Review of Disease-Specific microRNAs by Strategically Bridging Genetics and Epigenetics in Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is one of the most prevalent human malignancies and a global health concern with a poor prognosis despite some therapeutic advances, highlighting the need for a better understanding of its molecular etiology. The genomic landscape of OSCC is well-established and recent research has focused on miRNAs, which regulate gene expression and may be useful non-invasive biomarkers or therapeutic targets. A plethora of findings regarding miRNA expression have been generated, posing challenges for the interpretation and identification of disease-specific molecules. Hence, we opted to identify the most important regulatory miRNAs by bridging genetics and epigenetics, focusing on the key genes implicated in OSCC development. Based on published reports, we have developed custom panels of fifteen major oncogenes and five major tumor suppressor genes. Following a miRNA/target gene interaction analysis and a comprehensive study of the literature, we selected the miRNA molecules which target the majority of these panels that have been reported to be downregulated or upregulated in OSCC, respectively. As a result, miR-34a-5p, miR-155-5p, miR-124-3p, miR-1-3p, and miR-16-5p appeared to be the most OSCC-specific. Their expression patterns, verified targets, and the signaling pathways affected by their dysregulation in OSCC are thoroughly discussed.

Resveratrol attenuates cigarette smoke extract induced cellular senescence in human airway epithelial cells by regulating the miR-34a/SIRT1/NF-κB pathway

Chronic obstructive pulmonary disease (COPD) is characterized by accelerated lung aging. Smoking is the critical risk factor for COPD. Cellular senescence of airway epithelial cells is the cytological basis of accelerated lung aging in COPD, and the regulation of microRNAs (miRNAs) is the central epigenetic mechanism of cellular senescence. Resveratrol (Res) is a polyphenol with anti-aging properties. This study investigated whether Res attenuates cigarette smoke extract (CSE)-induced cellular senescence in human airway epithelial cells (BEAS-2B) through the miR-34a/SIRT1/nuclear factor-kappaB (NF-κB) pathway. BEAS-2B cells were treated with Res, CSE and transfected with miR-34a-5p mimics. Cellular senescence was evaluated by senescence -related β-galactosidase (SA-β-gal) staining and expression of senescence-related genes (p16, p21, and p53). The expressions of miR-34a-5p, SIRT1, and NF-κB p65 were examined using quantitative real time polymerase chain reaction and western blotting. The senescence-associated secretory phenotype (SASP) cytokines (IL-1β, IL-6, IL-8, TNF-α) were assessed by enzyme-linked immunosorbent assay. The binding between miR-34a-5p and SIRT1 was confirmed by dual-luciferase reporter assay. The results showed that CSE dose-dependently decreased cell viability and elevated cellular senescence, characterized by increased SA-β-gal staining and senescence-related gene expressions (p16, p21, and p53). Further, CSE dose-dependently increased the expression of miR-34a-5p and SASP cytokines (IL-1β, IL-6, IL-8, TNF-α) in BEAS-2B cells. Pretreatment with Res inhibited CSE-induced cellular senescence and secretion of SASP cytokines (IL-1β, IL-6, IL-8, TNF-α) in a dose-dependent manner. Moreover, Res reversed the CSE-induced down-regulation of SIRT1 and up-regulation of miR-34a-5p and NF-κB p65. SIRT1 is a target of miR-34a-5p. Overexpression of miR-34a-5p via transfection with miR-34a-5p mimic in BEAS-2B cells attenuated the inhibitory effect of Res on cellular senescence, accompanied by reversing the expression of SIRT1 and NF-κB p65. In conclusion, Res attenuated CSE-induced cellular senescence in BEAS-2B cells by regulating the miR-34a/SIRT1/NF-κB pathway, which may provide a new approach for COPD treatment.

MicroRNA34a is associated with chemotherapy resistance, metastasis, recurrence, survival, and prognosis in patient with osteosarcoma

BACKGROUND

Osteosarcoma (OS) is the primary malignant bone tumor that most commonly affects children, adolescents, and young adults. MicroRNA-34a (miR-34a) is involved in tumor metastasis and may be a prognostic marker for patients with cancer. The aim of the present study was to explore the role of miR-34a in patients with OS. The underlying associations between miR-34a expressions and metastasis, recurrence as well as and prognosis were comprehensively analyzed in OS patients.

METHODS

Reverse transcriptase quantitative PCR (RT-qPCR) was used to investigate serum level of miR-34a between clinical OS patients (n = 162) and age-matched healthy controls (n = 162). Expression of miR-34a in OS tissues and adjacent tissues was analyzed using RT-qPCR. RT-qPCR was used to compare the serum level of miR-34a in patients with OS before and after chemotherapy. Multivariate Cox-regression analysis was used to analyze the association between serum level of miR-34a and chemotherapy resistance, overall survival, as well as recurrence and prognosis of OS patients. Five-year recurrence and survival were estimated using Kaplan-Meier curves.

RESULTS

Serum level of miR-34a was downregulated in OS patients (n = 86) compared to age-matched healthy controls (n = 86). Expression of miR-34a was downregulated in OS tissue compared to adjacent tissues in clinical patients. The expression of serum miR-34a before and after chemotherapy was positively correlated with the expression of miR-34a in the corresponding tissues. Expression of miR-34a was higher in the group where chemotherapy was effective than that patient where chemotherapy was ineffective. Expression of miR-34a was negatively associated with chemotherapy resistance of OS patients. High serum levels of miR-34a were associated with longer overall survival in OS patients and lower metastasis. Multivariate Cox-regression analysis identified miR-34a serum level with potential prognostic significance.

CONCLUSION

The expression level of serum miR-34a in patients with OS is closely related to the chemotherapy resistance, metastasis, recurrence, and survival of osteosarcoma, which can be used as one of the potential biomarkers and prognosis for the treatment of OS patients. Therefore, miR-34a may be a potential molecular for prediction of the efficacy of chemotherapy and prognosis in OS patients.

Voluntary exercise improves sperm parameters in high fat diet receiving rats through alteration in testicular oxidative stress, mir-34a/SIRT1/p53 and apoptosis

OBJECTIVES

High fat diet can lead to testicular structural and functional disturbances, spermatogenesis disorders as well as infertility. So, the present investigation was proposed to clarify whether voluntary exercise could prevent high fat diet induced reproductive complications in rats through testicular stress oxidative and apoptosis.

METHODS

Forty male Wistar rats were randomly divided into four groups; control (C), voluntary exercise (VE), high fat diet (HFD) and high fat diet and voluntary exercise (VE + HFD) groups. The rats in the VE and VE + HFD groups were accommodated in apart cages that had running wheels and the running distance was assessed daily for 10 weeks. In VE + HFD group, animals were fed with HFD for five weeks before commencing exercise. The sperm parameters, the expressions of testicular miR-34a gene, and P53 and SIRT1 proteins as well as testicular apoptosis were analyzed in all groups.

RESULTS

The results indicated that voluntary exercise in VE + HFD group led to significantly increased GPX and SOD activities, SIRT1 protein expression, sperm parameters, and decreased the expression of miR34a gene and Acp53 protein, and cellular apoptosis index compared to HFD group (p<0.001 to p<0.05). The SOD and catalase activities, SIRT1 protein expression, sperm parameters in VE + HFD group were lower than of those of VE group, however, MDA content, expression of Acp53 protein, apoptosis indexes in VE + HFD group was higher than that of VE group (p<0.001 to p<0.05).

CONCLUSION

This study revealed that voluntary exercise improved spermatogenesis, in part by decreasing the testicular oxidative stress status, apoptosis through alteration in miR-34a/SIRT1/p53 pathway.

Regulatory effect of microRNA-34a on osteogenesis and angiogenesis in glucocorticoid-induced osteonecrosis of the femoral head

Glucocorticoid-induced osteonecrosis of the femoral head (GIOFH) is a common and devastating orthopedic disease, and its underlying mechanism remains unclear. The aim of this study was to determine the role of microRNA-34a (mir-34a) in GIOFH. C57 mouse mesenchymal stem cells (mMSCs) and human umbilical vein endothelial cells (HUVECs) were cultured with dexamethasone (Dex). A total of 48 adult rats were treated with glucocorticoids, and after the onset of GIOFH, each femoral head was removed. Mir-34a mimics, an inhibitor and over-expressing lentivirus were used in vitro and in vivo, respectively. Real-time PCR, immunohistochemistry, ELISA, cell proliferation assays, osteoblastic differentiation, and endothelial activity assays were employed to evaluate the effect of mir-34a on mMSCs, osteoblasts, and vascular endothelial cells in glucocorticoid-treated mice. We found that Dex inhibited mMSC proliferation and osteoblastic differentiation, as well as the viability and activity of endothelial cells. Dex also caused osteonecrosis and decreased new vessel formation in vivo. Mir-34a alleviated the inhibitory effects of Dex on mMSCs and osteoblasts, while facilitating its inhibitory effects on endothelial cells. Mir-34a is an important regulator in osteogenesis and angiogenesis, and it might be useful as a therapeutic target for GIOFH. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:417-424, 2018.

The Microtubule Network and Cell Death Are Regulated by an miR-34a/Stathmin 1/βIII-Tubulin Axis

MicroRNA-34a (miR-34a) is a master regulator of signaling networks that maintains normal physiology and disease and is currently in development as a miRNA-based therapy for cancer. Prior studies have reported low miR-34a expression in osteosarcoma; however, the molecular mechanisms underlying miR-34a activity in osteosarcoma are not well-defined. Therefore, this study evaluated the role of miR-34a in regulating signal transduction pathways that influence cell death in osteosarcoma. Levels of miR-34a were attenuated in human osteosarcoma cells and xenografts of the Pediatric Preclinical Testing Consortium (PPTC). Bioinformatics predictions identified stathmin 1 (STMN1) as a potential miR-34a target. Biotin pull-down assay and luciferase reporter analysis confirmed miR-34a target interactions within the STMN1 mRNA 3'-untranslated region. Overexpression of miR-34a in osteosarcoma cells suppressed STMN1 expression and reduced cell growth in vitro Restoration of miR-34a led to microtubule destabilization and increased βIII-tubulin expression, with corresponding G1-G2 phase cell-cycle arrest and apoptosis. Knockdown of the Sp1 transcription factor, by siRNA silencing, also upregulated βIII-tubulin expression in osteosarcoma cells, suggesting that miR-34a indirectly affects Sp1. Validating the coordinating role of miR-34a in microtubule destabilization, when miR-34a was combined with either microtubule inhibitors or chemotherapy, STMN1 phosphorylation was suppressed and there was greater cytotoxicity in osteosarcoma cells. These results demonstrate that miR-34a directly represses STMN1 gene and protein expression and upregulates βIII-tubulin, leading to disruption of the microtubule network and cell death.Implications: The miR-34a/STMN1/βIII-tubulin axis maintains the microtubule cytoskeleton in osteosarcoma, and combining miR-34a with microtubule inhibitors can be investigated as a novel therapeutic strategy. Mol Cancer Res; 15(7); 953-64. ©2017 AACR.

Regulation of podocyte lesions in diabetic nephropathy via miR-34a in the Notch signaling pathway

BACKGROUND

The activation of the Notch signaling pathway has been shown to play an important role in diabetic nephropathy (DN) development. Besides, Notch-1 is a target gene in miR-34a. However, the regulation of the podocyte lesions involved in DN by miR-34a has not been identified.

METHODS

This study utilized miR-34a mimics and small interfering RNA transfection to construct miR-34a overexpression and lower-expression model to investigate the effect of miR-34a on the regulation of the Notch signaling pathway and podocyte lesions in DN. Western blotting and real-time quantitative polymerase chain reaction were applied for the quantitative testing of mRNA and protein expression. Apoptosis of podocyte was detected by TUNEL staining.

RESULTS

In high-glucose (HG) conditions, miR-34a overexpression inhibited the expression of Notch 1, Jagged 1, NICD, Hes 1, and Hey 1 proteins. Further, cleaved caspase-3, Bax, and phosphorylation of p53 (p-p53) were reduced significantly. Therefore, miR-34a overexpression inhibited the Notch signaling pathway and podocyte lesions induced by HG. β-arrestin was slightly reduced in HG conditions. Meanwhile, miR-34a overexpression could remit the inhibition.

CONCLUSION

Results from this study provide evidence that miR-34a may offer a new approach for the treatment of diabetes.

Verification of microRNA expression in human endometrial adenocarcinoma

BACKGROUND

MicroRNAs are small non-coding RNAs that have been implicated in tumor initiation and progression. In a previous study we identified 138 miRNAs as differentially expressed in endometrial adenocarcinoma compared to normal tissues. One of these miRNAs was miRNA-34a, which regulates several genes involved in the Notch pathway, which is frequently altered in endometrial cancer. The aims of this study were to verify the differential expression of a subset of miRNAs and to scrutinize the regulatory role of mir-34a on the target genes NOTCH1 and DLL1.

METHODS

Twenty-five miRNAs that were previously identified as differentially expressed were subjected to further analysis using qPCR. To investigate the regulation of NOTCH1 and DLL1 by mir-34a, we designed gain- and loss-of-function experiments in Ishikawa and HEK293 cell lines by transfection with a synthetic mir-34a mimic and a mir-34a inhibitor.

RESULTS

Of the 25 validated miRNAs, seven were down-regulated and 18 were up-regulated compared to normal endometrium, which was fully consistent with our previous findings. In addition, the up-regulation of mir-34a led to a significant decrease in mRNA levels of NOTCH1 and DLL1, while down-regulation led to a significant increase in mRNA levels of these two genes.

CONCLUSIONS

We verified both up-regulated and down-regulated miRNAs in the tumor samples, indicating various roles of microRNAs during tumor development. Mir-34a functions as a regulator by decreasing the expression of NOTCH1 and DLL1. Our study is the first to identify a correlation between mir-34a and its target genes NOTCH1 and DLL1 in endometrial adenocarcinoma.

MiR-34a regulates blood-brain barrier permeability and mitochondrial function by targeting cytochrome c

The blood-brain barrier is composed of cerebrovascular endothelial cells and tight junctions, and maintaining its integrity is crucial for the homeostasis of the neuronal environment. Recently, we discovered that mitochondria play a critical role in maintaining blood-brain barrier integrity. We report for the first time a novel mechanism underlying blood-brain barrier integrity: miR-34a mediated regulation of blood-brain barrier through a mitochondrial mechanism. Bioinformatics analysis suggests miR-34a targets several mitochondria-associated gene candidates. We demonstrated that miR-34a triggers the breakdown of blood-brain barrier in cerebrovascular endothelial cell monolayer in vitro, paralleled by reduction of mitochondrial oxidative phosphorylation and adenosine triphosphate production, and decreased cytochrome c levels.

Dysregulation of miR-34a links neuronal development to genetic risk factors for bipolar disorder

Bipolar disorder (BD) is a heritable neuropsychiatric disorder with largely unknown pathogenesis. Given their prominent role in brain function and disease, we hypothesized that microRNAs (miRNAs) might be of importance for BD. Here we show that levels of miR-34a, which is predicted to target multiple genes implicated as genetic risk factors for BD, are increased in postmortem cerebellar tissue from BD patients, as well as in BD patient-derived neuronal cultures generated by reprogramming of human fibroblasts into induced neurons or into induced pluripotent stem cells (iPSCs) subsequently differentiated into neurons. Of the predicted miR-34a targets, we validated the BD risk genes ankyrin-3 (ANK3) and voltage-dependent L-type calcium channel subunit beta-3 (CACNB3) as direct miR-34a targets. Using human iPSC-derived neuronal progenitor cells, we further show that enhancement of miR-34a expression impairs neuronal differentiation, expression of synaptic proteins and neuronal morphology, whereas reducing endogenous miR-34a expression enhances dendritic elaboration. Taken together, we propose that miR-34a serves as a critical link between multiple etiological factors for BD and its pathogenesis through the regulation of a molecular network essential for neuronal development and synaptogenesis.

Attenuation of dexamethasone-induced cell death in multiple myeloma is mediated by miR-125b expression

Dexamethasone is a key front-line chemotherapeutic for B-cell malignant multiple myeloma (MM). Dexamethasone modulates MM cell survival signaling but fails to induce marked cytotoxicity when used as a monotherapy. We demonstrate here the mechanism behind this insufficient responsiveness of MM cells toward dexamethasone, revealing in MM a dramatic anti-apoptotic role for microRNA (miRNA)-125b in the insensitivity toward dexamethasone-induced apoptosis. MM cells responding to dexamethasone exhibited enhanced expression of oncogenic miR-125b. Dexamethasone also induced expression of miR-34a, which acts to suppress SIRT1 deacetylase, and thus allows maintained acetylation and inactivation of p53. p53 mRNA is also suppressed by miR-125b targeting. Reporter assays showed that both these dexamethasone-induced miRNAs act downstream of their target genes to prevent p53 tumor suppressor actions and, ultimately, resist cytotoxic responses in MM. Use of antisense miR-125b transcripts enhanced expression of pro-apoptotic p53, repressed expression of anti-apoptotic SIRT1 and, importantly, significantly enhanced dexamethasone-induced cell death responses in MM. Pharmacological manipulations showed that the key regulation enabling complete dexamethasone sensitivity in MM cells lies with miR-125b. In summary, dexamethasone-induced miR-125b induces cell death resistance mechanisms in MM cells via the p53/miR-34a/SIRT1 signaling network and provides these cells with an enhanced level of resistance to cytotoxic chemotherapeutics. Clearly, such anti-apoptotic mechanisms will need to be overcome to more effectively treat nascent, refractory and relapsed MM patients. These mechanisms provide insight into the role of miRNA regulation of apoptosis and their promotion of MM cell proliferative mechanisms.

Distinct microRNA expression profiles in prostate cancer stem/progenitor cells and tumor-suppressive functions of let-7

MiRNAs regulate cancer cells, but their potential effects on cancer stem/progenitor cells are still being explored. In this study, we used quantitative real-time-PCR to define miRNA expression patterns in various stem/progenitor cell populations in prostate cancer, including CD44+, CD133+, integrin α2β1+, and side population cells. We identified distinct and common patterns in these different tumorigenic cell subsets. Multiple tumor-suppressive miRNAs were downregulated coordinately in several prostate cancer stem/progenitor cell populations, namely, miR-34a, let-7b, miR-106a, and miR-141, whereas miR-301 and miR-452 were commonly overexpressed. The let-7 overexpression inhibited prostate cancer cell proliferation and clonal expansion in vitro and tumor regeneration in vivo. In addition, let-7 and miR-34a exerted differential inhibitory effects in prostate cancer cells, with miR-34a inducing G1 phase cell-cycle arrest accompanied by cell senescence and let-7 inducing G2-M phase cell-cycle arrest without senescence. Taken together, our findings define distinct miRNA expression patterns that coordinately regulate the tumorigenicity of prostate cancer cells.

Hepatic mRNA, microRNA, and miR-34a-target responses in mice after 28 days exposure to doses of benzo(a)pyrene that elicit DNA damage and mutation

Benzo(a)pyrene (BaP) is a mutagenic carcinogen that is ubiquitous in our environment. To better understand the toxic effects of BaP and to explore the relationship between toxicity and toxicogenomics profiles, we assessed global mRNA and microRNA (miRNA) expression in Muta™Mouse. Adult male mice were exposed by oral gavage to 25, 50, and 75 mg/kg/day BaP for 28 days. Liver tissue was collected 3 days following the last treatment. Initially, we established that exposure to BaP led to the formation of hepatic DNA adducts and mutations in the lacZ transgene of the Muta™Mouse. We then analyzed hepatic gene expression profiles. Microarray analysis of liver samples revealed 134 differentially expressed transcripts (adjusted P < 0.05; fold changes > 1.5). The mRNAs most affected were involved in xenobiotic metabolism, immune response, and the downstream targets of p53. In this study, we found a significant 2.0 and 3.6-fold increase following exposure to 50 and 75 mg/kg/day BaP, respectively, relative to controls for miR-34a. This miRNA is involved in p53 response. No other significant changes in miRNAs were observed. The protein levels of five experimentally confirmed miR-34a targets were examined, and no major down-regulation was present. The results suggest that liver miRNAs are largely unresponsive to BaP doses that cause both DNA adducts and mutations. In summary, the validated miRNA and mRNA expression profiles following 28 day BaP exposure reflect a DNA damage response and effects on the cell cycle, consistent with the observed increases in DNA adducts and mutations.

Restitution of tumor suppressor microRNAs using a systemic nanovector inhibits pancreatic cancer growth in mice

Mis-expression of microRNAs (miRNA) is widespread in human cancers, including in pancreatic cancer. Aberrations of miRNA include overexpression of oncogenic miRs (Onco-miRs) or downregulation of so-called tumor suppressor TSG-miRs. Restitution of TSG-miRs in cancer cells through systemic delivery is a promising avenue for pancreatic cancer therapy. We have synthesized a lipid-based nanoparticle for systemic delivery of miRNA expression vectors to cancer cells (nanovector). The plasmid DNA-complexed nanovector is approximately 100 nm in diameter and shows no apparent histopathologic or biochemical evidence of toxicity upon intravenous injection. Two miRNA candidates known to be downregulated in the majority of pancreatic cancers were selected for nanovector delivery: miR-34a, which is a component of the p53 transcriptional network and regulates cancer stem cell survival, and the miR-143/145 cluster, which together repress the expression of KRAS2 and its downstream effector Ras-responsive element binding protein-1 (RREB1). Systemic intravenous delivery with either miR-34a or miR-143/145 nanovectors inhibited the growth of MiaPaCa-2 subcutaneous xenografts (P < 0.01 for miR-34a; P < 0.05 for miR-143/145); the effects were even more pronounced in the orthotopic (intrapancreatic) setting (P < 0.0005 for either nanovector) when compared with vehicle or mock nanovector delivering an empty plasmid. Tumor growth inhibition was accompanied by increased apoptosis and decreased proliferation. The miRNA restitution was confirmed in treated xenografts by significant upregulation of the corresponding miRNA and significant decreases in specific miRNA targets (SIRT1, CD44 and aldehyde dehydrogenase for miR34a, and KRAS2 and RREB1 for miR-143/145). The nanovector is a platform with potential broad applicability in systemic miRNA delivery to cancer cells.

Oncogenic HPV infection interrupts the expression of tumor-suppressive miR-34a through viral oncoprotein E6

MicroRNAs (miRNA) play pivotal roles in controlling cell proliferation and differentiation. Aberrant miRNA expression in human is becoming recognized as a new molecular mechanism of carcinogenesis. However, the causes for alterations in miRNA expression remain largely unknown. Infection with oncogenic human papillomavirus types 16 (HPV16) and 18 (HPV18) can lead to cervical and other ano-genital cancers. Here, we have demonstrated that cervical cancer tissues and cervical cancer-derived cell lines containing oncogenic HPVs display reduced expression of tumor-suppressive miR-34a. The reduction of miR-34a expression in organotypic tissues derived from HPV-containing primary human keratinocytes correlates with the early productive phase and is attributed to the expression of viral E6, which destabilizes the tumor suppressor p53, a known miR-34a transactivator. Knockdown of viral E6 expression in HPV16(+) and HPV18(+) cervical cancer cell lines by siRNAs leads to an increased expression of p53 and miR-34a and accumulation of miR-34a in G(0)/G(1) phase cells. Ectopic expression of miR-34a in HPV18(+) HeLa cells and HPV(-) HCT116 cells results in a substantial induction of cell growth retardation and a moderate cell apoptosis. Together, this is the first time a viral oncoprotein has been shown to regulate cellular miRNA expression. Our data have provided new insights into mechanisms by which high-risk HPVs contribute to the development of cervical cancer.