointestinal stromal cancer and colon cancer, but not yet in gliomas where multiple pathways and targets may be involved. MicroRNAs are emerging as key regulators of multiple pathways involved in cancer development and progression and may become the next targeted therapies in glioma.

Areas covered in this review: This review covers the basics of microRNA biology and specifically focuses on the roles of miR-21 in glioma and its potential as target for glioma therapy.

What the reader will gain: This review will provide the reader with an in depth understanding of how miR-21 functions in glioma. We also review the current state of studies designed to specifically target miR-21 as a potential future therapeutic.

Take home message: Identifying novel targets for the treatment of glioma is critical for advancing the current state of the field. MicroRNAs provide a novel target; and in glioma, targeting miR-21 may have broad consequences for the tumor that make it an attractive potential therapeutic.     

Delivery of anti-microRNA-21 antisense-oligodeoxynucleotide using amphiphilic peptides for glioblastoma gene therapy

Inhibition of microRNA-21 (miR-21) has been shown to promote apoptosis of cancer cells and to reduce tumor size in glioblastoma. However, efficient carriers for antisense-oligodeoxynucleotide (antisense-ODN) against miR-21 have not yet been developed. In this study, the R3V6 peptide (R3V6) was evaluated as a carrier of antisense-ODN. In a gel retardation assay, R3V6 formed a complex with an antisense-ODN. The serum stability assay showed that R3V6 protected it from nucleases more efficiently than polyethylenimine (PEI; 25?kDa, PEI25k). A Renilla luciferase gene with a 3′-untranslated region (3′-UTR) recognizable by miR-21 (psiCHECK2-miR-21-UTR) was constructed for the antisense-ODN assay. psiCHECK2-miR-21-UTR expressed less Renilla luciferase in the cells with a higher level of miR-21 due to the effect of miR-21. In an in vitro transfection assay, the R3V6 peptide delivered anti-miR-21 antisense-ODN into cells more efficiently than PEI (25?kDa, PEI25k) and lipofectamine. As a result, antisense-ODN/R3V6 complex inhibited miR-21 and increased Renilla luciferase expression more efficiently than antisense-ODN/PEI25k or antisense-ODN/Lipofectamine complexes in both C6 and A172 glioblastoma cells. Furthermore, the antisense-ODN/R3V6 complexes reduced the level of miR-21 and induced apoptosis of glioblastoma cells. These results suggest that the R3V6 peptide may be a useful carrier of antisense-ODN for glioblastoma gene therapy.     

Therapeutic targeting of VEGF in the treatment of glioblastoma

Introduction: Glioblastoma (GBM) is the most common and aggressive type of primary malignant brain tumor in adults. Despite therapy with maximal safe surgical resection, radiation and temozolomide, prognosis remains poor at 14.6 months. Hence, there is an urgent need for developing novel therapeutic agents. In GBMs, the balance of angiogenic growth factors is skewed toward pro-angiogenesis and VEGF is identified as the key growth factor responsible for neovasculature. Targeting angiogenesis is hypothesized to arrest tumor growth and hence VEGF is an attractive therapeutic target.

Areas covered: The purpose of this review is to discuss VEGF pathway inhibitors, their efficacy as monotherapy or in combination with other drugs, the effects on the radiographic response/assessment for GBMs, mechanisms of resistance and associated biomarkers. A short summary of angiogenesis and of the biological characteristics of angiogenesis will also be provided to enhance the understanding of VEGF pathway inhibitors.

Expert opinion: Therapeutic targeting of VEGF has lead to improvements in progression-free survival in GBM patients without any change in the overall survival. VEGF-targeted therapy remains a promising therapeutic opportunity if improvements in biomarkers, imaging techniques and rational combination therapy are used to help advance the clinical efficacy of this approach.     

Therapeutic targeting of EGFR in malignant gliomas

Importance of the field: Despite the improved prognosis for many cancer patients, the survival of those with malignant gliomas (MGs) remains dismal. Even with aggressive intervention, including surgery, chemotherapy and radiotherapy, the overall 2-year survival rate is only 25% in the most optimistic series, and 5-year survival rates are consistently in the low single digits. Therefore, it is evident that novel therapeutic paradigms are necessary to overcome the inherent limitations of conventional treatments. EGFR gene overexpression can be found in 40 – 50% of patients with MGs, whereas its expression is very low in normal brain. Therapeutic targeting of EGFR has indicated clinical success in the treatment of MGs.

Areas covered in this review: The purpose of this review is to discuss the current status of several EGFR-targeted therapies in MGs patients and address the efficacy of these drugs as monotherapy or in combination with other drugs and/or treatments. We also emphasize the lessons learned and the future perspectives in the development of EGFR-targeted therapies for MGs.

What the reader will gain: A more comprehensive understanding of the molecular, structural and biological characteristics of EGFR and the mechanisms of action of EGFR-targeted antagonists will most likely contribute to the successful use of strategies of EGFR-targeted therapy in the clinic.

Take home message: Therapeutic targeting of EGFR include anti-EGFR mAbs, small-molecule EGFR tyrosine kinase inhibitors, peptide vaccination therapy and other therapeutic strategies. Each EGFR antagonist has its own advantages and limitations in terms of BBB crossing, ease of delivery, combination therapies and potential toxicity. Therefore, a multiple approach combining different agents that target EGFR signaling at multiple levels seems to have potential as future therapeutics for MGs, once the technical and safety issues unique to each of the approaches are overcome.     

Feasibility and toxicity of CCNU therapy in elderly patients with glioblastoma multiforme

In our institution, 103 glioblastoma multiforme (GBM) patients aged from 55 to 83 years were treated since November 1994 as follows. All patients underwent surgical intervention (gross total resection, n = 35; subtotal resection, n = 38; stereotactic biopsy, n = 30). Subsequently all patients were offered radiotherapy and chemotherapy with CCNU. Results were as follows: 101 patients started radiotherapy, 93 patients completed it (96% of the patients aged < 65 years and 85% of the patients > or =65 years). All patients received at least 1 cycle of chemotherapy (median 3 cycles). Chemotherapy-associated toxicity was generally mild, more pronounced in females and did not increase with age. Median time to progression was 10.5+/-3.2 months for the patients < 65 years and 5.1+/-1 months for patients > or =65 years. median overall survival was 17.5+/-3.8 months in patients < 65 years and 8.6+/-1 months in patients > or =65 years (p < 0.0001). In multivariate analysis, age and female sex remained independent prognostic factors. Our data indicate that a treatment concept including concomitant radio- and chemotherapy is feasible even in elderly patients with GBM.     

细胞载体靶向治疗研究进展

细胞具有归巢或迁移到特定组织或病理位点的能力,可用作基因、病毒等生物大分子药物靶向治疗的载体,细胞载体靶向治疗是一种新的治疗方法.本文介绍了细胞载体的特点、靶向治疗技术以及主要细胞载体在靶向治疗肿瘤及其他疾病中的研究进展.     

Therapeutic targeting of miRNAs in neuroblastoma

Importance of the field: Neuroblastomas arise from precursor cells of the sympathetic nervous system and are noted for highly heterogeneous clinical behavior. These tumors currently account for ～ 15% of all childhood cancer related deaths in spite of intensive multimodal chemotherapy and are a major problem in pediatric oncology. The identification of novel therapeutic targets is urgently required to reduce patient morbidity.

Areas covered in this review: The purpose of this article is to review and synthesize all of the rapidly expanding evidence for the contribution of microRNAs (miRNAs) in neuroblastoma aggressive disease pathogenesis, along with the prospect of using small RNAs as therapeutics.

What the reader will gain: The reader will obtain insight on the miRNAs that are dysregulated in neuroblastoma along with potential therapeutic strategies and the most promising targets.

Take home message: A number of miRNAs which are associated with aggressive disease pathogenesis in neuroblastoma patients have been demonstrated to contribute in major ways to cell proliferation rates, apoptosis, differentiation, invasiveness and tumor growth in vitro and in vivo. Directly or indirectly interfering with the function of these miRNAs may prove to be an important and novel form of therapy.     

Clinical impact of adjuvant chemotherapy in glioblastoma multiforme : a meta-analysis

BACKGROUND: A meta-analysis of chemotherapy for glioblastoma multiforme (GBM) was performed. We sought to update prior analyses by focusing exclusively on GBM, including new trials of novel treatments, assessing effectiveness of individual treatment categories and presenting data in a clinically useful format. METHODS: A search of MEDLINE and EMBASE was conducted for randomised controlled trials of chemotherapy in GBM. RESULTS: Relative risks (RRs) for survival in 16 trials comparing chemotherapy with no chemotherapy were 1.18 (95% CI 1.08, 1.30) at 6 months, 1.53 (95% CI 1.26, 1.86) at 12 months and 2.12 (95% CI 1.60, 2.80) at 24 months. Nitrosourea compounds, local therapy (e.g. carmustine [1,3-bis [2-chloroethyl]-1-nitrosourea] wafers) and temozolomide were all more effective than no chemotherapy. Absolute increases in survival at 6, 12 and 24 months were 11%, 8% and 1%, respectively, for nitrosourea compounds; 8%, 24% and 5%, respectively, for local therapy; and 4%, 15% and 17%, respectively, for temozolomide. Efficacy of local therapy and temozolomide peaked at 12 and 18 months, respectively. After 2 years, nitrosourea compounds no longer provided clinically relevant benefit (number needed-to-treat [NNT] = 100; effect size [ES] = 0.17 SD), local therapy had diminishing returns (NNT = 20) that remained clinically relevant (ES = 0.71 SD) and temozolomide continued to show good efficacy (NNT = 5.9; ES = 0.74 SD). Survival was not significantly improved with multi-agent versus single-agent nitrosourea-based therapy in five trials: 6-month RR 0.91 (95% CI 0.71, 1.16); 24-month RR 1.33 (95% CI 0.72, 2.46). CONCLUSION: Although nitrosourea compounds, local therapy and temozolomide are all effective in the treatment of GBM, local therapy and temozolomide may be associated with greater response, with clinically significant benefits extending to 24 months. The timing of peak benefits of local and temozolomide therapy suggests this combination may be more effective than single-agent chemotherapy and warrants further study.     

替莫唑胺治疗多形性胶质母细胞瘤的化疗耐药机制

胶质瘤约占原发性颅内肿瘤的50%以上,多形性胶质母细胞瘤(GBM)为WHOⅣ级胶质瘤,复发率高,5年生存率不到10%。化疗是GBM综合治疗中的重要一环,而替莫唑胺作为多形性胶质母细胞瘤基石化疗药物在临床广泛应用,然而因其化疗耐药性的存在,严重影响了治疗效果的进一步提高。本文针对目前胶质瘤化疗药物的主要耐药机制:多药耐药、DNA损伤修复机制、凋亡通路异常、胶质瘤干细胞学说等几个方面,结合替莫唑胺药理机制进行分析、总结,希望对提高替莫唑胺在多形性胶质母细胞瘤中的疗效有一定启示。     

In vitro evaluation of 225Ac‐DOTA‐substance P for targeted alpha therapy of glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most malignant form of brain tumors with dismal prognosis despite treatment by surgery combined with radiotherapy and chemotherapy. The neuropeptide Substance P (SP) is the physiological ligand of the neurokinin‐1 receptor, which is highly expressed in glioblastoma cells. Thus, SP represents a potential ligand for targeted alpha therapy. In this study, a protocol for the synthesis of SP labeled with the alpha emitter ²²⁵Ac was developed and binding affinity properties were determined. The effects of ²²⁵Ac‐DOTA‐SP were investigated on human glioblastoma cell lines (T98G, U87MG, U138MG) as well as GBM stem cells. A significant dose‐dependent reduction in cell viability was detected up to 6 days after treatment. Also, colony‐forming capacity was inhibited at the lower doses tested. In comparison, treatment with the conventional agent temozolomide showed higher cell viability and colony‐forming capacity. ²²⁵Ac‐DOTA‐SP treatment caused induction of late apoptosis pathways. Cells were arrested to G2/M‐phase upon treatment. Increasing doses and treatment time caused additional S‐phase arrest. Similar results were obtained using human glioblastoma stem cells, known to show radioresistance. Our data suggest that ²²⁵Ac‐DOTA‐SP is a promising compound for treatment of GBM.     

Cediranib: profile of a novel anti-angiogenic agent in patients with glioblastoma

Background: Treatment strategies targeting angiogenesis have revealed promising results in preclinical studies and early clinical trials in patients with glioblastomas. Objective: This review evaluates the preclinical and clinical data for cediranib (AZD2171), a potent oral inhibitor of the VEGF receptor tyrosine kinase. Methods: We summarize both preclinical and clinical data for cediranib, with a focus on the treatment of glioblastomas. Results/conclusion: Cediranib is an effective drug in patients with glioblastoma, acting through inhibition of angiogenesis and normalization of tumor vasculature. Reduction of vasogenic brain edema is a key component of its treatment effect in this patient population. The primary side effects of cediranib include fatigue, diarrhea and hypertension.     

Targeting microRNAs in epithelial-to-mesenchymal transition-induced cancer stem cells: therapeutic approaches in cancer

Introduction: Epithelial-to-mesenchymal transition (EMT) is a pathological phenomenon of cancer that confers tumor cells with increased cell motility, invasive and metastatic abilities with the acquisition of ‘cancer stem-like cell’ (CSC) phenotype. EMT endows tumor cells with intrinsic/acquired resistant phenotype at achievable doses of anticancer drugs and leads to tumor recurrence and progression. Besides the complex network of signaling pathways, microRNAs (miRNAs) are being evolved as a new player in the induction and regulation of EMT.

Areas covered: In this review article, the author has searched the PubMed and Google Scholar electronic databases for original research and review articles to gather current information on the association of EMT-induced CSCs with therapeutic resistance, tumor growth and metastasis, which are believed to be regulated by certain miRNAs.

Expert opinion: This review outlines not only the perspective on selective targeting of EMT-induced CSCs through altered expression of novel miRNAs and/or the use of conventional drugs that affect the levels of critical miRNAs but also the strategies on overcoming the drug resistance by interfering with EMT and modulating its associated pathways in CSCs that can be considered as potential therapeutic approaches toward eradicating the tumor recurrence and metastasis.     

胎盘来源microRNAs与子痫前期发病机制的研究进展

子痫前期是妊娠期间特有的疾病之一, 主要表现为妊娠20周后出现高血压并伴随有蛋白尿, 发病机制可能包括胎盘的异常形成及母体的炎症反应等过程。MicroRNAs是一种短链非编码RNA, 其作用是在转录水平上抑制下游靶基因的表达。一些研究提示microRNAs可作为潜在的生物学标志物评估疾病的发生发展及预后, 而胎盘来源的microRNAs的异常表达是否与子痫前期的发生、 发展密切相关仍存在争议。本文综述了胎盘来源的microRNAs与子痫前期发病机制的关系。     

DNA aptamers that target human glioblastoma multiforme cells overexpressing epidermal growth factor receptor variant III in vitro

Aim： Aptamers are oligonucleic acid or peptide molecules that bind to a specific target molecule in cells, thus may act as effective vehicles for drug or siRNA delivery. In this study we investigated the DNA aptamers that target human glioblastoma multiforme （GBM） cells overexpressing epidermal growth factor receptor variant III （EGFRvlII）, which was linked to radiation and chemotherapeutic resistance of this most aggressive brain tumor. Methods： A 73-mer ssDNA library containing molecules with 30 nt of random sequence flanked by two primer hybridization sites was chosen as the initial library. Cell systematic evolution of ligands by exponential enrichment （CelI-SELEX） method was used to select the DNA aptamers that target EGFRvlII. The binding affinity of the aptamers was measured using a cell-based biotin-avidin ELISA. Results： After 14 rounds of selection, four DNA aptamers （32, 41, 43, and 47） that specifically bound to the EGFRvlll-overexpressing human glioma U87A cells with K~ values of less than 100 nmol/L were discovered. These aptamers were able to distinguish the U87A cells from the negative control human glioma U87MG cells and HEK293 cells. Aptamer 32 specifically bound to the EGFRvlII protein with an affinity similar to the EGFR antibody （Kd values of aptamer 32 and the EGFR antibody were 0.62±0.04 and 0.32±0.01 nmol/L, respectively）, and this aptamer was localized in the cell nucleus. Conclusion： The DNA aptamers are promising molecular probes for the diagnosis and treatment of GBM.