MicroRNA and signal transduction pathways in tumor radiation response

Radiogenomics helps to achieve personalized therapy by evaluating patient responses to radiation treatment

Radiogenomics is the whole genome application of radiogenetics, which focuses on uncovering the underlying genetic causes of individual variation in sensitivity to radiation. There is a growing consensus that radiosensitivity is a complex, inherited polygenic trait, dependent on the interaction of many genes involved in multiple cell processes. An understanding of the genes involved in processes such as DNA damage response and oxidative stress response, has evolved toward examination of how genetic variants, most often, single nucleotide polymorphisms (SNPs), may influence interindividual radioresponse. Many experimental approaches, such as candidate SNP association studies, genome-wide association studies and massively parallel sequencing are being proposed to address these questions. We present a review focusing on recent advances in association studies of SNPs to radiotherapy response and discuss challenges and opportunities for further studies. We also highlight the clinical perspective of radiogenomics in the future of personalized treatment in radiation oncology.

miRNAs in tumor radiation response: bystanders or participants?

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

Modulation of microRNAs by ionizing radiation in human gastric cancer

Gastric cancer is one of the most common cancers in China. Although surgery is the primary therapeutic method, radiotherapy has become an integral part, particularly in the early and intermediate stages of gastric cancer. microRNAs (miRNAs) are involved in the regulation of diverse cellular processes in response to intrinsic and extrinsic stress. A change in miRNA expression profile has been identified in various types of tumor cells in response to radiation; however, there is no relevant information concerning gastric cancer. In the present study, we investigated the miRNA profiles of two clinical gastric cancer samples exposed to X‑rays using miRNA microarray. We found that 16 miRNAs were downregulated and 2 miRNAs were upregulated significantly in both irradiated samples when compared with the unirradiated samples. Decreases in the levels of miR‑300 and miR‑642 expression were confirmed by qRT‑PCR in more clinical samples and in cultured cell lines. We predicted the targets of the two miRNAs with TargetScan and classified all the candidate targets with Gene Ontology, which indicated that both miR‑300 and miR‑642 potentially regulate cellular radiation response by modulating apoptosis, cell cycle regulation and DNA damage and repair pathway-related genes. Cell cycle assay and immunofluorescence assay demonstrated that miR‑300 regulates radiation‑induced G2 cell cycle arrest and DNA damage repair. In conclusion, our findings indicate that ionizing radiation modulates the miRNA expression profile, and the changes in several specific miRNAs such as miR‑300 have the potential to be used in the treatment, diagnosis and prognosis of gastric cancer.

Epigenetics in radiation-induced fibrosis

Radiotherapy is a major cancer treatment option but dose-limiting side effects such as late-onset fibrosis in the irradiated tissue severely impair quality of life in cancer survivors. Efforts to explain radiation-induced fibrosis, for example, by genetic variation remained largely inconclusive. Recently published molecular analyses on radiation response and fibrogenesis showed a prominent role of epigenetic gene regulation. This review summarizes the current knowledge on epigenetic modifications in fibrotic disease and radiation response, and it points out the important role for epigenetic mechanisms such as DNA methylation, microRNAs and histone modifications in the development of this disease. The synopsis illustrates the complexity of radiation-induced fibrosis and reveals the need for investigations to further unravel its molecular mechanisms. Importantly, epigenetic changes are long-term determinants of gene expression and can therefore support those mechanisms that induce and perpetuate fibrogenesis even in the absence of the initial damaging stimulus. Future work must comprise the interconnection of acute radiation response and long-lasting epigenetic effects in order to assess their role in late-onset radiation fibrosis. An improved understanding of the underlying biology is fundamental to better comprehend the origin of this disease and to improve both preventive and therapeutic strategies.

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.

Role of microRNA in response to ionizing radiations: evidences and potential impact on clinical practice for radiotherapy

MicroRNAs (miRNA) are small, non-coding, RNAs with gene expression regulator roles. As an important class of regulators of many cellular pathways, miRNAs are involved in many signaling pathways and DNA damage repair processes, affecting cellular radiosensitivity. Their role has led to interest in oncological implications to improve treatment results. MiRNAs represent a great opportunity to enhance the efficacy of radiotherapy treatments-they can be used to profile the radioresistance of tumors before radiotherapy, monitor their response throughout the treatment, thus helping to select intensification strategies, and also to define the final response to therapy along with risks of recurrence or metastatization. Even though many interesting studies support such potential, nowadays most studies on patient data are limited to experiments profiling tumor aggressiveness and response to radiotherapy. Moreover many studies report different although not conflicting results on the miRNAs evaluated for each tumor type. Without doubt, the clinical potential of such molecules for radiotherapy is striking and of high interest.

MicroRNA expression profiles in human breast cancer cells after multifraction and single-dose radiation treatment

MicroRNAs (miRNAs) are small non-coding RNAs that contribute to modulating signaling pathways after radiation exposure and have emerged as a potential therapeutic target or biomarker in the radiation response of cancer. Exposing breast cancer cells to single-dose (SD) or multifractionated (MF) radiation may affect the cells differently. However, the roles of miRNAs in breast cancer cells after the response to SD or MF is not thoroughly understood. Therefore, the purpose of the present study was to comprehensively investigate the response of miRNAs in MDA-MB-361 by using various radiation exposing protocols. Our results revealed that only a small fraction of miRNAs exhibiting differential expressions (>1.5‑fold) was identified after MDA-MB-361 cells were exposed to SD (10 Gy) or MF radiation (2 Gy x 5 MF). In addition, we observed that several miRNAs in the MDA-MB-361 cells frequently exhibited differential responses to various types of radiation treatment. Among these miRNAs, the expression levels of an oncogenic miR-17-92 cluster increased following SD radiation treatment. Conversely, miR-19a-3p, miR-20a-5p, and miR-19b-3p expressions were inhibited by >1.5-fold in the following MF treatment. Further analysis of the miR-17-92 cluster expression levels revealed that miR-17, miR-18a, miR-19a/b and miR-20a were significantly overexpressed and miR-92a was downregulated in breast cancer. Functional annotation demonstrated that target genes of the miR-17-92 cluster were predominantly involved in the regulation of radiation-associated signal pathways such as mitogen-activated protein kinase (MAPK), ErbB, p53, Wnt, transforming growth factor-β (TGF-β), mTOR signaling pathways and cell cycles with an FDR <0.05. Overall, the results of the present study revealed distinct differences in the response of miRNAs to SD and MF radiation exposure, and these radiation-associated miRNAs may contribute to radiosensitivity and can be used as biomarkers for radiotherapy.

Integrated analysis of differential miRNA and mRNA expression profiles in human radioresistant and radiosensitive nasopharyngeal carcinoma cells

Background

The purpose of this study was to identify miRNAs and genes involved in nasopharyngeal carcinoma (NPC) radioresistance, and explore the underlying mechanisms in the development of radioresistance.

Methods

We used microarrays to compare the differences of both miRNA and mRNA expression profiles in the radioresistant NPC CNE2-IR and radiosensitive NPC CNE2 cells, applied qRT-PCR to confirm the reliability of microarray data, adopted databases prediction and anticorrelated analysis of miRNA and mRNA expression to identify the miRNA target genes, and employed bioinformatics tools to examine the functions and pathways in which miRNA target genes are involved, and construct a miRNA-target gene regulatory network. We further investigated the roles of miRNA-23a and its target gene IL-8 in the NPC radioresistance.

Results

The main findings were fourfold: (1) fifteen differential miRNAs and 372 differential mRNAs were identified, and the reliability of microarray data was validated for randomly selected eight miRNAs and nine genes; (2) 174 miRNA target were identified, and most of their functions and regulating pathways were related to tumor therapeutic resistance; (3) a posttranscriptional regulatory network including 375 miRNA-target gene pairs was constructed, in which the ten genes were coregulated by the six miRNAs; (4) IL-8 was a direct target of miRNA-23a, the expression levels of IL-8 were elevated in the radioresistant NPC tissues and showed inverse correlation with miRNA-23a expression, and genetic upregulation of miRNA-23a and antibody neutralization of secretory IL-8 could reduce NPC cells radioresistance.

Conclusions

We identified fifteen differential miRNAs and 372 differential mRNAs in the radioresistant NPC cells, constructed a posttranscriptional regulatory network including 375 miRNA-target gene pairs, discovered the ten target genes coregulated by the six miRNAs, and validated that downregulated miRNA-23a was involved in NPC radioresistance through directly targeting IL-8. Our data form a basis for further investigating the mechanisms of NPC radioresistance.

DNA-hybrid-gated multifunctional mesoporous silica nanocarriers for dual-targeted and microRNA-responsive controlled drug delivery

The design of an ideal drug delivery system with targeted recognition and zero premature release, especially controlled and specific release that is triggered by an exclusive endogenous stimulus, is a great challenge. A traceable and aptamer-targeted drug nanocarrier has now been developed; the nanocarrier was obtained by capping mesoporous silica-coated quantum dots with a programmable DNA hybrid, and the drug release was controlled by microRNA. Once the nanocarriers had been delivered into HeLa cells by aptamer-mediated recognition and endocytosis, the overexpressed endogenous miR-21 served as an exclusive key to unlock the nanocarriers by competitive hybridization with the DNA hybrid, which led to a sustained lethality of the HeLa cells. If microRNA that is exclusively expressed in specific pathological cell was screened, a combination of chemotherapy and gene therapy should pave the way for a targeted and personalized treatment of human diseases.

Comprehensive microRNA profiling of prostate cancer cells after ionizing radiation treatment

MicroRNAs (miRNAs) are small, non-coding RNAs that negatively regulate gene expression and have emerged as potential biomarkers in radiation response to human cancer. Only a few miRNAs have been identified in radiation response to prostate cancer and the involvement of the radiation-associated miRNA machinery in the response of prostate cancer cells to radiation is not thoroughly understood. Therefore, the purpose of the present study was to comprehensively investigate the expression levels, arm selection preference and isomiRs of radiation-response miRNAs in radiation-treated PC3 cells using a next-generation sequencing (NGS) approach. Our data revealed that the arm selection preference and 3′ modification of miRNAs may be altered in prostate cancer after radiation exposure. In addition, the proportion of AA dinucleotide modifications at the end of the read gradually increased in a time-dependent manner after PC3 radiation treatment. We also identified 6 miRNAs whose expression increased and 16 miRNAs whose expression decreased after exposure to 10 Gy of radiation. A pathway enrichment analysis revealed that the target genes of these radiation-induced miRNAs significantly co-modulated the radiation response pathway, including the mitogen-activated protein kinase (MAPK), Wnt, transforming growth factor-β (TGF-β) and ErbB signaling pathways. Furthermore, analysis of The Cancer Genome Atlas (TCGA) database revealed that the expression of these radiation-induced miRNAs was frequently dysregulated in prostate cancer. Our study identified radiation-induced miRNA candidates which may contribute to radiosensitivity and can be used as biomarkers for radiotherapy.

The advance of application for microRNAs in cancer gene therapy

MicroRNAs (miRNAs, miRs) are closely associated with biological processes of tumor cells as the key regulators by recognizing specific mRNA targets, and further mediating post-transcriptional inhibition of tumor related genes. Therefore, miRNAs may be used as optional therapeutic targets in tumors resulting from accumulation of multiple gene mutations and their interactions. Currently, there are many researches for making miRNAs safely and efficiently be applied in cancer gene therapy (CGT). This review summarizes miRNA anomalous biogenesis pathway, different roles in disease processes of tumors, by which it further clarifies miRNA implemented methods including the combined treatment related with miRNA in CGT; simultaneously, briefly illustrates the delivery systems of miRNA.

WITHDRAWN: miR-504 affects the radio-resistance in nasopharyngeal carcinoma by down-regulating the expression of nuclear respiratory factor 1

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