Repression of ATR pathway by miR-185 enhances radiation-induced apoptosis and proliferation inhibition

An ATR-PrimPol pathway confers tolerance to oncogenic KRAS-induced and heterochromatin-associated replication stress

Activation of the KRAS oncogene is a source of replication stress, but how this stress is generated and how it is tolerated by cancer cells remain poorly understood. Here we show that induction of KRASG12V expression in untransformed cells triggers H3K27me3 and HP1-associated chromatin compaction in an RNA transcription dependent manner, resulting in replication fork slowing and cell death. Furthermore, elevated ATR expression is necessary and sufficient for tolerance of KRASG12V-induced replication stress to expand replication stress-tolerant cells (RSTCs). PrimPol is phosphorylated at Ser255, a potential Chk1 substrate site, under KRASG12V-induced replication stress and promotes repriming to maintain fork progression and cell survival in an ATR/Chk1-dependent manner. However, ssDNA gaps are generated at heterochromatin by PrimPol-dependent repriming, leading to genomic instability. These results reveal a role of ATR-PrimPol in enabling precancerous cells to survive KRAS-induced replication stress and expand clonally with accumulation of genomic instability.

Radiation-induced pulmonary fibrosis: roles of therapy-induced senescence and microRNAs

PURPOSE

Progressive, irreversible radiation-induced pulmonary fibrosis (RIPF) is a clinically significant intermediate- to a late-occurring side effect of radiotherapy. Known mechanisms of RIPF include oxidative stress-induced activation of TGF-β with activation of SMAD signaling, TNF-α elaboration, and activation of the Angiotensin Converting Enzyme (ACE) mediated production of angiotensin II with resulting activation of profibrotic cytokine signaling and vasoconstriction. The pioneering work of John Moulder, to whom this paper is dedicated, and several of his colleagues demonstrated that inhibiting the conversion of ACE with drugs such as Captopril, Enalapril, and Losartan can ameliorate radiation fibrosis in various tissues. While this work led several groups to probe mechanism-based pharmacological mitigation of RIPF, in this article, we explore and discuss the roles of microRNAs (miRNA) and therapy-induced senescence (TIS) in the pathogenesis of and potential biomarkers for RIPF.

CONCLUSION

Our analysis of the published literature in the last decade on RIPF, miRNA, and TIS identifies TIS as a mechanism in the onset and progression of RIPF, which is regulated through several miRNAs. This work may lead to the discovery and development of the next generation of miRNA therapeutics and/or the repurposing of approved pharmaceutical agents and the development of early biomarker panels to predict RIPF.

Proteomic profiling reveals neuronal ion channel dysregulation and cellular responses to DNA damage-induced cell cycle arrest and senescence in human neuroblastoma SH-SY5Y cells exposed to cypermethrin

Cypermethrin (CYP), a synthetic pyrethroid of class II, is widely used as a pesticide worldwide. The primary target of cypermethrin is a voltage-gated sodium channel. The neurotoxicity of CYP has been extensively studied in terms of affecting neuronal development, increasing cellular oxidative stress, and apoptosis. However, little is known about how it affects the expression of channel proteins involved in synaptic transmission, as well as the effects of cypermethrin on DNA damage and cell cycle processes. We found that the ligand and voltage-gated calcium channels and proteins involved in synaptic transmission including NMDA 1 receptor subunit, alpha 1A-voltage-dependent calcium channel, synaptotagmin-17, and synaptojanin-2 were downregulated in CYP-treated cells. After 48h of CYP exposure, cell viability was reduced with flattened and enlarged morphology. The levels of 23 proteins regulating cell cycle processes were altered in CYP-treated cells, according to a proteomic study. The cell cycle analysis showed elevated G₀/G₁ cell cycle arrest and DNA fragmentation at the sub-G₀ stage after CYP exposure. CYP treatment also increased senescence-associated β-galactosidase positive cells, DNA damage, and apoptotic markers. Taken together, the current study showed that cypermethrin exposure caused DNA damage and hastened cellular senescence and apoptosis via disrupting cell cycle regulation. In addition, despite its primary target sodium channel, CYP might cause synaptic dysfunction via the downregulation of synaptic proteins and dysregulation of synapse-associated ion channels.

Effects of MicroRNA-195-5p on Biological Behaviors and Radiosensitivity of Lung Adenocarcinoma Cells via Targeting HOXA10

Objective

To explore the effects of miR-195-5p and its target gene HOXA10 on the biological behaviors and radiosensitivity of lung adenocarcinoma (LUAD) cells.

Methods

The effects of miR-195-5p on LUAD cell proliferation, migration, invasion, cycle arrest, apoptosis, and radiosensitivity were investigated by in vitro experiments. The bioinformatics analysis was used to assess its clinical value and predict target genes. Double-luciferase experiments were used to verify whether the miR-195-5p directly targeted HOXA10. A xenograft tumor-bearing mouse model was used to examine its effects on the radiosensitivity of LUAD in vivo.

Results

Both gain- and loss-of-function assays demonstrated that miR-195-5p inhibited LUAD cell proliferation, invasion, and migration, induced G1 phase arrest and apoptosis, and enhanced radiosensitivity. Double-luciferase experiments confirmed that miR-195-5p directly targeted HOXA10. Downregulation of HOXA10 also inhibited LUAD cell proliferation, migration, and invasion, induced G1 phase arrest and apoptosis, and enhanced radiosensitivity. The protein levels of β-catenin, c-myc, and Wnt1 were decreased by miR-195-5p and increased by its inhibitor. Moreover, the effects of the miR-195-5p inhibitor could be eliminated by HOXA10-siRNA. Furthermore, miR-195-5p improved radiosensitivity of LUAD cells in vivo.

Conclusion

miR-195-5p has excellent antitumor effects via inhibiting cancer cell growth, invasion, and migration, arresting the cell cycle, promoting apoptosis, and sensitizing LUAD cells to X-ray irradiation by targeting HOXA10. Thus, miR-195-5p may serve as a potential candidate for the treatment of LUAD.

MicroRNAs and the DNA damage response: How is cell fate determined?

It is becoming clear that the DNA damage response orchestrates an appropriate response to a given level of DNA damage, whether that is cell cycle arrest and repair, senescence or apoptosis. It is plausible that the alternative regulation of the DNA damage response (DDR) plays a role in deciding cell fate following damage. MicroRNAs (miRNAs) are associated with the transcriptional regulation of many cellular processes. They have diverse functions, affecting, presumably, all aspects of cell biology. Many have been shown to be DNA damage inducible and it is conceivable that miRNA species play a role in deciding cell fate following DNA damage by regulating the expression and activation of key DDR proteins. From a clinical perspective, miRNAs are attractive targets to improve cancer patient outcomes to DNA-damaging chemotherapy. However, cancer tissue is known to be, or to become, well adapted to DNA damage as a means of inducing chemoresistance. This frequently results from an altered DDR, possibly owing to miRNA dysregulation. Though many studies provide an overview of miRNAs that are dysregulated within cancerous tissues, a tangible, functional association is often lacking. While miRNAs are well-documented in 'ectopic biology', the physiological significance of endogenous miRNAs in the context of the DDR requires clarification. This review discusses miRNAs of biological relevance and their role in DNA damage response by potentially 'fine-tuning' the DDR towards a particular cell fate in response to DNA damage. MiRNAs are thus potential therapeutic targets/strategies to limit chemoresistance, or improve chemotherapeutic efficacy.

The Adaptive Responses in Non-Small Cell Lung Cancer A549 Cell Lines Induced by Low-Dose Ionizing Radiation and the Variations of miRNA Expression

Objective

To study the effects of adaptive response in A549 cells induced by low-dose radiation and the miRNAs expression.

Methods

A549 cells were irradiated with 50 mGy and 200 mGy initial doses, respectively, and then irradiated with a challenge dose 20 Gy at 6 hours interval. The biological effects and miRNA expression were detected.

Results

The apoptosis rates of 50 mGy-20 Gy and 200 mGy-20 Gy groups were significantly lower than that of only 20 Gy irradiation group (P < .05). The percentage of G2/M phase cells of 50 mGy-20 Gy and 200 mGy-20 Gy groups was significantly decreased relative to the 20 Gy group (P < .05). One miRNA (mir-3662) was upregulated and 15 miRNAs (mir-185, mir-1908, mir-307, mir-182, mir-92a, mir-582, mi-r501, mir138-5p, mir-1260, mir-484, mir-378d, mir-193b, mir-127-3p, mir-1303, and mir-654-5p) were downregulated both in 50 mGy-20 Gy and 200 mGy-20 Gy groups than that of the 20 Gy group. Go and KEGG enrichment analysis showed that the target genes were significantly enriched in cell communication regulation, metabolic process, enzyme binding, and catalytic activity signaling pathways.

Conclusion

Low-dose X-ray of 50 mGy and 200 mGy radiation can induce adaptive apoptosis response prior to 20 Gy in A549 cells. Sixteen differently expressed miRNAs may play important roles in the adaptive effect of low-dose radiation.

Current Implications of microRNAs in Genome Stability and Stress Responses of Ovarian Cancer

Genomic alterations and aberrant DNA damage signaling are hallmarks of ovarian cancer (OC), the leading cause of mortality among gynecological cancers worldwide. Owing to the lack of specific symptoms and late-stage diagnosis, survival chances of patients are significantly reduced. Poly (ADP-ribose) polymerase (PARP) inhibitors and replication stress response inhibitors present attractive therapeutic strategies for OC. Recent research has focused on ovarian cancer-associated microRNAs (miRNAs) that play significant regulatory roles in various cellular processes. While miRNAs have been shown to participate in regulation of tumorigenesis and drug responses through modulating the DNA damage response (DDR), little is known about their potential influence on sensitivity to chemotherapy. The main objective of this review is to summarize recent findings on the utility of miRNAs as cancer biomarkers, in particular, ovarian cancer, and their regulation of DDR or modified replication stress response proteins. We further discuss the suppressive and promotional effects of various miRNAs on ovarian cancer and their participation in cell cycle disturbance, response to DNA damage, and therapeutic functions in multiple cancer types, with particular focus on ovarian cancer. Improved understanding of the mechanisms by which miRNAs regulate drug resistance should facilitate the development of effective combination therapies for ovarian cancer.

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

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

The cross-talk between signaling pathways, noncoding RNAs and DNA damage response: Emerging players in cancer progression

The DNA damage response (DDR) pathway's primary purpose is to maintain the genome structure's integrity and stability. A great deal of effort has done to understand the exact molecular mechanisms of non-coding RNAs, such as lncRNA, miRNAs, and circRNAs, in distinct cellular and genomic processes and cancer progression. In this regard, the ncRNAs possible regulatory role in DDR via modulation of key components expression and controlling repair signaling pathway activation is validated. Therefore, in this article, we will discuss the latest developments of ncRNAs contribution in different aspects of DNA repair through regulation of ATM-ATR, P53, and other regulatory signaling pathways.

Let-7d and miR-185 Impede Epithelial-Mesenchymal Transition by Downregulating Rab25 in Breast Cancer

Objective:

MicroRNAs (miRNAs) expression has deregulated in several cancer types including breast cancer (BC). The present study aims at investigating the role, mechanism, clinical value of let-7d and miR-185 in BC, and the possible correlation these miRNAs with Rab25.

Materials and Methods:

Tumor samples as well adjacent normal tissues (ANT) were acquired from fresh surgical specimens from 110 patients and the expression levels of let-7d, miR-185, Rab25, and snail were evaluated using real-time PCR. The immunohistochemical (IHC) process and western blot were done to detect the level of Rab25 and Snail protein expression in BC samples.

Results:

By comparing miRNAs expression profiles in clinical tissues of 110 patients using real-time PCR, let-7d, and miR-185 expression were dramatically downregulated in BC tissues (P < 0.05). Tumor size, stage, and lymph node metastasis were significantly related to miRNAs expression. Based on qRT-PCR and bioinformatics database analyses, we also recognized Rab25 as a possible target of miR-185 and let-7d. Rab25 expression was enhanced in BC cells and associated inversely with the expression level of mentioned miRNAs. qRT-PCR, immunohistochemistry, and western blot studies verified that Rab25 upregulation increased the levels of the snail, that key transcription factor of epithelial-mesenchymal transition (EMT).

Conclusion:

These findings demonstrated that let-7d and miR-185 inhibited EMT by targeting Rab25 expression in BC. Therefore, targeting the let-7d and miR-185/Rab25 interaction may offer new therapeutic opportunities for treating BC patients.

MiR-185 targets POT1 to induce telomere dysfunction and cellular senescence

Protection of telomere 1 (POT1), the telomeric single-stranded DNA (ssDNA)-binding protein in the shelterin complex, has been implicated in the DNA damage response, tumorigenesis and aging. Telomere dysfunction induced by telomere deprotection could accelerate cellular senescence in primary human cells. While previous work demonstrated the biological mechanism of POT1 in aging and cancer, how POT1 is posttranscriptionally regulated remains largely unknown. To better understand the POT1 regulatory axis, we performed bioinformatic prediction, and selected candidates were further confirmed by dual-luciferase reporter assay. Collectively, our results revealed that miR-185 can significantly reduce POT1 mRNA and protein levels by directly targeting the POT1 3’-untranslated region (3’-UTR). Overexpression of miR-185 increased telomere dysfunction-induced foci (TIF) signals in both cancer cells and primary human fibroblasts. Elevated miR-185 led to telomere elongation in the telomerase-positive cell line HTC75, which was phenotypically consistent with POT1 knocking down. Moreover, miR-185 accelerated the replicative senescence process in primary human fibroblasts in a POT1-dependent manner. Interestingly, increased serum miR-185 could represent a potential aging-related biomarker. Taken together, our findings reveal miR-185 as a novel aging-related miRNA that targets POT1 and provide insight into the telomere and senescence regulatory network at both the intracellular and extracellular levels.

Participation of the ATR/CHK1 pathway in replicative stress targeted therapy of high-grade ovarian cancer

Ovarian cancer is one of the most lethal gynecologic malignancies reported throughout the world. The initial, standard-of-care, adjuvant chemotherapy in epithelial ovarian cancer is usually a platinum drug, such as cisplatin or carboplatin, combined with a taxane. However, despite surgical removal of the tumor and initial high response rates to first-line chemotherapy, around 80% of women will develop cancer recurrence. Effective strategies, including chemotherapy and new research models, are necessary to improve the prognosis. The replication stress response (RSR) is characteristic of the development of tumors, including ovarian cancer. Hence, RSR pathway and DNA repair proteins have emerged as a new area for anticancer drug development. Although clinical trials have shown poly (ADP-ribose) polymerase inhibitors (PARPi) response rates of around 40% in women who carry a mutation in the BRCA1/2 genes, PARPi is responsible for tumor suppression, but not for complete tumor regression. Recent reports suggest that cells with impaired homologous recombination (HR) activities due to mutations in TP53 gene or specific DNA repair proteins are specifically sensitive to ataxia telangiectasia and Rad3-related protein (ATR) inhibitors. Replication stress activates DNA repair checkpoint proteins (ATR, CHK1), which prevent further DNA damage. This review describes the use of DNA repair checkpoint inhibitors as single agents and strategies combining these inhibitors with DNA-damaging compounds for ovarian cancer therapy, as well as the new platforms used for optimizing ovarian cancer therapy.

miR-335 Acts as a Tumor Suppressor and Enhances Ionizing Radiation-Induced Tumor Regression by Targeting ROCK1

Recent development of integrative therapy against melanoma combines surgery, radiotherapy, targeted therapy, and immunotherapy; however, the clinical outcomes of advanced stage and recurrent melanoma are poor. As a skin cancer, melanoma is generally resistant to radiotherapy. Hence, there is an urgent need for evaluation of the mechanisms of radioresistance. The present study identified miR-335 as one of the differential expression of miRNAs in recurrent melanoma biopsies post-radiotherapy. The expression of miR-335 declined in melanoma tissues compared to the adjacent tissues. Moreover, miR-335 expression correlated with advanced stages of melanoma negatively. Consistent with the prediction of STARBASE and miRDB database, miR-335 targeted ROCK1 via binding with 3′-UTR of ROCK1 directly, resulting in attenuation of proliferation, migration, and radioresistance of melanoma cells. The authors validated that overexpression of miR-335 enhanced X-ray-induced tumor regression by B16 mouse models. Briefly, the present findings gained insights into miR-335/ROCK1-mediated radiosensitivity and provided a promising therapeutic strategy for improving radiotherapy against melanoma.

MicroRNAs, DNA damage response and ageing

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

Non-coding RNA and lung cancer progression

Lung cancer (LC) is a major killer disease globally. This situation is further supported by yearly increase in new LC cases and its poor 5-year survival which is less than 15%. Although a large percentage of LC cases have been attributed to smoking, a considerable amount of nonsmokers also develops this disease, thereby suggesting a genetic and/or epigenetic undertone to LC development. Several growth-related genes such as epidermal growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF) as well as tumor suppressor genes such as p53 have been implicated in LC pathogenesis and progression. Likewise, the genome only contains approximately 1% of coding regions. Hence, noncoding portion of the genome such as noncoding RNAs (ncRNAs) has been studied and discovered to play a cogent role in LC pathogenesis. More precisely, microRNAs (miRNAs) and long ncRNAs (lncRNAs) have been studied for decades. Posttranscriptional gene modulation function of miRNAs is well established and characterized. Likewise, the antagonizing interaction between lncRNAs and miRNAs had also been proven to further control gene expression during healthy and disease conditions like LC. More recently, renewed attention toward circular RNAs [circular RNAs (circRNAs)] study showed that circRNAs can also sponge miRNAs to modulate gene expressions too. Hence, miRNAs, lncRNAs, and circRNAs seem to function within a circuit to optimally determine which gene is needed to be upregulated or downregulated in biological system. Therefore, this review will discuss important ncRNAs, namely miRNA, lncRNA, and circRNA in LC progression. Paracrine effect of exosomal ncRNA will be also reviewed. In addition, the prospect of these ncRNAs in enhancing better LC treatment will be highlighted as well.

miR-222 enhances radiosensitivity of cancer cells by inhibiting the expression of CD47

Radiotherapy is one of the most common and effective treatments for localized cancer. However, radiotherapy kills tumor cells while causing damage to surrounding normal cells. Enhancing the radiation sensitivity of tumor cells and reducing the radiation damage to normal cells is a difficult problem. Here, we find that the expression of a human microRNA (miRNA), hsa-miR-222, is upregulated in response to ionizing radiation. TargetScan analysis shows that the 3' UTR of CD47 is potentially targeted by miR-222. This prediction was validated by luciferase reporter and mutation assays. It was demonstrated that miR-222 negatively regulates CD47 expression at mRNA and protein levels, and overexpression of the miR-222 enhances cancer cell radiosensitivity by the CD47-pERK pathway in cancer cells. Our findings enrich the complex relationship between miRNA and CD47 in irradiation stress and shed light on the potential of miRNAs both for direct cancer therapeutics and as tools to sensitize tumor cells to radiotherapy.

Analysis of Expression Patterns of MicroRNAs That Are Closely Associated With Renal Carcinogenesis

Background: MicroRNAs (miRNA) are frequently dysregulated in clear cell renal cell carcinoma (ccRCC). Objective: This study aimed to elucidate the role of miRNA expression patterns in renal carcinogenesis and to identify the specific miRNAs that exhibit expression patterns closely associated with patient outcomes. Methods: We examined the expression patterns of selected miRNAs, including miRNA-155-5p, miRNA-122-5p, miRNA-21-5p, miRNA-185-5p, miRNA-106a-5p, miRNA-106b-3p, miRNA-34b-3p, miRNA-210-3p, miRNA-141-3p, miRNA-200c-3p, miRNA-135a-5p, miRNA-30a-5p, miRNA-218-5p, miRNA-429, miRNA-200a-3p and miRNA-200b-3p, in 96 samples of ccRCCs using the TaqMan real-time PCR method. In addition, cluster analysis was performed to stratify expression patterns of multiple miRNAs. Results: In the present study, three distinct subgroups could be clearly stratified in ccRCCs. Subgroup 1 was characterized by upregulation of miRNA-155-5p, miRNA-122-5p, miRNA-21-5p, miRNA-185-5p, miRNA-106a-5p, miRNA-106b-3p, miRNA-34b-3p and miRNA-210-3p. Subgroup 2 was closely associated with downregulation of miRNA-141-3p, miRNA200c-3p, miRNA-30a-5p, miRNA-218-5p, miRNA-429, miRNA-200a-3p and miRNA-200b-3p. Moreover, significant lower expression of miRNA-135a-5p was a distinctive feature of subgroup 3, which was correlated with metachronous metastasis. Among the individual markers in subgroup 3, miRNA-135a-5p was retained in multivariate analysis. The cutoff value of miRNA-135a-5p expression to identify the association of an altered level of miRNA-135a-5p with metachronous metastasis in ccRCCs was determined and showed excellent specificity. Conclusion: We suggest that the expression pattern of the chosen miRNAs is useful to identify renal carcinogenesis and to help identify the association of such expression patterns with metachronous metastasis in ccRCCs. In addition, miRNA-135a-5p was an excellent marker for prediction of metachronous metastasis.

miR-483-5p decreases the radiosensitivity of nasopharyngeal carcinoma cells by targeting DAPK1

Recurrence or metastasis resulting from radioresistance are the main challenges for the treatment of nasopharyngeal carcinoma (NPC). A great deal of evidence supports the role of abnormal expression of miRNAs in radioresistance and malignancy. In some cancers, miR-483-5p is associated with inferior disease-specific survival. Therefore, we investigated the role of miR-483-5p in NPC radiosensitivity and the mechanism by which the miR-483-5p affects the radiosensitivity of NPC cells. In this study, we show that the overexpression of miR-483-5p decreases the radiosensitivity of NPC cells in vitro and in vivo. Mechanistically, miR-483-5p exerts these functions by decreasing radiation-induced apoptosis and DNA damage, and by increasing NPC cell colony formation, via targeting death-associated protein kinase 1 (DAPK1). Finally, our results confirm that the upregulation of miR-483-5p is correlated with advanced clinical stage and inferior overall survival of patients with NPC. These findings provide novel insights into our understanding of the molecular mechanisms underlying therapy failure in NPC. Modulation of miR-483-5p and DAPK1 levels may provide a new approach for increasing the radiosensitivity of these tumors.

MicroRNA-mediated redox regulation modulates therapy resistance in cancer cells: clinical perspectives

BACKGROUND

Chemotherapy and radiation therapy are the most common types of cancer therapy. The development of chemo/radio-resistance remains, however, a major obstacle. Altered redox balances are among of the main factors mediating therapy resistance. Therefore, redox regulatory strategies are urgently needed to overcome this problem. Recently, microRNAs have been found to act as major redox regulatory factors affecting chemo/radio-resistance. MicroRNAs play critical roles in regulating therapeutic resistance through the regulation of antioxidant enzymes, redox-sensitive signaling pathways, cancer stem cells, DNA repair mechanisms and autophagy.

CONCLUSIONS

Here, we summarize current knowledge on microRNA-mediated redox regulatory mechanisms underlying chemo/radio-resistance. This knowledge may form a basis for a better clinical management of cancer patients.

MicroRNA-185 inhibits cell proliferation while promoting apoptosis and autophagy through negative regulation of TGF-β1/mTOR axis and HOXC6 in nasopharyngeal carcinoma

OBJECTIVE

Accumulating studies have revealed that microRNAs (miRs) play a critical role in the development and progression of nasopharyngeal carcinoma (NPC), which is a disease with a remarkable racial and geographical distribution. In our study, through the alteration in the expression of microRNA-185 (miR-185) in NPC cells by microarray-based gene expression profiling, we subsequently evaluated its ability to influence NPC cells and associated mechanism.

METHODS

The expressions of miR-185 and HOXC6 in NPC and paracancerous tissues collected from patients with NPC were detected. The CNE-2 cells with the lowest miR-185 among the five NPC cell lines (CNE-1, CNE-2, HNE-1, HNE-2, and 5-8F) were selected and transfected with a series of mimic or inhibitor of miR-185, or shRNA-against HOXC6. The Kaplan-Meier method was used to analyze the survival of patients. Besides, the reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blot analysis were used to determine the levels of related genes/proteins. By means of cell counting kit-8 (CCK-8) assay, transwell assay, flow cytometry, and AO staining, the influences miR-185 has on the processes associated with NPC, including cell proliferation, invasion, apoptosis and autophagy were evaluated.

RESULTS

NPC was observed to decrease miR-185 but increase HOXC6. Dual luciferase reporter gene assay demonstrated that HOXC6 is a target gene of miR-185. Increased mRNA and protein levels of Bax, caspase-3, LC3 and Beclin1 and reduced levels of HOXC6, TGF-β1, mTOR, Cyclin D1, PCNA, Bcl-2 were found by overexpression of miR-185. High expression of miR-185 and low expression of HOXC6 had longer survival time of NPC patients. Overexpressed miR-185 enhanced cell apoptosis and autophagy, and reduced cell proliferation and invasion, while miR-185 inhibitor was observed to have induced effects on the CNE-2 cells.

CONCLUSION

Overall, the data show that miR-185 could negatively target HOXC6 to suppress cell proliferation, promotes apoptosis and autophagy through inhibiting TGF-β1/mTOR axis in NPC. Thus, miR-185 is useful strategy for the treatment of NPC.

Alterations of MicroRNA Expression in the Liver, Heart, and Testis of Mice Upon Exposure to Repeated Low-Dose Radiation

MicroRNAs (miRs), which regulate target gene expression at the post-transcriptional level, play a crucial role in inducing biological effects upon high-dose ionizing radiation. Yet, the miR expression profiles in response to repeated low-dose radiation (LDR) in vivo have not been elucidated. This study investigated the response profiles of 11 miRs with functions involved in metabolism, DNA damage and repair, inflammation, and fibrosis in mouse liver, heart, and testis upon repeated LDR exposure for 4 months. The expression profiles were evaluated using stem-loop quantitative reverse transcription polymerase chain reaction immediately and at 2 months after LDR exposure. The expression profiles varied significantly at both time points. At the organ level, the heart was the most affected, followed by the liver and testis, in which significant miR upregulation related to DNA damage response was found. Metabolism-related miRs decreased in the liver and increased in the testis. The current results showed immediate and long-lasting alterations in the miR expression profiles in response to repeated LDR in different organs.

MiR-185 inhibits tumor growth and enhances chemo-resistance via targeting SRY-related high mobility group box transcription factor 13 in non-small-cell carcinoma

MicroRNA-185 (miR-185) is down-regulated in various tumor types. However, the cytological mechanism for inhibiting and restraining tumor growth of non-small-cell carcinoma (NSCLC) remains to be elucidated. In this study, it was revealed that miR-185 is significantly down-regulated in both NSCLC tumor tissues and cell lines, and over-expression of miR-185 inhibited cell growth, migration and invasion. To investigate the cellular machinery involved in miR-185's regulation of tumor growth, it was found that miR-185 directly targets SRY-Box 13 (SOX13). In addition, miR-185 regulated cell proliferation, migration, invasion and increased chemo-sensitivity in H1975 cells by inhibiting SOX13. MiR-185 also inhibited tumor growth and suppressed SOX13 in nude mouse xenograft tumors. To investigate the clinical relevance of these consequences, 24 pairs of NSCLC tissues and adjacent normal tissues were collected to determine expression of miR-185 and SOX13. It was demonstrated that miR-185 levels are significantly and inversely correlated with SOX13 levels in these NSCLC tissues, suggesting that these findings have implications for translational application with respect to NSCLC diagnostics and therapy.

miR-503-3p induces apoptosis of lung cancer cells by regulating p21 and CDK4 expression

Studies have shown that microRNAs (miRNAs) can promote or suppress tumor growth and therefore act as targets for cancer therapy. Hsa-miR-503-5p, a mature miRNA derived from 5' ends of pre-miR-503, has been proved to regulate cell proliferation, transformation, migration and invasion. However, the biological function of miR-503-3p derived from 3' ends of pre-miR-503 has never been reported. In current study, we found that miR-503-3p inhibits lung cancer cell viability and induces cell apoptosis. To better understand the molecular mechanism underlying the miR-503-3p participating in this process, PCR array and RNA-sequencing (RNA-seq) were performed and some differential expression genes were discovered between NC and miR-503-3p treated groups. Biological interaction network showed that p21 and CDK4 are the most important proteins involving miR-503-3p signal pathway. Dual-luciferase assay results shown miR-503-3p directly regulates the expression of p21 by targeting 3'-UTR of its mRNA. These results shed light on the potential roles of miR-503-3p, indicating that it may act as an anti-oncogene factor to inhibit lung cancer cell viability.

Autophagy-regulating microRNAs: potential targets for improving radiotherapy

BACKGROUND

Radiotherapy (RT) is one of the most important therapeutic strategies against cancer. However, resistance of cancer cells to radiation remains a major challenge for RT. Thus, novel strategies to overcome cancer cell radioresistance are urgent. Macroautophagy (hereafter referred to as autophagy) is a biological process by which damaged cell components can be removed and accordingly represent a cytoprotective mechanism. Because radiation-induced autophagy is associated with either cell death or radioresistance of cancer cells, a deeper understanding of the autophagy mechanism triggered by radiation will expedite a development of strategies improving the efficacy of RT. MicroRNAs (miRNAs) are involved in many biological processes. Mounting evidence indicates that many miRNAs are involved in regulation of the autophagic process induced by radiation insult, but the underlying mechanisms remain obscure. Therefore, a deep understanding of the mechanisms of miRNAs in regulating autophagy and radioresistance will provide a new perspective for RT against cancer.

METHODS

We summarized the recent pertinent literature from various electronic databases, including PubMed. We reviewed the radiation-induced autophagy response and its association of the role, function and regulation of miRNAs, and discussed the feasibility of targeting autophagy-related miRNAs to improve the efficacy of RT.

CONCLUSION

The beneficial or harmful effect of autophagy may depend on the types of cancer and stress. The cytoprotective role of autophagy plays a dominant role in cancer RT. For most tumor cells, reducing radiation-induced autophagy can improve the efficacy of RT. MiRNAs have been confirmed to take part in the autophagy regulatory network of cancer RT, the autophagy-regulating miRNAs therefore could be developed as potential targets for improving RT.

MicroRNA-196b enhances the radiosensitivity of SNU-638 gastric cancer cells by targeting RAD23B

Gastric cancer is characterized by resistance to ionizing radiation. The development of resistance to radiotherapy in gastric cancer patients is one of the obstacles to effective radiotherapy. MicroRNAs are small well-conserved non-coding RNA species that regulate post-transcriptional activation. Our study aimed to investigate the role of miR-196b in radiation-induced gastric cancer. In the present study, we found that miR-196b expression was significantly reduced following radiation. The ectopic miR-196b expression sensitized SNU-638 gastric cancer cells and increased γ-H2AX foci upon radiation treatment. Bioinformatics analysis suggested that the DNA repair protein RAD23B was a putative target gene of miR-196b. Overexpression of miR-196b suppressed RAD23B expression in SNU-638 cells. Reporter assays further showed that miR-196b inhibited RAD23B 3'-UTR luciferase activity. Knockdown of RAD23B by small interfering RNA transfection closely mimicked the outcomes of miR-196b transfection, leading to impaired DNA damage repair in gastric cancer cells. Our results show that miR-196b improved radiosensitivity of SNU-638 cells by targeting RAD23B. Our data indicate that miR-196b is a potential target to enhance the effect of radiation treatment on gastric cancer cells. These findings will provide evidence for a new therapeutic target in radiotherapy.

The Role of MicroRNAs in Environmental Risk Factors, Noise-Induced Hearing Loss, and Mental Stress

SIGNIFICANCE

MicroRNAs (miRNAs) are important regulators of gene expression and define part of the epigenetic signature. Their influence on every realm of biomedicine is established and progressively increasing. The impact of environment on human health is enormous. Among environmental risk factors impinging on quality of life are those of chemical nature (toxic chemicals, heavy metals, pollutants, and pesticides) as well as those related to everyday life such as exposure to noise or mental and psychosocial stress. Recent Advances: This review elaborates on the relationship between miRNAs and these environmental risk factors.

CRITICAL ISSUES

The most relevant facts underlying the role of miRNAs in the response to these environmental stressors, including redox regulatory changes and oxidative stress, are highlighted and discussed. In the cases wherein miRNA mutations are relevant for this response, the pertinent literature is also reviewed.

FUTURE DIRECTIONS

We conclude that, even though in some cases important advances have been made regarding close correlations between specific miRNAs and biological responses to environmental risk factors, a need for prospective large-cohort studies is likely necessary to establish causative roles. Antioxid. Redox Signal. 28, 773-796.

High intensity focused ultrasound inhibits melanoma cell migration and metastasis through attenuating microRNA-21-mediated PTEN suppression

High intensity focused ultrasound (HIFU) technology is becoming a potential noninvasive treatment for solid tumor. To explore whether HIFU can be applied to treat melanoma and its metastasis, we investigated the effect of HIFU on murine melanoma model. While there was little influence on cell survival, viability or apoptosis, HIFU exposure suppressed melanoma cell migration in vitro and metastasis in vivo. The expression of microRNA-21(miR-21) was down-regulated and PTEN expression was up-regulated in response to HIFU exposure, which was in concomitant with the reduction of AKT activity. Furthermore, ectopic miR-21 expression suppressed this effect of HIFU. These results demonstrate that HIFU exposure can inhibit AKT-mediated melanoma metastasis via miR-21 inhibition to restore PTEN expression. Therefore, targeting the miR-21/PTEN/AKT pathway might be a novel strategy of HIFU in treatment of melanoma.

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

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

miR-300 regulates cellular radiosensitivity through targeting p53 and apaf1 in human lung cancer cells

microRNAs (miRNAs) play a crucial role in mediation of the cellular sensitivity to ionizing radiation (IR). Previous studies revealed that miR-300 was involved in the cellular response to IR or chemotherapy drug. However, whether miR-300 could regulate the DNA damage responses induced by extrinsic genotoxic stress in human lung cancer and the underlying mechanism remain unknown. In this study, the expression of miR-300 was examined in lung cancer cells treated with IR, and the effects of miR-300 on DNA damage repair, cell cycle arrest, apoptosis and senescence induced by IR were investigated. It was found that IR induced upregulation of endogenous miR-300, and ectopic expression of miR-300 by transfected with miR-300 mimics not only greatly enhanced the cellular DNA damage repair ability but also substantially abrogated the G2 cell cycle arrest and apoptosis induced by IR. Bioinformatic analysis predicted that p53 and apaf1 were potential targets of miR-300, and the luciferase reporter assay showed that miR-300 significantly suppressed the luciferase activity through binding to the 3'-UTR of p53 or apaf1 mRNA. In addition, overexpression of miR-300 significantly reduced p53/apaf1 and/or IR-induced p53/apaf1 protein expression levels. Flow cytomertry analysis and colony formation assay showed that miR-300 desensitized lung cancer cells to IR by suppressing p53-dependent G2 cell cycle arrest, apoptosis and senescence. These data demonstrate that miR-300 regulates the cellular sensitivity to IR through targeting p53 and apaf1 in lung cancer cells.

MiR-185 inhibits 3T3-L1 cell differentiation by targeting SREBP-1

Adipogenesis involves a highly orchestrated series of complex events in which microRNAs (miRNAs) may play an essential role. In this study, we found that the miR-185 expression increased gradually during 3T3-L1 cells differentiation. To explore the role of miR-185 in adipogenesis, miRNA agomirs and antagomirs were used to perform miR-185 overexpression and knockdown, respectively. Overexpression of miR-185 dramatically reduced the mRNA expression of the adipogenic markers, PPARγ, FABP4, FAS, and LPL, and the protein level of PPARγ and FAS. MiR-185 overexpression also led to a notable reduction in lipid accumulation. In contrast, miR-185 inhibition promoted differentiation of 3T3-L1 cells. By target gene prediction and luciferase reporter assay, we demonstrated that sterol regulatory element binding protein 1 (SREBP-1) may be the target of miR-185. These results indicate that miR-185 negatively regulates the differentiation of 3T3-L1 cells by targeting SREBP-1, further highlighting the importance of miRNAs in adipogenesis.

miR-15a/miR-16 down-regulates BMI1, impacting Ub-H2A mediated DNA repair and breast cancer cell sensitivity to doxorubicin

The B-lymphoma Moloney murine leukemia virus insertion region-1 protein (BMI1) acts as an oncogene in various cancers, including breast cancer. Recent evidence suggests that BMI1 is rapidly recruited to sites of DNA double strand breaks where it facilitates histone H2A ubiquitination and DNA double strand break repair by homologous recombination. Here we show that miR-15a and miR-16 expressionis decreased during the initial period after DNA damage where it would otherwise down-regulate BMI1, impairing DNA repair. Elevated miR-15a and miR-16 levels down-regulated BMI1 and other polycomb group proteins like RING1A, RING1B, EZH2 and also altered the expression of proteins associated with the BMI1 dependent ubiquitination pathway. Antagonizing the expression of miR-15a and miR-16, enhanced BMI1 protein levels and increased DNA repair. Further, overexpression of miR-15a and miR-16 sensitized breast cancer cells to DNA damage induced by the chemotherapeutic drug doxorubicin. Our results suggest that miR-15a and miR-16 mediate the down-regulation of BMI1, which impedes DNA repair while elevated levels can sensitize breast cancer cells to doxorubicin leading to apoptotic cell death. This data identifies a new target for manipulating DNA damage response that could impact the development of improved therapeutics for breast cancer.

Radiation-inducible miR-770-5p sensitizes tumors to radiation through direct targeting of PDZ-binding kinase

Radiotherapy represents the most effective non-surgical modality in cancer treatment. MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression, and are involved in many biological processes and diseases. To identify miRNAs that influence the radiation response, we performed miRNA array analysis using MCF7 cells at 2, 8, and 24 h post irradiation. We demonstrated that miR-770-5p is a novel radiation-inducible miRNA. When miR-770-5p was overexpressed, relative cell number was reduced due to increased apoptosis in MCF7 and A549 cells. Transcriptomic and bioinformatic analyses revealed that PDZ-binding kinase (PBK) might be a possible target of miR-770-5p for regulation of radiosensitivity. PBK regulation mediated by direct targeting of miR-770-5p was demonstrated using luciferase reporter assays along with wild-type and mutant PBK-3′untranslated region constructs. Radiation sensitivity increased and decreased in miR-770-5p- and anti-miR-770-5p-transfected cells, respectively. Consistent with this result, transfection of short interfering RNA against PBK inhibited cell proliferation, while ectopic expression of PBK restored cell survival from miR-770-5p-induced cell death. In addition, miR-770-5p suppressed tumor growth, and miR-770-5p and PBK levels were inversely correlated in xenograft model mice. Altogether, these data demonstrated that miR-770-5p might be a useful therapeutic target miRNA that sensitizes tumors to radiation via negative regulation of PBK.

miR-185 enhances the inhibition of proliferation and migration induced by ionizing radiation in melanoma

Melanoma is an aggressive malignancy that is increasingly common and exhibits a poor patient survival rate. Radiotherapy is the primary option for patients with melanoma, particularly those who are not candidates for surgery; however, the therapeutic effect is limited due to the relative radioresistance of melanoma to ionizing radiation (IR). It has been reported that microRNAs (miRNAs) serve a vital role in determining the radiosensitivity of tumors; however, little is known concerning the radiosensitization of melanoma using miRNA. In the present study, the radiosensitization effect of miRNA 185 (miR-185), which has been demonstrated to reduce renal cancer radioresistance, was investigated in B16 cells, a skin melanoma cell line derived from C57/BL mice, was investigated. Cell proliferation and scratch wound healing assays were used to determine the proliferative and migratory abilities of B16 cells. Annexin V/propidium iodide double staining was used to determine the apoptosis induced by IR. A tumor formation assay was performed to determine the radiosensitization effect of miR-185 on melanoma cells in vivo. Proliferation marker protein Ki-67, and hematoxylin and eosin staining were used to assess the proliferative activity and histological changes, respectively. The results of the present study demonstrated that miR-185 suppresses cellular proliferation and migration, and enhances IR-induced apoptosis, and the inhibition of proliferation and migration, in vitro and in vivo, which provides an insight into understanding the radiosensitization of melanoma using miRNA.

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.

Regulation of DNA repair by non-coding miRNAs

DNA repair is an important signaling mechanism that is necessary to maintain genomic stability. Various types of DNA repair proteins are involved in the repair of different types of DNA damage. However, most of the DNA repair proteins are modified post-translation in order to activate their repair function, such as, ubiquitination, phosphorylation, acetylation, etc. Similarly, DNA repair proteins are also regulated by posttranscriptional modifications. Non-coding microRNAs (miRNAs) induced posttranscriptional regulation of mRNAs has gained attention in recent years. MiRNA-induced regulation of DNA repair proteins is of great interest, owing to its potential role in cancer therapy. In this review, we have summarized the role of different miRNAs in the regulation of various types of DNA repair proteins, which are essential for the maintenance of genomic stability.

MiR-29a Regulates Radiosensitivity in Human Intestinal Cells by Targeting PTEN Gene

Two major challenges encountered during radiotherapy for colorectal cancer (CRC) are radioresistance of tumor cells and damage to normal cells. An understanding of the mechanisms of radioresistance in CRC may lead to new strategies for overcoming obstacles to affective clinical therapy. In this study, the miR-29a expression was compared among four cell lines: the normal human intestinal epithelial crypt cell line, HIEC and three CRC cell lines, HT29, DLD-1 and HCT116. The roles of miR-29a in regulating cellular radiosensitivity were then investigated. The findings from this study showed that miR-29a mimic enhanced radioresistance in HIEC, HT29 and DLD-1 cells with low levels of intrinsic miR-29a. On the other hand, a miR-29a inhibitor significantly sensitized HCT116 cells with high levels of miR-29a after irradiation. Further studies indicated that PTEN was the direct functional target of miR-29a and was involved in radiosensitivity. MiR-29a could activate the PI3K/Akt signaling pathway through negatively regulated PTEN expression. In conclusion, miR-29a may regulate the radiosensitivity of intestinal cell lines by targeting the PTEN gene, which indicates miR-29a might serve as a novel approach to enhance radiosensitivity in CRC.

MicroRNAs and Their Impact on Radiotherapy for Cancer

Resistance to radiation is considered to be an important reason for local failure after radiotherapy and tumor recurrence. However, the exact mechanisms of tumor resistance remain poorly understood. Current investigations of microRNAs as potential diagnostic and therapeutic tools for cancer treatment have shown promising results. With respect to radiotherapy resistance and response, there is now emerging evidence that microRNAs modulate key cellular pathways that mediate response to radiation. These data suggest that microRNAs might have significant potential as targets for the development of new therapeutic strategies to overcome radioresistance in cancer. This review summarizes the current literature pertinent to the influence of microRNAs in the response to radiotherapy for cancer treatment, with an emphasis on microRNAs as novel diagnostic and prognostic markers, as well as their potential to alter radiosensitivity.

MicroRNA: a connecting road between apoptosis and cholesterol metabolism

Resistance to apoptosis leads to tumorigenesis and failure of anti-cancer therapy. Recent studies also highlight abrogated lipid/cholesterol metabolism as one of the root causes of cancer that can lead to metastatic transformations. Cancer cells are dependent on tremendous supply of cellular cholesterol for the formation of new membranes and continuation of cell signaling. Cholesterol homeostasis network tightly regulates this metabolic need of cancer cells on cholesterol and other lipids. Genetic landscape is also shared between apoptosis and cholesterol metabolism. MicroRNAs (miRNAs) are the new fine tuners of signaling pathways and cellular processes and are known for their ability to post-transcriptionally repress gene expression in a targeted manner. This review summarizes the current knowledge about the cross talk between apoptosis and cholesterol metabolism via miRNAs. In addition, we also emphasize herein recent therapeutic modulations of specific miRNAs and their promising potential for the treatment of deadly diseases including cancer and cholesterol related pathologies. Understanding of the impact of miRNA-based regulation of apoptosis and metabolic processes is still at its dawn and needs further research for the development of future miRNA-based therapies. As both these physiological processes affect cellular homeostasis, we believe that this comprehensive summary of miRNAs modulating both apoptosis and cholesterol metabolism will open uncharted territory for scientific exploration and will provide the foundation for discovering novel drug targets for cancer and metabolic diseases.

DNA damage response in cisplatin-induced nephrotoxicity

Cisplatin and its derivatives are widely used chemotherapeutic drugs for cancer treatment. However, they have debilitating side effects in normal tissues and induce ototoxicity, neurotoxicity, and nephrotoxicity. In kidneys, cisplatin preferentially accumulates in renal tubular cells causing tubular cell injury and death, resulting in acute kidney injury (AKI). Recent studies have suggested that DNA damage and the associated DNA damage response (DDR) are an important pathogenic mechanism of AKI following cisplatin treatment. Activation of DDR may lead to cell cycle arrest and DNA repair for cell survival or, in the presence of severe injury, kidney cell death. Modulation of DDR may provide novel renoprotective strategies for cancer patients undergoing cisplatin chemotherapy.

Mini but mighty: microRNAs in the pathobiology of periodontal disease

MicroRNAs (miRNAs) are a family of small, noncoding RNA molecules that negatively regulate protein expression either by inhibiting initiation of the translation of mRNA or by inducing the degradation of mRNA molecules. Accumulating evidence suggests that miRNA-mediated repression of protein expression is of paramount importance in a broad range of physiologic and pathologic conditions. In particular, miRNA-induced dysregulation of molecular processes involved in inflammatory pathways has been shown to contribute to the development of chronic inflammatory diseases. In this review, first of all we provide an overview of miRNA biogenesis, the main mechanisms of action and the miRNA profiling tools currently available. Then, we summarize the available evidence supporting a specific role for miRNAs in the pathobiology of periodontitis. Based on a review of available data on the differential expression of miRNAs in gingival tissues in states of periodontal health and disease, we address specific roles for miRNAs in molecular and cellular pathways causally linked to periodontitis. Our review points to several lines of evidence suggesting the involvement of miRNAs in periodontal tissue homeostasis and pathology. Although the intricate regulatory networks affected by miRNA function are still incompletely mapped, further utilization of systems biology tools is expected to enhance our understanding of the pathobiology of periodontitis.

MiR-663 inhibits radiation-induced bystander effects by targeting TGFB1 in a feedback mode

The mechanisms of radiation-induced bystander effects (RIBE) have been investigated intensively over the past two decades. Although quite a few reports demonstrated that cytokines such as TGF-β1 are induced within the directly irradiated cells and play critical roles in mediating the bystander effects, little is known about the signaling pathways that occur in bystander cells. The crucial question as to why RIBE signals cannot be infinitely transmitted, therefore, remains unclear. In the present study, we showed that miR-663, a radiosensitive microRNA, participates in the regulation of biological effects in both directly irradiated and bystander cells via its targeting of TGF-β1. MiR-663 was downregulated, while TGFB1 was upregulated in directly irradiated cells. The regulation profile of miR-663 and TGFB1, on the other hand, was reversed in bystander cells, in which an elevated miR-663 expression was exhibited and led to downregulation of TGF-β1. Further studies revealed that miR-663 interacts with TGFB1 directly and that through its binding to the core regulation sequence, miR-663 suppresses the expression of TGFB1. Based on the results, we propose that miR-663 inhibits the propagation of RIBE in a feedback mode, in which the induction of TGF-β1 by reduced miR-663 in directly irradiated cells leads to increased level of miR-663 in bystander cells. The upregulation of miR-663 in turn suppresses the expression of TGF-β1 and limits further transmission of the bystander signals.

Analysis of plasma microRNA expression profiles in male textile workers with noise-induced hearing loss

BACKGROUND

Circulating microRNAs (miRNAs) have attracted interests as non-invasive biomarkers of physiological and pathological conditions, which may be applied in noise-induced hearing loss (NIHL). However, no epidemiology studies have yet examined the potential effects of NIHL or noise exposure on miRNA expression profiles.

OBJECTIVES

We sought to identify permanent NIHL-related miRNAs and to predict the biological functions of the putative genes encoding the indicated miRNAs.

METHODS

In the discovery stage, we used a microarray assay to detect the miRNA expression profiles between pooled plasma samples from 10 noise-exposed individuals with normal hearing and 10 NIHL patients. In addition, we conducted a preliminary validation of six candidate miRNAs in the same 20 workers. Subsequently, three miRNAs were selected for expanded validation in 23 non-exposed individuals with normal hearing and 46 noise-exposed textile workers which including 23 noise-exposed workers with normal hearing and 23 NIHL patients. Moreover, we predicted the biological functions of the putative target genes using a Gene Ontology (GO) function enrichment analysis.

RESULTS

In the discovery stage, compared with the noise exposures with normal hearing, 73 miRNAs demonstrated at least a 1.5-fold differential expression in the NIHL patients. In the preliminary validation, compared with the noise exposures, the plasma levels of miR-16-5p, miR-24-3p, miR-185-5p and miR-451a were all upregulated (P < 0.001) in the NIHL patients. In the expanded validation stage, compared with the non-exposures, the plasma levels of miR-24, miR-185-5p and miR-451a were all significantly downregulated (P < 0.001) in the exposures. And compared with the noise exposures, the plasma levels of miR-185-5p and miR-451a were slightly elevated (P < 0.001) in the NIHL patients, which were consistent with the results of preliminary validation and microarray analysis.

CONCLUSION

The two indicated plasma miRNAs may be biomarkers of indicating responses to noise exposure. However, further studies are necessary to prove the causal association between miRNAs changes and noise exposure, and to determine whether these two miRNAs are clear biomarkers to noise exposure.

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

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

MicroRNA-185 inhibits cell proliferation and induces cell apoptosis by targeting VEGFA directly in von Hippel-Lindau-inactivated clear cell renal cell carcinoma

OBJECTIVES

The von Hippel-Lindau (VHL) gene acts as a tumor suppressor in most clear cell renal cell carcinomas (ccRCCs). Tumor growth in ccRCCs relies on many factors that result from the loss of VHL. This study aims to identify new microRNAs with therapeutic potential for VHL-inactivated ccRCCs.

MATERIALS AND METHODS

We used 786O, A498 (VHL inactivated), and Caki-1 (VHL intact) ccRCC cell lines and 40 ccRCC samples and their adjacent nontumor tissues to measure the expression of microRNA-185 (miR-185) by real-time quantitative polymerase chain reaction. Overexpression or knockdown of VEGFA expression in renal cancer cells was fulfilled by transfecting expression plasmids or small interfering RNAs. Overexpression of miR-185 in ccRCC cell lines was fulfilled by transfecting chemically synthesized miR-185 mimics. The effects of miR-185 on ccRCC cell lines were detected by MTS assay, colony formation assay, and flow cytometric analysis.

RESULTS

Compared with adjacent nontumor renal tissues, miR-185 expression levels decreased significantly in ccRCC tissues. The expression of miR-185 had a negative correlation with tumor size, Fuhrman grade, and TNM staging. Luciferase assay showed that VEGFA was a direct target gene of miR-185. The overexpression of miR-185 significantly inhibited cell proliferation and induced cell apoptosis by down-regulating VEGFA expression in VHL-inactivated ccRCC cells.

CONCLUSIONS

Our results suggest that the miR-185, as a tumor suppressor, plays a pivotal role by inhibiting VEGFA in VHL-inactivated ccRCC.