Long and short non-coding RNA and radiation response: a review.

Once thought of as arising from "junk DNA," noncoding RNAs (ncRNAs) have emerged as key molecules in cellular processes and response to stress. From diseases such as cancer, coronary artery disease, and diabetes to the effects of ionizing radiation (IR), ncRNAs play important roles in disease progression and as biomarkers of damage. Noncoding RNAs regulate cellular processes by competitively binding DNA, mRNA, proteins, and other ncRNAs. Through these interactions, specific ncRNAs can modulate the radiosensitivity of cells and serve as diagnostic and prognostic biomarkers of radiation damage, whether from incidental exposure in radiotherapy or in accidental exposure scenarios. Analysis of RNA expression after radiation exposure has shown alterations not only in mRNAs, but also in ncRNAs (primarily miRNA, circRNA, and lncRNA), implying an important role in cellular stress response. Due to their abundance and stability in serum and other biofluids, ncRNAs also have great potential as minimally invasive biomarkers with advantages over current biodosimetry methods. Several studies have examined changes in ncRNA expression profiles in response to IR and other forms of oxidative stress. Furthermore, some studies have reported modulation of radiosensitivity by altering expression levels of these ncRNAs. This review discusses the roles of ncRNAs in the radiation response and evaluates prior research on ncRNAs as biomarkers of radiation damage. Future directions and applications of ncRNAs in radiation research are introduced, including the potential for a clinical ncRNA assay for assessing radiation damage and for the therapeutic use of RNA interference (RNAi).

Effects of Amifostine Pre-treatment on MIRNA, LNCRNA, and MRNA Profiles in the Hypothalamus of Mice Exposed to 60Co Gamma Radiation.

There is increasing evidence that the expression of non-coding RNA and mRNA (messenger RNA) is significantly altered following high-dose ionizing radiation (IR), and their expression may play a critical role in cellular responses to IR. However, the role of non-coding RNA and mRNA in radiation protection, especially in the nervous system, remains unknown. In this study, microarray profiles were used to determine microRNA (miRNA), long non-coding RNA (lncRNA), and mRNA expression in the hypothalamus of mice that were pretreated with amifostine and subsequently exposed to high-dose IR. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed. We found that fewer miRNAs, lncRNAs, and mRNAs were induced by amifostine pre-treatment in exposed mice, which exhibited antagonistic effects compared to IR, indicating that amifostine attenuated the IR-induced effects on RNA profiles. GO and KEGG pathway analyses showed changes in a variety of signaling pathways involved in inflammatory responses during radioprotection following amifostine pre-treatment in exposed mice. Taken together, our study revealed that amifostine treatment altered or attenuated miRNA, lncRNA, and mRNA expression in the hypothalamus of exposed mice. These data provide a resource to further elucidate the mechanisms underlying amifostine-mediated radioprotection in the hypothalamus.

Effect of simulated microgravity and ionizing radiation on expression profiles of miRNA, lncRNA, and mRNA in human lymphoblastoid cells.

In space, multiple unique environmental factors, particularly microgravity and space radiation, pose a constant threat to astronaut health. MicroRNAs (miRNAs) and long noncoding RNAs (lncRNAs) are functional RNAs that play critical roles in regulating multiple cellular processes. To gain insight into the role of non-coding RNAs in response to radiation and microgravity, we analyzed RNA expression profiles in human lymphoblastoid TK6 cells incubated for 24 h under static or rotating conditions to stimulate microgravity in space, after 2-Gy γ-ray irradiation. The expression of 14 lncRNAs and 17 mRNAs (differentially-expressed genes, DEGs) was found to be significantly downregulated under simulated microgravity conditions. In contrast, irradiation upregulated 55 lncRNAs and 56 DEGs, whereas only one lncRNA, but no DEGs, was downregulated. Furthermore, two miRNAs, 70 lncRNAs, and 87 DEGs showed significantly altered expression in response to simulated microgravity after irradiation, and these changes were independently induced by irradiation and simulated microgravity. GO enrichment and KEGG pathway analyses indicated that the associated target genes showed similar patterns to the noncoding RNAs and were suggested to be involved in the immune/inflammatory response including LPS/TLR, TNF, and NF-κB signaling pathways. However, synergistic effects on RNA expression and cellular responses were also observed with a combination of simulated microgravity and irradiation based on microarray and RT-PCR analysis. Together, our results indicate that simulated microgravity and irradiation additively alter expression patterns but synergistically modulate the expression levels of RNAs and their target genes in human lymphoblastoid cells.

Competing endogenous network analysis identifies lncRNA Meg3 activates inflammatory damage in UVB induced murine skin lesion by sponging miR-93-5p/epiregulin axis.

In this study, we obtained the RNA expression data of murine skin tissues of control, and UVB irradiated groups. After the re-annotation of lncRNAs, a gene expression similarity analysis was done by WGCNA. The target mRNA prediction of lncRNAs, miRNAs, and ceRNA regulatory networks were constructed by five lncRNAs, 14 miRNAs and 54 mRNAs, respectively. Based on the ceRNA network of UVB-induced skin lesions, it was evident that the dysregulation of Meg3 has critical effects on the UVB-induced inflammatory lesion of murine skin tissues. The overexpression of Meg3 after UVB irradiation was observed in primary murine skin fibroblasts, and the up-regulated Meg3 expression was related to the activation of the inflammatory cytokines. These functional experiments demonstrated that the RNA silencing of Meg3 in murine skin fibroblasts could suppress the expression of the cytokines (in vitro) and UVB-induced skin lesions (in vivo). Moreover, the Meg3 functioned as a competing endogenous RNA (ceRNA) that acted as a sponge for miR-93-5p and thereby modulated the expression of Epiregulin (Ereg). Our results proved that Meg3 was involved in UVB-induced skin inflammation and that the ceRNA networks, which includes miR-93-5p and Ereg, could prove to be a potential therapeutic target for UVB-induced skin damage.

Analysis of changes to lncRNAs and their target mRNAs in murine jejunum after radiation treatment.

LncRNAs have been reported to play an important role in various diseases. However, their role in the radiation-induced intestinal injury is unknown. The goal of the present study was to analyse the potential mechanistic role of lncRNAs in the radiation-induced intestinal injury. Mice were divided into two groups: Control (non-irradiated) and irradiated. Irradiated mice were administered 14 Gy of abdominal irradiation (ABI) and were assessed 3.5 days after irradiation. Changes to the jejuna of ABI mice were analysed using RNA-Seq for alterations to both lncRNA and mRNA. These results were validated using qRT-PCR. LncRNAs targets were predicted based on analysis of lncRNAs-miRNAs-mRNAs interaction. 29 007 lncRNAs and 17 142 mRNAs were detected in the two groups. At 3.5 days post-irradiation, 91 lncRNAs and 57 lncRNAs were significantly up- and downregulated respectively. Similarly, 752 mRNAs and 400 mRNAs were significantly up- and downregulated respectively. qRT-PCR was used to verify the altered expression of four lncRNAs (ENSMUST00000173070, AK157361, AK083183, AK038898) and four mRNAs (Mboat1, Nek10, Ccl24, Cyp2c55). Gene ontology and KEGG pathway analyses indicated the predicted genes were mainly involved in the VEGF signalling pathway. This study reveals that the expression of lncRNAs was altered in the jejuna of mice post-irradiation. Moreover, it provides a resource for the study of lncRNAs in the radiation-induced intestinal injury.

Correlation study between long non-coding RNA MALAT1 and radiotherapy efficiency on cervical carcinoma and generation of radiotherapy resistant model of cancer.

OBJECTIVE: This study aims to construct a radiotherapy model on cervical carcinoma cells and to illustrate the correlation between long non-coding RNA (lncRNA) metastasis-associated lung adenocarcinoma transcription 1 (MALAT1) and radiotherapy efficiency. PATIENTS AND METHODS: A total of 60 cervical carcinoma patients were recruited, and quantitative PCR (qPCR) was employed to detect MALAT1 expression. A dosage-time curve helped to construct radiotherapy resistant model on cervical carcinoma cell CaSki. Lentivirus transfection was used to silence MALAT1 expression, followed by quantification of clonal formation, apoptosis, and cycle after combined radiotherapy. Bioinformatics tool (miRcode.org), reporter gene and qPCR were used to predict microRNA (miR) interaction with MALAT1. By combining MALAT1 silencing, miR over-expression and radiotherapy, effects on the cervical cancer cell clonal formation, apoptosis, and cycle were observed. RESULTS: Comparing to radiotherapy sensitive tissues, the MALAT1 level was significantly elevated in radiotherapy resistant tissues (0.52 ± 0.18 vs. 1.29 ± 0.34, p<0.05). MALAT1 expression in cervical carcinoma cell CaSki was further elevated with elongated radiation time and dosage (p<0.05). Comparing to controlled cells, MALAT1 silencing decreased viable cell percentage, enhanced apoptosis, increased G1 phase cells, and decreased G2/M ratio. Bioinformatics, reporter gene, and qPCR showed that MALAT1 exerted its roles in cervical carcinoma cells via interacting with miR-143, both of which had a significant correlation (r=0.77, p<0.01). MALAT1 silencing combined with miR-143 plus radiotherapy decreased viable cell percentage, enhanced apoptosis, increased G1 phase ratio, and decreased S or G2/M cells. CONCLUSIONS: In cervical carcinoma, MALAT1 can interact with miR-143 to modulate tumor cell survival, apoptosis and cell cycle, thus affecting radiotherapy efficiency.

UPA-seq: prediction of functional lncRNAs using differential sensitivity to UV crosslinking.

While a large number of long noncoding RNAs (lncRNAs) are transcribed from the genome of higher eukaryotes, systematic prediction of their functionality has been challenging due to the lack of conserved sequence motifs or structures. Assuming that some lncRNAs function as large ribonucleoprotein complexes and thus are easily crosslinked to proteins upon UV irradiation, we performed RNA-seq analyses of RNAs recovered from the aqueous phase after UV irradiation and phenol-chloroform extraction (UPA-seq). As expected, the numbers of UPA-seq reads mapped to known functional lncRNAs were remarkably reduced upon UV irradiation. Comparison with ENCODE eCLIP data revealed that lncRNAs that exhibited greater decreases upon UV irradiation preferentially associated with proteins containing prion-like domains (PrLDs). Fluorescent in situ hybridization (FISH) analyses revealed the nuclear localization of novel functional lncRNA candidates, including one that accumulated at the site of transcription. We propose that UPA-seq provides a useful tool for the selection of lncRNA candidates to be analyzed in depth in subsequent functional studies.

LncRNA HULC mediates radioresistance via autophagy in prostate cancer cells.

Prostate cancer (PCa) is the second leading cause of cancer death in men. Irradiation is one of the available options for treatment of PCa, however, approximately 10-45% of PCa are resistant to irradiation. We aimed to explore the role of long non-coding RNA highly upregulated in liver cancer (HULC) in the sensitivity of PCa cells to irradiation. Survival rate, cell apoptosis, cycle, expressions of related proteins, and caspase-3 activity were assessed to explore the effects of HULC on sensitivity of PCa cells to irradiation. Expression of HULC in DU-145, PC3, LNCaP, and RWPE-1 cells was determined and the influence of HULC on DU-145 cells was explored. Then, PC3 cells aberrantly expressing HULC were implanted into NOD-SCID mice for tumor xenograft study. Changes of autophagy after aberrant expression of HULC in vivo and in vitro were tested. Furthermore, the interacted protein of HULC and involved signaling pathway were investigated. In PC3 and LNCaP cells under irradiation, survival rate and cell cycle were decreased and apoptosis was increased by HULC knockdown. HULC knockdown arrested PC3 cells at G0/G1 phase. DU-145 was sensitive to irradiation, and resistance to irradiation of DU-145 cells was enhanced by HULC overexpression. Moreover, HULC knockdown enhanced the sensitivity of PC3 xenografts to irradiation. HULC knockdown promoted autophagy through interaction with Beclin-1 and inhibition of mTOR, resulting in increased apoptosis. HULC knockdown improved sensitivity of PCa cells to irradiation both in vivo and in vitro. HULC suppressed Beclin-1 phosphorylation, thereby reduced autophagy, involving the mTOR pathway.

LncRNA HULC mediates radioresistance via autophagy in prostate cancer cells

Prostate cancer (PCa) is the second leading cause of cancer death in men. Irradiation is one of the available options for treatment of PCa, however, approximately 10-45% of PCa are resistant to irradiation. We aimed to explore the role of long non-coding RNA highly upregulated in liver cancer (HULC) in the sensitivity of PCa cells to irradiation. Survival rate, cell apoptosis, cycle, expressions of related proteins, and caspase-3 activity were assessed to explore the effects of HULC on sensitivity of PCa cells to irradiation. Expression of HULC in DU-145, PC3, LNCaP, and RWPE-1 cells was determined and the influence of HULC on DU-145 cells was explored. Then, PC3 cells aberrantly expressing HULC were implanted into NOD-SCID mice for tumor xenograft study. Changes of autophagy after aberrant expression of HULC in vivo and in vitro were tested. Furthermore, the interacted protein of HULC and involved signaling pathway were investigated. In PC3 and LNCaP cells under irradiation, survival rate and cell cycle were decreased and apoptosis was increased by HULC knockdown. HULC knockdown arrested PC3 cells at G0/G1 phase. DU-145 was sensitive to irradiation, and resistance to irradiation of DU-145 cells was enhanced by HULC overexpression. Moreover, HULC knockdown enhanced the sensitivity of PC3 xenografts to irradiation. HULC knockdown promoted autophagy through interaction with Beclin-1 and inhibition of mTOR, resulting in increased apoptosis. HULC knockdown improved sensitivity of PCa cells to irradiation both in vivo and in vitro. HULC suppressed Beclin-1 phosphorylation, thereby reduced autophagy, involving the mTOR pathway.

Integrative analysis of gene expression in response to low-dose ionizing radiation in a human skin model.

The advance in medical imaging and utilization has raised the concern about exposure to low-dose ionizing radiation (LDIR). Cellular and molecular responses to high-dose ionizing radiation have been characterized, but in the range of low dose, these responses are poorly understood. Here, we investigate the gene expression in response to LDIR (10 cGy) in the EpiDermFT human skin model. We identified 3299 differentially expressed genes (DEGs) in response to LDIR. Among these DEGs, we noted several well-characterized long noncoding RNAs. Gene Ontology and KEGG pathway analysis were performed to detect altered molecular response. GO and KEGG pathway results showed that genes corresponding to "regulation of cell proliferation" were enriched. Gene set enrichment analysis showed that KRAS signaling pathway was enriched in response to LDIR and transcription targets of NF-κB were also enriched when exposed to LDIR.

Time, dose and ataxia telangiectasia mutated (ATM) status dependency of coding and noncoding RNA expression after ionizing radiation exposure.

Studies of gene expression have proved important in defining the molecular mechanisms of radiation action and identifying biomarkers of ionizing radiation exposure and susceptibility. The full transcriptional response to radiation is very complex since it also involves epigenetic mechanisms triggered by radiation exposure such as modifications of expression of noncoding RNA such as microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) that have not been fully characterized. To improve our understanding of the transcriptional response to radiation, we simultaneously monitored the expression of ten protein-coding genes, as well as 19 miRNAs and 3 lncRNAs in a time- and dose-dependent manner in stimulated human T lymphocytes obtained from two healthy donors (C1 and C2) and one patient with ataxia telangiectasia (AT), which is a well characterized radiosensitivity disorder. After 2 Gy X irradiation, expression levels were monitored at time points ranging from 15 min up to 24 h postirradiation. The majority of genes investigated responded rapidly to radiation exposure, with the peak up-regulation (CDKN1A, SESN1, ATF3, MDM2, PUMA and GADD45A) or down-regulation (CCNB1) occurring 2-3 h postirradiation, while DDB2, FDXR and CCNG1 responded with slower kinetics reaching a peak of expression between 5 and 24 h. A significant modification of expression after radiation exposure was observed for miR-34a-5p and miR-182-5p, with an up-regulation occurring at late time points reaching two to threefold at 24 h. Differences between two donors in miR-182-5p response to radiation were detected: for C2, up-regulation reached a plateau-phase around 5 Gy, while for C1, up-regulation was at its maximum around 3 Gy and then decreased at higher doses. Among the three lncRNAs studied, TP53TG1 demonstrated a weak up-regulation, reaching a maximum of 1.5-fold at 24 h after radiation exposure. Conversely, FAS-AS1 was up-regulated up to fivefold by 5 Gy irradiation. Our results indicate that expression of the majority of protein-coding genes allows discrimination of the AT from healthy donors when analyzed at 2 h. However, differences in expression between AT and healthy donors are no longer detectable 24 h postirradiation although, interestingly, linear dose responses for some of the genes studied are obtained at this time point. Furthermore, our study shows that miRNAs miR-34a-5p and miR-182-5p are responsive to radiation exposure in a dose- and time-dependent manner. Additionally, to the best of our knowledge, this is the first study to report that FAS-AS1 lncRNA is up-regulated by radiation exposure in an ATM-dependent fashion in human T lymphocytes.