MiR-26a enhances the radiosensitivity of glioblastoma multiforme cells through targeting of ataxia-telangiectasia mutated

miR-15a targets the HSP90 co-chaperone Morgana in chronic myeloid leukemia

Morgana is a ubiquitous HSP90 co-chaperone protein coded by the CHORDC1 gene. Morgana heterozygous mice develop with age a myeloid malignancy resembling human atypical myeloid leukemia (aCML), now renamed MDS/MPN with neutrophilia. Patients affected by this pathology exhibit low Morgana levels in the bone marrow (BM), suggesting that Morgana downregulation plays a causative role in the human malignancy. A decrease in Morgana expression levels is also evident in the BM of a subgroup of Philadelphia-positive (Ph+) chronic myeloid leukemia (CML) patients showing resistance or an incomplete response to imatinib. Despite the relevance of these data, the mechanism through which Morgana expression is downregulated in patients' bone marrow remains unclear. In this study, we investigated the possibility that Morgana expression is regulated by miRNAs and we demonstrated that Morgana is under the control of four miRNAs (miR-15a/b and miR-26a/b) and that miR-15a may account for Morgana downregulation in CML patients.

miRNAs mediate the impact of smoking on dental pulp stem cells via the p53 pathway

Cigarette smoke changes the genomic and epigenomic imprint of cells. In this study, we investigated the biological consequences of extended cigarette smoke exposure on dental pulp stem cells (DPSCs) and the potential roles of miRNAs. DPSCs were treated with various doses of cigarette smoke condensate (CSC) for up to 6 weeks. Cell proliferation, survival, migration, and differentiation were evaluated. Cytokine and miRNA expression were profiled. The results showed that extended exposure to CSC significantly impaired the regenerative capacity of the DPSCs. Bioinformatic analysis showed that the cell cycle pathway, cancer pathways (small cell lung cancer, pancreatic, colorectal, and prostate cancer), and pathways for TNF, TGF-β, p53, PI3K-Akt, mTOR, and ErbB signal transduction, were associated with altered miRNA profiles. In particular, 3 miRNAs has-miR-26a-5p, has-miR-26b-5p, and has-miR-29b-3p fine-tune the p53 and cell cycle signaling pathways to regulate DPSC cellular activities. The work indicated that miRNAs are promising targets to modulate stem cell regeneration and understanding miRNA-targeted genes and their associated pathways in smoking individuals have significant implications for disease control and prevention.

Pancreatic cancer cells hijack tumor suppressive microRNA-26a to promote radioresistance and potentiate tumor repopulation

Pancreatic cancer is one of the most lethal cancers with significant radioresistance and tumor repopulation after radiotherapy. As a type of short non-coding RNA that regulate various biological and pathological processes, miRNAs might play vital role in radioresistance. We found by miRNA sequencing that microRNA-26a (miR-26a) was upregulated in pancreatic cancer cells after radiation, and returned to normal state after a certain time. miR-26a was defined as a tumor suppressive miRNA by conventional tumor biology experiments. However, transient upregulation of miR-26a after radiation significantly promoted radioresistance, while stable overexpression inhibited radioresistance, highlighting the importance of molecular dynamic changes after treatment. Mechanically, transient upregulation of miR-26a promoted cell cycle arrest and DNA damage repair to promote radioresistance. Further experiments confirmed HMGA2 as the direct functional target, which is an oncogene but enhances radiosensitivity. Moreover, PTGS2 was also the target of miR-26a, which might potentiate tumor repopulation via delaying the synthesis of PGE2. Overall, this study revealed that transient upregulation of miR-26a after radiation promoted radioresistance and potentiated tumor repopulation, highlighting the importance of dynamic changes of molecules upon radiotherapy.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Differential Expression of ATM, NF-KB, PINK1 and Foxo3a in Radiation-Induced Basal Cell Carcinoma

Research in normal tissue radiobiology is in continuous progress to assess cellular response following ionizing radiation exposure especially linked to carcinogenesis risk. This was observed among patients with a history of radiotherapy of the scalp for ringworm who developed basal cell carcinoma (BCC). However, the involved mechanisms remain largely undefined. We performed a gene expression analysis of tumor biopsies and blood of radiation-induced BCC and sporadic patients using reverse transcription-quantitative PCR. Differences across groups were assessed by statistical analysis. Bioinformatic analyses were conducted using miRNet. We showed a significant overexpression of the FOXO3a, ATM, P65, TNF-α and PINK1 genes among radiation-induced BCCs compared to BCCs in sporadic patients. ATM expression level was correlated with FOXO3a. Based on receiver-operating characteristic curves, the differentially expressed genes could significantly discriminate between the two groups. Nevertheless, TNF-α and PINK1 blood expression showed no statistical differences between BCC groups. Bioinformatic analysis revealed that the candidate genes may represent putative targets for microRNAs in the skin. Our findings may yield clues as to the molecular mechanism involved in radiation-induced BCC, suggesting that deregulation of ATM-NF-kB signaling and PINK1 gene expression may contribute to BCC radiation carcinogenesis and that the analyzed genes could represent candidate radiation biomarkers associated with radiation-induced BCC.

The role of microRNA-induced apoptosis in diverse radioresistant cancers

Resistance to cancer radiotherapy is one of the biggest concerns for success in treating and preventing recurrent disease. Malignant tumors may develop when they block genetic mutations associated with apoptosis or abnormal expression of apoptosis; Tumor treatment may induce the expression of apoptosis-related genes to promote tumor cell apoptosis. MicroRNAs have been shown to contribute to forecasting prognosis, distinguishing between cancer subtypes, and affecting treatment outcomes in cancer. Constraining these miRNAs may be an attractive treatment strategy to help overcome radiation resistance. The delivery of these future treatments is still challenging due to the excess downstream targets that each miRNA can control. Understanding the role of miRNAs brings us one step closer to attaining patient treatment and improving patient outcomes. This review summarized the current information on the role of microRNA-induced apoptosis in determining the radiosensitivity of various cancers.

Epigenetic regulation of radioresistance: insights from preclinical and clinical studies

INTRODUCTION

Oftentimes, radiation therapy (RT) is ineffective due to the development of radioresistance (RR). However, studies have shown that targeting epigenetic modifiers to enhance radiosensitivity represents a promising direction of clinical investigation.

AREAS COVERED

This review discusses the mechanisms by which epigenetic modifiers alter radiosensitivity through dysregulation of MAPK-ERK and AKT-mTOR signaling. Finally, we discuss the clinical directions for targeting epigenetic modifiers and current radiology techniques used in the clinic.

METHODOLOGY

We searched PubMed and ScienceDirect databases from April 4^th, 2022 to October 18^th, 2022. We examined 226 papers related to radioresistance, epigenetics, MAPK, and PI3K/AKT/mTOR signaling. 194 papers were selected for this review. Keywords used for this search include, 'radioresistance,' 'radiosensitivity,' 'radiation,' 'radiotherapy,' 'particle radiation,' 'photon radiation,' 'epigenetic modifiers,' 'MAPK,' 'AKT,' 'mTOR,' 'cancer,' and 'PI3K.' We examined 41 papers related to clinical trials on the aforementioned topics. Outcomes of interest were safety, overall survival (OS), dose-limiting toxicities (DLT), progression-free survival (PFS), and maximum tolerated dose (MTD).

EXPERT OPINION

Current studies focusing on epigenetic mechanisms of RR strongly support the use of targeting epigenetic modifiers as adjuvants to standard cancer therapies. To further the success of such treatments and their clinical benefit , both preclinical and clinical studies are needed to broaden the scope of known radioresistant mechanisms.

Involvement of Non-Coding RNAs in Chemo- and Radioresistance of Nasopharyngeal Carcinoma

The crucial treatment for nasopharyngeal carcinoma (NPC) is radiation therapy supplemented by chemotherapy. However, long-term radiation therapy can cause some genetic and proteomic changes to produce radiation resistance, leading to tumour recurrence and poor prognosis. Therefore, the search for new markers that can overcome the resistance of tumor cells to drugs and radiotherapy and improve the sensitivity of tumor cells to drugs and radiotherapy is one of the most important goals of pharmacogenomics and cancer research, which is important for predicting treatment response and prognosis. Non-coding RNAs (ncRNAs), such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), may play important roles in regulating chemo- and radiation resistance in nasopharyngeal carcinoma by controlling the cell cycle, proliferation, apoptosis, and DNA damage repair, as well as other signalling pathways. Recent research has suggested that selective modulation of ncRNA activity can improve the response to chemotherapy and radiotherapy, providing an innovative antitumour approach based on ncRNA-related gene therapy. Therefore, ncRNAs can serve as biomarkers for tumour prediction and prognosis, play a role in overcoming drug resistance and radiation resistance in NPC, and can also serve as targets for developing new therapeutic strategies. In this review, we discuss the involvement of ncRNAs in chemotherapy and radiation resistance in NPC. The effects of these molecules on predicting therapeutic cancer are highlighted.

The Role of RNA in DNA Breaks, Repair and Chromosomal Rearrangements

Incorrect reparation of DNA double-strand breaks (DSB) leading to chromosomal rearrangements is one of oncogenesis's primary causes. Recently published data elucidate the key role of various types of RNA in DSB formation, recognition and repair. With growing interest in RNA biology, increasing RNAs are classified as crucial at the different stages of the main pathways of DSB repair in eukaryotic cells: nonhomologous end joining (NHEJ) and homology-directed repair (HDR). Gene mutations or variation in expression levels of such RNAs can lead to local DNA repair defects, increasing the chromosome aberration frequency. Moreover, it was demonstrated that some RNAs could stimulate long-range chromosomal rearrangements. In this review, we discuss recent evidence demonstrating the role of various RNAs in DSB formation and repair. We also consider how RNA may mediate certain chromosomal rearrangements in a sequence-specific manner.

Glioblastoma and MiRNAs

Glioblastoma (GB) is one of the most common types of lethal brain tumors. Although several treatment options are available including surgery, along with adjuvant chemo and radiotherapy, the disease has a poor prognosis and patients generally die within 14 months of diagnosis. GB is chemo and radio resistant. Thus, there is a critical need for new insights into GB treatment to increase the chance of therapeutic success. This is why microRNA (miRNA) is being potentially considered in the diagnosis and treatment of glioblastoma. The objective of our review is to provide a holistic picture of GB up-regulated and down-regulated miRNA, in relationship with the expression of other genes, cell signaling pathways, and their role in GB diagnosis and treatment. MiRNA treatment is being considered to be used against GB together with radiotherapy and chemotherapy. Moreover, the use of miRNA as a diagnostic tool has also begun. Knowing that miRNAs are isolated in almost all human body fluids and that there are more than 3000 miRNAs in the human genome, plus the fact that each miRNA controls hundreds of different mRNAs, there is still much study needed to explore how miRNAs relate to GB for its proliferation, progression, and inhibition.

Exosomes and exosomal microRNA in non-targeted radiation bystander and abscopal effects in the central nervous system

Localized cranial radiotherapy is a dominant treatment for brain cancers. After being subjected to radiation, the central nervous system (CNS) exhibits targeted effects as well as non-targeted radiation bystander effects (RIBE) and abscopal effects (RIAE). Radiation-induced targeted effects in the CNS include autophagy and various changes in tumor cells due to radiation sensitivity, which can be regulated by microRNAs. Non-targeted radiation effects are mainly induced by gap junctional communication between cells, exosomes containing microRNAs can be transduced by intracellular endocytosis to regulate RIBE and RIAE. In this review, we discuss the involvement of microRNAs in radiation-induced targeted effects, as well as exosomes and/or exosomal microRNAs in non-targeted radiation effects in the CNS. As a target pathway, we also discuss the Akt pathway which is regulated by microRNAs, exosomes, and/or exosomal microRNAs in radiation-induced targeted effects and RIBE in CNS tumor cells. As the CNS-derived exosomes can cross the blood-brain-barrier (BBB) into the bloodstream and be isolated from peripheral blood, exosomes and exosomal microRNAs can emerge as promising minimally invasive biomarkers and therapeutic targets for radiation-induced targeted and non-targeted effects in the CNS.

The Role of Exosomes in Stemness and Neurodegenerative Diseases-Chemoresistant-Cancer Therapeutics and Phytochemicals

Exosomes exhibit a wide range of biological properties and functions in the living organisms. They are nanometric vehicles and used for delivering drugs, as they are biocompatible and minimally immunogenic. Exosomal secretions derived from cancer cells contribute to metastasis, immortality, angiogenesis, tissue invasion, stemness and chemo/radio-resistance. Exosome-derived microRNAs (miRNAs) and long non-coding RNAs (lnc RNAs) are involved in the pathophysiology of cancers and neurodegenerative diseases. For instance, exosomes derived from mesenchymal stromal cells, astrocytes, macrophages, and acute myeloid leukemia (AML) cells are involved in the cancer progression and stemness as they induce chemotherapeutic drug resistance in several cancer cells. This review covered the recent research advances in understanding the role of exosomes in cancer progression, metastasis, angiogenesis, stemness and drug resistance by illustrating the modulatory effects of exosomal cargo (ex. miRNA, lncRNAs, etc.) on cell signaling pathways involved in cancer progression and cancer stem cell growth and development. Recent reports have implicated exosomes even in the treatment of several cancers. For instance, exosomes-loaded with novel anti-cancer drugs such as phytochemicals, tumor-targeting proteins, anticancer peptides, nucleic acids are known to interfere with drug resistance pathways in several cancer cell lines. In addition, this review depicted the need to develop exosome-based novel diagnostic biomarkers for early detection of cancers and neurodegenerative disease. Furthermore, the role of exosomes in stroke and oxidative stress-mediated neurodegenerative diseases including Alzheimer’s disease (AD), and Parkinson’s disease (PD) is also discussed in this article.

Regulation of DNA Damage Response and Homologous Recombination Repair by microRNA in Human Cells Exposed to Ionizing Radiation

Ionizing radiation may be of both artificial and natural origin and causes cellular damage in living organisms. Radioactive isotopes have been used significantly in cancer therapy for many years. The formation of DNA double-strand breaks (DSBs) is the most dangerous effect of ionizing radiation on the cellular level. After irradiation, cells activate a DNA damage response, the molecular path that determines the fate of the cell. As an important element of this, homologous recombination repair is a crucial pathway for the error-free repair of DNA lesions. All components of DNA damage response are regulated by specific microRNAs. MicroRNAs are single-stranded short noncoding RNAs of 20–25 nt in length. They are directly involved in the regulation of gene expression by repressing translation or by cleaving target mRNA. In the present review, we analyze the biological mechanisms by which miRNAs regulate cell response to ionizing radiation-induced double-stranded breaks with an emphasis on DNA repair by homologous recombination, and its main component, the RAD51 recombinase. On the other hand, we discuss the ability of DNA damage response proteins to launch particular miRNA expression and modulate the course of this process. A full understanding of cell response processes to radiation-induced DNA damage will allow us to develop new and more effective methods of ionizing radiation therapy for cancers, and may help to develop methods for preventing the harmful effects of ionizing radiation on healthy organisms.

Non-Coding RNAs in Cancer Radiosensitivity: MicroRNAs and lncRNAs as Regulators of Radiation-Induced Signaling Pathways

Radiotherapy is a cancer treatment that applies high doses of ionizing radiation to induce cell death, mainly by triggering DNA double-strand breaks. The outcome of radiotherapy greatly depends on radiosensitivity of cancer cells, which is determined by multiple proteins and cellular processes. In this review, we summarize current knowledge on the role of microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), in determining the response to radiation. Non-coding RNAs modulate ionizing radiation response by targeting key signaling pathways, including DNA damage repair, apoptosis, glycolysis, cell cycle arrest, and autophagy. Additionally, we indicate miRNAs and lncRNAs that upon overexpression or inhibition alter cellular radiosensitivity. Current data indicate the potential of using specific non-coding RNAs as modulators of cellular radiosensitivity to improve outcome of radiotherapy.

MicroRNAs, DNA damage response and ageing

Ageing is a multifactorial and integrated gradual deterioration affecting the most of biological process of cells. MiRNAs are differentially expressed in the cellular senescence and play important role in regulating of genes expression involved in features of ageing. The perception of miRNAs functions in ageing regulation can be useful in clarifying the mechanisms underlying ageing and designing of therapeutic strategies. The preservation of genomic integrity through DNA damage response (DDR) is related to the process of cellular senescence. The recent studies have shown that miRNAs has directly regulated the expression of numerous proteins in DDR pathways. In this review study, DDR pathways, miRNA biogenesis and functions, current finding on DDR regulations, molecular biology of ageing and the role of miRNAs in these processes have been studied. Finally, a brief explanation about the therapeutic function of miRNAs in ageing regarding its regulation of DDR has been provided.

microRNAs Orchestrate Pathophysiology of Breast Cancer Brain Metastasis: Advances in Therapy

Brain metastasis (BM) predominantly occurs in triple-negative (TN) and epidermal growth factor 2 (HER2)-positive breast cancer (BC) patients, and currently, there is an unmet need for the treatment of these patients. BM is a complex process that is regulated by the formation of a metastatic niche. A better understanding of the brain metastatic processes and the crosstalk between cancer cells and brain microenvironment is essential for designing a novel therapeutic approach. In this context, the aberrant expression of miRNA has been shown to be associated with BM. These non-coding RNAs/miRNAs regulate metastasis through modulating the formation of a metastatic niche and metabolic reprogramming via regulation of their target genes. However, the role of miRNA in breast cancer brain metastasis (BCBM) is poorly explored. Thus, identification and understanding of miRNAs in the pathobiology of BCBM may identify a novel candidate miRNA for the early diagnosis and prevention of this devastating process. In this review, we focus on understanding the role of candidate miRNAs in the regulation of BC brain metastatic processes as well as designing novel miRNA-based therapeutic strategies for BCBM.

miR-26a attenuates cardiac apoptosis and fibrosis by targeting ataxia-telangiectasia mutated in myocardial infarction

Apoptosis and fibrosis play a vital role in myocardial infarction (MI) induced tissue injury. Although microRNAs have been the focus of many studies on cardiac apoptosis and fibrosis in MI, the detailed effects of miR-26a is needed to further understood. The present study demonstrated that miR-26a was downregulated in ST-elevation MI (STEMI) patients and oxygen-glucose deprivation (OGD)-treated H9c2 cells. Downregulation of miR-26a was closely correlated with the increased expression of creatine kinase, creatine kinase-MB and troponin I in STEMI patients. Further analysis identified that ataxia-telangiectasia mutated (ATM) was a target gene for miR-26a based on a bioinformatics analysis. miR-26a overexpression effectively reduced ATM expression, apoptosis, and apoptosis-related proteins in OGD-treated H9c2 cells. In a mouse model of MI, the expression of miR-26a was significantly decreased in the infarct zone of the heart, whereas apoptosis and ATM expression were increased. miR-26a overexpression effectively reduced ATM expression and cardiac apoptosis at Day 1 after MI. Furthermore, we demonstrated that overexpression of miR-26a improved cardiac function and reduced cardiac fibrosis by the reduced expression of collagen type I and connective tissue growth factor (CTGF) in mice at Day 14 after MI. Overexpression of miR-26a or ATM knockdown decreased collagen I and CTGF expression in cultured OGD-treated cardiomyocytes. Taken together, these data demonstrate a prominent role for miR-26a in linking ATM expression to ischemia-induced apoptosis and fibrosis, key features of MI progression. miR-26a reduced MI development by affecting ATM expression and could be targeted in the treatment of MI.

Deregulated MicroRNA Signature Following Glioblastoma Irradiation

Glioblastoma (GBM), the most common and aggressive brain tumor in adults, shows resistance to treatment, particularly radiotherapy. One method for effective treatment is using a group of radiosensitizers that make tumor cells responsive to radiotherapy. A class of molecules whose expression is affected by radiotherapy is the microRNAs (miRNAs) that present promising regulators of the radioresponse. Eighteen miRNAs (miR-26a, -124, -128, -135b, -145, -153, -181a/b, -203, -21, -210, -212, -221/222, -223, -224, -320, and -590), involved in the pathogenesis of GBM and its radioresponsive state, were reviewed to identify their role in GBM and their potential as radiosensitizing agents. MicroRNAs-26a, -124, -128, -145, -153, -181a/b, -203, -221/222, -223, -224, -320, and -590 promoted GBM radiosensitivity, while microRNAs-135b, -21, -210, and -212 encouraged radioresistance. Ectopic overexpression of the radiosensitivity promoting miRNAs and knockdown of the radioresistant miRNAs represent a prospective radiotherapy enhancement opportunity. This offers a glimmer of hope for a group of the most unfortunate patients known to medicine.

microRNAs: Potential glioblastoma radiosensitizer by targeting radiation-related molecular pathways

Glioblastoma (GBM) is the most lethal type of primary brain tumor. Currently, even with optimal and multimodal cancer therapies, the survival rate of GBM patients remains poor. One reason for inadequate response of GBM tumors to radiotherapy is radioresistance (RR). Thus, there is a critical need for new insights about GBM treatment to increase the chance of treatment. microRNAs (miRNAs) are important regulatory molecules that can effectively control GBM radiosensitivity (RS) by affecting radiation-related signal transduction pathways such as apoptosis, proliferation, DNA repair and cell cycle regulation. miRNAs provide new clinical perspectives for developing effective GBM treatments. A growing body of literature has demonstrated that GBM RS can be modified by modulating the expression of miRNAs such as miR-7, miR-10b, miR-124, miR-128, miR-320, miR-21, miR-203, and miR-153. This paper highlights the miRNAs and the underlying molecular mechanisms that are involved in the RS of GBM. Besides highlighting the role of miRNAs in different signaling pathways, we explain the mechanisms that affect RS of GBM for modulating radiation response at the clinical level.

Aberrant miRNAs Regulate the Biological Hallmarks of Glioblastoma

GBM is the highest incidence in primary intracranial malignancy, and it remains poor prognosis even though the patient is gave standard treatment. Despite decades of intense research, the complex biology of GBM remains elusive. In view of eight hallmarks of cancer which were proposed in 2011, studies related to the eight biological capabilities in GBM have made great progress. From these studies, it can be inferred that miRs, as a mode of post-transcriptional regulation, are involved in regulating these malignant biological hallmarks of GBM. Herein, we discuss state-of-the-art research on how aberrant miRs modulate the eight hallmarks of GBM. The upregulation of 'oncomiRs' or the genetic loss of tumor suppressor miRs is associated with these eight biological capabilities acquired during GBM formation. Furthermore, we also discuss the applicable clinical potential of these research results. MiRs may aid in the diagnosis and prognosis of GBM. Moreover, miRs are also therapeutic targets of GBM. These studies will develop and improve precision medicine for GBM in the future.

[MicroRNA-26a and Tumor]

微小RNA（microRNAs, miRNAs）是一类由20个-22个核苷酸组成的小片段非编码RNA，通过靶向结合基因mRNA的3’非翻译区（3’-UTR）调控其表达。许多研究报道miRNAs参与肿瘤的发生发展。MiR-26a在不同的肿瘤中发挥不同的作用，在肿瘤增殖、转移侵袭、血管形成、生物代谢及诊断预后中都有作用。本文就miR-26a与肿瘤关系的研究进展进行综述。

miR‑328‑3p enhances the radiosensitivity of osteosarcoma and regulates apoptosis and cell viability via H2AX

Osteosarcoma is a kind of high-risk sarcoma of the skeleton typically observed in people under 25 years old. Currently, radiotherapy is widely applied in cancer treatment. However, osteosarcoma is radioresistant and accordingly new, more effective radiosensitizers are needed. miRNAs have been reported to play an important role in osteosarcoma radiosensitivity. We examined the modulating effect of miR-328-3p in vivo and in vitro. miR-328-3p was downregulated in HOS-2R cells. The overexpression of miR-328-3p enhanced the radiosensitivity of osteosarcoma cells. miR-328-3p inhibited proliferation and promoted apoptosis in osteosarcoma cells under radiation conditions. In cells overexpressing miR-328-3p, H2AX expression was downregulated. We found that miR-328-3p targets H2AX and inhibits its expression. It was concluded, that miR-328-3p enhances the radiosensitization of osteosarcoma following X-ray irradiation, and determined that it directly targets H2AX to regulate radiosensitization.

Targeting MicroRNAs in Prostate Cancer Radiotherapy

Radiotherapy is one of the most important treatment options for localized early-stage or advanced-stage prostate cancer (CaP). Radioresistance (relapse after radiotherapy) is a major challenge for the current radiotherapy. There is great interest in investigating mechanisms of radioresistance and developing novel treatment strategies to overcome radioresistance. MicroRNAs (miRNAs) are small, non-coding RNAs that regulate gene expression at the post-transcriptional level, participating in numerous physiological and pathological processes including cancer invasion, progression, metastasis and therapeutic resistance. Emerging evidence indicates that miRNAs play a critical role in the modulation of key cellular pathways that mediate response to radiation, influencing the radiosensitivity of the cancer cells through interplaying with other biological processes such as cell cycle checkpoints, apoptosis, autophagy, epithelial-mesenchymal transition and cancer stem cells. Here, we summarize several important miRNAs in CaP radiation response and then discuss the regulation of the major signalling pathways and biological processes by miRNAs in CaP radiotherapy. Finally, we emphasize on microRNAs as potential predictive biomarkers and/or therapeutic targets to improve CaP radiosensitivity.

MicroRNA-590-3p enhances the radioresistance in glioblastoma cells by targeting LRIG1

microRNA (miR)-590 has been found to serve potential roles in cancer development; however, the expression and function of miR-590 in human gliomas remains to be elucidated. The present study aimed to investigate the expression of miR-590 in human glioma tissues and radioresistant human glioblastoma cells (U251R), and to determine the effect and related molecular mechanism of miR-590-3p on the radiosensitivity of U251R cells in vitro. The results from reverse transcription-quantitative polymerase chain reaction indicated that miR-590-3p was upregulated in human glioma tissues and radioresistant human glioblastoma cells, and that miR-590-3p expression was higher in high grade than in low grade gliomas. In vitro experiments revealed that the miR-590-3p inhibitor enhanced the radiosensitivity of U251R cells by suppressing cell viability, decreasing colony formation capacity and increasing cell apoptosis rate, as demonstrated by MTT, colony formation and flow cytometry analyses. A luciferase reporter assay demonstrated that leucine-rich repeats and immunoglobulin-like domains protein 1 (LRIG1) was a direct target of miR-590-3p. Furthermore, it was demonstrated that the effect of miR-590-3p suppression on cell viability, colony formation capacity and cell apoptosis rate was attenuated by the knockdown of LRIG1 in the U251R cells. In conclusion, the present study revealed that miR-590-3p was upregulated in human glioma tissues and radioresistant human glioblastoma cells, and miR-590-3p contributes to the radioresistance of human glioblastoma cells by directly targeting LRIG1. These findings may provide potential therapeutic strategies to prevent radioresistance in human gliomas.

MicroRNA‑210 negatively regulates the radiosensitivity of nasopharyngeal carcinoma cells

Radiotherapy is one of the primary methods of treatment of malignant tumors, however, resistance to radiation is a major problem. The reasons for the radioresistance are still poorly understood. However, it is generally accepted that microRNAs (miRNAs or miRs) can regulate the radiosensitivity of tumors. The present study therefore aimed to identify specific miRNAs and their effects on radioresistant cells. More specifically, the aim was to investigate specific miRNAs and their effects on radioresistant tumor cells. The radioresistant tumor cells (CNE‑2R) were established using a dose gradient method, and the miRNA expression profiles of CNE‑2R cells and the parental cells (CNE‑2) were determined. The expression of miR‑210 in CNE‑2R cells was significantly higher than in CNE‑2 cells. CNE‑2R cells were transfected with LV‑hsa‑miR‑210‑inhibitor, and CNE‑2 cells were transfected with LV‑hsa‑miR‑210. The expression of miR‑210 was confirmed by reverse transcription quantitative‑polymerase chain reaction. The percentages of CNE‑2R‑miR‑210‑inhibitor and CNE‑2 cells in the G2/M phase were higher than in the CNE‑2R and CNE‑2‑miR‑210 cells, and the percentages of cells in S phase were lower than in the CNE‑2R and CNE‑2‑miR‑210 cells. Following 4 Gy of radiation, CNE‑2R‑miR‑210‑inhibitor and CNE‑2 cells, which express low levels of miR‑210, had a higher apoptosis rate than CNE‑2R and CNE‑2‑miR‑210 cells. Following 4, 8 and 12 Gy of radiation, cell viability and survival fraction of CNE‑2R‑miR‑210‑inhibitor cells were lower than those of CNE‑2R and CNE‑2‑miR‑210 cells, and similar to those of CNE‑2 cells. Together, these findings strongly suggest that miR‑210 negatively regulates the radiosensitivity of tumor cells, and may therefore have therapeutic potential for the treatment of radiation resistance.

MicroRNA-26a inhibits proliferation and metastasis of human hepatocellular carcinoma by regulating DNMT3B-MEG3 axis

miR-26a is known to play an important oncosuppressive role in HCC. However, its regulatory role and relationship with other non-coding RNAs is less clear. In the present study, we report that the expression levels of miR-26a and long non-coding RNA (lncRNA) maternally expressed gene 3 (MEG3) were frequently downregulated in HCC tissues compared to matched non-malignant tissues. In addition, the expression levels of miR-26a and MEG3 were negatively correlated with the tumor sizes and TNM clinical stage in HCC patients. Overexpression of miR-26a significantly reduced the capacity of proliferation, invasion and migration of HCC cells. Moreover, we demonstrated that DNA methyltransferase 3b (DNMT3B) was a direct target gene of miR-26a. Overexpression of miR-26a suppressed the expression level of DNMT3B. Inhibited expression of DNMT3B showed similar tumor suppressive effects induced by miR-26a upregulation, and resulted in the upregulation of MEG3. Furthermore, we found that the expression levels of DNMT3B were upregulated in the HCC tissues compared with non-malignant tissues, and it was inversely correlated with miR-26a and MEG3 in HCC tissues. Thus, these results provided a plausible link between the observed reduction of miR-26a and MEG3 in HCCs. Together, the present study added miR-26a/DNMT3B/MEG3 axis to the complex mechanisms of HCC development.

miR-101 Enhances Cisplatin-Induced DNA Damage Through Decreasing Nicotinamide Adenine Dinucleotide Phosphate Levels by Directly Repressing Tp53-Induced Glycolysis and Apoptosis Regulator Expression in Prostate Cancer Cells

Tp53-induced glycolysis and apoptosis regulator (TIGAR) enhances the pentose phosphate pathway, thereby contributing directly to DNA repair due to generation of nicotinamide adenine dinucleotide phosphate (NADPH) and ribose-5-phosphate, two key precursors of DNA synthesis and repair. Targetscan database showed that miR-101 was predicted to potentially target TIGAR. Therefore, we speculated that miR-101 could enhance cisplatin-induced DNA damage by directly repressing TIGAR expression in prostate cancer cells. We found that upregulation of miR-101 inhibited viability, induced apoptosis, increased glycolysis rate and fructose-2,6-bisphosphate levels, decreased glucose-6-phosphate dehydrogenase expression and NADPH levels, and enhanced cisplatin-induced DNA damage in prostate cancer cells. We also demonstrated that TIGAR was a direct target of miR-101 by using luciferase activity assay. Furthermore, this study revealed that the roles of knockdown of TIGAR were similar to miR-101 upregulation in prostate cancer cells. Taken together, miR-101 inhibited viability, induced apoptosis, reprogramed glucose metabolism, and enhanced cisplatin-induced DNA damage through decreasing NADPH levels by directly suppressing the expression of TIGAR in prostate cancer cells.

MicroRNA-19b-3p regulates nasopharyngeal carcinoma radiosensitivity by targeting TNFAIP3/NF-κB axis

Background

Nasopharyngeal carcinoma (NPC) is among the most common squamous cell carcinoma in South China and Southeast Asia. Radiotherapy is the primary treatment for NPC. However, radioresistance acts as a significant factor that limits the efficacy of radiotherapy for NPC patients. Growing evidence supports that microRNAs (miRNAs) play an important role in radiation response.

Methods

Real-time quantitative PCR was used to analyze the expression of miR-19b-3p in NPC cell lines and NP69. miR-19b-3p expression profiles in NPC tissues were obtained from the Gene Expression Omnibus database. The effect of miR-19b-3p on radiosensitivity was evaluated by cell viability assays, colony formation assays and in vivo experiment. Apoptosis and cell cycle were examined by flow cytometry. Luciferase reporter assay was used to assess the target genes of miR-19b-3p. Expression of target proteins and downstream molecules were analyzed by Western blot.

Results

miR-19b-3p was upregulated in NPC and served as an independent predictor for reduced patient survival. Radioresponse assays showed that miR-19b-3p overexpression resulted in decreased sensitivity to irradiation, whereas miR-19b-3p downregulation resulted in increased sensitivity to irradiation in vitro. Moreover, miR-19b-3p decreased the sensitivity of NPC cells to irradiation in vivo. Luciferase reporter assay confirmed that TNFAIP3 was a direct target gene of miR-19b-3p. Knockdown of TNFAIP3 reduced sensitivity to irradiation, whereas upregulation of TNFAIP3 expression reversed the inhibitory effects of miR-19b-3p on NPC cell radiosensitivity. Mechanistically, we found that miR-19b-3p increased NPC cell radioresistance by activating the TNFAIP3/ NF-κB axis.

Conclusions

miR-19b-3p contributes to the radioresistance of NPC by activating the TNFAIP3/ NF-κB axis. miR-19b-3p is a determinant of NPC radioresponse and may serve as a potential therapeutic target in NPC treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0465-1) contains supplementary material, which is available to authorized users.

MicroRNAs in glioblastoma multiforme pathogenesis and therapeutics

Glioblastoma multiforme (GBM) is the most common and lethal cancer of the adult brain, remaining incurable with a median survival time of only 15 months. In an effort to identify new targets for GBM diagnostics and therapeutics, recent studies have focused on molecular phenotyping of GBM subtypes. This has resulted in mounting interest in microRNAs (miRNAs) due to their regulatory capacities in both normal development and in pathological conditions such as cancer. miRNAs have a wide range of targets, allowing them to modulate many pathways critical to cancer progression, including proliferation, cell death, metastasis, angiogenesis, and drug resistance. This review explores our current understanding of miRNAs that are differentially modulated and pathologically involved in GBM as well as the current state of miRNA-based therapeutics. As the role of miRNAs in GBM becomes more well understood and novel delivery methods are developed and optimized, miRNA-based therapies could provide a critical step forward in cancer treatment.

Loss of miR-26a-5p promotes proliferation, migration, and invasion in prostate cancer through negatively regulating SERBP1

The biological role of miR-26a involved in the carcinogenesis of prostate cancer (PC) has been controversial. Besides, the underlying mechanism by which miR-26a plays a role in PC has been unclear. To investigate the role of miR-26a-5p in the PC, miR-26a-5p was detected and statistically analyzed in clinical PC tissues and a panel of PC cell lines. Using bioinformatics analysis, we found that serpine1 messenger RNA (mRNA) binding protein 1 (SERBP1) was a potential downstream target of miR-26a-5p. Using luciferase reporter and western blot, we identified that miR-26a-5p negatively regulated SERBP1 on the PC cell line level. It was confirmed that miR-26a-5p was markedly downregulated in PC tissues compared with normal controls whose reduced expression was significantly associated with metastasis and poor overall prognosis and found that miR-26a-5p was able to prevent proliferation and motility of PC cells in vitro. Additionally, SERBP1 was identified as a downstream target of miR-26a-5p. Moreover, it was observed that SERBP1 was markedly upregulated in prostate cancer tissues and was significantly associated with tissue metastasis and Gleason score. Taken together, our results for the first time demonstrate that the loss of miR-26a-5p promotes proliferation, migration, and invasion through targeting SERBP1 in PC, supporting the tumor-suppressing role of miR-26a-5p in PC.

Long non-coding RNA TUG1 acts as a miR-26a sponge in human glioma cells

BACKGROUND

Long non-coding RNA taurine upregulated gene 1 (TUG1) acts as an important regulator in cancer pathogenesis; however, its functional mechanism in glioma development remains unclear. This study aims to explore the potential function of TUG1 in glioma by sponging miR-26a.

METHODS

The expression of TUG1, miR-26a, and phosphatase and tensin homolog (PTEN) in 20 paired glioma tissues was detected by quantitative real-time PCR and subjected to correlation analysis. Bioinformatics analysis was performed by using DIANA Tools. Abnormal TUG1 expression was conducted in two glioma cells to analyze its regulation on miR-26a and PTEN using real-time PCR, western blot, and luciferase reporter assay.

RESULTS

TUG1 expression was confirmed to be upregulated in glioma tissues, and showed an inverse correlation with downregulated miR-26a. TUG1 could negatively regulate the expression of miR-26a in glioma cells. The bioinformatics prediction revealed putative miR-26a binding sites within TUG1 transcripts. Further experiments demonstrated the positive regulation of TUG1 on the miR-26a target, PTEN, wherein TUG1 could inhibit the negative regulation of miR-26a on PTEN by binding its 3'UTR. Additionally, the expression of PTEN was also upregulated in glioma tissues, showing a positive or negative correlation with TUG1 or miR-26a, respectively.

CONCLUSION

TUG1 could serve as a miR-26a sponge in human glioma cells, contributing to the upregulation of PTEN. This study revealed a new TUG1/miR-26a/PTEN regulatory mechanism and provided a further understanding of the tumor-suppressive role of TUG1 in glioma development.

The role of microRNA-26a in human cancer progression and clinical application

MicroRNAs, a class of endogenous, small (18-25 nucleotides) noncoding RNAs, regulate gene expression by directly binding to the 3'-untranslated regions of target messenger RNAs. Evidence has shown that alteration of microRNAs is involved in cancer initial and progression. MicroRNA-26a is commonly dysregulated in diverse cancers and is involved in various biological processes, including proliferation, migration, invasion, angiogenesis, and metabolism by targeting multiple mRNAs. This review summarizes current research on the physiology and pathological functions of miR-26a and its applications for clinical therapy.

Analysis of EZH2: micro-RNA network in low and high grade astrocytic tumors

Enhancer of Zeste homologue2 (EZH2) is an epigenetic regulator that functions as oncogene in astrocytic tumors, however, EZH2 regulation remains little studied. In this study, we measured EZH2 levels in low (Gr-II,DA) and high grade (Gr-IV,GBM) astrocytic tumors and found significant increased EZH2 transcript level with grade(median DA-8.5, GBM-28.9).However, a different trend was reflected in protein levels, with GBMs showing high EZH2 LI(median-26.5) compared to DA (median 0.3). This difference in correlation of EZH2 protein and RNA levels suggested post-transcriptional regulation of EZH2, likely mediated by miRNAs. We selected eleven miRNAs that strongly predicted to target EZH2 and measured their expression. Three miRNAs (miR-26a-5p,miR27a-3p and miR-498) showed significant correlation with EZH2 protein, suggesting them as regulators of EZH2, however miR-26a-5p levels decreased with grade. ChIP analyses revealed H3K27me3 modifications in miR-26a promoter suggesting feedback loop between EZH2 and miR26a. We further measured six downstream miRNA targets of EZH2 and found significant downregulation of four (miR-181a/b and 200b/c) in GBM. Interestingly, EZH2 associated miRNAs were predicted to target 25 genes in glioma-pathway, suggesting their role in tumor formation or progression. Collectively, our work suggests EZH2 and its miRNA interactors may serve as promising biomarkers for progression of astrocytic tumors and may offer novel therapeutic strategies.

MicroRNA-378g enhanced radiosensitivity of NPC cells partially by targeting protein tyrosine phosphatase SHP-1

PURPOSE

To investigate the influence of microRNA-378g (miR-378g) on radiosensitivity and metastasis of nasopharyngeal carcinoma cells and study how miR-378g regulated Src homology region 2 domain-containing phosphatase-1 (SHP-1) expression.

MATERIALS AND METHODS

Polymerase chain reaction (PCR) was used to detect the expression level of miR-378g and SHP-1 mRNA in different nasopharyngeal carcinoma (NPC) cell lines. MiR-378g mimics were transfected into NPC cells and radiosensitivity was determined by colony formation assay. Cell apoptotic rate was determined by flow cytometry analysis. Cell invasion was examined by transwell assay. SHP-1 transcriptional activity was examined by luciferase assay. SHP-1 expression level was determined by Western blot. Lentivirus containing SHP-1 gene and miR-378g mimics were co-transfected into NPC cells and radiosensitivity and metastasis were detected by colony formation assay and transwell assay again.

RESULTS

Expression of miR-378g and SHP-1 mRNA was negatively correlated in NPC cell lines. MiR-378g mimics enhanced radiosensitivity, promoted apoptosis and decreased invasion in NPC cells. SHP-1 expression was inhibited by miR-378g mimics. Luciferase reporter assay showed that miR-378g directly targeted SHP-1 by binding to 3' untranslated region (3'UTR) of SHP-1 mRNA. Overexpression of SHP-1 partially inversed the effect of miR-378g mimics on radiosensitivity, but had no effect on cell invasion.

CONCLUSION

MiR-378g enhanced radiosensitivity partially by targeting SHP-1 in NPC cells. Cell invasion was also partially inhibited by miR-378g, but the effect was not mediated by SHP-1.

Genomic integrity and the ageing brain

DNA damage is correlated with and may drive the ageing process. Neurons in the brain are postmitotic and are excluded from many forms of DNA repair; therefore, neurons are vulnerable to various neurodegenerative diseases. The challenges facing the field are to understand how and when neuronal DNA damage accumulates, how this loss of genomic integrity might serve as a 'time keeper' of nerve cell ageing and why this process manifests itself as different diseases in different individuals.

MicroRNA-203 Modulates the Radiation Sensitivity of Human Malignant Glioma Cells

PURPOSE

We investigated whether miR-203 could modulate the radiation sensitivity of glioblastoma (GBM) cells and which target gene(s) could be involved.

METHODS AND MATERIALS

Three human malignant glioma (MG) cell lines and normal human astrocytes were transfected with control microRNA, pre-miR-203, or antisense miR-203. Real-time PCR (RT-PCR), clonogenic assays, immunofluorescence, and invasion/migration assays were performed. To predict the target(s), bioinformatics analyses using microRNA target databases were performed.

RESULTS

Overexpression of miR-203 increased the radiation sensitivity of all 3 human MG cell lines and prolonged radiation-induced γ-H2AX foci formation. Bioinformatics analyses suggested that miR-203 could be involved in post-transcriptional control of DNA repair, PI3K/AKT, SRC, and JAK/STAT3 and the vascular signaling pathway. Western blot analysis validated the fact that miR-203 downregulated ATM, RAD51, SRC, PLD2, PI3K-AKT, JAK-STAT3, VEGF, HIF-1α, and MMP2. Overexpression of miR-203 inhibited invasion and migration potentials, downregulated SLUG and Vimentin, and upregulated Claudin-1 and ZO1.

CONCLUSIONS

These data demonstrate that miR-203 potentially controls DNA damage repair via the PI3K/AKT and JAK/STAT3 pathways and may collectively contribute to the modulation of radiation sensitivity in MG cells by inhibiting DNA damage repair, prosurvival signaling, and epithelium-mesenchyme transition. Taken together, these findings demonstrate that miR-203 could be a target for overcoming the radiation resistance of GBM.

MicroRNAs and cell cycle of malignant glioma

The control of malignant glioma cell cycle by microRNAs (miRNAs) is well established. The deregulation of miRNAs in glioma may contribute to tumor proliferation by directly targeting the critical cell-cycle regulators. Tumor suppressive miRNAs inhibit cell cycle through repressing the expression of positive cell-cycle regulators. However, oncogenic miRNAs promote the cell-cycle progression by targeting cell-cycle negative regulators. Recent studies have identified that transcription factors had involved in the expression of miRNAs. Transcription factors and miRNAs are implicated in regulatory network of glioma cell cycle, the deregulation of these transcription factors might be a cause of the deregulation of miRNAs. Abnormal versions of miRNAs have been implicated in the cell cycle of glioma. Based on those, miRNAs are excellent biomarker candidates and potential targets for therapeutic intervention in glioma.

Knockdown of microRNA-1323 restores sensitivity to radiation by suppression of PRKDC activity in radiation-resistant lung cancer cells

Resistance to radiation is a major problem in cancer treatment. The mechanisms of radioresistance remain poorly understood; however, mounting evidence supports a role for microRNAs (miRNAs) in the modulation of key cellular pathways mediating the response to radiation. The present study aimed to identify specific miRNAs and their effect on radioresistant cells. The global miRNA profile of an established radioresistant lung cancer cell line and the corresponding control cells was determined. Differential expression of the miRNAs was confirmed by quantitative real-time PCR (qRT-PCR). The binding effect of identical novel miRNAs and target mRNAs was determined by luciferase assay. Lung cancer cells were transfected with miRNA-specific mimics or inhibitors. The DNA-dependent protein kinase (DNA-PKcs) protein level was tested by western blot analysis. Radiosensitivity of cancer cells was determined using colony formation assay. Among the differentially expressed miRNAs, 25 miRNAs were overexpressed while 18 were suppressed in the radioresistant cells, both basally and in response to radiation compared to their control. An miRNA signature miR-1323 exhibited a >5-fold increase in the radioresistant cells. miR-1323 was demonstrated to bind to PRKDC 3'UTR, which is involved in DNA repair. Ectopic expression of miR-1323 significantly increased the survival fraction of irradiated cancer cells. Inhibition of miR-1323 reversed the radioresistance of cancer cells and subsequently suppressed the expression of miR-1323-regulated DNA-PKcs protein. The present study indicated that miRNAs are involved in the radioresistance of human lung cancer cells. A possible mechanism for resistance to radiation was via enhanced DNA repair. The present study demonstrated a role for miR-1323 in modulating radioresistance and highlights the need for further study investigating the potential role of miR-1323 as both a predictive marker of response and a novel therapeutic agent with which to enhance the efficacy of radiotherapy.

Glioblastoma: molecular pathways, stem cells and therapeutic targets

Glioblastoma (GBM), a WHO-defined Grade IV astrocytoma, is the most common and aggressive CNS malignancy. Despite current treatment modalities, the survival time remains dismal. The main cause of mortality in patients with this disease is reoccurrence of the malignancy, which is attributed to treatment-resistant cancer stem cells within and surrounding the primary tumor. Inclusion of novel therapies, such as immuno- and DNA-based therapy, may provide better means of treating GBM. Furthermore, manipulation of recently discovered non-coding microRNAs, some of which regulate tumor growth through the development and maintenance of GBM stem cells, could provide new prospective therapies. Studies conducted by The Cancer Genome Atlas (TCGA) also demonstrate the role of molecular pathways, specifically the activated PI3K/AKT/mTOR pathway, in GBM tumorigenesis. Inhibition of the aforementioned pathway may provide a more direct and targeted method to GBM treatment. The combination of these treatment modalities may provide an innovative therapeutic approach for the management of GBM.

ATM has a major role in the double-strand break repair pathway dysregulation in sporadic breast carcinomas and is an independent prognostic marker at both mRNA and protein levels

BACKGROUND

Ataxia telangiectasia mutated (ATM) is a kinase that has a central role in the maintenance of genomic integrity by activating cell cycle checkpoints and promoting repair of DNA double-strand breaks (DSB). In breast cancer, a low level of ATM was correlated with poor outcome; however, the molecular mechanism of this downregulation is still unclear.

METHODS

We used qRT-PCR assay to quantify mRNA levels of ATM gene in 454 breast tumours from patients with known clinical/pathological status and outcome; reverse phase protein arrays (RPPA) were used to assess the levels of ATM and 14 proteins in 233 breast tumours.

RESULTS

ATM mRNA was associated with poor metastasis-free survival (MFS) (P=0.00012) on univariate analysis. ATM mRNA and protein levels were positively correlated (P=0.00040). A low level of ATM protein was correlated with poorer MFS (P=0.000025). ATM expression at mRNA or protein levels are independent prognostic factors on multivariate analysis (P=0.00046 and P=0.00037, respectively). The ATM protein level was positively correlated with the levels of six proteins of the DSB repair pathway: H2AX (P<0.0000001), XRCC5 (P<0.0000001), NBN (P<0.0000001), Mre11 (P=0.0000029), Rad50 (P=0.0064), and TP53BP1 (P=0.026), but not with proteins involved in other pathways that are altered in cancer. Low expression of ATM protein was significantly associated with high miR-203 expression (P=0.011).

CONCLUSION

We confirmed that ATM expression is an independent prognostic marker at both RNA and protein levels. We showed that alteration of ATM is involved in dysregulation of the DSB repair pathway. Finally, miR-203 may be responsible for downregulation of ATM in breast cancers.

MicroRNAs Used in Combination with Anti-Cancer Treatments Can Enhance Therapy Efficacy

MicroRNAs (miRNAs), a recently discovered class of small non-coding RNAs, constitute a promising approach to anti-cancer treatments when they are used in combination with other agents. MiRNAs are evolutionarily conserved non-coding RNAs that negatively regulate gene expression by binding to the complementary sequence in the 3'-untranslated region (UTR) of target genes. MiRNAs typically suppress gene expression by direct association with target transcripts, thus decreasing the expression levels of target proteins. The delivery to cells of synthetic miRNAs that mimic endogenous miRNA targeting genes involved in the DNA-Damage Response (DDR) can perturb the process, making cells more sensitive to chemotherapy or radiotherapy. This review examines how cells respond to combined therapy and it provides insights into the role of miRNAs in targeting the DDR repair pathway when they are used in combination with chemical compounds or ionizing radiation to enhance cellular sensitivity to treatments.

MiR-26a enhances the sensitivity of gastric cancer cells to cisplatin by targeting NRAS and E2F2

BACKGROUND/AIMS

MiR-26a has been identified as a tumor suppressor in various tumors, but the relationship between miR-26a and the sensitivity of gastric cancer to chemotherapies has not been established. The present study was performed to investigate the effect of miR-26a on drug sensitivity in gastric cancer (GC).

MATERIALS AND METHODS

The expression level of miRNA-26a in cisplatin-resistant SGC-7901/DDP cells and parent SGC-7901 cells was evaluated by qRT-PCR. The effect of miR-26a on sensitivity of GC cells to cisplatin was assayed using MTS method. The effect of miR-26a on cisplatin-induced apoptosis were determined by Annexin V/propidium iodide (PI) double staining method and flow cytometry. The targets of miR-26a were identified using a luciferase activity assay and miR-26a-mediated target genes expression analysis. Furthermore, the role of the targets neuroblastoma RAS viral (v-ras) oncogene homolog (NRAS) and E2F2 on sensitivity of chemotherapy in GC by MTS and apoptotic cell analysis was assessed.

RESULTS

We found that miR-26a was downregulated in cisplatin-resistant SGC-7901/DDP cells compared with SGC-7901 cells. Using both gain- and loss-of-function analyses, we further revealed that miR-26a could improve the sensitivity of GC cells to cisplatin. Furthermore, miR-26a has target sites in the 3'-UTR of NRAS and E2F2 by luciferase reporter assay and reduces the expression levels of NRAS and E2F2. In addition, knockdown of NRAS or E2F2 sensitize GC cells to cisplatin.

CONCLUSION

Our results suggest that miR-26a can improve the sensitivity of GC cells to cisplatin-based chemotherapies through targeting NRAS and E2F2, and provide the first evidence of the potential utility of miR-26a as a sensitizer in chemotherapy for GC.

MiR-451 increases radiosensitivity of nasopharyngeal carcinoma cells by targeting ras-related protein 14 (RAB14)

Radioresistance severely impedes the treatment of nasopharyngeal carcinoma (NPC). Recent evidence has shown that the abnormal expression of microRNAs (miRNAs) contributes to radiosensitivity. The aim of this study, therefore, was to investigate whether expression of the miRNAs correlated with radiosensitivity in the context of NPC. Quantitative reverse transcription polymerase chain reaction (RT-PCR) was used to quantify miR-451 expression in two representative NPC cell lines. The role of miR-451 in NPC radiosensitivity was analyzed using a colony formation assay and an immunofluorescence assay with overexpression of miR-451 in NPC cells. Luciferase reporter assays, RT-PCR, and Western blot were performed to confirm the target of miR-451. High levels of miR-451 expression enhanced radiosensitivity in NPC cells by inhibiting the repair of irradiation-induced double-strand breaks (DSBs) and increasing apoptosis. The results also demonstrated that miR-451 directly targeted ras-related protein 14 (RAB14). Downregulation of RAB14 partially replicated the miR-451-mediated DSBs induced by ionizing radiation (IR). MiR-451 could be a potential target for enhancing radiosensitivity of NPC cells by targeting RAB14.

miRNAs in tumor radiation response: bystanders or participants?

There is increasing interest in defining a functional association between miRNAs and tumor radiation response, with the double aim of rationally designing miRNA-based strategies to increase patient radiosensitivity and identifying novel biomarkers of treatment response. Although it has been demonstrated that several miRNAs directly regulate the expression of components of cell pathways relevant to radiosensitivity, and miRNA expression profiles change upon irradiation, understanding the causal role exerted by individual miRNAs in determining tumor radiation response is still at an early stage. Based on available experimental and clinical evidence, we discuss here the potential of miRNAs as targets and/or tools for modulating radioresponsivity at the clinical level, as well as possible predictive biomarkers, underlining present limits and future perspectives.

MiR-124 Radiosensitizes human colorectal cancer cells by targeting PRRX1

One of the challenges in the treatment of colorectal cancer patients is that these tumors show resistance to radiation. MicroRNAs (miRNAs) are involved in essential biological activities, including chemoresistance and radioresistance. Several research studies have indicated that miRNA played an important role in sensitizing cellular response to ionizing radiation (IR). In this study, we found that miR-124 was significantly down-regulated both in CRC-derived cell lines and clinical CRC samples compared with adjacent non-tumor colorectal tissues, MiR-124 could sensitize human colorectal cancer cells to IR in vitro and in vivo. We identified PRRX1, a new EMT inducer and stemness regulator as a novel direct target of miR-124 by using target prediction algorithms and luciferase assay. PRRX1 knockdown could sensitize CRC cells to IR similar to the effects caused by miR-124. Overexpression of PRRX1 in stably overexpressed-miR-124 cell lines could rescue the effects of radiosensitivity enhancement brought by miR-124. Taking these observations into consideration, we illustrated that miR-124 could increase the radiosensitivity of CRC cells by blocking the expression of PRRX1, which indicated miR-124 could act as a great therapeutic target for CRC patients.