Involvement of microRNA-24 and DNA methylation in resistance of nasopharyngeal carcinoma to ionizing radiation

DNA repair in tumor radioresistance: insights from fruit flies genetics

BACKGROUND

Radiation therapy (RT) is a key anti-cancer treatment that involves using ionizing radiation to kill tumor cells. However, this therapy can lead to short- and long-term adverse effects due to radiation exposure of surrounding normal tissue. The type of DNA damage inflicted by radiation therapy determines its effectiveness. High levels of genotoxic damage can lead to cell cycle arrest, senescence, and cell death, but many tumors can cope with this damage by activating protective mechanisms. Intrinsic and acquired radioresistance are major causes of tumor recurrence, and understanding these mechanisms is crucial for cancer therapy. The mechanisms behind radioresistance involve processes like hypoxia response, cell proliferation, DNA repair, apoptosis inhibition, and autophagy.

CONCLUSION

Here we briefly review the role of genetic and epigenetic factors involved in the modulation of DNA repair and DNA damage response that promote radioresistance. In addition, leveraging our recent results on the effects of low dose rate (LDR) of ionizing radiation on Drosophila melanogaster we discuss how this model organism can be instrumental in the identification of conserved factors involved in the tumor resistance to RT.

The promising role of miRNAs in radioresistance and chemoresistance of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignant epithelial tumor that develops in the nasopharynx. It has a distinct ethnic and geographical distribution, and emerging evidence suggests that it is an ecological disease. Most patients respond well to radiation combined with chemotherapy as the primary treatment for NPC. However, some patients will eventually develop radio resistance and chemoresistance, resulting in recurrence and metastasis, which is a primary cause of poor prognosis. The processes underlying radio resistance and chemoresistance in NPC are complex and unknown. MicroRNAs (miRNAs) are endogenic non-coding RNA molecules. They play a role in a variety of cell functions as well as development of disease such as cancer. There has been considerable data demonstrating the existence of numerous aberrant miRNAs in cancer tissues, cells, and biofluids, which indicates the importance of studying the influence of miRNAs on NPC. Therefore, this review comprehensively analyzes the elaborate mechanisms of miRNAs affecting the radio resistance and chemoresistance of NPC. Multiple tumor-specific miRNAs can be employed as therapeutic and prognostic biological indicators.

YAP nuclear translocation facilitates radiation resistance in nasopharyngeal carcinoma cells

OBJECTIVES

Investigate the role of the Hippo-YAP signaling pathway in radioresistant Nasopharyngeal Carcinoma (NPC).

METHODS

Establishment of radioresistant CNE-1 cells (CNE-1-RR) by gradually increasing ionizing radiation (IR) doses, and identifying the apoptosis of CNE-1-RR by flow cytometry. We employed immunoblot and immunofluorescence staining to detect the expression of YAP in both CNE-1-RR and control group cells. Moreover, we validated the role of YAP in CNE-1-RR by inhibiting its nuclear translocation.

RESULTS

In contrast to the control group, radioresistant NPC cells demonstrated significant YAP dephosphorylation and nuclear translocation. CNE-1-RR cells exhibited enhanced activation of γ-H2AX (Ser139) upon exposure to IR and greater recruitment of double-strand breaks (DSBs) repair-related proteins. Additionally, inhibiting YAP nuclear translocation in radioresistant CNE-1-RR cells significantly increased their sensitivity to radiotherapy.

CONCLUSIONS

The present investigation has unveiled the intricate mechanisms and physiological roles of YAP in CNE-1-RR cells exhibiting resistance to IR. Based on our findings, it can be inferred that a combinational therapeutic strategy involving radiotherapy and inhibitors that impede the nuclear translocation of YAP holds promising potential for treating radioresistant NPC.

Current advances in the selection of adjuvant radiotherapy regimens for keloid

Keloid is a common benign skin tumor in the outpatient department, and patients are often accompanied by itching and pain. Since the pathogenesis is unknown, the effect of single method treatment is unsatisfactory, and therefore the recurrence rate is high. Therefore, comprehensive treatment is mostly used in clinical treatment. Adjuvant radiotherapy is currently one of the most effective treatments for keloid. After long-term clinical practice, brachytherapy and electron beam radiotherapy has increasingly become the gold standard of treatment, because brachytherapy provides more focused radiation treatment to focal tissue to significantly reduce recurrence rate, and better preserve normal tissue. With the development of new radiotherapy techniques, more options for the treatment of keloid. Currently, adjuvant radiotherapy has been widely recognized, but there is no consensus on the optimal protocol for adjuvant radiotherapy for keloids. This review provides a review of published treatment options and new radiotherapy techniques for adjuvant radiotherapy of keloids and gives a comprehensive evaluation for clinical treatment.

Versatile role of miR-24/24-1*/24-2* expression in cancer and other human diseases

MiRNAs (miRs) have been proven to be well-validated therapeutic targets. Emerging evidence has demonstrated that intricate, intrinsic and paradoxical functions of miRs are context-dependent because of their multiple upstream regulators, broad spectrum of downstream molecular targets and distinct expression in various tissues, organs and disease states. Targeted therapy has become an emerging field of research. One key for the development of successful miR-based/targeted therapy is to acquire integrated knowledge of its regulatory network and its association with disease phenotypes to identify critical nodes of the underlying pathogenesis. Herein, we systematically summarized the comprehensive role of miR-24-3p (miR-24), along with its passenger strands miR-24-1-5p* (miR-24-1) and miR-24-2-5p* (miR-24-2), emphasizing their microenvironment, intracellular targets, and associated gene networks and regulatory phenotypes in 18 different cancer types and 13 types of other disorders. MiR-24 targets and regulates numerous genes in various cancer types and enhances the expression of several oncogenes (e.g., cMyc, BCL2 and HIF1), which are challenging in terms of druggability. In contrast, several tumor suppressor proteins (p21 and p53) have been reported to be downregulated by miR-24. MiR-24 also regulates the cell cycle and is associated with numerous cancer hallmarks such as apoptosis, proliferation, metastasis, invasion, angiogenesis, autophagy, drug resistance and other diseases pathogenesis. Overall, miR-24 plays an emerging role in the diagnosis, prognosis and pathobiology of various diseases. MiR-24 is a potential target for targeted therapy in the era of precision medicine, which expands the landscape of targetable macromolecules, including undruggable proteins.

TMEM130 regulates cell migration through DNA methylation in nasopharyngeal carcinoma

BACKGROUND

Nasopharyngeal carcinoma (NPC), the common malignant head and neck cancer, is highly prevalent in southern China. The molecular mechanism underlying NPC tumorigenesis is unclear. We used 5-Aza-CdR, a DNA methyltransferase inhibitor, to treat NPC cell lines and discovered that the expression of TMEM130 changed significantly compared with the untreatment cells. This study aimed to identify the relationship between the DNA methylation status of TMEM130 and NPC, and to explore the function of TMEM130 in NPC cell migration.

METHODS

qRT-PCR was performed to investigate the transcriptional expression of TMEM130 in NPC. Bisulfite sequencing PCR and 5-Aza-CdR treatment were used to detect the methylation level of the TMEM130 promoter. Gene Expression Omnibus (GEO) datasets were obtained to identifiy the methylation status and mRNA expression of TMEM130 in NPC and normal control tissues. Transwell and western blot analyses were used to detect cell migration ability after transfection of TMEM130/NC plasmids in NPC cells.

RESULTS

The transcriptional expression of TMEM130 was decreased in NPC cell lines compared with in the NP69 cell line. TMEM130 promoter was significantly hyper methylated in three NPC cell lines (C666, CNE, and HONE) but hypo methylated in NP69 cells. The methylation level was higher in NPC than normal control tissues. Additionally, treatment of NPC cells with 5-Aza-CdR increased the TMEM130 mRNA expression level. Overexpression of TMEM130 in NPC cell lines suppressed cell migration ability and affected some epithelial-mesenchymal transition-associated gene expression.

CONCLUSIONS

This study is the first to investigate the expression and function of TMEM130 in NPC. It was found that TMEM130 hyper methylation might contribute to NPC migration and this gene might act as a tumor suppressor gene. TMEM130 is a promising biomarker for NPC diagnosis.

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.

Insulin receptor substrate-1 and dishevelled 2 are negatively regulated by microRNA-144 and inhibit nasopharyngeal carcinoma cell malignancy

Insulin receptor substrate-1 (IRS-1) is reported to play a critical role in the development, progression, invasion and metastasis of several types of tumors and is abnormally expressed in nasopharyngeal carcinoma (NPC). Although IRS-1 is predicted to be targeted by microRNA (miR)-144, the biological roles and potential mechanisms of miR-144 in NPC remain unclear. In the present study, the expression levels of miR-144 and IRS-1 in several NPC cell lines were first examined, and found that they were negatively correlated. Following the introduction of the miR-144 mimic, IRS-1 was downregulated at the protein level without affecting the mRNA level. The Cell Counting Kit-8 assay showed that the miR-144 mimic and siRNA targeting IRS-1 mRNA significantly decreased cell proliferation by arresting the cell cycle at the G₁/G₀ phase. The malignant behaviours of NPC cell lines, including migration, invasion and tumour formation in soft agar, were then analyzed after regulating miR-144 levels; as expected, the results showed that both the miR-144 mimic and siIRS-1 decreased these malignant behaviours. Furthermore, the downregulation of IRS-1 by miR-144 decreased the expression level of dishevelled 2 (Dvl2) protein without affecting its mRNA level, and Dvl2 overexpression abolished the inhibitory effect of the miR-144 mimic in NPC, indicating that miR-144 potentially regulates NPC by indirectly regulating Dvl2. Taken together, the present study results suggest that miR-144 acts as a tumour suppressor in NPC cell lines by regulating IRS-1 and Dvl2, which indicates that it is a potential therapeutic target for NPC treatment.

A Five-MicroRNA Signature Predicts the Prognosis in Nasopharyngeal Carcinoma

Background

There is no effective prognostic signature that could predict the prognosis of nasopharyngeal carcinoma (NPC).

Methods

We constructed a prognostic signature based on five microRNAs using random forest and Least Absolute Shrinkage And Selection Operator (LASSO) algorithm on the GSE32960 cohort (N = 213). We verified its prognostic value using three independent external validation cohorts (GSE36682, N = 62; GSE70970, N = 246; and TCGA-HNSC, N = 523). Through principal component analysis, receiver operating characteristic curve analysis, and C-index calculation, we confirmed the predictive accuracy of this prognostic signature.

Results

We calculated the risk score based on the LASSO algorithm and divided the patients into high- and low-risk groups according to the calculated optimal cutoff value. The patients in the high-risk group tended to have a worse prognosis outcome and chemotherapy response. The time-dependent receiver operating characteristic curve showed that the 1-year overall survival rate of the five-microRNA signature had an area under the curve of more than 0.83. A functional annotation analysis of the five-microRNA signature showed that the patients in the high-risk group were usually accompanied by activation of DNA repair and MYC-target pathways, while the patients in the low-risk group had higher immune-related pathway signals.

Conclusions

We constructed a five-microRNA prognostic signature, which could accurately predict the prognosis of nasopharyngeal carcinoma, and constructed a nomogram that could conveniently predict the overall survival of patients.

DNA methylome perturbations: an epigenetic basis for the emergingly heritable neurodevelopmental abnormalities associated with maternal smoking and maternal nicotine exposure†

Maternal smoking during pregnancy is associated with an ensemble of neurodevelopmental consequences in children and therefore constitutes a pressing public health concern. Adding to this burden, contemporary epidemiological and especially animal model research suggests that grandmaternal smoking is similarly associated with neurodevelopmental abnormalities in grandchildren, indicative of intergenerational transmission of the neurodevelopmental impacts of maternal smoking. Probing the mechanistic bases of neurodevelopmental anomalies in the children of maternal smokers and the intergenerational transmission thereof, emerging research intimates that epigenetic changes, namely DNA methylome perturbations, are key factors. Altogether, these findings warrant future research to fully elucidate the etiology of neurodevelopmental impairments in the children and grandchildren of maternal smokers and underscore the clear potential thereof to benefit public health by informing the development and implementation of preventative measures, prophylactics, and treatments. To this end, the present review aims to encapsulate the burgeoning evidence linking maternal smoking to intergenerational epigenetic inheritance of neurodevelopmental abnormalities, to identify the strengths and weaknesses thereof, and to highlight areas of emphasis for future human and animal model research therein.

Radio-Susceptibility of Nasopharyngeal Carcinoma: Focus on Epstein- Barr Virus, MicroRNAs, Long Non-Coding RNAs and Circular RNAs

Nasopharyngeal carcinoma (NPC) is a type of head and neck cancer. As a neoplastic disorder, NPC is a highly malignant squamous cell carcinoma that is derived from the nasopharyngeal epithelium. NPC is radiosensitive; radiotherapy or radiotherapy combining with chemotherapy are the main treatment strategies. However, both modalities are usually accompanied by complications and acquired resistance to radiotherapy is a significant impediment to effective NPC therapy. Therefore, there is an urgent need to discover effective radio-sensitization and radio-resistance biomarkers for NPC. Recent studies have shown that Epstein-Barr virus (EBV)-encoded products, microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs), which share several common signaling pathways, can function in radio-related NPC cells or tissues. Understanding these interconnected regulatory networks will reveal the details of NPC radiation sensitivity and resistance. In this review, we discuss and summarize the specific molecular mechanisms of NPC radio-sensitization and radio-resistance, focusing on EBV-encoded products, miRNAs, lncRNAs and circRNAs. This will provide a foundation for the discovery of more accurate, effective and specific markers related to NPC radiotherapy. EBVencoded products, miRNAs, lncRNAs and circRNAs have emerged as crucial molecules mediating the radio-susceptibility of NPC. This understanding will improve the clinical application of markers and inform the development of novel therapeutics for NPC.

Deciphering the epigenetic network in cancer radioresistance

Radiotherapy, in addition to surgery and systemic chemotherapy, remains the core of the current clinical management of cancer. Radioresistance is one of the major causes of disease progression and mortality in cancer; therefore, it is a significant challenge in the treatment of locally advanced, recurrent and metastatic cancer. Epigenetic mechanisms that control hallmarks of cancer have a key role in the development of radiation resistance of cancer cells. Recent advances in DNA methylation, histone modification, chromatin remodeling and non-coding RNAs identified in the control of signal transduction pathways in cancer and cancer stem cells have provided even greater promise in the improvement of understanding cancer radioresistance. Many epigenetic drugs that target epigenetic enzymes revert the radioresistant phenotypes decreasing the possibility that resistant cancer cells will develop refractory tumors to radiotherapy. Epigenetic profiles identified as regulators of DNA damage repair, hypoxia, cell survival, apoptosis and invasion are determinants in the development of tumor radioresistance; hence, they also are promising in personalized medicine to develop novel targeted therapies or biomarkers to follow-up the effectiveness of radiotherapy. Now, it is clear that radiotherapy can influence a complex epigenetic network for transcriptional reprogramming, enabling the cells to adapt and avoid the effect of radiotherapy. This review aims to highlight the epigenetic modifications identified in cancer radioresistance and to discuss approaches to disable epigenetic networks to increase the sensitivity and specificity of radiotherapy.

The molecular march of primary and recurrent nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) results from the aberrant and uncontrolled growth of the nasopharyngeal epithelium. It is highly associated with the Epstein-Barr virus, especially in regions where it is endemic. In the last decade, significant advances in genetic sequencing techniques have allowed the discovery of many new abnormal molecular processes that undoubtedly contribute to the establishment, growth and spread of this deadly disease. In this review, we consider NPC as EBV induced. We summarise the recent discoveries and how they add to our understanding of the pathophysiology of NPC in the context of genomics first in primary and then in recurrent disease. Overall, we find key early events lead to p16 inactivation and cyclin D1 expression, allowing latent viral infection. Host and viral factors work together to affect a variety of molecular pathways, the most fundamental being activation of NF-κB. Nonetheless, much still yearns to be discovered, especially in recurrent NPC.

Role of Non-coding RNAs on the Radiotherapy Sensitivity and Resistance of Head and Neck Cancer: From Basic Research to Clinical Application

Head and neck cancers (HNCs) rank as the sixth common and the seventh leading cause of cancer-related death worldwide, with an estimated incidence of 600,000 cases and 40-50% mortality rate every year. Radiotherapy is a common local therapeutic modality for HNC mainly through the function of ionizing radiation, with approximately 60% of patients treated with radiotherapy or chemoradiotherapy. Although radiotherapy is more advanced and widely used in clinical practice, the 5-year overall survival rates of locally advanced HNCs are still less than 40%. HNC cell resistance to radiotherapy remains one of the major challenges to improve the overall survival in HNC patients. Non-coding RNAs (ncRNAs) are newly discovered functional small RNA molecules that are different from messenger RNAs, which can be translated into a protein. Many previous studies have reported the dysregulation and function of ncRNAs in HNC. Importantly, researchers reported that several ncRNAs were also dysregulated in radiotherapy-sensitive or radiotherapy-resistant HNC tissues compared with the normal cancer tissues. They found that ectopically elevating or knocking down expression of some ncRNAs could significantly influence the response of HNC cancer cells to radiotherapy, indicating that ncRNAs could regulate the sensitivity of cancer cells to radiotherapy. The implying mechanism for ncRNAs in regulating radiotherapy sensitivity may be due to its roles on affecting DNA damage sensation, inducing cell cycle arrest, regulating DNA damage repair, modulating cell apoptosis, etc. Additionally, clinical studies reported that in situ ncRNA expression in HNC tissues may predict the response of radiotherapy, and circulating ncRNA from body liquid serves as minimally invasive therapy-responsive and prognostic biomarkers in HNC. In this review, we aimed to summarize the current function and mechanism of ncRNAs in regulating the sensitivity of HNC cancer cells to radiotherapy and comprehensively described the state of the art on the role of ncRNAs in the prognosis prediction, therapy monitoring, and prediction of response to radiotherapy in HNC.

Effects of Dicer1 targeted by EBV-miR-BART6-5p on biological properties and radiosensitivity of nasopharyngeal carcinoma

OBJECTIVE

To discuss the effects of Epstein-Barr virus (EBV)-encoded BamHI A rightward transcript (BART) microRNA (miR-BART6-5p) by targeting Dicer1 on biological properties and radiosensitivity of nasopharyngeal carcinoma (NPC).

METHODS

NPC patients (n = 96) treated with radiotherapy were collected from Jan 2010 to Jan 2011. Real-time quantitative PCR (qRT-PCR) and western blot were carried out to measure the expression of miR-BART6-5p and Dicer1. Dual luciferase reporter gene assay verified that miR-BART6-5p targeted Dicer1. CCK8, wound-healing, Transwell and Annexin-FITC/PI were employed to evaluate the effects of Dicer1 mediated by miR-BART6-5p on biological characteristics of NPC cells. The radiosensitivity of miR-BART6-5p targeting Dicer1 was assessed in vitro and in vivo.

RESULTS

Increased miR-BART6-5p and decreased Dicer1 were discovered in NPC patients, displaying a close association with T-stage, clinical stage, as well as Pre-DNA of NPC. While elevated Dicer1 and miR-BART6-5p down-regulation in NPC patients were found after effective radiotherapy. Both miR-BART6-5p and Dicer1 were prognostic factors of NPC. Down-regulation of miR-BART6-5p could enhance Dicer1 expression and inhibit NPC cell proliferation, invasion and migration with promoted apoptosis. Clone formation assay also showed miR-BART6-5p down-regulation reduced planting efficiency (PE), which further decreased with the increased dose of irradiation. Injection with miR-BART6-5p inhibitors in nude mice after 6-Gy irradiation contributed to the overexpression of Dicer1 and the inhibition of tumor growth.

CONCLUSIONS

EBV-miR-BART6-5p may target Dicer1 to facilitate proliferation and metastasis of NPC cells and suppress apoptosis, thus being a new target for NPC therapy.

miRNA as promising theragnostic biomarkers for predicting radioresistance in cancer: A systematic review and meta-analysis

Radioresistance remains as an obstacle in cancer treatment. This systematic review and meta-analysis aimed to evaluate the association between the expression of miRNAs and responses to radiotherapy and the prognosis of different tumors. In total, 77 miRNAs in 19 cancer types were studied, in which 24 miRNAs were upregulated and 58 miRNAs were downregulated in cancer patients. Five miRNAs were differentially expressed. Moreover, 75 miRNAs were found to be related to radioresistance, while 5 were observed to be related to radiosensitivity. The pooled HR and 95 % confidence interval for the combined studies was 1.135 (0.819-1.574; P-value = 0.4). The HR values of the subgroup analysis for miR-21 (HR = 2.344; 95 % CI: 1.927-2.850; P-value = 0.000), nasopharyngeal carcinoma (HR = 0.448; 95 % CI: 0.265-0.760; P = 0.003) and breast cancer (HR = 1.131; 95 % CI: 0.311-4.109; P = .85) were obtained. Our results highlighted that across the published literature, miRNAs can modulate tumor radioresistance or sensitivity by affecting radiation-related signaling pathways. It seems that miRNAs could be considered as a theragnostic biomarker to predict and monitor clinical response to radiotherapy. Thus, the prediction of radioresistance in malignant patients will improve radiotherapy outcomes and radiotherapeutic resistance.

miRNA profiling of primate cervicovaginal lavage and extracellular vesicles reveals miR-186-5p as a potential antiretroviral factor in macrophages

Cervicovaginal secretions, or their components collected, are referred to as cervicovaginal lavage (CVL). CVL constituents have utility as biomarkers and play protective roles in wound healing and against HIV-1 infection. However, several components of cervicovaginal fluids are less well understood, such as extracellular RNAs and their carriers, for example, extracellular vesicles (EVs). EVs comprise a wide array of double-leaflet membrane extracellular particles and range in diameter from 30 nm to over one micron. The aim of this study was to determine whether differentially regulated CVL microRNAs (miRNAs) might influence retrovirus replication. To this end, we characterized EVs and miRNAs of primate CVL during the menstrual cycle and simian immunodeficiency virus (SIV) infection of macaques. EVs were enriched by stepped ultracentrifugation, and miRNA profiles were assessed with a medium-throughput stem-loop/hydrolysis probe qPCR platform. Whereas hormone cycling was abnormal in infected subjects, EV concentration correlated with progesterone concentration in uninfected subjects. miRNAs were present predominantly in the EV-depleted CVL supernatant. Only a small number of CVL miRNAs changed during the menstrual cycle or SIV infection, for example, miR-186-5p, which was depleted in retroviral infection. This miRNA inhibited HIV replication in infected macrophages in vitro. In silico target prediction and pathway enrichment analyses shed light on the probable functions of miR-186-5p in hindering HIV infections via immunoregulation, T-cell regulation, disruption of viral pathways, etc. These results provide further evidence for the potential of EVs and small RNAs as biomarkers or effectors of disease processes in the reproductive tract.

Multiple Mechanisms Involving in Radioresistance of Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is the malignant tumor with ethnic and geographical distribution preference. Although intensity-modulated radiotherapy (IMRT)-based radiotherapy combined with chemotherapy and targeted therapy has dramatically improved the overall survival of NPC patients, there are still some patients suffering from recurrent tumors and the prognosis is poor. Multiple mechanisms may be responsible for radioresistance of NPC, such as cancer stem cells (CSCs) existence, gene mutation or aberrant expression of genes, epigenetic modification of genes, abnormal activation of certain signaling pathways, alteration of tumor microenvironment, stress granules (SGs) formation, etc. We conduct a comprehensive review of the published literatures focusing on the causes of radioresistance, retrospect the regulation mechanisms following radiation, and discuss future directions of overcoming the resistance to radiation.

Radiation-Induced DNMT3B Promotes Radioresistance in Nasopharyngeal Carcinoma through Methylation of p53 and p21

Radiotherapy with or without concurrent chemotherapy is the standard treatment for nasopharyngeal carcinoma (NPC) patients, whose efficacy is limited partly by intrinsic and acquired radioresistance. DNA methyltransferase 3B (DNMT3B) has been reported to participate in tumorigenesis via DNA methylation, but its role in mediating progression and radioresistance of NPC remains unclear. Therefore, we conducted the following studies to explore the relationship between DNMT3B and NPC. Here, we found that DNMT3B was elevated in NPC tissues and predicted the poor prognosis of NPC patients. We demonstrated for the first time that ionizing radiation could induce DNMT3B, which might be one of the reasons for radioresistance. Silencing of DNMT3B inhibited migration and invasion via suppressing epithelial-mesenchymal transition (EMT) in NPC cells. Furthermore, silencing DNMT3B restored and activated p53 and p21 via DNA demethylation, which led to cell cycle arrest and apoptosis, resulting in increased radiosensitivity of NPC both in vitro and in vivo. DNMT3B functions as a novel oncogene in the radioresistance of NPC through regulating EMT, cell cycle, and apoptosis. Therefore, DNMT3B could be a potential target for NPC treatment.

MiRNAs in Radiotherapy Resistance of Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is one of the most common malignant tumors of the head and neck in Southeast Asia and southern China. Although the comprehensive treatment based on intensity-modulated radiation therapy improves outcomes, the five-year survival rate of NPC patients is low, and the recurrence remains high. Radiotherapy resistance is the main cause of poor prognosis in NPC patients. MicroRNAs (miRNAs) are a class of endogenous non-coding RNAs regulating various biological functions in eukaryotes. These miRNAs can regulate the development and progression of nasopharyngeal carcinoma by affecting the proliferation, apoptosis, movement, invasion and metastasis of NPC cells. The abnormal expression of miRNAs is closely related to radiotherapy sensitivity and prognosis of NPC patients, which can affect the transmission of related signaling pathways by regulating the expression of tumor suppressor genes and / or oncogenes, and therefore participate in radiotherapy resistance in nasopharyngeal carcinoma. Here, we review the mechanisms by which miRNAs may be involved in the radiotherapy resistance of nasopharyngeal carcinoma.

Developmental nicotine exposure engenders intergenerational downregulation and aberrant posttranslational modification of cardinal epigenetic factors in the frontal cortices, striata, and hippocampi of adolescent mice

BACKGROUND

Maternal smoking of traditional or electronic cigarettes during pregnancy, which constitutes developmental nicotine exposure (DNE), heightens the risk of neurodevelopmental disorders including ADHD, autism, and schizophrenia in children. Modeling the intergenerationally transmissible impacts of smoking during pregnancy, we previously demonstrated that both the first- and second-generation adolescent offspring of nicotine-exposed female mice exhibit enhanced nicotine preference, hyperactivity and risk-taking behaviors, aberrant rhythmicity of home cage activity, nicotinic acetylcholine receptor and dopamine transporter dysfunction, impaired furin-mediated proBDNF proteolysis, hypocorticosteronemia-related glucocorticoid receptor hypoactivity, and global DNA hypomethylation in the frontal cortices and striata. This ensemble of multigenerational DNE-induced behavioral, neuropharmacological, neurotrophic, neuroendocrine, and DNA methylomic anomalies recapitulates the pathosymptomatology of neurodevelopmental disorders such as ADHD, autism, and schizophrenia. Further probing the epigenetic bases of DNE-induced multigenerational phenotypic aberrations, the present study examined the expression and phosphorylation of key epigenetic factors via an array of immunoblot experiments.

RESULTS

Data indicate that DNE confers intergenerational deficits in corticostriatal DNA methyltransferase 3A (DNMT3A) expression accompanied by downregulation of methyl-CpG-binding protein 2 (MeCP2) and histone deacetylase 2 (HDAC2) in the frontal cortices and hippocampi, while the expression of ten-eleven translocase methylcytosine dioxygenase 2 (TET2) is unaltered. Moreover, DNE evokes multigenerational abnormalities in HDAC2 (Ser394) but not MeCP2 (Ser421) phosphorylation in the frontal cortices, striata, and hippocampi.

CONCLUSIONS

In light of the extensive gene regulatory roles of DNMT3A, MeCP2, and HDAC2, the findings of this study that DNE elicits downregulation and aberrant posttranslational modification of these factors in both first- and second-generation DNE mice suggest that epigenetic perturbations may constitute a mechanistic hub for the intergenerational transmission of DNE-induced neurodevelopmental disorder-like phenotypes.

miR-181a Upregulation Promotes Radioresistance of Nasopharyngeal Carcinoma by Targeting RKIP

Background

Radioresistance is the leading cause of treatment failure for nasopharyngeal carcinoma (NPC). Therefore, screening the critical regulators in radioresistance and revealing the underlying mechanisms is imperative for improvement of therapeutical efficacy in NPC.

Materials and methods

Our previous study has proved that miR-181a may serve as a pro-radioresistant miRNA. In this study, we explored the expression of miR-181a in NPC, especially in radioresistant NPC samples, by qPCR. Moreover, the clinical significance of miR-181a level was also analyzed. Furthermore, the functions of miR-181a, both in vitro and in vivo, were detected via a serial of assays such as CCK-8, plate clone survival, apoptosis, and xenograft tumor model. The downstream target of miR-181a was also validated by dual luciferase reporter assay and the roles of miR-181a’s target in the regulation of NPC radioresistance were investigated.

Results

The results revealed that miR-181a was significantly upregulated in NPC, especially in radioresistant NPC. MiR-181a level is positively correlated to lymph node metastasis and advanced TNM stages and negatively associated with overall survival rate in NPC. Ectopic expression of miR-181a in radiosensitive NPC cells, or overexpression of miR-181a inhibitor in radioresistant NPC cells, could enhance or impair the radioresistance of NPC cells supported by the results from both in vitro and in vivo, respectively. Mechanistically, dual luciferase report assay indicated that miR-181a could directly target RKIP. Moreover, both in vitro and in vivo experimental outcomes indicated that RKIP restoration and knockdown could antagonize the effects of miR-181a and miR-181a inhibitor in the regulation of NPC radioresistance.

Conclusion

Collectively, the findings of this study proved that miR-181a is upregulated and promotes radioresistance by targeting RKIP in NPC. Targeting miR-181a/RKIP axis may be a valid path for reinforcing radiosensitivity and eventually improving the outcomes of clinical treatment in NPC.

microRNAs Tune Oxidative Stress in Cancer Therapeutic Tolerance and Resistance

Relapsed disease following first-line therapy remains one of the central problems in cancer management, including chemotherapy, radiotherapy, growth factor receptor-based targeted therapy, and immune checkpoint-based immunotherapy. Cancer cells develop therapeutic resistance through both intrinsic and extrinsic mechanisms including cellular heterogeneity, drug tolerance, bypassing alternative signaling pathways, as well as the acquisition of new genetic mutations. Reactive oxygen species (ROSs) are byproducts originated from cellular oxidative metabolism. Recent discoveries have shown that a disabled antioxidant program leads to therapeutic resistance in several types of cancers. ROSs are finely tuned by dysregulated microRNAs, and vice versa. However, mechanisms of a crosstalk between ROSs and microRNAs in regulating therapeutic resistance are not clear. Here, we summarize how the microRNA-ROS network modulates cancer therapeutic tolerance and resistance and direct new vulnerable targets against drug tolerance and resistance for future applications.

Phase II study of CC-486 (oral azacitidine) in previously treated patients with locally advanced or metastatic nasopharyngeal carcinoma

BACKGROUND

Treatment options are limited for recurrent nasopharyngeal carcinoma (NPC). We report results from a phase II study of CC-486 (oral azacitidine) in advanced NPC.

PATIENTS AND METHODS

Patients with locally advanced or metastatic NPC and 1-2 prior treatment regimens received CC-486 300 mg daily on days 1-14 of 21-day cycles until disease progression or unacceptable toxicity. The first 6 patients of Asian-Pacific Islander (API) ethnicity received a reduced dose of 200 mg to preserve safety and tolerability; if well tolerated, subsequent API patients received CC-486 300 mg. The study could advance to stage 2 if > 4 patients achieved a response. Co-primary end-points were overall response rate (ORR) and progression-free survival (independent review). Key secondary end-points were overall survival and safety.

RESULTS

Owing to faster-than-anticipated enrolment, 36 patients, including 13 of API ethnicity, were enrolled; the median age was 54.0 years. Most patients were male (81%) and had an Eastern Cooperative Oncology Group performance status ≤ 1 (97%). Among 25 efficacy-evaluable patients, the ORR was 12%; the median progression-free and overall survival were 4.7 and 18.0 months, respectively. The most common grade III/IV treatment-emergent adverse events were neutropenia (33%) and febrile neutropenia (11%). Twenty-one posttreatment deaths, primarily due to progressive disease or disease complications, and 1 on-treatment death (epistaxis, unrelated to study drug) occurred. The study did not advance to stage 2.

CONCLUSION

CC-486 did not show sufficient clinical activity to support further development as monotherapy in this patient population. The safety profile of CC-486 in NPC was consistent with that in other solid tumours.

MicroRNA-17 acts as a tumor chemosensitizer by targeting JAB1/CSN5 in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the breast cancer subtype with the poorest prognosis. Evidence indicates that aberrant JAB1/CSN5 expression is associated with advanced tumor stage and poor prognosis in breast cancer. In this study, we evaluated expression of JAB1 in TNBC and potential mechanisms regulating this expression. We found that miR-17 expression was lower in TNBC than in normal breast tissue, and miR-17 expression in patients with TNBC was associated with a good prognosis. Furthermore, JAB1 expression was regulated by miR-17 in TNBC cells, and mice with miR-17-overexpressing tumors had less tumor growth and lower tumor JAB1 expression than control mice. We also demonstrated that miR-17 suppressed JAB1's oncogenic function, leading to tumor growth inhibition and sensitizing TNBC cells to chemotherapy treatment. JAB1 knockdown in TNBC cells mimicked the effect of miR-17 overexpression and led to significant decreases in cell proliferation, colony formation, and migration, increased p27 expression, and enhanced cisplatin sensitivity. Our findings suggest that miR-17 acts as a tumor suppressor by directly targeting JAB1 in TNBC; this may lead to novel therapeutic targets and strategies for treating TNBC patients.

Effects of CKMT1 on radiosensitivity of nasopharyngeal carcinoma cells

PURPOSE

Radioresistance is an important factor for unsatisfactory prognosis in Nasopharyngeal carcinoma (NPC) patients. Ubiquitous mitochondrial creatine kinase (CKMT1) is always associated with malignancy in a variety of cancers. However, its significance in NPC progression and radiosensitivity remains unclear. The present study focused on investigating the effects of CKMT1 on NPC cell radiosensitivity.

MATERIAL AND METHODS

CKMT1 was overexpressed in NPC cell line CNE-1 or knocked out in CNE-2. Biological changes were detected after cells exposing to different doses of X-ray to determine the role of CKMT1 on NPC cell radiosensitivity.

RESULTS

CKMT1 promotes proliferation and migration in NPC cell lines CNE-1 and CNE-2. Overexpression of CKMT1 in CNE-1 cells enhanced colony formation rates, reduced G2/M phase cell cycle arrest, lowered apoptosis rate and c-PARP level, and elevated STAT3 phosphorylation level after radiation treatment. While knocking out CKMT1 using the CRISPR/Cas9 system in CNE-2 cells lowered colony formation rates, increased G2/M phase cell cycle arrest, apoptosis rates, and c-PARP levels, and decreased STAT3 phosphorylation in response to radiation treatment.

CONCLUSIONS

NPC cells with higher CKMT1 exhibited lower radiosensitivity through promoting phosphorylation of STAT3. Our findings suggest that CKMT1 may be an alternative radiotherapeutic target in NPC therapy.

Human nasopharyngeal carcinoma can be radiosensitized by trichosanthin via inhibition of the PI3K pathway

Nasopharyngeal carcinoma (NPC) is a prevalent tumor that affects the head and neck. Radiation therapy is typically used to treat NPC; however, poor prognoses and distant metastases are common due to radiation resistance. The antitumor activities of trichosanthin (TCS) have been reported in several types of tumors. The aim of the present study was to investigate whether TCS may serve as a potential radiosensitizer in the treatment of NPC tumors. In the present study, NPC cells were treated with radiation alone or together with TCS and radiosensitivity was compared. Clonogenic assay, flow cytometry and an animal study were performed to assess cell death in NPC. The clonogenic assay demonstrated that TCS had a significant radiosensitizing effect on NPC cells. Western blotting indicated that phosphorylated protein kinase B and signal-regulated kinase [phosphoinositide 3-kinase (PI3K) pathway] were downregulated, and that cleaved caspase-3 was upregulated by combined treatment with TCS and radiation. Furthermore, TCS potently radiosensitized NPC xenografts in vivo. In conclusion, TCS radiosensitized NPC in vitro and in vivo via downregulation of PI3K pathways and the upregulation of cleaved caspase-3.

Serum microRNA as potential biomarker to detect breast atypical hyperplasia and early-stage breast cancer

AIM

The present study aimed to identify microRNA (miRNA) that can be used for not only detecting early-stage breast cancer (BC) but also diagnosing atypical hyperplasia (AH).

MATERIALS & METHODS

RT-qPCR detected the expression levels of miRNAs and receiver operating characteristic curves were constructed to evaluate sensitivity and specificity of the assay.

RESULTS

miR-24 and miR-103a were expressed in an upward trend in serum of benign proliferative tumor subjects, while they were downregulated significantly in serum of AH (p < 0.005) and early-stage BC subjects (p < 0.005) with high sensitivity and specificity as compared with controls. Bioinformatics analysis also revealed the potential molecular mechanism through which miR-24 and miR-103a regulate tumorigenesis in BC.

CONCLUSION

miR-24 and miR-103a were valuable biomarkers for distinguishing AH and early-stage BC from healthy individuals/benign proliferative tumor patients.

hsa‑miR‑24 suppresses metastasis in nasopharyngeal carcinoma by regulating the c‑Myc/epithelial‑mesenchymal transition axis

Distant metastasis is the major contributor to treatment failure and mortality in patients with nasopharyngeal carcinoma (NPC). The lack of effective treatment strategies for metastatic NPC is the major cause for the low survival rate. Therefore, it is crucial to understand the molecular mechanisms underlying NPC metastasis and to identify potential biomarkers for targeted therapy. MicroRNA (miRNAs or miRs) have been shown to play an important role in tumorigenesis and metastasis. In the present study, we aimed to evaluate the significance of hsa-miR-24 in NPC metastasis. Significantly lower hsa-miR-24 levels were observed in NPC metastatic tumors and higher hsa-miR-24 levels were associated with longer progression-free and metastasis-free survival durations. hsa-miR-24 overexpression inhibited cell proliferation, invasion and migration. Using bioinformatics approaches together with functional luciferase reporter assays, we demonstrated that the c-Myc 3′-UTR was a direct target of hsa-miR-24 in regulating NPC metastasis. Protein profiling analysis revealed that a high c-Myc expression was inversely associated with metastasis-free overall survival and with epithelial-mesenchymal transition (EMT). Furthermore, the overexpression of hsa-miR-24 decreased NPC cell invasive ability induced by the overexpression of c-Myc, associated with EMT epithelial marker (E-cadherin) restoration. Thus, on the whole, the findings of this study demonstrate that hsa-miR-24 suppresses metastasis in NPC by regulating the c-Myc/EMT axis, suggesting that hsa-miR-24 may be used as a prognostic factor and as a novel target for the prevention of NPC metastasis.

The pivotal role of DNA methylation in the radio-sensitivity of tumor radiotherapy

Radiotherapy is an important modality for treatment of carcinomas; however, radio‐resistance is still a difficult problem. Aberrant epigenetic alterations play an important role in cancer development. Among epigenetic parameters, DNA methylation has arguably attracted the most attention in the radio‐resistance process. To determine the role of DNA methylation in radiation resistance, several studies were conducted. We summarized previous studies on the role of DNA methylation in radiotherapy. We observed this significant role of DNA methylation in genes related to DNA repair, cell proliferation, cell cycle process, and re‐oxygenation. Furtherly, we also conclude the predictive effect of DNA methylation on tumor radio‐sensitivity and the using of DNA methyltransferase inhibitors in clinical practice. DNA methylation plays a pivotal role in the radio‐sensitivity of tumor radio‐therapy. While hyper‐methylation or hypo‐methylation of genes is related to gene functions.

Selenium unmasks protective iron armor: A possible defense against cutaneous inflammation and cancer

BACKGROUND

A link between selenium deficiency and inflammatory skin diseases have been noted by many, but this link is still not well understood. We have previously studied the efficacy of ceramide analogs, based on the fire ant venom Solenopsin A, against our psoriasis animal model. Treatment of animals with solenopsin analogs resulted in significantly improved skin as well as in a coordinate downregulation of selenoproteins, namely Glutathione Peroxidase 4 (GPX4). We thus hypothesize that ferroptosis may be a physiologic process that may protect the skin from both inflammatory and neoplastic processes.

METHODS

We analyze and compare gene expression profiles in the GEO database from clinical skin samples taken from healthy patients and psoriasis patients (both involved and noninvolved skin lesions). We validated the gene expression results against a second, independent, cohort from the GEO database.

RESULTS

Significant reduction in gene expression of GPX4, elevated expression of Nrf2 downstream targets, and expression profiles mirroring erastin-inhibition of Cystine/Glutamate Antiporter-System X_C activity in psoriatic skin lesions, compared to both noninvolved skin and healthy patient samples, suggest an innately inducible mechanism of ferroptosis.

CONCLUSIONS

We present data that may indicate selenoproteins, particularly GPX4, in resolving inflammation and skin cancer, including the novel hypothesis that the human organism may downregulate GPX4 and reactive oxygen (REDOX) regulating proteins in the skin as a way of resolving psoriasis and nonmelanoma skin cancer through increased reactive oxygen species. Further studies are needed to investigate ferroptosis as a possible physiologic mechanism for eliminating inflammatory and malignant tissues.

GENERAL SIGNIFICANCE

This study provides a fresh framework for understanding the seemingly contradictory effects of selenium supplementation. In addition, it offers a novel explanation of how physiologic upregulation of ferroptosis and downregulation of selenoprotein synthesis may mediate resolution of inflammation and carcinogenesis. This is of therapeutic significance.

Influence of POLG on Radiosensitivity of Nasopharyngeal Carcinoma Cells

BACKGROUND AND OBJECTIVE

There is a high incidence of nasopharyngeal carcinoma (NPC), malignant head and neck tumors, in southern China. Radioresistance is the main cause affecting the efficacy of NPC treatments. The POLG gene particularly plays an important role in radiation-induced damage repair. In this study, the authors established RNAi CNE-1 and CNE-2 knockdown in two NPC cell lines to observe whether this gene affects the radiosensitivity of NPC cells.

MATERIALS AND METHODS

Four short hairpin RNA (shRNA) expression plasmids targeting POLG gene were constructed and transfected into the NPC cell lines CNE-1 and CNE-2. Screening was performed to evaluate the stable expression of cloned cells, which were named CNE-1/POLG-shRNA1, CNE-1/POLG-shRNA2, CNE-2/POLG-shRNA1, and CNE-2/POLG-shRNA2. The negative controls CNE-1/Neg-shRNA and CNE-2/Neg-shRNA were additionally used. The MTT method, flow cytometry, clone formation analysis, cell migration, and other experimental methods were employed to verify changes in the radiosensitivity of the NPC cells.

RESULTS

Fluorescent quantitative PCR and Western blot confirmed the downregulation of the PLOG gene through diminished PLOG messenger RNA and protein levels. Consequently, the authors report the stable knockdown of the POLG gene in an NPC model. Dose-dependent radiation exposure of POLG inhibited NPC cell growth and increased apoptosis compared with control cells (p < 0.01), as demonstrated through colony formation assay and flow cytometry. Functional assays indicated that knockdown of the POLG in CNE-1 and CNE-2 cells remarkably reduced cell viability and proliferation. Specifically, POLG knockdown led to G1 phase arrest and apoptosis.

CONCLUSIONS

Overall, the authors conclude that POLG downregulation alters the radiosensitivity of NPC cells, indicating that the gene is likely involved in conferring the radiation response of the cells. In addition, findings in this study suggest a novel role for POLG as a potential predictive marker for NPC radiotherapy efficiency. POLG gene can be used as a potential clinical target to effectively improve the radiosensitivity of NPC.

Impact of DNA and RNA Methylation on Radiobiology and Cancer Progression

Radiotherapy is a well-established regimen for nearly half the cancer patients worldwide. However, not all cancer patients respond to irradiation treatment, and radioresistance is highly associated with poor prognosis and risk of recurrence. Elucidation of the biological characteristics of radioresistance and development of effective prognostic markers to guide clinical decision making clearly remain an urgent medical requirement. In tumorigenic and radioresistant cancer cell populations, phenotypic switch is observed during the course of irradiation treatment, which is associated with both stable genetic and epigenetic changes. While the importance of epigenetic changes is widely accepted, the irradiation-triggered specific epigenetic alterations at the molecular level are incompletely defined. The present review provides a summary of current studies on the molecular functions of DNA and RNA m⁶A methylation, the key epigenetic mechanisms involved in regulating the expression of genetic information, in resistance to irradiation and cancer progression. We additionally discuss the effects of DNA methylation and RNA N⁶-methyladenosine (m⁶A) of specific genes in cancer progression, recurrence, and radioresistance. As epigenetic alterations could be reversed by drug treatment or inhibition of specific genes, they are also considered potential targets for anticancer therapy and/or radiotherapy sensitizers. The mechanisms of irradiation-induced alterations in DNA and RNA m⁶A methylation, and ways in which this understanding can be applied clinically, including utilization of methylation patterns as prognostic markers for cancer radiotherapy and their manipulation for anticancer therapy or use as radiotherapy sensitizers, have been further discussed.

Epigenetics and MicroRNAs in Cancer

The ability to reprogram the transcriptional circuitry by remodeling the three-dimensional structure of the genome is exploited by cancer cells to promote tumorigenesis. This reprogramming occurs because of hereditable chromatin chemical modifications and the consequent formation of RNA-protein-DNA complexes that represent the principal actors of the epigenetic phenomena. In this regard, the deregulation of a transcribed non-coding RNA may be both cause and consequence of a cancer-related epigenetic alteration. This review summarizes recent findings that implicate microRNAs in the aberrant epigenetic regulation of cancer cells.

Downregulation of lncRNA X Inactive Specific Transcript (XIST) Suppresses Cell Proliferation and Enhances Radiosensitivity by Upregulating mir-29c in Nasopharyngeal Carcinoma Cells

Background

LncRNA X inactive specific transcript (XIST) was reported to function as an oncogene in nasopharyngeal carcinoma cells (NPC) by sponging miR-34a-5p. However, the role of XIST in modulating the radiosensitivity of NPC cells and its mechanism still remain undefined.

Material/Methods

The expressions of XIST and miR-29c in NPC cells were evaluated by qRT-PCR. CNE1 and CNE2 cells were transfected with si-XIST, pcDNA-XIST, miR-29c mimics, anti-miR-29c, or respective controls by Lipofectamine 2000. The effects of XIST knockdown and miR-29c overexpression on cell proliferation, survival fraction, and γ-H2AX expression were investigated by CCK-8 assay, colony formation assay, immunofluorescence, and Western blot, respectively. Luciferase reporter assay and qRT-PCR analysis were performed to confirm whether XIST interacts with miR-29c and regulates its expression.

Results

XIST was upregulated and miR-29c was downregulated in NPC cells. The expressions of XIST and miR-29c changed reversely in response to irradiation. Knockdown of XIST and miR-29c overexpression both resulted in a dramatic suppression of cell proliferation, a marked enhancement of radiosensitivity, and an obvious increase of γ-H2AX foci formation in NPC cells. Luciferase reporter assay and qRT-PCR analysis demonstrated that XIST interacts with miR-29c and negatively regulates its expression. Moreover, miR-29c inhibition abrogated XIST knockdown-induced cell proliferation inhibition and radiosensitivity increase in NPC cells.

Conclusions

XIST knockdown suppressed cell proliferation and enhanced radiosensitivity of NPC cells by upregulating miR-29c, providing a novel therapeutic target to improve radiotherapy efficiency for patients with NPC.

Epigenetic silencing of miR-493 increases the resistance to cisplatin in lung cancer by targeting tongue cancer resistance-related protein 1(TCRP1)

Background

The potential mechanisms regarding how methylation of microRNA(miRNA) CpG Island could regulate cancer cell chemo-resistance remains unclear. This study aims to explore the epigenetic dysregulation mechanism of miRNA-493 and the ability to modulate lung cancer cell chemotherapy resistance.

Methods

Real-time quantitative PCR (qRT-PCR) and In situ hybridization (ISH) were used to analyze the expression of miR-493 in lung cancer cell lines and tumor tissue, respectively. Bisulfite sequencing PCR (BSP) was used to exam the promoter CpG Island of miR-493. The effect of miR-493 on chemosensitivity was evaluated by cell viability assays, apoptosis assays and in vivo experiment. The DNA damage was measured by γ-H2AX immunofluorescence. Luciferase reporter assay was used to assess the target genes of miR-493. Expression of target proteins and downstream molecules were analyzed by Western blot.

Results

miR-493 is silenced in resistant lung cancer cell due to the aberrant DNA methylation. Enforced expression of miR-493 in lung cancer cells promotes chemotherapy sensitivity to cisplatin through impairing the DNA damage repair and increasing the cells apoptosis in vitro and in vivo. Furthermore, we identify that TCRP1 is a direct functional target of miR-493. Ectopic expression of TCRP1 attenuated increased apoptosis in miR-493-overexpressing lung cancer cells upon cisplatin treatment. Meanwhile, miR-493 level is negatively correlated with TCRP1 expression in lung cancer patients and TCRP1 expression were correlated with poor survival.

Conclusions

Our results highlight that hyper-methylation of miR-493CpG island might play important roles in the development of lung cancer chemo-resistance by targeting TCRP1, which might be used as a potential therapeutic target in preventing the chemo-resistance of lung cancer.

Exosomal miR-24-3p impedes T-cell function by targeting FGF11 and serves as a potential prognostic biomarker for nasopharyngeal carcinoma

Recent studies have shown that extracellular microRNAs are not only potential biomarkers but are also involved in cell interactions to regulate the intercommunication between cancer cells and their microenvironments in various types of malignancies. In this study, we isolated exosomes from nasopharyngeal carcinoma (NPC) cell lines and patient sera (T-EXOs), or control NP69 cells and healthy donor sera (HD-EXOs). We found that miR-24-3p was markedly enriched in T-EXOs as compared with HD-EXOs; the serum exosomal miR-24-3p level was correlated with worse disease-free survival of patients (p < 0.05). Knockdown of exosomal miR-24-3p (miR-24-3p-sponge-T-EXOs) by a sponge RNA targeting miR-24-3p restored the T-EXO-mediated (control-sponge-T-EXO) inhibition of T-cell proliferation and Th1 and Th17 differentiation, and the induction of regulatory T cells (Tregs). Mechanistic analyses revealed that administration of exosomal miR-24-3p increased P-ERK, P-STAT1 and P-STAT3 expression while decreasing P-STAT5 expression during T-cell proliferation and differentiation. Moreover, by in vivo and in vitro assessments, we found FGF11 to be a direct target of miR-24-3p. However, both miR-24-3p-sponge-T-EXOs and T-EXOs (control-sponge-T-EXOs) impeded proliferation and Th1 and Th17 differentiation, but induced Treg differentiation, of lenti-shFGF11-transfected T cells. The levels of phosphorylated ERK and STAT proteins were different in lenti-ScshRNA-transfected T cells and lenti-shFGF11-transfected T cells following administration of miR-24-3p-sponge-T-EXO. Interestingly, tumour FGF11 expression was positively correlated with the number of CD4⁺ and CD8⁺ T cells in vivo, and predicted favourable patient DFS (p < 0.05). Additionally, hypoxia increased cellular and exosomal miR-24-3p levels and enhanced the inhibitory effect of T-EXO on T-cell proliferation and differentiation. Collectively, our findings suggest that exosomal miR-24-3p is involved in tumour pathogenesis by mediating T-cell suppression via repression of FGF11, and may serve as a potential prognostic biomarker in NPC. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Interplay of DNA methyltransferase 1 and EZH2 through inactivation of Stat3 contributes to β-elemene-inhibited growth of nasopharyngeal carcinoma cells

β-elemene, a compound extracted from Curcuma wenyujin plant, exhibits anticancer activity in many cancer types. However, the detailed mechanism by which β-elemene inhibits growth of nasopharyngeal carcinoma (NPC) cells remains unknown. We showed that β-elemene reduced phosphorylation of signal transducer and activator of transcription 3 (Stat3), and protein expressions of DNA methyltransferase 1 (DNMT1) and enhancer of zeste homolog 2 (EZH2). Exogenously expressed Stat3 antagonized the effect of β-elemene on DNMT1 and EZH2 expressions. Furthermore, overexpressions of DNMT1 and EZH2 reversed the effect of β-elemene on phosphorylation of Stat3 and cell growth inhibition. Intriguingly, exogenously expressed DNMT1 overcame β-elemene-inhibited EZH2 protein expression and promoter activity. On the contrary, silencing of EZH2 and DNMT1 genes feedback strengthened the effect of β-elemene on phosphorylation of Stat3. Consistent with this, β-elemene inhibited tumor growth, phosphorylation of Stat3, expressions of DNMT1 and EZH2 in a mouse xenograft model. Collectively, this study shows that β-elemene inhibits NPC cell growth via inactivation of Stat3, and reduces DNMT1 and EZH2 expressions. The interplay of DNMT1 and EZH2, and the mutual regulations among Stat3, EZH2 and DNMT1 contribute to the overall responses of β-elemene. This study uncovers a novel mechanism by which β-elemene inhibits growth of NPC cells.

mRNA and methylation profiling of radioresistant esophageal cancer cells: the involvement of Sall2 in acquired aggressive phenotypes

Esophageal squamous cell carcinoma (ESCC) is one of the deadliest malignancies worldwide. Radiotherapy plays a critical role in the curative management of inoperable ESCC patients. However, radioresistance restricts the efficacy of radiotherapy for ESCC patients. The molecules involved in radioresistance remain largely unknown, and new approaches to sensitize cells to irradiation are in demand. Technical advances in analysis of mRNA and methylation have enabled the exploration of the etiology of diseases and have the potential to broaden our understanding of the molecular pathways of ESCC radioresistance. In this study, we constructed radioresistant TE-1 and Eca-109 cell lines (TE-1/R and Eca-109/R, respectively). The radioresistant cells showed an increased migration ability but reduced apoptosis and cisplatin sensitivity compared with their parent cells. mRNA and methylation profiling by microarray revealed 1192 preferentially expressed mRNAs and 8841 aberrantly methylated regions between TE-1/R and TE-1 cells. By integrating the mRNA and methylation profiles, we related the decreased expression of transcription factor Sall2 with a corresponding increase in its methylation in TE-1/R cells, indicating its involvement in radioresistance. Upregulation of Sall2 decreased the growth and migration advantage of radioresistant ESCC cells. Taken together, our present findings illustrate the mRNA and DNA methylation changes during the radioresistance of ESCC and the important role of Sall2 in esophageal cancer malignancy.

MicroRNAs Involvement in Radioresistance of Head and Neck Cancer

Resistance to the ionizing radiation is a current problem in the treatment and clinical management of various cancers including head and neck cancer. There are several biological and molecular mechanisms described to be responsible for resistance of the tumors to radiotherapy. Among them, the main mechanisms include alterations in intracellular pathways involved in DNA damage and repair, apoptosis, proliferation, and angiogenesis. It has been found that regulation of these complex processes is often controlled by microRNAs. MicroRNAs are short endogenous RNA molecules that posttranscriptionally modulate gene expression and their deregulated expression has been observed in many tumors including head and neck cancer. Specific expression patterns of microRNAs have also been shown to predict prognosis and therapeutic response in head and neck cancer. Therefore, microRNAs present promising biomarkers and therapeutic targets that might overcome resistance to radiation and improve prognosis of head and neck cancer patients. In this review, we summarize the current knowledge of the functional role of microRNAs in radioresistance of cancer with special focus on head and neck cancer.

Cyclin-Dependent Kinase Inhibitor 3 Promotes Cancer Cell Proliferation and Tumorigenesis in Nasopharyngeal Carcinoma by Targeting p27

Nasopharyngeal carcinoma (NPC) is a common malignancy of the head and neck that arises from the nasopharynx epithelium and is highly invasive. Cyclin-dependent kinase inhibitor 3 (CDKN3) belongs to the dual-specificity protein phosphatase family, which plays a key role in regulating cell division. Abnormal expression of CDKN3 has been found in numerous types of cancer. In the current study, we explored the possible role of CDKN3 in cell proliferation, ability to invade, and radiosensitivity in NPC cells. We reported that CDKN3 was upregulated and p27 was downregulated in NPC tissues and is associated with a worse prognosis for patients. In addition, downregulation of CDKN3 and upregulation of p27 decreased cell proliferation, induced cell cycle arrest, increased apoptosis, decreased cell invasion, and enhanced radiosensitivity. Silencing of p27 significantly inhibited the effects of the knockdown of CDKN3. Moreover, downregulation of CDKN3 and upregulation of p27 inhibited the increase in tumor volume and weight in implanted tumors, decreased the phosphorylation of Akt, and increased the expression of cleaved caspase 3 in tumors. CDKN3 expression was also inversely correlated with p27 expression in NPC patients. Knockdown of CDKN3 increased p27 expression. Silencing of p27 markedly inhibited the effects of CDKN3 on cell proliferation, cell cycle progression, apoptosis, invasion, and radiosensitivity. These results demonstrate that upregulation of p27 is involved in the knockdown of CDKN3-induced decrease in cell proliferation, increase in cell cycle arrest and apoptosis, decrease in invasion, and increase in radiosensitivity. The results demonstrate that the CDKN3/p27 axis may be a novel target in the treatment of NPC.

miR clusters target cellular functional complexes by defining their degree of regulatory freedom

Using the two paralog miR-23∼27∼24 clusters as an example and combining experimental and clinical data in a systematical approach to microRNA (miR) function and dysregulation, a complex picture of their roles in cancer is drawn. Various findings appear to be contradictory to a larger extent and cannot be fully explained by the classical regulatory network models and feedback loops that are mainly considered by one-to-one regulatory interactions of the involved molecules. Here, we propose an extended model of the regulatory role of miRs that, at least, supplements the usually considered single/oligo-target regulation of certain miRs. The cellular availability of the participating miR members in this model reflects an upper hierarchy level of intracellular and extracellular environmental influences, such as neighboring cells, soluble factors, hypoxia, chemotherapeutic drugs, and irradiation, among others. The novel model is based on the understanding of cellular functional complexes, such as for apoptosis, migration, and proliferation. These complexes consist of many regulatory components that can be targeted by miR cluster members to a different extent but may affect the functional complex in different ways. We propose that the final miR-related effect is a result of the possible degree of regulatory freedom provided by the miR effects on the whole functional complex structure. This degree of regulatory freedom defines to which extent the cellular functional complex can react in response to regulatory triggers, also understood as sensitization (more regulatory response options) or de-sensitization (less regulatory response options) of the system rather than single molecules.

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.

Hsa-miR-24-3p increases nasopharyngeal carcinoma radiosensitivity by targeting both the 3'UTR and 5'UTR of Jab1/CSN5

Radiotherapy is the standard therapy for nasopharyngeal carcinoma (NPC); however, radioresistance can hinder successful treatment. Here we report that microRNA (miR)-24 acts as a tumor suppressor and radiosensitizer in NPC cells and xenografts by targeting Jab1/CSN5. Although accumulating evidence has shown that Jab1/CSN5 functions as an oncoprotein in human cancers, its regulation through miRs has not been described. In this study, we found that Jab1/CSN5 functioned in a manner opposite to that of miR-24 in NPC tumorigenesis and radioresistance. We demonstrated that miR-24 inhibits Jab1/CSN5 translation via direct binding to its 3' untranslated region (3'UTR) and 5'UTR, leading to tumor growth inhibition, and sensitizes NPC tumors to radiation in vivo. Furthermore, silencing Jab1/CSN5 phenocopied the function of miR-24 in NPC cells after ionizing radiation treatment, resulting in increased apoptosis. Finally, we analyzed 50 paired samples of primary and matched recurrent NPC tissues from 25 NPC patients and subjected them to high-throughput genomic quantitative nuclease protection assay for quantifying simultaneously miR and mRNA levels. Our results showed that miR-24 levels were significantly decreased in recurrent NPC and that levels of Jab1/CSN5, as its target, were higher than those in primary NPC. Together, our findings indicate that miR-24 inhibits NPC tumor growth and increases NPC radiosensitivity by directly regulating Jab1/CSN5 and that both miR-24 and Jab1/CSN5 can serve as prognostic markers for NPC recurrence; this, in turn, may provide a promising therapeutic strategy for reversing NPC radioresistance.

MiR-24 enhances radiosensitivity in nasopharyngeal carcinoma by targeting SP1

Radioresistance remains a major problem in the treatment of patients suffering from nasopharyngeal carcinoma (NPC). A better understanding of the mechanisms of radioresistance may generate new strategies to improve NPC patients' responses to therapy. This study was designed to investigate the effect of microRNA on the radiosensitivity of NPC cells. A microRNA microarray indicated that miR‐24 was downregulated in NPC cell lines and tissues. Furthermore, cell proliferation was suppressed and radiosensitivity increased when miR‐24 was ectopically expressed in NPC cells. Specificity protein 1 (SP1) was additionally verified as a direct functional target of miR‐24, which was found to be involved in cell viability as well as the radiosensitivity of NPC cells. In conclusion, the results of this study suggest that the miR‐24/SP1 pathway contributed to the reduction in radioresistance in human NPC and that it may thus represent a therapeutic target.

MiR-24 functions as a tumor suppressor in nasopharyngeal carcinoma through targeting FSCN1

Background

Increasing evidence indicates that the dysregulation of miRNAs expression is involved in the tumorigenesis by acting as tumor suppressors or oncogenes. However, no study investigates the function and mechanisms of miR-24 in nasopharyngeal carcinoma (NPC).

Methods

Quantitative RT-PCR, MTT, colony formation, soft-agar, wound healing, Transwell migration and invasion assays, and xenograft tumor growth and lung metastasis models were performed to test the expression levels and functions of miR-24 in NPC. Luciferase reporter assay, quantitative RT-PCR, Western blotting, and immunohistochemistry were used to identify and verify the target of miR-24.

Results

The results showed that MiR-24 was obviously downregulated in NPC cell lines and tissue samples (P < 0.05). Ectopic expression of miR-24 inhibited the cell viability, proliferation, migration, and invasion in vitro (all P < 0.05), and suppressed the xenograft tumor growth and lung metastasis formation in vivo (all P < 0.05). Fascin homologue 1 (FSCN1) was verified as a direct target of miR-24, and silencing FSCN1 expression with small interfering RNA inhibited NPC cell proliferation and invasion (all P < 0.05).

Conclusions

Overall, miR-24 acts as a novel tumor suppressor in the development and progression of NPC through targeting FSCN1, which providing new insight into the mechanisms of NPC carcinogenesis and suggesting the possibility of miR-24 as a therapeutic target.

Reversal effect of GnT-V on the radioresistance of human nasopharyngeal carcinoma cells by alteration β1, 6-GlcNAc branched N-glycans

Radiotherapy is the primary treatment for human nasopharyngeal carcinoma (NPC), yet radioresistance remains a major obstacle to successful treatment in many cases. N-acetylglucosaminyltransferase V (GnT-V), which synthesizes β1, 6-GlcNAc branched N-glycans, is closely related to the radiosensitivity of NPC cells. However, a better understanding of the functional role of GnT-V in NPC radioresistance and the related mechanisms is urgently needed. In the present study, a radioresistant NPC cell line, CNE-2R, was established by repeated γ-irradiation. We found that GnT-V levels, as well as β1, 6-GlcNAc branched N-glycans were significantly increased in the CNE-2R cells as compared with that in the parental cells. Meanwhile, knockdown of GnT-V in the CNE-2R cells enhanced cell radiosensitivity and inhibited the formation of β1, 6-branched N-glycans. In addition, the regulated expression of GnT-V in the CNE-2R cells converted the heterogeneous N-glycosylated forms of CD147. Furthermore, swainsonine, an inhibitor of N-glycan biosynthesis, was also able to reverse the radioresistance of the CNE-2R cells. Taken together, the present study revealed a novel mechanism of GnT-V as a regulator of radioresistance in NPC cells, which may be useful for fully understanding the biological role of N-glycans in NPC radioresistance.

The emerging role of miRNAs in combined cancer therapy

MicroRNAs (miRNAs) control physiological and fundamental processes in cellular development and differentiation by modulating the expression of their target genes. They have been found to participate in cell transformation and multiplication by functioning as oncomiRs and tumor suppressors in diverse cancers. Introduction of antisense miRNAs (antagomiRs) into primary cells such as immune cells by lipofection, viral vectors or electroporation can achieve the specific silencing of individual miRNAs. Therefore, harnessing miRNAs may lead to promising cancer therapeutics. There is emerging evidence demonstrating the involvement of miRNAs in combined cancer therapies, including chemotherapy, radiotherapy and immunotherapy combining with miRNA therapy.