Real-Time PCR Analysis of Micro-RNA Expression in Ionizing Radiation-Treated Cells

microRNA 146a ameliorates retinal damage in experimental autoimmune uveitis

Introduction

Uveitis and related intraocular inflammations are a major cause of blindness due to retinal damage caused by degeneration and loss of the photoreceptor cells. In mouse experimental autoimmune uveitis (EAU) previously we have shown mitochondrial oxidative stress with marked upregulation of αA crystallin in the inner segments of the photoreceptors. Furthermore, αA crystallin treatment prevented photoreceptor mitochondrial oxidative stress by suppressing innate and adaptive immunity in EAU.

Methods

Since these immune processes are modulated by microRNAs, in this study we investigated (a) modulation of microRNAs during development of EAU by αA crystallin administration and (b) microRNA therapeutic intervention.

Results

Few microRNAs were significantly upregulated in EAU mice with intravenous injection of αA crystallin and among these, computational bioinformatic analysis revealed that the upregulated microRNA 146a targets the innate and adaptive immune responses. In EAU, intravenous as well as intravitreal administration of this microRNA prevented inflammatory cell infiltration in uvea and retina and preserved photoreceptor cells.

Discussion

This protective function suggests that microRNA146a can be a novel therapeutic agent in preventing retinal damage in uveitis.

The Advances in Epigenetics for Cancer Radiotherapy

Cancer is an important factor threatening human life and health; in recent years, its morbidity and mortality remain high and demosntrate an upward trend. It is of great significance to study its pathogenesis and targeted therapy. As the complex mechanisms of epigenetic modification has been increasingly discovered, they are more closely related to the occurrence and development of cancer. As a reversible response, epigenetic modification is of great significance for the improvement of classical therapeutic measures and the discovery of new therapeutic targets. It has become a research focusto explore the multi-level mechanisms of RNA, DNA, chromatin and proteins. As an important means of cancer treatment, radiotherapy has made great progress in technology, methods, means and targeted sensitization after years of rapid development, and even research on radiotherapy based on epigenetic modification is rampant. A series of epigenetic effects of radiation on DNA methylation, histone modification, chromosome remodeling, RNA modification and non-coding RNA during radiotherapy affects the therapeutic effects and prognosis. Starting from the epigenetic mechanism of tumorigenesis, this paper reviews the latest progress in the mechanism of interaction between epigenetic modification and cancer radiotherapy and briefly introduces the main types, mechanisms and applications of epigenetic modifiers used for radiotherapy sensitization in order to explore a more individual and dynamic approach of cancer treatment based on epigenetic mechanism. This study strives to make a modest contribution to the progress of human disease research.

Radiation-resistance increased by overexpression of microRNA-21 and inhibition of its target PTEN in esophageal squamous cell carcinoma

Objective

Overexpression of microRNA-21 (miR-21) increases the radiation resistance of esophageal squamous cell carcinoma (ESCC). However, the molecular mechanism responsible for this action is still unclear. In the present study, we investigated the role of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) in miR-21-enhanced radiation resistance in patients with ESCC.

Methods

We evaluated the association between miR-21 levels and radiation resistance in patients with ESCC. We also investigated the role of PTEN in the proliferation and apoptosis of ESCC cells transfected with miR-21 inhibitor during irradiation, using PTEN small interfering RNA (siRNA).

Results

MiR-21 levels were significantly higher in radiation-resistant patients. Downregulation of miR-21 during irradiation suppressed the radiation resistance of ESCC cells, demonstrated by decreased cell proliferation and increased cell apoptosis. PTEN siRNA attenuated miR-21-induced suppression of radiation resistance in ESCC cells.

Conclusions

These results suggest that miR-21 enhanced the radiation resistance of ESCC by inhibiting PTEN. MiR-21 and PTEN are potential therapeutic biotargets for ESCC.

Development of acoustically isolated extracellular plasma vesicles for biomarker discovery in allogeneic hematopoietic stem cell transplantation

Background

Infection and graft-versus-host disease (GvHD) are the major causes for mortality and morbidity of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Plasma-derived extracellular vesicles (EVs) contain disease-related proteins, DNAs and RNAs, and have recently been suggested as potential biomarker candidates for transplantation complications. However, EV isolation from small plasma volumes in clinical biomarker studies using conventional methods is challenging. We therefore investigated if EVs isolated by novel automated acoustic trapping could be developed as potential biomarkers for allo-HSCT complications by performing a clinical proof-of-principle study.

Results

Plasma samples were collected from twenty consecutive patients with high-risk/relapsed hematologic malignancies undergoing allo-HSCT before transplantation and post-transplant up to 12 weeks. EVs were isolated from small plasma sample volumes (150 μl) by an automated, acoustofluidic-based particle trapping device, which utilizes a local λ/2 ultrasonic standing wave in a borosilicate glass capillary to capture plasma EVs among pre-seeded polystyrene microbeads through sound scatter interactions. We found that EVs could be reliably isolated from all plasma samples (n = 173) and that EV numbers increased more than 2-fold in the majority of patients after transplantation. Also, sufficient quantities of RNA for downstream microRNA (miRNA) analysis were obtained from all samples and EV miRNA profiles were found to differ from whole plasma profiles. As a proof of principle, expression of platelet-specific miR-142-3p in EVs was shown to correlate with platelet count kinetics after transplantation as expected. Importantly, we identified plasma EV miRNAs that were consistently positively correlated with infection and GvHD, respectively, as well as miRNAs that were consistently negatively correlated with these complications.

Conclusions

This study demonstrates that acoustic enrichment of EVs in a clinical biomarker study setting is feasible and that downstream analysis of acoustically-enriched EVs presents a promising tool for biomarker development in allo-HSCT. Certainly, these findings warrant further exploration in larger studies, which will have significant implications not only for biomarker studies in transplantation but also for the broad field of EV-based biomarker discovery.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40364-020-00259-4.

A microRNA signature and TGF-β1 response were identified as the key master regulators for spaceflight response

Translating fundamental biological discoveries from NASA Space Biology program into health risk from space flights has been an ongoing challenge. We propose to use NASA GeneLab database to gain new knowledge on potential systemic responses to space. Unbiased systems biology analysis of transcriptomic data from seven different rodent datasets reveals for the first time the existence of potential “master regulators” coordinating a systemic response to microgravity and/or space radiation with TGF-β1 being the most common regulator. We hypothesized the space environment leads to the release of biomolecules circulating inside the blood stream. Through datamining we identified 13 candidate microRNAs (miRNA) which are common in all studies and directly interact with TGF-β1 that can be potential circulating factors impacting space biology. This study exemplifies the utility of the GeneLab data repository to aid in the process of performing novel hypothesis–based research.

MicroRNA-30 inhibits antiapoptotic factor Mcl-1 in mouse and human hematopoietic cells after radiation exposure

We previously reported that microRNA-30 (miR-30) expression was initiated by radiation-induced proinflammatory factor IL-1β and NFkB activation in mouse and human hematopoietic cells. However, the downstream effectors of miR-30 and its specific role in radiation-induced cell death are not well understood. In the present study, we evaluated effects of radiation on miR-30 expression and activation of intrinsic apoptotic pathway Bcl-2 family factors in in vivo mouse and in vitro human hematopoietic cells. CD2F1 mice and human CD34+ cells were exposed to different doses of gamma-radiation. In addition to survival studies, mouse blood, bone marrow (BM) and spleen cells and human CD34+ cells were collected at 4 h, and 1, 3 and 4 days after irradiation to determine apoptotic and stress response signals. Our results showed that mouse serum miR-30, DNA damage marker γ-H2AX in BM, and Bim, Bax and Bak expression, cytochrome c release, and caspase-3 and -7 activation in BM and/or spleen cells were upregulated in a radiation dose-dependent manner. Antiapoptotic factor Mcl-1 was significantly downregulated, whereas Bcl-2 was less changed or unaltered in the irradiated mouse cells and human CD34+ cells. Furthermore, a putative miR-30 binding site was found in the 3′ UTR of Mcl-1 mRNA. miR-30 directly inhibits the expression of Mcl-1 through binding to its target sequence, which was demonstrated by a luciferase reporter assay, and the finding that Mcl-1 was uninhibited by irradiation in miR-30 knockdown CD34+ cells. Bcl-2 expression was not affected by miR-30. Our data suggest miR-30 plays a key role in radiation-induced apoptosis through directly targeting Mcl-1in hematopoietic cells.

Wound fluids affect miR-21, miR-155 and miR-221 expression in breast cancer cell lines, and this effect is partially abrogated by intraoperative radiation therapy treatment

Breast cancer is the most common malignant disease occurring in women. Conservative breast cancer surgery followed by radiation therapy is currently the standard treatment for this type of cancer. The majority of metastases occur within the scar, which initiated a series of studies. As a result, clinical trials aimed to assess whether localized radiotherapy, as intraoperative radiotherapy (IORT), may more effective in inhibiting the formation of local recurrence compared with the standard postoperative whole breast radiotherapy. The present study determined the role of postoperative wound fluids (WFs) from patients diagnosed with breast cancer subsequent to breast conserving surgery or breast conserving surgery followed by IORT on the expression of three microRNAs (miRNAs), consisting of miR-21, miR-155 and miR-221, in distinct breast cancer cell lines that represent the general subtypes of breast cancer. It was determined that the miRNAs responsible for breast cancer progression, induction of tumorigenesis and enrichment of the cancer stem cell phenotype, which is responsible for resistance to tumor therapy, were highly upregulated in the human epidermal growth factor receptor 2-positive breast cancer SK-BR-3 cell line following stimulation with WFs. It is worth emphasizing, that those changes were more significant in WFs collected from patients after surgery alone. The BT-549 cell line showed altered expression only of miR-155 following incubation with WFs. Notably, this change was not associated with IORT. Additionally, it was indicated that both WFs and RT-WF strongly downregulated the expression of miR-21, miR-155 and miR-221 in basal/epithelial and luminal subtypes of breast cancer. It was concluded that the present study contributes to an increased understanding of the role of surgical WFs and IORT treatment in the regulation of miRNA expression. This may enable the development of the current knowledge of breast cancer biology subsequent to IORT treatment and substantially to improve the therapy in the future.

Let-7e sensitizes epithelial ovarian cancer to cisplatin through repressing DNA double strand break repair

BACKGROUND

Resistance to platinum-based chemotherapy remains a great challenge for ovarian cancer treatment. The human let-7 family contains 13 members located on nine different chromosomes, and most members have been implicated in the modulation of drug sensitivity in cancers. Our previous study showed that deregulation of let-7e in epithelial ovarian cancer (EOC) promoted the development of resistance to cisplatin. In the present study, we aimed to investigate the underlying mechanism and further evaluate the clinical value of let-7e in predicting chemo-response and prognosis in EOC.

RESULTS

In situ hybridization assays revealed a significantly decreased expression of let-7e in chemo-resistant EOC tissues compared with chemo-sensitive cases. Transfection with let-7e agomir sensitized EOC cells to cisplatin, down-regulated BRCA1 and Rad51 expression, and repressed the repair of cisplatin-induced DNA double strand break, while let-7e inhibitor exerted the opposite effects. In human EOC tissues, BRCA1 and Rad51 levels were increased in the chemo-resistant group compared with the sensitive group and were negatively correlated with let-7e. Low let-7e and high Rad51 were significantly associated with poor progression-free survival and overall survival and multivariate regression analyses showed that let-7e was an independent predictor for overall survival and chemotherapy response in EOC. Receiver operating characteristic analysis indicated that let-7e level was highly predictive of resistance to platinum-taxane chemotherapy with an area under the curve of 0.826.

CONCLUSIONS

In EOC, low let-7e leads to activation of BRCA1 and Rad51 expression and subsequent enhancement of DSB repair, which in turn results in cisplatin-resistance. Let-7e is a potential predictor for survival and chemo-response in EOC and re-expression of let-7e might be an effective strategy for overcoming chemo-resistance.

Emergence of miR-34a in radiation therapy

Expressions of many microRNAs (miRNAs) in response to ionizing radiation (IR) have already been investigated and some of them seem to play an important role in the tumor radioresistance, normal tissue radiotoxicity or as predictive biomarkers to radiation. miR-34a is an emerging miRNA in recent radiobiology studies. Here, we review this miR-34 family member by detailing its different roles in radiation response and we will discuss about the role that it can play in radiation treatment. Thus, we will show that IR regulates miR-34a by increasing its expression. We will also highlight different biological processes involved in cellular response to IR and regulated by miR-34a in order to demonstrate the role it can play in tumor radio-response or normal tissue radiotoxicity as a radiosensitizer or radioprotector. miR-34a is poised to assert itself as an important player in radiobiology and should become more and more important in radiation therapy management.

Zebrafish as an In Vivo Model to Assess Epigenetic Effects of Ionizing Radiation

Exposure to ionizing radiations (IRs) is ubiquitous in our environment and can be categorized into “targeted” effects and “non-targeted” effects. In addition to inducing deoxyribonucleic acid (DNA) damage, IR exposure leads to epigenetic alterations that do not alter DNA sequence. Using an appropriate model to study the biological effects of radiation is crucial to better understand IR responses as well as to develop new strategies to alleviate exposure to IR. Zebrafish, Danio rerio, is a scientific model organism that has yielded scientific advances in several fields and recent studies show the usefulness of this vertebrate model in radiation biology. This review briefly describes both “targeted” and “non-targeted” effects, describes the findings in radiation biology using zebrafish as a model and highlights the potential of zebrafish to assess the epigenetic effects of IR, including DNA methylation, histone modifications and miRNA expression. Other in vivo models are included to compare observations made with zebrafish, or to illustrate the feasibility of in vivo models when the use of zebrafish was unavailable. Finally, tools to study epigenetic modifications in zebrafish, including changes in genome-wide DNA methylation, histone modifications and miRNA expression, are also described in this review.

MicroRNAs, DNA Damage Response, and Cancer Treatment

As a result of various stresses, lesions caused by DNA-damaging agents occur constantly in each cell of the human body. Generally, DNA damage is recognized and repaired by the DNA damage response (DDR) machinery, and the cells survive. When repair fails, the genomic integrity of the cell is disrupted—a hallmark of cancer. In addition, the DDR plays a dual role in cancer development and therapy. Cancer radiotherapy and chemotherapy are designed to eliminate cancer cells by inducing DNA damage, which in turn can promote tumorigenesis. Over the past two decades, an increasing number of microRNAs (miRNAs), small noncoding RNAs, have been identified as participating in the processes regulating tumorigenesis and responses to cancer treatment with radiation therapy or genotoxic chemotherapies, by modulating the DDR. The purpose of this review is to summarize the recent findings on how miRNAs regulate the DDR and discuss the therapeutic functions of miRNAs in cancer in the context of DDR regulation.

Let-7b overexpression leads to increased radiosensitivity of uveal melanoma cells

Uveal melanoma (UM) is an intraocular malignant tumor in adults that is characterized by rapid progression and recurrence. Irradiation has become the primary therapy for UM patients who are not candidates for surgery. However, after large-dose fraction irradiation treatment, some patients undergo subsequent enucleation because of radiotherapy-related complications. This situation has raised concerns on how to optimize the effectiveness of radiation treatment. Recent investigations of microRNAs are changing our understanding of UM tumor biology and are helping to identify novel targets for radiotherapy. The radioresistant UM cell lines OM431 and OCM1 were selected and exposed to irradiation, and let-7b was found to be downregulated after exposure. We then confirmed that let-7b mimics could inhibit UM growth both in vitro and in vivo. More specifically, transfection with let-7b mimics markedly resensitized OCM1 and OM431 cells to irradiation by reducing the population of S-phase cells. Cyclin D1 plays a vital role in cell cycle arrest, which is induced by let-7b overexpression. Cyclin D1 is also a target of let-7b and its expression is suppressed by upregulation of let-7b. Collectively, our results indicate that let-7b overexpression can in turn downregulate cyclin D1 expression and enhance the radiosensitivity of UM through cell cycle arrest. Let-7b could serve as a marker for radiosensitivity and could enhance the therapeutic benefit of UM cell irradiation.

MDM4 regulation by the let-7 miRNA family in the DNA damage response of glioma cells

Despite extensive investigation into the role of let-7 miRNAs in pathological tumor processes, their involvement in the DNA damage response remains unclear. Here we show that most let-7 family members down-regulate MDM4 expression via binding to MDM4 mRNA at a conserved DNA sequence. Expression of exogenous let-7 miRNA mimics decreased MDM4 protein but not mRNA levels. Several DNA damage reagents increased let-7 expression, thereby decreasing MDM4 protein levels in glioma cells. Inhibition of endogenous let-7 with antisense RNAs rescued MDM4 protein levels with or without MG132, a proteasome-dependent degradation inhibitor. An MDM4 mutation identified in a glioma patient was associated with loss of the putative MDM4 target site. Therefore, let-7 binding to MDM4 is implicated in the DNA damage response.

Delta-tocotrienol suppresses radiation-induced microRNA-30 and protects mice and human CD34+ cells from radiation injury

We reported that microRNA-30c (miR-30c) plays a key role in radiation-induced human cell damage through an apoptotic pathway. Herein we further evaluated radiation-induced miR-30 expression and mechanisms of delta-tocotrienol (DT3), a radiation countermeasure candidate, for regulating miR-30 in a mouse model and human hematopoietic CD34+ cells. CD2F1 mice were exposed to 0 (control) or 7–12.5 Gy total-body gamma-radiation, and CD34+ cells were irradiated with 0, 2 or 4 Gy of radiation. Single doses of DT3 (75 mg/kg, subcutaneous injection for mice or 2 μM for CD34+ cell culture) were administrated 24 h before irradiation and animal survival was monitored for 30 days. Mouse bone marrow (BM), jejunum, kidney, liver and serum as well as CD34+ cells were collected at 1, 4, 8, 24, 48 or 72 h after irradiation to determine apoptotic markers, pro-inflammatory cytokines interleukin (IL)-1β and IL-6, miR-30, and stress response protein expression. Our results showed that radiation-induced IL-1β release and cell damage are pathological states that lead to an early expression and secretion of miR-30b and miR-30c in mouse tissues and serum and in human CD34+ cells. DT3 suppressed IL-1β and miR-30 expression, protected against radiation-induced apoptosis in mouse and human cells, and increased survival of irradiated mice. Furthermore, an anti-IL-1β antibody downregulated radiation-induced NFκBp65 phosphorylation, inhibited miR-30 expression and protected CD34+ cells from radiation exposure. Knockdown of NFκBp65 by small interfering RNA (siRNA) significantly suppressed radiation-induced miR-30 expression in CD34+ cells. Our data suggest that DT3 protects human and mouse cells from radiation damage may through suppression of IL-1β-induced NFκB/miR-30 signaling.

The mystery of let-7d - a small RNA with great power

miRNAs belong to a class of small non-coding RNAs which can modulate gene expression. Disturbances in their expression and function may cause cancer formation, progression and cell response to various types of stress. The let-7 family is one of the most studied groups of miRNAs. The family contains 13 members with similar sequences and a wide spectrum of target genes. In this paper, we mostly focus on one member of the family – let-7d. This miRNA is dysregulated in many types of cancers. It can be over- or down-expressed, and it acts as a tumor suppressor or oncogene. It regulates various genes such as LIN28, C-MYC, K-RAS, HMGA2 and IMP-1. Moreover, let-7d has a significant impact on epithelial-to-mesenchymal transition (EMT) and formation of cancer initiating cells which are resistant to irradiation and chemical exposure and responsible for cancer metastasis. Let-7d can serve as a prognostic and predictive marker for personalization of the treatment. Let-7d is a small RNA with great power, but in different cell genetic backgrounds it acts in different ways, which makes this molecule still mysterious.

microRNA expression and biogenesis in cellular response to ionizing radiation

Increasing evidence demonstrates that the expression levels of microRNAs (miRNAs) significantly change upon ionizing radiation (IR) and play a critical role in cellular response to IR. Although several radiation responsive miRNAs and their targets have been identified, little is known about how miRNAs expression and biogenesis is regulated by IR-caused DNA damage response (DDR). Hence, in this review, we summarize miRNA expression and biogenesis in cellular response to IR and mainly elucidate the regulatory mechanisms of miRNA expression and biogenesis from different aspects including ataxia-telangiectasia mutated (ATM) kinase, p53/p63/p73 family and other potential factors. Furthermore, we focus on ΔNp73, which might be a potential regulator of miRNA expression and biogenesis in cellular response to IR. miRNAs could effectively activate the IR-induced DDR and modulate the radiation response and cellular radiosensitivity, which have an important potential clinical application. Therefore, thoroughly understanding the regulatory mechanisms of miRNAs expression and biogenesis in radiation response will provide new insights for clinical cancer radiotherapy.

MiR-34a regulates apoptosis in liver cells by targeting the KLF4 gene

MicroRNAs (miRNAs) regulate gene expression by inhibiting translation or targeting messenger RNA (mRNA) for degradation in a posttranscriptional fashion. In this study, we show that ectopic expression of miR-34a-5p reduces the mRNA and protein levels of Krüppel-like factor 4 (KLF4). We also demonstrate that miR-34a targets the 3′-untranslated mRNA region of KLF4 and show that overexpression of miR-34a induces a significant level of apoptosis in BNL CL.2 cells exposed to doxorubicin or 10 Gy X-ray. Our data suggest that the effects of miR-34a on apoptosis occur due to the downregulation of KLF4.

Identification of radiation-induced microRNA transcriptome by next-generation massively parallel sequencing

Gene regulation in cells exposed to ionizing radiation (IR) occurs at the transcriptional and post-transcriptional levels. Recent studies have suggested that micro-RNA (miRNA) play a significant role in post-transcriptional gene regulation in irradiated cells. miRNA are RNA molecules 18-24 nucleotides in length that are involved in negatively regulating the stability or translation of target messenger RNA. Previous studies from our laboratory have shown that the expression of various miRNA is altered in IR-treated cells. In the present study we monitored genome-wide expression changes of miRNA transcriptome by massively parallel sequencing of human cells irradiated with X-rays. The baseline expression of 402 miRNA indicated a wide range of modulation without exposure to IR. Differences in the expression of many miRNA were observed in a time-dependent fashion following radiation treatment. The Short Time-series Expression Miner (STEM) clustering tool was used to characterize 190 miRNA to six statistically significant temporal expression profiles. miR-19b and miR-93 were induced and miR-222, miR-92a, and miR-941 were repressed after radiation treatment. miR-142-3p, miR-142-5p, miR-107, miR-106b, miR-191, miR-21, miR-26a, miR-182, miR-16, miR-146a, miR-22 and miR-30e exhibited two peaks of induction: one at 8 h and the other at 24 h post-irradiation. miR-378, miR-let-7a, miR-let-7g, miR-let-7f, miR-103b, miR-486-3p, miR-423-5p, miR-4448, miR-3607-5p, miR-20b, miR-130b, miR-155, miR-181, miR-30d and miR-378c were induced only at the 8-h time-point. This catalogue of the inventory of miRNA that are modulated as a response to radiation exposure will be useful for explaining the mechanisms of gene regulation under conditions of stress.

Transcription poisoning by Topoisomerase I is controlled by gene length, splice sites, and miR-142-3p

Topoisomerase I (Top1) relaxes DNA supercoiling by forming transient cleavage complexes (Top1cc) up- and downstream of transcription complexes. Top1cc can be trapped by carcinogenic and endogenous DNA lesions and by camptothecin, resulting in transcription blocks. Here, we undertook genome-wide analysis of camptothecin-treated cells at exon resolution. RNA samples from HCT116 and MCF7 cells were analyzed with the Affy Exon Array platform, allowing high-resolution mapping along 18,537 genes. Long genes that are highly expressed were the most susceptible to downregulation, whereas short genes were preferentially upregulated. Along the body of genes, downregulation was most important toward the 3'-end and increased with the number of exon-intron junctions. Ubiquitin and RNA degradation-related pathway genes were selectively downregulated. Parallel analysis of microRNA with the Agilent miRNA microarray platform revealed that miR-142-3p was highly induced by camptothecin. More than 10% of the downregulated genes were targets of this p53-dependent microRNA. Our study shows the profound impact of Top1cc on transcription elongation, especially at intron-exon junctions and on transcript stability by microRNA miR-142-3p upregulation.

K-ras 4A and 4B mRNA levels correlate with superoxide in lung adenocarcinoma cells, while at the protein level, only mutant K-ras 4A protein correlates with superoxide

The K-ras gene is frequently mutated in lung and other cancers. K-ras protein includes two splice variants, K-ras 4A and 4B. While K-ras 4B is more widely expressed, recent evidence implicates K-ras 4A in lung tumorigenesis. We found that K-ras 4A protein has a wide range of expression in a large panel of human lung adenocarcinoma cell lines. In cell lines with mutant K-ras, but not those with wildtype K-ras, the K-ras 4A protein had a strong positive correlation with levels of cellular superoxide. We investigated whether K-ras 4A protein was involved in superoxide production, or alternatively was modulated by elevated superoxide. Experiments with small interfering RNA targeting K-ras 4A did not confirm its role in superoxide generation. However, decreasing cellular superoxide with the scavenger Tiron tended to reduce levels of K-ras 4A protein. K-ras 4A and 4B mRNA were also quantified in a number of NSCLC cell lines. 4A mRNA correlated with 4A protein only in K-ras-mutant cells. K-ras 4A mRNA also correlated with superoxide, but with no difference between cell lines with mutant or wildtype K-ras. K-ras 4B mRNA correlated with 4A mRNA and with superoxide, in both K-ras mutant and wildtype cells. The results are consistent with superoxide directly or indirectly up-regulating expression of all K-ras genes, and also increasing the stability of K-ras 4A mutant protein selectively.

Mitochondria-related gene expression changes are associated with fatigue in patients with nonmetastatic prostate cancer receiving external beam radiation therapy

BACKGROUND

Cancer-related fatigue (CRF) is associated with negative health outcomes and decreased health-related quality of life; however, few longitudinal studies have investigated molecular-genetic mechanisms of CRF.

OBJECTIVE

The objective of this study was to describe relationships between mitochondria-related gene expression changes and self-reported fatigue in prostate cancer patients receiving external beam radiation therapy (EBRT).

METHODS

A prospective, exploratory, and repeated-measures design was used. Self-report questionnaires and peripheral whole-blood samples were collected from 15 patients at 7 time points. Baseline data were compared against 15 healthy controls. The Human Mitochondria RT Profiler PCR Array was used to identify differential regulation of genes involved in mitochondrial biogenesis and function.

RESULTS

Compared with baseline, there were significant increases in fatigue scores (P = .02-.04) and changes in mitochondria-related gene expression (P = .001-.05) over time. Mean fatigue scores were 1.66 (SD, 1.66) at baseline, 3.06 (SD, 1.95) at EBRT midpoint, 2.98 (SD, 2.20) at EBRT completion, and 2.64 (SD, 2.56) at 30 days after EBRT. Over time, 11 genes related to mitochondrial function and structure were differentially expressed. Of these 11 genes, 3 (BCL2L1, FIS1, SLC25A37) were more than 2.5 fold up-regulated, and 8 (AIFM2, BCL2, IMMP2L, MIPEP, MSTO1, NEFL, SLC25A23, SLC25A4) were greater than 2-fold down-regulated. Furthermore, 8 genes (AIFM2, BCL2, FIS1, IMMP2L, MSTO1, SLC25A23, SLC25A37, SLC25A4) were significantly associated with the changes in fatigue scores.

CONCLUSION

This study provides preliminary evidence that 8 mitochondrial function genes were significantly associated with fatigue in prostate cancer patients during EBRT.

IMPLICATIONS FOR PRACTICE

These findings identify possible pathways and early biomarkers for targeting novel interventions for CRF.

Expression pattern of small nucleolar RNA host genes and long non-coding RNA in X-rays-treated lymphoblastoid cells

A wide variety of biological effects are induced in cells that are exposed to ionizing radiation. The expression changes of coding mRNA and non-coding micro-RNA have been implicated in irradiated cells. The involvement of other classes of non-coding RNAs (ncRNA), such as small nucleolar RNAs (snoRNAs), long ncRNAs (lncRNAs), and PIWI-interacting RNAs (piRNAs) in cells recovering from radiation-induced damage has not been examined. Thus, we investigated whether these ncRNA were undergoing changes in cells exposed to ionizing radiation. The modulation of ncRNAs expression was determined in human TK6 (p53 positive) and WTK1 (p53 negative) cells. The snoRNA host genes SNHG1, SNHG6, and SNHG11 were induced in TK6 cells. In WTK1 cells, SNHG1 was induced but SNHG6, and SNHG11 were repressed. SNHG7 was repressed in TK6 cells and was upregulated in WTK1 cells. The lncRNA MALAT1 and SOX2OT were induced in both TK6 and WTK1 cells and SRA1 was induced in TK6 cells only. Interestingly, the MIAT and PIWIL1 were not expressed in TK6 cells before or after the ionizing radiation treatment. The MIAT and PIWIL1 were upregulated in WTK1 cells. This data provides evidence that altered ncRNA expression is a part of the complex stress response operating in radiation-treated cells and this response depends on functional p53.

Radiation resistance due to high expression of miR-21 and G2/M checkpoint arrest in breast cancer cells

Background

There is evidence that the extent of the G2/M arrest following irradiation is correlated with tumour cell survival and hence therapeutic success. We studied the regulation of cellular response to radiation treatment by miR-21-mediated modulation of cell cycle progression in breast cancer cells and analysed miR-21 expression in breast cancer tissue samples with long-term follow up.

Methods

The miR-21 expression levels were quantified (qRT-PCR) in a panel of 86 cases of invasive breast carcinomas in relation to metastasis free survival. The cellular radiosensitivity of human breast cancer cells after irradiation was determined comparing two cell lines (T47D and MDA-MB-361) by cell proliferation and colony forming assays. The influence of miR-21 overexpression or downregulation on cell cycle progression and G2/M checkpoint arrest after irradiation was assessed by flow cytometric analysis.

Results

The expression of miR-21 was transiently increased 8 hours after irradiation in the radioresistant T47D cells and significantly changed with lower extent in radiosensitive MDA-MB-361 cells. Anti-miR-21 treated breast cancer cells failed to exhibit the DNA damage-G2 checkpoint increase after irradiation. Apoptotic activity was significantly enhanced from 7% to 27% in T47D cells and from 18% to 30% in MDA-MB-361 cells 24 hours after 5 Gy irradiation. Additionally, we characterized expression of miR-21 in invasive breast carcinomas. In comparison to non-cancerous adjacent breast tissue, tumours samples had increased miR-21 expression that inversely correlated with the distant metastases-free survival of patients (p = 0.029).

Conclusions

Our data indicate that miR-21 expression in breast cancer cells contributes to radiation resistance by compromising cell cycle progression. These data point to the potential of combining radiotherapy with an anti-miR-21 as a potent G2/M check point inhibitor in overcoming radiation resistance of tumours.

Expression of microRNAs in the NCI-60 cancer cell-lines

The NCI-60 panel of 60 human cancer cell-lines of nine different tissues of origin has been extensively characterized in biological, molecular and pharmacological studies. Analyses of data from such studies have provided valuable information for understanding cellular processes and developing strategies for the diagnosis and treatment of cancer. Here, Affymetrix® GeneChip™ miRNA version 1 oligonucleotide microarrays were used to quantify 847 microRNAs to generate an expression dataset of 495 (58.4%) microRNAs that were identified as expressed in at least one cell-line of the NCI-60 panel. Accuracy of the microRNA measurements was partly confirmed by reverse transcription and polymerase chain reaction assays. Similar to that seen among the four existing NCI-60 microRNA datasets, the concordance of the new expression dataset with the other four was modest, with mean Pearson correlation coefficients of 0.37–0.54. In spite of this, comparable results with different datasets were noted in clustering of the cell-lines by their microRNA expression, differential expression of microRNAs by the lines’ tissue of origin, and correlation of specific microRNAs with the doubling-time of cells or their radiation sensitivity. Mutation status of the cell-lines for the TP53, PTEN and BRAF but not CDKN2A or KRAS cancer-related genes was found to be associated with changes in expression of specific microRNAs. The microRNA dataset generated here should be valuable to those working in the field of microRNAs as well as in integromic studies of the NCI-60 panel.

Interactome of Radiation-Induced microRNA-Predicted Target Genes

The microRNAs (miRNAs) function as global negative regulators of gene expression and have been associated with a multitude of biological processes. The dysfunction of the microRNAome has been linked to various diseases including cancer. Our laboratory recently reported modulation in the expression of miRNA in a variety of cell types exposed to ionizing radiation (IR). To further understand miRNA role in IR-induced stress pathways, we catalogued a set of common miRNAs modulated in various irradiated cell lines and generated a list of predicted target genes. Using advanced bioinformatics tools we identified cellular pathways where miRNA predicted target genes function. The miRNA-targeted genes were found to play key roles in previously identified IR stress pathways such as cell cycle, p53 pathway, TGF-beta pathway, ubiquitin-mediated proteolysis, focal adhesion pathway, MAPK signaling, thyroid cancer pathway, adherens junction, insulin signaling pathway, oocyte meiosis, regulation of actin cytoskeleton, and renal cell carcinoma pathway. Interestingly, we were able to identify novel targeted pathways that have not been identified in cellular radiation response, such as aldosterone-regulated sodium reabsorption, long-term potentiation, and neutrotrophin signaling pathways. Our analysis indicates that the miRNA interactome in irradiated cells provides a platform for comprehensive modeling of the cellular stress response to IR exposure.

Proton radiation-induced miRNA signatures in mouse blood: characterization and comparison with 56Fe-ion and gamma radiation

PURPOSE

Previously, we showed that microRNA (miRNA) signatures derived from the peripheral blood of mice are highly specific for both radiation energy (γ-rays or high linear energy transfer [LET] (56)Fe ions) and radiation dose. Here, we investigate to what extent miRNA expression signatures derived from mouse blood can be used as biomarkers for exposure to 600 MeV proton radiation.

MATERIALS AND METHODS

We exposed mice to 600 MeV protons, using doses of 0.5 or 1.0 Gy, isolated total RNA at 6 h or 24 h after irradiation, and used quantitative real-time polymerase chain reaction (PCR) to determine the changes in miRNA expression.

RESULTS

A total of 26 miRNA were differentially expressed after proton irradiation, in either one (77%) or multiple conditions (23%). Statistical classifiers based on proton, γ, and (56)Fe-ion miRNA expression signatures predicted radiation type and proton dose with accuracies of 81% and 88%, respectively. Importantly, gene ontology analysis for proton-irradiated cells shows that genes targeted by radiation-induced miRNA are involved in biological processes and molecular functions similar to those controlled by miRNA in γ ray- and (56)Fe-irradiated cells.

CONCLUSIONS

Mouse blood miRNA signatures induced by proton, γ, or (56)Fe irradiation are radiation type- and dose-specific. These findings underline the complexity of the miRNA-mediated radiation response.

Micro RNA responses to chronic or acute exposures to low dose ionizing radiation

Human health risks of exposure to low dose ionizing radiation remain ambiguous and are the subject of intense debate. A wide variety of biological effects are induced after cellular exposure to ionizing radiation, but the underlying molecular mechanism(s) remain to be completely understood. We hypothesized that low dose γ-radiation-induced effects are controlled by the modulation of micro RNA (miRNA) that participate in the control of gene expression at the posttranscriptional level and are involved in many cellular processes. We monitored the expression of several miRNA in human cells exposed to acute or chronic low doses of 10 cGy or a moderate dose of 400 cGy of (137)Cs γ-rays. Dose, dose rate and time dependent differences in the relative expression of several miRNA were investigated. The expression patterns of many miRNA differed after exposure to either chronic or acute 10 cGy. The expression of miRNA let-7e, a negative regulator of RAS oncogene, and the c-MYC miRNA cluster were upregulated after 10 cGy chronic dose but were downregulated after 3 h of acute 10 cGy. The miR-21 was upregulated in chronic or acute low dose and moderate dose treated cells and its target genes hPDCD4, hPTEN, hSPRY2, and hTPM1 were found to be downregulated. These findings provide evidence that low dose and dose rate γ-irradiation dictate the modulation of miRNA, which can result in a differential cellular response than occurs at high doses. This information will contribute to understanding the risks to human health after exposure to low dose radiation.

Analysis of miRNA and mRNA expression profiles highlights alterations in ionizing radiation response of human lymphocytes under modeled microgravity

BACKGROUND

Ionizing radiation (IR) can be extremely harmful for human cells since an improper DNA-damage response (DDR) to IR can contribute to carcinogenesis initiation. Perturbations in DDR pathway can originate from alteration in the functionality of the microRNA-mediated gene regulation, being microRNAs (miRNAs) small noncoding RNA that act as post-transcriptional regulators of gene expression. In this study we gained insight into the role of miRNAs in the regulation of DDR to IR under microgravity, a condition of weightlessness experienced by astronauts during space missions, which could have a synergistic action on cells, increasing the risk of radiation exposure.

METHODOLOGY/PRINCIPAL FINDINGS

We analyzed miRNA expression profile of human peripheral blood lymphocytes (PBL) incubated for 4 and 24 h in normal gravity (1 g) and in modeled microgravity (MMG) during the repair time after irradiation with 0.2 and 2Gy of γ-rays. Our results show that MMG alters miRNA expression signature of irradiated PBL by decreasing the number of radio-responsive miRNAs. Moreover, let-7i*, miR-7, miR-7-1*, miR-27a, miR-144, miR-200a, miR-598, miR-650 are deregulated by the combined action of radiation and MMG. Integrated analyses of miRNA and mRNA expression profiles, carried out on PBL of the same donors, identified significant miRNA-mRNA anti-correlations of DDR pathway. Gene Ontology analysis reports that the biological category of "Response to DNA damage" is enriched when PBL are incubated in 1 g but not in MMG. Moreover, some anti-correlated genes of p53-pathway show a different expression level between 1 g and MMG. Functional validation assays using luciferase reporter constructs confirmed miRNA-mRNA interactions derived from target prediction analyses.

CONCLUSIONS/SIGNIFICANCE

On the whole, by integrating the transcriptome and microRNome, we provide evidence that modeled microgravity can affects the DNA-damage response to IR in human PBL.

Unraveling the global microRNAome responses to ionizing radiation in human embryonic stem cells

MicroRNAs (miRNA) comprise a group of short ribonucleic acid molecules implicated in regulation of key biological processes and functions at the post-transcriptional level. Ionizing radiation (IR) causes DNA damage and generally triggers cellular stress response. However, the role of miRNAs in IR-induced response in human embryonic stem cells (hESC) has not been defined yet. Here, by using system biology approaches, we show for the first time, that miRNAome undergoes global alterations in hESC (H1 and H9 lines) after IR. Interrogation of expression levels of 1,090 miRNA species in irradiated hESC showed statistically significant changes in 54 genes following 1 Gy of X-ray exposures; global miRNAome alterations were found to be highly temporally and cell line - dependent in hESC. Time-course studies showed that the 16 hr miRNAome radiation response of hESC is much more robust compared to 2 hr-response signature (only eight genes), and may be involved in regulating the cell cycle. Quantitative real-time PCR performed on some miRNA species confirms the robustness of our miRNA microarray platform. Positive regulation of differentiation-, cell cycle-, ion transport- and endomembrane system-related processes were predicted to be negatively affected by miRNAome changes in irradiated hESC. Our findings reveal a fundamental role of miRNAome in modulating the radiation response, and identify novel molecular targets of radiation in hESC.

Cellular stress induced alterations in microRNA let-7a and let-7b expression are dependent on p53

Genotoxic stressors, such as radiation, induce cellular damage that activates pre-programmed repair pathways, some of which involve microRNAs (miRNA) that alter gene expression. The let-7 family of miRNA regulates multiple cellular processes including cell division and DNA repair pathways. However, the role and mechanism underlying regulation of let-7 genes in response to stress have yet to be elucidated. In this study we demonstrate that let-7a and let-7b expression decreases significantly following exposure to agents that induce stress including ionizing radiation. This decrease in expression is dependent on p53 and ATM in vitro and is not observed in a p53^−/− colon cancer cell line (HCT116) or ATM^−/− human fibroblasts. Chromatin Immunoprecipitation (ChIP) analysis showed p53 binding to a region upstream of the let-7 gene following radiation exposure. Luciferase transient transfections demonstrated that this p53 binding site is necessary for radiation-induced decreases in let-7 expression. A radiation-induced decrease in let-7a and let-7b expression is also observed in radiation-sensitive tissues in vivo and correlates with altered expression of proteins in p53-regulated pro-apoptotic signaling pathways. In contrast, this decreased expression is not observed in p53 knock-out mice suggesting that p53 directly repress let-7 expression. Exogenous expression of let-7a and let-7b increased radiation-induced cytotoxicity in HCT116 p53^+/+ cells but not HCT116 p53^−/− cells. These results are the first demonstration of a mechanistic connection between the radiation-induced stress response and the regulation of miRNA and radiation-induced cytotoxicity and suggest that this process may be a molecular target for anticancer agents.

Non-targeted radiation effects-an epigenetic connection

Ionizing radiation (IR) is a pivotal diagnostic and treatment modality, yet it is also a potent genotoxic agent that causes genome instability and carcinogenesis. While modern cancer radiation therapy has led to increased patient survival rates, the risk of radiation treatment-related complications is becoming a growing problem. IR-induced genome instability has been well-documented in directly exposed cells and organisms. It has also been observed in distant 'bystander' cells. Enigmatically, increased instability is even observed in progeny of pre-conceptually exposed animals, including humans. The mechanisms by which it arises remain obscure and, recently, they have been proposed to be epigenetic in nature. Three major epigenetic phenomena include DNA methylation, histone modifications and small RNA-mediated silencing. This review focuses on the role of DNA methylation and small RNAs in directly exposed and bystander tissues and in IR-induced transgenerational effects. Here, we present evidence that IR-mediated effects are maintained by epigenetic mechanisms.

Radiation-induced micro-RNA expression changes in peripheral blood cells of radiotherapy patients

PURPOSE

MicroRNAs (miRNAs), a class of noncoding small RNAs that regulate gene expression, are involved in numerous physiologic processes in normal and malignant cells. Our in vivo study measured miRNA and gene expression changes in human blood cells in response to ionizing radiation, to develop miRNA signatures that can be used as biomarkers for radiation exposure.

METHODS AND MATERIALS

Blood from 8 radiotherapy patients in complete remission 1 or 2 was collected immediately before and 4 hours after total body irradiation with 1.25 Gy x-rays. Both miRNA and gene expression changes were measured by means of quantitative polymerase chain reaction and microarray hybridization, respectively. Hierarchic clustering, multidimensional scaling, class prediction, and gene ontology analysis were performed to investigate the potential of miRNAs to serve as radiation biomarkers and to elucidate their likely physiologic roles in the radiation response.

RESULTS

The expression levels of 45 miRNAs were statistically significantly upregulated 4 hours after irradiation with 1.25 Gy x-rays, 27 of them in every patient. Nonirradiated and irradiated samples form separate clusters in hierarchic clustering and multidimensional scaling. Out of 223 differentially expressed genes, 37 were both downregulated and predicted targets of the upregulated miRNAs. Paired and unpaired miRNA-based classifiers that we developed can predict the class membership of a sample with unknown irradiation status, with accuracies of 100% when all 45 upregulated miRNAs are included. Both miRNA control of and gene involvement in biologic processes such as hemopoiesis and the immune response are increased after irradiation, whereas metabolic processes are underrepresented among all differentially expressed genes and the genes controlled by miRNAs.

CONCLUSIONS

Exposure to ionizing radiation leads to the upregulation of the expression of a considerable proportion of the human miRNAome of peripheral blood cells. These miRNA expression signatures can be used as biomarkers of radiation exposure.

MicroRNA dysregulation in human thyroid cells following exposure to ionizing radiation

BACKGROUND

Ionizing radiation is a well-known mutagen and a risk factor for thyroid cancer. MicroRNAs (miRNAs) play an important role in the regulation of gene expression on post-transcriptional level and are dysregulated in thyroid cancer. The goal of this study was to investigate the effects of acute exposure to 1 and 10 Gy of γ-irradiation on miRNA expression in normal human thyroid cells.

METHODS

Expression of 319 miRNAs was studied in primary cultures of normal human thyroid cells 4 and 24 hours postirradiation using a miRNA expression array with further confirmation of miRNAs expression by reverse transcription-polymerase chain reaction.

RESULTS

We identified 30 miRNAs that were unregulated or downregulated more than twofold after irradiation as compared to nonirradiated thyroid cells, with no significant difference found between 1 and 10 Gy of radiation. Four distinct patterns of miRNA expression change were observed: miRNAs downregulated at 4 hours and returned to normal levels at 24 hours, miRNAs upregulated at 4 hours and returned to normal levels at 24 hours, and miRNAs either upregulated or downregulated at both time points. No dysregulation of miRNAs known to occur in thyroid cancer was observed.

CONCLUSIONS

Acute exposure of thyroid cells to γ-radiation results in several specific patterns of miRNA response. It appears that alteration in miRNA expression seen 4-24 hours after irradiation has no direct association with carcinogenesis. However, it is likely to affect other cell functions, such as DNA repair.

Whole mouse blood microRNA as biomarkers for exposure to γ-rays and (56)Fe ion

PURPOSE

Biomarkers of ionising radiation exposure are useful in a variety of scenarios, such as medical diagnostic imaging, occupational exposures, and spaceflight. This study investigates to what extent microRNA (miRNA) expression signatures in mouse peripheral blood can be used as biomarkers for exposures to radiation with low and high linear energy transfers.

MATERIALS AND METHODS

Mice were irradiated with doses of 0.5, 1.5, or 5.0 Gy γ-rays (dose rate of 0.0136 Gy/s) or with doses of 0.1 or 0.5 Gy (56)Fe ions (dose rate of 0.00208 Gy/s). Total RNA was isolated from whole blood at 6 h or 24 h after irradiation. Three animals per irradiation condition were used. Differentially expressed miRNA were determined by means of quantitative real-time polymerase chain reaction.

RESULTS

miRNA expression signatures were radiation type-specific and dose- and time-dependent. The differentially expressed miRNA were expressed in either one condition (71%) or multiple conditions (29%). Classifiers based on the differentially expressed miRNA predicted radiation type or dose with accuracies between 75% and 100%. Gene-ontology analyses show that miRNA induced by irradiation are involved in the control of several biological processes, such as mRNA transcription regulation, nucleic-acid metabolism, and development.

CONCLUSION

miRNA signatures induced by ionising radiation in mouse blood are radiation type- and radiation dose-specific. These findings underline the complexity of the radiation response and the importance of miRNA in it.

Detection of novel human MiRNAs responding to X-ray irradiation

Up to now, more than 1048 human miRNAs have been identified. However, the recognition of new human miRNAs is becoming more and more difficult. Based on the hypothesis that the expression of some miRNAs can be induced by ionizing radiation, total RNAs of HeLa cells were isolated 1 h after exposure to 2 Gy of X-rays, and total small RNAs were enriched and sequenced by PAGE and Solexa technology, respectively. As a result, 421 kinds of known miRNAs and 337 kinds of unknown sequences were identified, among which 10 novel miRNAs were characterized by bioinformatic approach and verified by qRT-PCR. Finally, putative targets of these miRNAs were predicted by TargetScan software and compared with known proteins down-regulated by radiation. It was confirmed that some of the targets of these novel miRNAs were radiation-related proteins. These results imply that these 10 novel miRNAs are radiation-related miRNAs. This study reveals a new way to find novel miRNAs.

Radiation-induced micro-RNA modulation in glioblastoma cells differing in DNA-repair pathways

Human glioblastomas often develop resistance to radiation therapy. The molecular details of this phenomenon are not completely understood. Recent studies have suggested that deficiency in DNA repair pathways may alter the resistance to ionizing radiation in gliobastomas. The human glioma cell line M059J is deficient in DNA-dependent protein kinase (DNA-PK), whereas cell line M059K, isolated from the same malignant tumor, has normal DNA-PK activity. DNA-PK plays a central role in the repair of ionizing-radiation-induced double-strand break repair, and its deficiency has been correlated with ionizing radiation sensitivity in these glioblastoma cells. We argued that other cellular pathways could also play a role in the resistance to radiation therapy in gliomas. We hypothesized that micro-RNAs (miRNAs) are differentially modulated in M059J and M059K cells exposed to ionizing radiation and that the miRNA modulation contributes to the resistance to ionizing radiation. miRNAs are small nonprotein coding single-stranded RNA molecules, which are crucial posttranscriptional regulators of gene expression. Numerous studies have documented the participation of miRNAs in a wide range of biological processes. The contribution of miRNAs in mediating resistance of glioblastoma cell to ionizing radiation treatment has not been elucidated. To test this hypothesis, we examined the expression patterns of a number of miRNAs involved in carcinogenesis in irradiated M059J and M059K cells. The relative expression level as determined by real-time quantitative PCR for miRNAs belonging to the let-7 family indicated an upregulation in irradiated M059K cells. On the contrary, the analysis of irradiated M059J cells for the modulation of let-7 family of miRNAs revealed an overall downregulation. The miR-17-3p, miR-17-5p, miR-19a, miR-19b, miR-142-3p, and miR-142-5p were upregulated in both M059K and M059J cells. The miR-15a, miR-16, miR-143, miR-155, and miR-21 were upregulated in M059K, and the modulation of these miRNAs fluctuated in M059J cells in a time-dependent manner. These results indicate the involvement of miRNAs in the differential response of glioblastoma cells to ionizing radiation treatment.

Transcriptional modulation of micro-RNA in human cells differing in radiation sensitivity

PURPOSE

The molecular basis of gene regulation in cells exposed to ionising radiation is not fully understood. Gene regulation occurs at the transcriptional and post-transcriptional levels. Recent studies have suggested that micro-RNA (miRNA) plays a significant role at the post-transcriptional gene regulation. miRNA are a recently identified class of RNA molecules 18-24 nucleotides in length that have been shown to negatively regulate the stability or translation of target messenger RNA. We hypothesised that ionising radiation induced stress response is controlled in part by miRNA and that a difference in tumour protein 53 (p53) status corresponds with altered expression in miRNA responses to ionising radiation.

MATERIALS AND METHODS

To test this hypothesis, we investigated the relative expression of several miRNA by quantitative real-time polymerase chain reaction (QPCR) in human cell lines TK6 and WTK1 that differ in p53 status and radiosensitivity after exposure to high and low doses of X-radiation.

RESULTS

The suitability of several endogenous miRNA controls was tested for relative quantification by QPCR. The baseline expression of 21 miRNA targets in TK6 and WTK1 cells indicated a wide range of modulation between the two cell lines without exposure to ionising radiation. Differences in the relative expression of miRNA were observed among the two cell lines after radiation treatment. The expression patterns of many miRNA markedly differed within the same cell line after exposure to either 0.5 Gy or 2 Gy doses of X-rays. The expression of eight miRNA belonging to the lethal-7 (let-7) family, which are negative regulators of the rat sarcoma, RAS oncogene, was upregulated in irradiated TK6 cells but was downregulated in WTK1 cells. Alterations in the myelocytomatosis oncogene, c-MYC induced cluster of miRNA were also observed. The micro RNA, miR-15a and miR-16 were upregulated in 0.5 Gy-irradiated TK6 cells but were downregulated after a 2 Gy dose of X-rays. In contrast miR-15 and miR-16 were repressed in 0.5 Gy-exposed WTK1. The miR-21 was upregulated in 0.5 Gy-treated TK6 cells and its target genes programmed cell death factor 4 (hPDCD4) phosphatase and tensin homolog (hPTEN), and sprouty homolog 2 (hSPRY2) were found to be downregulated in these cells. The miR-21 was downregulated in 2 Gy-irradiated TK6 cells, and all three of its target genes were upregulated in 2 Gy-exposed TK6 cells.

CONCLUSION

Taken together, these results establish the involvement of miRNA in radiation response and may potentially help explain the mechanisms of gene regulation in the cellular response to ionising radiation exposure.

Heavy ions, radioprotectors and genomic instability: implications for human space exploration

The risk associated with space radiation exposure is unique from terrestrial radiation exposures due to differences in radiation quality, including linear energy transfer (LET). Both high- and low-LET radiations are capable of inducing genomic instability in mammalian cells, and this instability is thought to be a driving force underlying radiation carcinogenesis. Unfortunately, during space exploration, flight crews cannot entirely avoid radiation exposure. As a result, chemical and biological countermeasures will be an important component of successful extended missions such as the exploration of Mars. There are currently several radioprotective agents (radioprotectors) in use; however, scientists continue to search for ideal radioprotective compounds-safe to use and effective in preventing and/or reducing acute and delayed effects of irradiation. This review discusses the agents that are currently available or being evaluated for their potential as radioprotectors. Further, this review discusses some implications of radioprotection for the induction and/or propagation of genomic instability in the progeny of irradiated cells.

MicroRNA expression in head and neck cancer associates with alcohol consumption and survival

The contribution of microRNAs (miRNAs) to carcinogenesis in many tumors, including head and neck squamous cell carcinomas (HNSCCs), is clear, but the etiology and clinical significance of their alteration remain important questions. Our previous work has identified four miRNAs as differentially expressed HNSCCs compared with non-diseased epithelia and showed that there is potential diagnostic utility in examining their expression. Here, we used quantitative real-time polymerase chain reaction to determine the relative expression of these miRNAs in a larger independent case series of HNSCC tumors (n = 169), examining associations of miRNA expression with exposures and clinical features associated with HNSCC. In multivariate analyses, expression of miR-375 was shown to increase with alcohol consumption (P = 0.002) and showed higher expression in tumors of pharyngeal and laryngeal origin compared with oral tumors (P < 0.05 and P < 0.01, respectively). Additionally, high miR-21 expression was associated with significantly decreased 5 year survival in patients (hazard ratio, 1.68; 95% CI: 1.04-2.77) in a model controlled for patient age, gender and tumor stage. Together, these data suggest that alterations in miRNA expression are related to exposures causal in head and neck cancer and may be useful biomarkers of patient outcome.