C/EBPα regulated microRNA-34a targets E2F3 during granulopoiesis and is down-regulated in AML with CEBPA mutations

MicroRNA Profiles in Hematopoietic Stem Cell Transplant Recipients

Background: Hematopoietic Stem Cell Transplant (HCT) is a potentially curative treatment for hematologic malignancies, including multiple myeloma. Biomarker investigation can guide identification of HCT recipients at-risk for poor outcomes. MicroRNAs (miRNAs) are a class of non-coding RNAs involved in the modulation and regulation of pathological processes and are emerging as prognostic and predictive biomarkers for multiple health conditions. This pilot study aimed to examine miRNA profiles associated with HCT-related risk factors and outcomes in patients undergoing autologous HCT. Methods: Patients eligible for autologous HCT were recruited and blood samples and HCT-related variables were collected. Differential expression analysis of miRNA was conducted on 24 patient samples to compare changes in miRNA profile in HCT eligible patients before and after transplant. Results: Unsupervised clustering of differentially expressed (p < .05) miRNAs pre- and post- HCT identified clusters of up- and down-regulated miRNAs. Four miRNAs (miR-125a-5p, miR-99b-5p, miR-382-5p, miR-145-5p) involved in hematopoiesis (differentiation of progenitor cells, granulocyte function, thrombopoiesis, and tumor suppression) were significantly downregulated post-HCT. Correlation analyses identified select miRNAs associated with risk factors (such as frailty, fatigue, cognitive decline) and quality of life pre- and post-HCT. Select miRNAs were correlated with platelet engraftment. Conclusion: Future studies should examine miRNA signatures in larger cohorts in association with HCT outcomes; and expand investigations in patients receiving allogeneic transplants. This will lead to identification of biomarkers for risk stratification of HCT recipients.

Long noncoding RNA LINC00675 drives malignancy in acute myeloid leukemia via the miR-6809 -CDK6 axis

Hematological malignancies such as acute myeloid leukemia (AML) have a low cure rate and a high recurrence rate. Long noncoding RNAs (LNCs) are essential regulators of tumorigenesis and progression. The role of lncRNA LINC00675 in AML has rarely been reported. This study revealed elevated LINC00675 expression in AML that promotes proliferation and inhibits apoptosis. Mechanistically, LINC00675 combines with miR-6809 to promote the expression of CDK6 in vitro and in vivo. Immune-checkpoint genes were expressed more highly in LINC00675-high patients. A high level of LINC00675 expression may make patients more susceptible to palbociclib treatments. In conclusion, our study demonstrated that LINC00675 is an oncogenic lncRNA that enhances the malignancy of AML by upregulating CDK6 expression through miR-6809 sponging, providing a new perspective and feasible target for the diagnosis and treatment of AML.

Bone marrow microRNA-34a is a good indicator for response to treatment in acute myeloid leukemia

Background

microRNA-34a (miR-34a) had been reported to have a diagnostic role in acute myeloid leukemia (AML). However, its value in the bone marrow (BM) of AML patients, in addition to its role in response to therapy is still unclear. The current study was designed to assess the diagnostic, prognostic, and predictive significance of miR-34a in the BM of AML patients.

Methods

The miR-34a was assessed in BM aspirate of 82 AML patients in relation to 12 normal control subjects using qRT-PCR. The data were assessed for correlation with the relevant clinical criteria, response to therapy, disease-free survival (DFS), and overall survival (OS) rates.

Results

miR-34a was significantly downregulated in AML patients [0.005 (3.3 × 10-6-1.32)], compared to the control subjects [0.108 (3.2 × 10-4-1.64), p = 0.021]. The median relative quantification (RQ) of miR-34a was 0.106 (range; 0-32.12). The specificity, sensitivity, and area under the curve (AUC) for the diagnosis of AML were (58.3%, 69.5%, 0.707, respectively, p = 0.021). patients with upregulated miR-34a showed decreased platelets count <34.5 × 109/L, and achieved early complete remission (CR, p = 0.031, p = 0.044, respectively). Similarly, patients who were refractory to therapy showed decreased miR-34a levels in comparison to those who achieved CR [0.002 (0-0.01) and 0.12 (0-32.12), respectively, p = 0.002]. Therefore, miR-34a could significantly identify patients with CR with a specificity of 75% and sensitivity of 100% at a cut-off of 0.014 (AUC = 0.927, p = 0.005). There was no considerable association between miR-34a expression and survival rates of the included AML patients.

Conclusion

miR-34a could be a beneficial diagnostic biomarker for AML patients. In addition, it serves as a good indicator for response to therapy, which could possibly identify patients who are refractory to treatment with 100% sensitivity and 75% specificity.

miR-603 promotes cell proliferation and differentiation by targeting TrkB in acute promyelocytic leukemia

Arsenic trioxide (ATO) treatment effectively prolongs the overall survival of patients with acute promyelocytic leukemia (APL). Mutations in the oncogene PML::RARA were found in patients with ATO-resistant and relapsed APL. However, some relapsed patients do not have such mutations. Here, we performed microarray analysis of samples from newly diagnosed and relapsed APL, and found different microRNA (miRNA) expression patterns between these two groups. Among the differentially expressed miRNAs, miR-603 was expressed at the lowest level in relapsed patients. The expression of miR-603 and its predicted target tropomyosin-related kinase B (TrkB) were determined by PCR and Western blot. Proliferation was measured using an MTT assay, while apoptosis, cell cycle and CD11b expression were analyzed using flow cytometry. In APL patients, the expression of miR-603 was negatively correlated with that of TrkB. miR-603 directly targeted TrkB and downregulated TrkB expression in the APL cell line NB4. miR-603 increased cell proliferation by promoting the differentiation and inhibiting the apoptosis of NB4 cells. This study shows that the miR-603/ TrkB axis may be a potent therapeutic target for relapsed APL.

Evaluation of MicroRNA as Minimal Residual Disease in Leukemia: Diagnostic and Prognostic Approach: A Review

Various factors are effective in the development of minimal residual disease (MRD), one of which is MicroRNAs (miRNAs). miRNAs and their dysfunction in gene expression have influential role in the pathogenesis of leukemia. Nowadays, treatments that lead to the suppression or replacement of miRNAs have been developed. Focusing on the role of miRNAs in managing the treatment of leukemia, in this review article we have investigated the miRNAs and signaling pathways involved in the process of apoptosis and cell proliferation, as well as miRNAs with oncogenic function in malignant leukemia cells. Among the studied miRNAs, miR-99a, and miR-181a play an essential role in apoptosis, proliferation and oncogenesis via AKT, MAPK, RAS, and mTOR signaling pathways. miR-223 and miR-125a affect apoptosis and oncogenesis via Wnt/B-catenin, PTEN/PI3K, and STAT5/AKT/ERK/Src signaling pathways. miR-100 also affects both apoptosis and oncogenesis; it acts via IGF1 and mTOR signaling pathways.

Intracellular Compartmentalization: A Key Determinant of MicroRNA Functions

Being an integral part of the eukaryotic transcriptome, miRNAs are regarded as vital regulators of diverse developmental and physiological processes. Clearly, miRNA activity is kept in check by various regulatory mechanisms that control their biogenesis and decay pathways. With the increasing technical depth of RNA profiling technologies, novel insights have unravelled the spatial diversity exhibited by miRNAs inside a cell. Compartmentalization of miRNAs adds complexity to the regulatory circuits of miRNA expression, thereby providing superior control over the miRNA function. This review provides a bird's eye view of miRNAs expressed in different subcellular locations, thus affecting the gene regulatory pathways therein. Occurrence of miRNAs in diverse intracellular locales also reveals various unconventional roles played by miRNAs in different cellular organelles and expands the scope of miRNA functions beyond their traditionally known repressive activities.

An Immunocompetent Environment Unravels the Proto-Oncogenic Role of miR-22

MiR-22 was first identified as a proto-oncogenic microRNA (miRNA) due to its ability to post-transcriptionally suppress the expression of the potent PTEN (Phosphatase And Tensin Homolog) tumor suppressor gene. miR-22 tumorigenic role in cancer was subsequently supported by its ability to positively trigger lipogenesis, anabolic metabolism, and epithelial-mesenchymal transition (EMT) towards the metastatic spread. However, during the following years, the picture was complicated by the identification of targets that support a tumor-suppressive role in certain tissues or cell types. Indeed, many papers have been published where in vitro cellular assays and in vivo immunodeficient or immunosuppressed xenograft models are used. However, here we show that all the studies performed in vivo, in immunocompetent transgenic and knock-out animal models, unanimously support a proto-oncogenic role for miR-22. Since miR-22 is actively secreted from and readily exchanged between normal and tumoral cells, a functional immune dimension at play could well represent the divider that allows reconciling these contradictory findings. In addition to a critical review of this vast literature, here we provide further proof of the oncogenic role of miR-22 through the analysis of its genomic locus vis a vis the genetic landscape of human cancer.

microRNA expression in acute myeloid leukaemia: New targets for therapy?

Recent studies have shown that short non-coding RNAs, known as microRNAs (miRNAs) and their dysregulation, are implicated in the pathogenesis of acute myeloid leukaemia (AML). This is due to their role in the control of gene expression in a variety of molecular pathways. Therapies involving miRNA suppression and replacement have been developed. The normalisation of expression and the subsequent impact on AML cells have been investigated for some miRNAs, demonstrating their potential to act as therapeutic targets. Focussing on miRs with therapeutic potential, we have reviewed those that have a significant impact on the aberrant biological processes associated with AML, and crucially, impact leukaemic stem cell survival. We describe six miRNAs in preclinical trials (miR-21, miR-29b, miR-126, miR-181a, miR-223 and miR-196b) and two miRNAs that are in clinical trials (miR-29 and miR-155). However none have been used to treat AML patients and greater efforts are needed to develop miRNA therapies that could benefit AML patients in the future.

NF-κB: A Druggable Target in Acute Myeloid Leukemia

Acute Myeloid Leukemia (AML) is an aggressive hematological malignancy that relies on highly heterogeneous cytogenetic alterations. Although in the last few years new agents have been developed for AML treatment, the overall survival prospects for AML patients are still gloomy and new therapeutic options are still urgently needed. Constitutive NF-κB activation has been reported in around 40% of AML patients, where it sustains AML cell survival and chemoresistance. Given the central role of NF-κB in AML, targeting the NF-κB pathway represents an attractive strategy to treat AML. This review focuses on current knowledge of NF-κB's roles in AML pathogenesis and summarizes the main therapeutic approaches used to treat NF-κB-driven AML.

Small Non-Coding RNAs in Leukemia

In 2020, more than 60,500 people were diagnosed with leukemia in the USA, and more than 23,000 died. The incidence of leukemia is still rising, and drug resistance development is a serious concern for patients' wellbeing and survival. In the past two decades, small non-coding RNAs have been studied to evaluate their functions and possible role in cancer pathogenesis. Small non-coding RNAs are short RNA molecules involved in several cellular processes by regulating the expression of genes. An increasing body of evidence collected by many independent studies shows that the expression of these molecules is tissue specific, and that their dysregulation alters the expression of genes involved in tumor development, progression and drug response. Indeed, small non-coding RNAs play a pivotal role in the onset, staging, relapse and drug response of hematological malignancies and cancers in general. These findings strongly suggest that small non-coding RNAs could function as biomarkers and possible targets for therapy. Thus, in this review, we summarize the regulatory mechanisms of small non-coding RNA expression in different types of leukemia and assess their potential clinical implications.

CEBPA Mutations in 4708 Patients with Acute Myeloid Leukemia - Differential Impact of bZIP and TAD Mutations on Outcome

Biallelic mutations of the CEBPA gene (CEBPAbi) define a distinct entity associated with favorable prognosis, however the role of monoallelic mutations (CEBPAsm) is poorly understood. We retrospectively analyzed 4708 adult AML patients recruited into Study Alliance Leukemia trials to investigate the prognostic impact of CEBPAsm. CEBPA mutations were identified in 240 patients (5.1%), 131 CEBPAbi and 109 CEBPAsm (60 affecting the amino-terminal transactivation domains (CEBPAsmTAD) and 49 the carboxy-terminal DNA-binding or basic leucine zipper region (CEBPAsmbZIP)). Interestingly, CEBPAbi and CEBPAsmbZIP patients shared several clinical factors, i.e. were significantly younger (median 46 years and 50 years) and had higher WBC counts at diagnosis (median 23.7 and 35.7 109/l) compared to CEBPAsmTAD patients (median age 63 yrs., median WBC 13.1 109/l; p<.001). Co-mutations were also similar in both groups, e.g. GATA2 mutations (35.1% CEBPAbi; 36.7% CEBPAsmbZIP vs. 6.7% CEBPAsmTAD; p<.001) or NPM1 mutations (3.1% CEBPAbi; 8.2% CEBPAsmbZIP vs. 38.3% CEBPAsmTAD; p<.001). CEBPAbi and CEBPAsmbZIP, but not CEBPAsmTAD were associated with significantly improved overall (median OS: 103 and 63 vs. 13 months) and event-free survival (median EFS: 20.7 and 17.1 vs. 5.7 months), in univariate and multivariable analyses. More detailed analysis revealed that the clinical and molecular features as well as the favorable survival were confined to patients showing in-frame mutations in bZIP (CEBPAbZIP-inf). When grouping patients into CEBPAbZIP-inf and CEBPAother (including CEBPAsmTAD and other non-CEBPAbZIP-inf patients), only CEBPAbZIP-inf patients showed superior CR rates and the longest median OS and EFS, arguing for a previously undefined prognostic role of this type of mutations.

The comprehensive landscape of miR-34a in cancer research

MicroRNA-34 (miR-34) plays central roles in human diseases, especially cancers. Inactivation of miR-34 is detected in cancer cell lines and tumor tissues versus normal controls, implying its potential tumor-suppressive effect. Clinically, miR-34 has been identified as promising prognostic indicators for various cancers. In fact, members of the miR-34 family, especially miR-34a, have been convincingly proved to affect almost the whole cancer progression process. Here, a total of 512 (miR-34a, 10/21), 85 (miR-34b, 10/16), and 114 (miR-34c, 10/14) putative targets of miR-34a/b/c are predicted by at least ten miRNA databases, respectively. These targets are further analyzed in gene ontology (GO), KEGG pathway, and the Reactome pathway dataset. The results suggest their involvement in the regulation of signal transduction, macromolecule metabolism, and protein modification. Also, the targets are implicated in critical signaling pathways, such as MAPK, Notch, Wnt, PI3K/AKT, p53, and Ras, as well as apoptosis, cell cycle, and EMT-related pathways. Moreover, the upstream regulators of miR-34a, mainly including transcription factors (TFs), lncRNAs, and DNA methylation, will be summarized. Meanwhile, the potential TF upstream of miR-34a/b/c will be predicted by PROMO, JASPAR, Animal TFDB 3.0, and GeneCard databases. Notably, miR-34a is an attractive target for certain cancers. In fact, miR-34a-based systemic delivery combined with chemotherapy or radiotherapy can more effectively control tumor progression. Collectively, this review will provide a panorama for miR-34a in cancer research.

MicroRNA-34a: Potent Tumor Suppressor, Cancer Stem Cell Inhibitor, and Potential Anticancer Therapeutic

Overwhelming evidence indicates that virtually all treatment-naive tumors contain a subpopulation of cancer cells that possess some stem cell traits and properties and are operationally defined as cancer cell stem cells (CSCs). CSCs manifest inherent heterogeneity in that they may exist in an epithelial and proliferative state or a mesenchymal non-proliferative and invasive state. Spontaneous tumor progression, therapeutic treatments, and (epi)genetic mutations may also induce plasticity in non-CSCs and reprogram them into stem-like cancer cells. Intrinsic cancer cell heterogeneity and induced cancer cell plasticity, constantly and dynamically, generate a pool of CSC subpopulations with varying levels of epigenomic stability and stemness. Despite the dynamic and transient nature of CSCs, they play fundamental roles in mediating therapy resistance and tumor relapse. It is now clear that the stemness of CSCs is coordinately regulated by genetic factors and epigenetic mechanisms. Here, in this perspective, we first provide a brief updated overview of CSCs. We then focus on microRNA-34a (miR-34a), a tumor-suppressive microRNA (miRNA) devoid in many CSCs and advanced tumors. Being a member of the miR-34 family, miR-34a was identified as a p53 target in 2007. It is a bona fide tumor suppressor, and its expression is dysregulated and downregulated in various human cancers. By targeting stemness factors such as NOTCH, MYC, BCL-2, and CD44, miR-34a epigenetically and negatively regulates the functional properties of CSCs. We shall briefly discuss potential reasons behind the failure of the first-in-class clinical trial of MRX34, a liposomal miR-34a mimic. Finally, we offer several clinical settings where miR-34a can potentially be deployed to therapeutically target CSCs and advanced, therapy-resistant, and p53-mutant tumors in order to overcome therapy resistance and curb tumor relapse.

MicroRNAs Associated With a Good Prognosis of Acute Myeloid Leukemia and Their Effect on Macrophage Polarization

Acute myeloid leukemia (AML) is an aggressive myeloid malignancy with poor outcomes despite very intensive therapeutic approaches. For the majority of patients which are unfit and treated less intensively, the prognosis is even worse. There has been unspectacular progress in outcome improvement over the last decades and the development of new approaches is of tremendous interest. The tumor microenvironment is credited with an important role in supporting cancer growth, including leukemogenesis. Macrophages are part of the tumor microenvironment and their contribution in this setting is increasingly being deciphered, these cells being credited with a tumor supporting role. Data on macrophage role and polarization in leukemia is scarce. MicroRNAs (miRNAs) have a role in the post-transcriptional regulation of gene expression, by impending translation and promoting degradation of messenger RNAs. They are important modulators of cellular pathways, playing major roles in normal hematopoietic differentiation. miRNA expression is significantly correlated with the prognosis of hematopoietic malignancies, including AML. Oncogenic miRNAs correlate with poor prognosis, while tumor suppressor miRNAs, which inhibit the expression of proto-oncogenes, are correlated with a favorable prognosis. miRNAs are proposed as biomarkers for diagnosis and prognosis and are regarded as therapeutic approaches in many cancers, including AML. miRNAs with epigenetic or modulatory activity, as well as with synergistic activity with chemotherapeutic agents, proved to be promising therapeutic targets in experimental, pre-clinical approaches. The clinical availability of emerging compounds with mimicking or suppressor activity provides the opportunity for future therapeutic targeting of miRNAs. The present paper is focusing on miRNAs which, according to current knowledge, favorably impact on AML outcomes, being regarded as tumor suppressors, and reviews their role in macrophage polarization. We are focusing on miRNA expression in the setting of AML, but data on correlations between miRNA expression and macrophage polarization is mostly coming from studies involving normal tissue.

MicroRNA-34a: the bad guy in age-related vascular diseases

The age-related vasculature alteration is the prominent risk factor for vascular diseases (VD), namely, atherosclerosis, abdominal aortic aneurysm, vascular calcification (VC) and pulmonary arterial hypertension (PAH). The chronic sterile low-grade inflammation state, alias inflammaging, characterizes elderly people and participates in VD development. MicroRNA34-a (miR-34a) is emerging as an important mediator of inflammaging and VD. miR-34a increases with aging in vessels and induces senescence and the acquisition of the senescence-associated secretory phenotype (SASP) in vascular smooth muscle (VSMCs) and endothelial (ECs) cells. Similarly, other VD risk factors, including dyslipidemia, hyperglycemia and hypertension, modify miR-34a expression to promote vascular senescence and inflammation. miR-34a upregulation causes endothelial dysfunction by affecting ECs nitric oxide bioavailability, adhesion molecules expression and inflammatory cells recruitment. miR-34a-induced senescence facilitates VSMCs osteoblastic switch and VC development in hyperphosphatemia conditions. Conversely, atherogenic and hypoxic stimuli downregulate miR-34a levels and promote VSMCs proliferation and migration during atherosclerosis and PAH. MiR34a genetic ablation or miR-34a inhibition by anti-miR-34a molecules in different experimental models of VD reduce vascular inflammation, senescence and apoptosis through sirtuin 1 Notch1, and B-cell lymphoma 2 modulation. Notably, pleiotropic drugs, like statins, liraglutide and metformin, affect miR-34a expression. Finally, human studies report that miR-34a levels associate to atherosclerosis and diabetes and correlate with inflammatory factors during aging. Herein, we comprehensively review the current knowledge about miR-34a-dependent molecular and cellular mechanisms activated by VD risk factors and highlight the diagnostic and therapeutic potential of modulating its expression in order to reduce inflammaging and VD burn and extend healthy lifespan.

Current Understandings of Myeloid Differentiation Inducers in Leukemia Therapy

Differentiation therapy using all-trans retinoic acid for acute promyelocytic leukemia (APL) is well established. Several attempts have been made to treat non-APL, AML patients by employing differentiation inducers, such as hypomethylating agents (HMAs), and low-dose cytarabine (Ara-C) (LDAC), with encouraging results. Other than HMAs and LDAC, various inducers of myeloid cell differentiation have been identified. This review describes and categorizes these inducers, which include glycosylation modifiers, epigenetic modifiers, vitamin derivatives, cytokines, and chemotherapeutic agents. Some of these inducers are currently being used in clinical trials. I highlight the potential applications of glycosylation modifiers and epigenetic modifiers, which are attracting increasing attention in their use as differentiation therapy against AML. Among the agents described in this review, epigenomic modifiers seem particularly promising, and particular attention should also be paid to glycosylation modifiers. These drugs may signal a new era for AML differentiation therapy.

A Loop-Based and AGO-Incorporated Virtual Screening Model Targeting AGO-Mediated miRNA-mRNA Interactions for Drug Discovery to Rescue Bone Phenotype in Genetically Modified Mice

Several virtual screening models are proposed to screen small molecules only targeting primary miRNAs without selectivity. Few attempts have been made to develop virtual screening strategies for discovering small molecules targeting mature miRNAs. Mature miRNAs and their specific target mRNA can form unique functional loops during argonaute (AGO)-mediated miRNA-mRNA interactions, which may serve as potential targets for small-molecule drug discovery. Thus, a loop-based and AGO-incorporated virtual screening model is constructed for targeting the loops. The previously published studies have found that miR-214 can target ATF4 to inhibit osteoblastic bone formation, whereas miR-214 can target TRAF3 to promote osteoclast activity. By using the virtual model, the top ten candidate small molecules targeting miR-214-ATF4 mRNA interactions and top ten candidate small molecules targeting miR-214-TRAF3 mRNA interactions are selected, respectively. Based on both in vitro and in vivo data, one small molecule can target miR-214-ATF4 mRNA to promote ATF4 protein expression and enhance osteogenic potential, whereas one small molecule can target miR-214-TRAF3 mRNA to promote TRAF3 protein expression and inhibit osteoclast activity. These data indicate that the loop-based and AGO-incorporated virtual screening model can help to obtain small molecules specifically targeting miRNA-mRNA interactions to rescue bone phenotype in genetically modified mice.

miR-144 Mediates High Fat-Induced Changes of Cholesterol Metabolism via Direct Regulation of C/EBPα in the Liver and Isolated Hepatocytes of Yellow Catfish

BACKGROUND

microRNAs (miRNAs) post-transcriptionally regulate gene expression and act as important modulators of cholesterol homeostasis.

OBJECTIVE

The study explores the mechanism by which miRNAs mediate high fat-induced changes of cholesterol metabolism in yellow catfish.

METHODS

Yellow catfish (weight: 3.79 ± 0.16 g, 3 mo old, mixed sex) were fed 2 diets containing lipids at 11.3% [control (CON)] or 15.4% [high-fat diet (HFD)] (by weight) for 8 wk. Cholesterol content was measured; hematoxylin-eosin (H&E) staining, qPCR assays, and small RNA sequencing were conducted in the liver. Hepatocytes were isolated from separate, untreated fish and incubated for 24 h in control solution or palmitic acid (PA; 0.25 mM)/oleic acid (OA; 0.5 mM) after 4 h pretreatment with or without miR-144 inhibitor/mimic (40 nM). Cholesterol content was measured; qPCR assays and Western blotting were conducted in the hepatocytes. HEK293T cells were co-transfected with plasmids to validate miR-144 target genes. The promoter activities of miR-144 were analyzed in HEK293T cells with PA (0.25 mM) or OA (0.25 or 0.5 mM) treatment for 24 h. Luciferase activity assays, electrophoretic mobility shift assay, and Western blotting were conducted in HEK293T cells.

RESULTS

Compared with CON, HFD induced hepatic cholesterol accumulation (31.5%), and upregulated miR-144 expression (8.40-fold, P < 0.05). miR-144 directly targeted hydroxymethylglutaryl-CoA reductase (hmgcr), cholesterol 7α-monooxygenase A1 (cyp7a1), and adenosine triphosphate binding cassette transporter A1 (abca1) in HEK293T cells. In the hepatocytes of yellow catfish, miR-144 inversely regulated the expression of hmgcr, cyp7a1, and abca1 (30.3-78.5%, P < 0.05); loss of miR-144 function alleviated PA- or OA-induced cholesterol accumulation (19.5-61.1%, P < 0.05). We also characterized the C/EBPα binding site in the miR-144 promoter, and found that C/EBPα positively regulated miR-144 expression through binding to the miR-144 promoter.

CONCLUSIONS

miR-144 mediated HFD-induced changes in the liver and hepatocytes of yellow catfish, suggesting a possible mechanism for HFD-induced dysfunction in cholesterol metabolism.

Decitabine and all-trans retinoic acid synergistically exhibit cytotoxicity against elderly AML patients via miR-34a/MYCN axis

This study aimed to investigate the efficacy and mechanism of decitabine (DAC) and all-trans retinoic acid (ATRA) in elderly acute myeloid leukemia (AML) patients and cultured cells. Our clinical trial enrolled 36 elderly patients who were judged ineligible for conventional chemotherapy, receiving DAC and ATRA regimen (DAC 20 mg/m² days 1-5; ATRA 20 mg/m² days 4-28 in the first cycle and days 1-28 in the subsequent cycle). Treated with a median of 3 cycles (range 1-6), 44.4 % of patients achieved complete remission (CR), 11.1 % achieved CR with incomplete peripheral count recovery (CRi) and 13.9 % achieved partial remission (PR). The median overall survival (OS) was 12.1 months; the 1-year and 2-year OS rates were 49.6 % and 17.2 %. In addition, our in vitro studies indicated that the antineoplastic activities of DAC and ATRA mutually reinforced, which induced growth inhibition, cell cycle arrest and apoptosis of AML cells. Meanwhile, we found DAC and ATRA inhibited DNMT1, activated miR-34a via promoter hypomethylation, down-regulated its target MYCN and thus exerted a synergistic antineoplastic effect. In conclusion, DAC plus ATRA regimen might be effective and well-tolerated for elderly patients partially through modulating miR-34a/MYCN axis.

Long non-coding RNA SNHG1 indicates poor prognosis and facilitates disease progression in acute myeloid leukemia

The role of long non-coding RNAs (lncRNAs) in acute myeloid leukemia (AML) is becoming increasingly questioned. Previous studies have reported that the lncRNA small nucleolar RNA host gene 1 (SNHG1) is involved in multiple human malignant tumors, while its expression and role in AML is still unexplored. Here, we show that SNHG1 is highly expressed in AML specimens from non-M3 patients, as well as AML cell lines. Meanwhile, upregulation of SNHG1 is correlated with poor prognosis. Notably, SNHG1 facilitates the proliferation and inhibits the apoptosis of AML cells in vitro Consistent with these findings, knockdown of SNHG1 significantly inhibits AML progression in an immunodeficient mouse model. Mechanistically, we found that an anti-tumor microRNA-101 (miR-101) is upregulated and its target genes are downregulated in AML cells after SNHG1 knockdown. Further investigations display that SNHG1 can serve as a competing endogenous RNA to inhibit miR-101. In conclusion, our data indicate that SNHG1 plays an important role in facilitating AML progression at least in part by negatively regulating miR-101, and provides a new target for treating AML.

Role of microRNAs, circRNAs and long noncoding RNAs in acute myeloid leukemia

Acute myeloid leukemia (AML) is a malignant tumor of the immature myeloid hematopoietic cells in the bone marrow (BM). It is a highly heterogeneous disease, with rising morbidity and mortality in older patients. Although researches over the past decades have improved our understanding of AML, its pathogenesis has not yet been fully elucidated. Long noncoding RNAs (lncRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs) are three noncoding RNA (ncRNA) molecules that regulate DNA transcription and translation. With the development of RNA-Seq technology, more and more ncRNAs that are closely related to AML leukemogenesis have been discovered. Numerous studies have found that these ncRNAs play an important role in leukemia cell proliferation, differentiation, and apoptosis. Some may potentially be used as prognostic biomarkers. In this systematic review, we briefly described the characteristics and molecular functions of three groups of ncRNAs, including lncRNAs, miRNAs, and circRNAs, and discussed their relationships with AML in detail.

MicroRNA-34a suppresses aggressiveness of hepatocellular carcinoma by modulating E2F1, E2F3, and Caspase-3

Background: Accumulating evidence suggests an antineoplastic role of MicroRNA-34a (miR-34a) in human cancer. However, its precise biological functions stay largely elusive. Purpose: Our study was aimed to investigate the impact of miR-34a on hepatocellular carcinoma (HCC) and its underlying apoptosis related mechanisms in vitro, as well as the association of miR-34a, E2F1 and E2F3 expression with patient survival of HCC using publicly accessed datasets. Methods: The HBV-expressing Hep3B and SNU-449 cell lines with or without enforced expression of miR-34a were in vitro cultured for cell proliferation, colony formation, wound healing, cell invasion, and 3D spheroid formation. Quantitative reverse transcription PCR (RT-qPCR) was performed for E2F1, E2F3 expression. Caspase-3 (CASP3) activity was determined using a CaspACE^TM Assay System. Kaplan-Meier survival curves were used to analyze the associations of miR-34a, E2F1 and E2F3 expression and overall survival in HCC. Meta-analysis was performed to examine the differential expression of E2F1 and E2F3 between primary HCC vs normal tissues. Results: The results in vitro showed that enforced miR-34a expression significantly inhibited cell proliferation, migration, and invasion of both Hep3B and SNU-449. RT-qPCR results demonstrated that miR-34a could significantly suppress E2F1 and E2F3 expression, particularly in SNU-449. CASP3 activity in both Hep3B and SNU-449 increased in miR-34a treatment group. Overexpressed E2F1 and E2F3 were observed in primary HCC vs normal tissues. Survival analyses showed that HCC patients with either high miR-34a, or low E2F1, or low E2F3 expression had better survival than their opposite counterparts, respectively. Conclusion: Our study suggested thatmiR-34a can modulate the expression of E2F1, E2F3, and CASP3 activity, thereby repressing tumor aggressiveness and expediting apoptosis in liver cancer cells.

MicroRNA miR-34a downregulates FOXP1 during DNA damage response to limit BCR signalling in chronic lymphocytic leukaemia B cells

The variable clinical course in chronic lymphocytic leukaemia (CLL) largely depends on p53 functionality and B-cell receptor (BCR) signalling propensity; however, it is unclear if there is any crosstalk between these pathways. We show that DNA damage response (DDR) activation leads to down-modulating the transcriptional factor FOXP1, which functions as a positive BCR signalling regulator and its high levels are associated with worse CLL prognosis. We identified microRNA (miRNA) miR-34a as the most prominently upregulated miRNA during DDR in CLL cells in vitro and in vivo during FCR therapy (fludarabine, cyclophosphamide, rituximab). MiR-34a induced by DDR activation and p53 stabilization potently represses FOXP1 expression by binding in its 3'-UTR. The low FOXP1 levels limit BCR signalling partially via derepressing BCR-inhibitory molecule CD22. We also show that low miR-34a levels can be used as a biomarker for worse response or shorter progression free survival in CLL patients treated with FCR chemoimmunotherapy, and shorter overall survival, irrespective of TP53 status. Additionally, we have developed a method for the absolute quantification of miR-34a copies and defined precise prognostic/predictive cutoffs. Overall, herein, we reveal for the first time that B cells limit their BCR signalling during DDR by down-modulating FOXP1 via DDR-p53/miR-34a axis.

MicroRNA-143 targets ERK5 in granulopoiesis and predicts outcome of patients with acute myeloid leukemia

Hematopoiesis, the formation of blood cells from hematopoietic stem cells (HSC), is a highly regulated process. Since the discovery of microRNAs (miRNAs), several studies have shown their significant role in the regulation of the hematopoietic system. Impaired expression of miRNAs leads to disrupted cellular pathways and in particular causes loss of hematopoietic ability. Here, we report a previously unrecognized function of miR-143 in granulopoiesis. Hematopoietic cells undergoing granulocytic differentiation exhibited increased miR-143 expression. Overexpression or ablation of miR-143 expression resulted in accelerated granulocytic differentiation or block of differentiation, respectively. The absence of miR-143 in mice resulted in a reduced number of mature granulocytes in blood and bone marrow. Additionally, we observed an association of high miR-143 expression levels with a higher probability of survival in two different cohorts of patients with acute myeloid leukemia (AML). Overexpression of miR-143 in AML cells impaired cell growth, partially induced differentiation, and caused apoptosis. Argonaute2-RNA-Immunoprecipitation assay revealed ERK5, a member of the MAPK-family, as a target of miR-143 in myeloid cells. Further, we observed an inverse correlation of miR-143 and ERK5 in primary AML patient samples, and in CD34⁺ HSPCs undergoing granulocytic differentiation and we confirmed functional relevance of ERK5 in myeloid cells. In conclusion, our data describe miR-143 as a relevant factor in granulocyte differentiation, whose expression may be useful as a prognostic and therapeutic factor in AML therapy.

[Roles of CCAAT enhancer binding protein α in acute myeloblastic leukemia]

The CCAAT enhancer binding protein α (C/EBP α:p42 and p30),which encoded by CCAAT enhancer binding protein α (C/EBPα) gene,plays a pretty crucial role in the regulation of myeloid hematopoiesis.The disorder of CEBPA gene expression is an pivotal mechanism of acute myeloid leukemia (AML). The result of uncontrolled expression of C/EBP α gene is the over-expression of p30 and the incomplete loss of p42, both of which contribute to the occurrence of AML. Restoring the expression ratio of C/EBP α such as over-expression of p42 or blocking the carcinogenic pathway of p30 seems to be important for the treatment of AML caused by such causes. In order to better guide medical decision-making, this article reviews research progress on C/EBPα in the pathogenesis of AML.

Identifying microRNA determinants of human myelopoiesis

Myelopoiesis involves differentiation of hematopoietic stem cells to cellular populations that are restricted in their self-renewal capacity, beginning with the common myeloid progenitor (CMP) and leading to mature cells including monocytes and granulocytes. This complex process is regulated by various extracellular and intracellular signals including microRNAs (miRNAs). We characterised the miRNA profile of human CD34⁺CD38⁺ myeloid progenitor cells, and mature monocytes and granulocytes isolated from cord blood using TaqMan Low Density Arrays. We identified 19 miRNAs that increased in both cell types relative to the CMP and 27 that decreased. miR-125b and miR-10a were decreased by 10-fold and 100-fold respectively in the mature cells. Using in vitro granulopoietic differentiation of human CD34⁺ cells we show that decreases in both miR-125b and miR-10a correlate with a loss of CD34 expression and gain of CD11b and CD15 expression. Candidate target mRNAs were identified by co-incident predictions between the miRanda algorithm and genes with increased expression during differentiation. Using luciferase assays we confirmed MCL1 and FUT4 as targets of miR-125b and the transcription factor KLF4 as a target of miR-10a. Together, our data identify miRNAs with differential expression during myeloid development and reveal some relevant miRNA-target pairs that may contribute to physiological differentiation.

The interplay between critical transcription factors and microRNAs in the control of normal and malignant myelopoiesis

Myelopoiesis is a complex process driven by essential transcription factors, including C/EBPα, PU.1, RUNX1, KLF4 and IRF8. Together, these factors are critical for the control of myeloid progenitor cell expansion and lineage determination in the development of granulocytes and monocytes/macrophages. MicroRNAs (miRNAs) are expressed in a cell type and lineage specific manner. There is increasing evidence that miRNAs fine-tune the expression of hematopoietic lineage-specific transcription factors and drive the lineage decisions of hematopoietic progenitor cells. In this review, we discuss recently discovered self-activating and feed-back mechanisms in which transcription factors and miRNAs interact during myeloid cell development. Furthermore, we delineate how some of these mechanisms are affected in acute myeloid leukemia (AML) and how disrupted transcription factor-miRNA interplays contribute to leukemogenesis.

MicroRNAs as New Biomarkers for Diagnosis and Prognosis, and as Potential Therapeutic Targets in Acute Myeloid Leukemia

Acute myeloid leukemias (AML) are clonal disorders of hematopoietic progenitor cells which are characterized by relevant heterogeneity in terms of phenotypic, genotypic, and clinical features. Among the genetic aberrations that control disease development there are microRNAs (miRNAs). miRNAs are small non-coding RNAs that regulate, at post-transcriptional level, translation and stability of mRNAs. It is now established that deregulated miRNA expression is a prominent feature in AML. Functional studies have shown that miRNAs play an important role in AML pathogenesis and miRNA expression signatures are associated with chemotherapy response and clinical outcome. In this review we summarized miRNA signature in AML with different cytogenetic, molecular and clinical characteristics. Moreover, we reviewed the miRNA regulatory network in AML pathogenesis and we discussed the potential use of cellular and circulating miRNAs as biomarkers for diagnosis and prognosis and as therapeutic targets.

A double-negative feedback loop between E2F3b and miR- 200b regulates docetaxel chemosensitivity of human lung adenocarcinoma cells

MicroRNAs (miRNAs) are non-coding small RNAs which negatively regulate gene expressions mainly through 3'-untranslated region (3'-UTR) binding of target mRNAs. Recent studies have highlighted the feedback loops between miRNAs and their target genes in physiological and pathological processes including chemoresistance of cancers. Our previous study identified miR-200b/E2F3 axis as a chemosensitivity restorer of human lung adenocarcinoma (LAD) cells. Moreover, E2F3b was bioinformatically proved to be a potential transcriptional regulator of pre-miR-200b gene promoter. The existance of this double-negative feedback minicircuitry comprising E2F3b and miR-200b was confirmed by chromatin immunoprecipitation (ChIP) assay, site-specific mutation and luciferase reporter assay. And the underlying regulatory mechanisms of this feedback loop on docetaxel resistance of LAD cells were further investigated by applying in vitro chemosensitivity assay, colony formation assay, flow cytometric analysis of cell cycle and apoptosis, as well as mice xenograft model. In conclusion, our results suggest that the double-negative feedback loop between E2F3b and miR-200b regulates docetaxel chemosensitivity of human LAD cells mainly through cell proliferation, cell cycle distribution and apoptosis.

miR-34a Regulates Expression of the Stathmin-1 Oncoprotein and Prostate Cancer Progression

In aggressive prostate cancers, the oncoprotein STMN1 (also known as stathmin 1 and oncoprotein 18) is often overexpressed. STMN1 is involved in various cellular processes, including cell proliferation, motility, and tumor metastasis. Here, it was found that the expression of STMN1 RNA and protein is elevated in metastatic prostate cancers. Knockdown of STMN1 resulted in reduced proliferation and invasion of cells and tumor growth and metastasis in vivo Furthermore, miR-34a downregulated STMN1 by directly binding to its 3'-UTR. Overexpression of miR-34a in prostate cancer cells reduced proliferation and colony formation, suggesting that it is a tumor suppressor. The transcriptional corepressor C-terminal binding protein 1 (CtBP1) negatively regulated expression of miR-34a. Furthermore, gene expression profiling of STMN1-modulated prostate cancer cells revealed molecular alterations, including elevated expression of growth differentiation factor 15 (GDF15), which is involved in cancer progression and potentially in STMN1-mediated oncogenesis. Thus, in prostate cancer, CtBP1-regulated miR-34a modulates STMN1 expression and is involved in cancer progression through the CtBP1\miR-34a\STMN1\GDF15 axis.Implications: The CtBP1\miR-34a\STMN1\GDF15 axis is a potential therapeutic target for treatment of aggressive prostate cancer. Mol Cancer Res; 16(7); 1125-37. ©2017 AACR.

C/EBPα deregulation as a paradigm for leukemogenesis

Myeloid master regulator CCAAT enhancer-binding protein alpha (C/EBPα) is deregulated by multiple mechanisms in leukemia. Inhibition of C/EBPα function plays pivotal roles in leukemogenesis. While much is known about how C/EBPα orchestrates granulopoiesis, our understanding of molecular transformation events, the role(s) of cooperating mutations and clonal evolution during C/EBPα deregulation in leukemia remains elusive. In this review, we will summarize the latest research addressing these topics with special emphasis on CEBPA mutations. We conclude by describing emerging therapeutic strategies to restore C/EBPα function.

Granulopoiesis and granules of human neutrophils

Granules are essential for the ability of neutrophils to fulfill their role in innate immunity. Granule membranes contain proteins that react to environmental cues directing neutrophils to sites of infection and initiate generation of bactericidal oxygen species. Granules are densely packed with proteins that contribute to microbial killing when liberated to the phagosome or extracellularly. Granules are, however, highly heterogeneous and are traditionally subdivided into azurophil granules, specific granules, and gelatinase granules in addition to secretory vesicles. This review will address issues pertinent to formation of granules, which is a process intimately connected to maturation of neutrophils from their precursors in the bone marrow. We further discuss possible mechanisms by which decisions are made regarding sorting of proteins to constitutive secretion or storage in granules and how degranulation of granule subsets is regulated.

Specific Depletion of Leukemic Stem Cells: Can MicroRNAs Make the Difference?

For over 40 years the standard treatment for acute myeloid leukemia (AML) patients has been a combination of chemotherapy consisting of cytarabine and an anthracycline such as daunorubicin. This standard treatment results in complete remission (CR) in the majority of AML patients. However, despite these high CR rates, only 30–40% (<60 years) and 10–20% (>60 years) of patients survive five years after diagnosis. The main cause of this treatment failure is insufficient eradication of a subpopulation of chemotherapy resistant leukemic cells with stem cell-like properties, often referred to as “leukemic stem cells” (LSCs). LSCs co-exist in the bone marrow of the AML patient with residual healthy hematopoietic stem cells (HSCs), which are needed to reconstitute the blood after therapy. To prevent relapse, development of additional therapies targeting LSCs, while sparing HSCs, is essential. As LSCs are rare, heterogeneous and dynamic, these cells are extremely difficult to target by single gene therapies. Modulation of miRNAs and consequently the regulation of hundreds of their targets may be the key to successful elimination of resistant LSCs, either by inducing apoptosis or by sensitizing them for chemotherapy. To address the need for specific targeting of LSCs, miRNA expression patterns in highly enriched HSCs, LSCs, and leukemic progenitors, all derived from the same patients’ bone marrow, were determined and differentially expressed miRNAs between LSCs and HSCs and between LSCs and leukemic progenitors were identified. Several of these miRNAs are specifically expressed in LSCs and/or HSCs and associated with AML prognosis and treatment outcome. In this review, we will focus on the expression and function of miRNAs expressed in normal and leukemic stem cells that are residing within the AML bone marrow. Moreover, we will review their possible prospective as specific targets for anti-LSC therapy.

Disruption of the C/EBPα-miR-182 balance impairs granulocytic differentiation

Transcription factor C/EBPα is a master regulator of myelopoiesis and its inactivation is associated with acute myeloid leukemia. Deregulation of C/EBPα by microRNAs during granulopoiesis or acute myeloid leukemia development has not been studied. Here we show that oncogenic miR-182 is a strong regulator of C/EBPα. Moreover, we identify a regulatory loop between C/EBPα and miR-182. While C/EBPα blocks miR-182 expression by direct promoter binding during myeloid differentiation, enforced expression of miR-182 reduces C/EBPα protein level and impairs granulopoiesis in vitro and in vivo. In addition, miR-182 expression is highly elevated particularly in acute myeloid leukemia patients with C-terminal CEBPA mutations, thereby depicting a mechanism by which C/EBPα blocks miR-182 expression. Furthermore, we present miR-182 expression as a prognostic marker in cytogenetically high-risk acute myeloid leukemia patients. Our data demonstrate the importance of a controlled balance between C/EBPα and miR-182 for the maintenance of healthy granulopoiesis.

C/EBPα is a critical transcription factor involved in myelopoiesis and its inactivation is associated with acute myeloid leukemia (AML). Here the authors show a negative feedback loop between C/EBPα and miR-182 and identify this miRNA as a marker of high-risk AML.

MicroRNA-34 dysregulation in gastric cancer and gastric cancer stem cell

Gastric cancer is a major cause of cancer mortality worldwide, with a low survival rate for patients with advanced forms of the disease. Over the recent decades, the investigation of the pathophysiological mechanisms of tumourigenesis has opened promising avenues to understand some of the complexities of cancer treatment. However, tumour regeneration and metastasis impose great difficulty for gastric cancer cure. In recent years, cancer stem cells - a small subset of tumour cells in many cancers - have become a major focus of cancer research. Cancer stem cells are capable of self-renewal and are known to be responsible for tumour initiation, metastasis, therapy resistance and cancer recurrence. Recent studies have revealed the key role of microRNAs - small noncoding RNAs regulating gene expression - in these processes. MicroRNAs play crucial roles in the regulation of a wide range of biological processes in a post-transcriptional manner, though their expression is dysregulated in most malignancies, including gastric cancer. In this article, we review the consequences of aberrant expression of microRNA-34 in cancer and cancer stem cells, with a specific focus on the miR-34 dysregulation in gastric cancer and gastric cancer stem cells. We address the critical effects of the aberrant expression of miR-34 and its target genes in maintaining cancer stem cell properties. Information collection and discussion about the advancements in gastric cancer stem cells and microRNAs can be useful for providing novel insights into patient treatment.

Tuning of major signaling networks (TGF-β, Wnt, Notch and Hedgehog) by miRNAs in human stem cells commitment to different lineages: Possible clinical application

Two distinguishing characteristics of stem cells, their continuous division in the undifferentiated state and growth into any cell types, are orchestrated by a number of cell signaling pathways. These pathways act as a niche factor in controlling variety of stem cells. The core stem cell signaling pathways include Wingless-type (Wnt), Hedgehog (HH), and Notch. Additionally, they critically regulate the self-renewal and survival of cancer stem cells. Conversely, stem cells' main properties, lineage commitment and stemness, are tightly controlled by epigenetic mechanisms such as DNA methylation, histone modifications and non-coding RNA-mediated regulatory events. MicroRNAs (miRNAs) are cellular switches that modulate stem cells outcomes in response to diverse extracellular signals. Numerous scientific evidences implicating miRNAs in major signal transduction pathways highlight new crosstalks of cellular processes. Aberrant signaling pathways and miRNAs levels result in developmental defects and diverse human pathologies. This review discusses the crosstalk between the components of main signaling networks and the miRNA machinery, which plays a role in the context of stem cells development and provides a set of examples to illustrate the extensive relevance of potential novel therapeutic targets.

MiRNAs and E2F3: a complex network of reciprocal regulations in human cancers

E2F transcription factor 3 (E2F3) is oncogenic in tumorigenesis. Alterations in E2F3 functions correspond with poor prognosis in various cancers, underscoring their status for the clinical cancer phenotype. Latest reports discovered intricate networks between microRNAs (miRNAs) and E2F3 in regulating the balance of these events, including proliferation, apoptosis, metastasis, as well as drug resistance. miRNAs are non-coding small RNAs which negatively regulate gene expressions post-transcriptionally mainly through 3′-UTR binding of target mRNAs. Increasing evidence shows that E2F3 can be activated/inhibited by numerous miRNAs whose dysregulation has been implicated in malignancy. In turn, miRNAs themselves can be transcriptionally regulated by E2F3, thus forming a negative feedback loop. These findings add a new challenging layer of complexity to E2F3 network. Current understanding of the reciprocal link between E2F3 and miRNAs in human cancers were summarized, which could help to develop potential therapeutic strategies.

LF-MF inhibits iron metabolism and suppresses lung cancer through activation of P53-miR-34a-E2F1/E2F3 pathway

Our previous studies showed that low frequency magnetic fields (LF-MF) suppressed tumor growth and influenced the function of immune system. Nevertheless the mechanisms behind the effect of LF-MF still remain to be elucidated. In this study, Tumor- bearing mice subcutaneously inoculated with Lewis lung cancer cells were exposed to a LF-MF (0.4T, 7.5 Hz) for 35 days and Survival rate, tumor growth and the tumor markers were measured. Results showed that tumor growth was obviously inhibited with a prolonged survival of tumor- bearing mice by LF-MF exposure. In vitro experiments, LF-MF was found to induce cell growth arrest, cell senescence and inhibit iron metabolism of lung cancer cells. Moreover, LF-MF stabilized p53 protein via inhibiting cell iron metabolism and the stabilized p53 protein enhanced miR-34a transcription. Furthermore, increased expression of miR-34a induced cell proliferation inhibition, cell cycle arrest and cell senescence of lung cancer cells by targeting E2F1/E2F3. We also detected the relevant indicator in tumor tissue such as the iron content, the level of miR-34a and related protein, corresponding results were obtained. Taken together, these observations imply that LF-MF suppressed lung cancer via inhibiting cell iron metabolism, stabilizing p53 protein and activation P53- miR-34a-E2F1/E2F3 pathway.

Effects of miR-146a on the osteogenesis of adipose-derived mesenchymal stem cells and bone regeneration

Increasing evidence has indicated that bone morphogenetic protein 2 (BMP2) coordinates with microRNAs (miRNAs) to form intracellular networks regulating mesenchymal stem cells (MSCs) osteogenesis. This study aimed to identify specific miRNAs in rat adipose-derived mesenchymal stem cells (ADSCs) during BMP2-induced osteogenesis, we selected the most significantly down-regulated miRNA, miR-146a, to systematically investigate its role in regulating osteogenesis and bone regeneration. Overexpressing miR-146a notably repressed ADSC osteogenesis, whereas knocking down miR-146a greatly promoted this process. Drosophila mothers against decapentaplegic protein 4 (SMAD4), an important co-activator in the BMP signaling pathway, was miR-146a’s direct target and miR-146a exerted its repressive effect on SMAD4 through interacting with 3′-untranslated region (3′-UTR) of SMAD4 mRNA. Furthermore, knocking down SMAD4 attenuated the ability of miR-146a inhibitor to promote ADSC osteogenesis. Next, transduced ADSCs were incorporated with poly(sebacoyl diglyceride) (PSeD) porous scaffolds for repairing critical-sized cranial defect, the treatment of miR-146a inhibitor greatly enhanced ADSC-mediated bone regeneration with higher expression levels of SMAD4, Runt-related transcription factor 2 (Runx2) and Osterix in newly formed bone. In summary, our study showed that miR-146a negatively regulates the osteogenesis and bone regeneration from ADSCs both in vitro and in vivo.

Cell-free microRNAs in blood and other body fluids, as cancer biomarkers

The discovery of cell-free microRNAs (miRNAs) in serum, plasma and other body fluids has yielded an invaluable potential source of non-invasive biomarkers for cancer and other non-malignant diseases. miRNAs in the blood and other body fluids are highly stable in biological samples and are resistant to environmental conditions, such as freezing, thawing or enzymatic degradation, which makes them convenient as potential biomarkers. In addition, they are more easily sampled than tissue miRNAs. Altered levels of cell-free miRNAs have been found in every type of cancer analysed, and increasing evidence indicates that they may participate in carcinogenesis by acting as cell-to-cell signalling molecules. This review summarizes the biological characteristics and mechanisms of release of cell-free miRNAs that make them promising candidates as non-invasive biomarkers of cancer.

MicroRNA: Defining a new niche in Leukemia

MicroRNAs (miRNAs) are endogenous short non-coding RNAs found to play key roles in the pathogenesis of leukemia. Apart from being traditionally identified as modulators of oncogenes, the potential roles of miRNAs seems to be growing with novel and recent findings among different subtypes of hematological malignancies. Leukemia is one of the earliest malignancies to be linked to abnormal expression of miRNAs. However, a clear understanding of the involvement of miRNAs in intricate mechanisms of leukemogenesis is still a necessity. This review summarizes the multiple roles of miRNAs in the pathogenesis of leukemia and highlights major research findings contributing to these aspects.

Urinary miR-16 transactivated by C/EBPβ reduces kidney function after ischemia/reperfusion-induced injury

Ischemia-reperfusion (I/R) induced acute kidney injury (AKI) is regulated by transcriptional factors and microRNAs (miRs). However, modulation of miRs by transcriptional factors has not been characterized in AKI. Here, we found that urinary miR-16 was 100-fold higher in AKI patients. MiR-16 was detected earlier than creatinine in mouse after I/R. Using TargetScan, the 3′UTR of B-cell lymphoma 2 (BCL-2) was found complementary to miR-16 to decrease the fluorescent reporter activity. Overexpression of miR-16 in mice significantly attenuated renal function and increased TUNEL activity in epithelium tubule cells. The CCAAT enhancer binding protein beta (C/EBP-β) increased the expression of miR-16 after I/R injury. The ChIP and luciferase promoter assay indicated that about −1.0 kb to −0.5 kb upstream of miR-16 genome promoter region containing C/EBP-β binding motif transcriptionally regulated miR-16 expression. Meanwhile, the level of pri-miR-16 was higher in mice infected with lentivirus containing C/EBP-β compared with wild-type (WT) mice and overexpression of C/EBP-β in the kidney of WT mice reduced kidney function, increased kidney apoptosis, and elevated urinary miR-16 level. Our results indicated that miR-16 was transactivated by C/EBP-β resulting in aggravated I/R induced AKI and that urinary miR-16 may serve as a potential biomarker for AKI.

C/EBPα-p30 protein induces expression of the oncogenic long non-coding RNA UCA1 in acute myeloid leukemia

Accumulating evidences indicate that different long non-coding RNAs (lncRNAs) might play a relevant role in tumorigenesis, with their expression and function already associated to cancer development and progression. CCAAT/enhancer-binding protein-α (CEBPA) is a critical regulator of myeloid differentiation whose inactivation contributes to the development of acute myeloid leukemia (AML). Mutations in C/EBPα occur in around 10% of AML cases, leading to the expression of a 30-kDa dominant negative isoform (C/EBPα-p30). In this study, we identified the oncogenic urothelial carcinoma associated 1 (UCA1) lncRNA as a novel target of the C/EBPα-p30. We show that wild-type C/EBPα and C/EBPα-p30 isoform can bind the UCA1 promoter but have opposite effects on UCA1 expression. While wild-type C/EBPα represses, C/EBPα-p30 can induce UCA1 transcription. Notably, we also show that UCA1 expression increases in cytogenetically normal AML cases carrying biallelic CEBPA mutations. Furthermore, we demonstrate that UCA1 sustains proliferation of AML cells by repressing the expression of the cell cycle regulator p27^kip1. Thus, we identified, for the first time, an oncogenic lncRNA functioning in concert with the dominant negative isoform of C/EBPα in AML.

The mirn23a microRNA cluster antagonizes B cell development

Ablation of microRNA synthesis by deletion of the microRNA-processing enzyme Dicer has demonstrated that microRNAs are necessary for normal hematopoietic differentiation and function. However, it is still unclear which specific microRNAs are required for hematopoiesis and at what developmental stages they are necessary. This is especially true for immune cell development. We previously observed that overexpression of the products of the mirn23a gene (microRNA-23a, -24-2, and 27a) in hematopoietic progenitors increased myelopoiesis with a reciprocal decrease in B lymphopoiesis, both in vivo and in vitro. In this study, we generated a microRNA-23a, -24-2, and 27a germline knockout mouse to determine whether microRNA-23a, -24-2, and 27a expression was essential for immune cell development. Characterization of hematopoiesis in microRNA-23a, -24-2, and 27a^-/- mice revealed a significant increase in B lymphocytes in both the bone marrow and the spleen, with a concomitant decrease in myeloid cells (monocytes/granulocytes). Analysis of the bone marrow progenitor populations revealed a significant increase in common lymphoid progenitors and a significant decrease in both bone marrow common myeloid progenitors and granulocyte monocyte progenitors. Gene-expression analysis of primary hematopoietic progenitors and multipotent erythroid myeloid lymphoid cells showed that microRNA-23a, -24-2, and 27a regulates essential B cell gene-expression networks. Overexpression of microRNA-24-2 target Tribbles homolog 3 can recapitulate the microRNA-23a, -24-2, and 27a^-/- phenotype in vitro, suggesting that increased B cell development in microRNA-23a, -24-2, and 27a null mice can be partially explained by a Tribbles homolog 3-dependent mechanism. Data from microRNA-23a, -24-2, and 27a^-/- mice support a critical role for this microRNA cluster in regulating immune cell populations through repression of B lymphopoiesis.

Bioinformatic analysis of microRNA networks following the activation of the constitutive androstane receptor (CAR) in mouse liver

The constitutive androstane receptor (CAR; NR1I3) is a member of the nuclear receptor superfamily that functions as a xenosensor, serving to regulate xenobiotic detoxification, lipid homeostasis and energy metabolism. CAR activation is also a key contributor to the development of chemical hepatocarcinogenesis in mice. The underlying pathways affected by CAR in these processes are complex and not fully elucidated. MicroRNAs (miRNAs) have emerged as critical modulators of gene expression and appear to impact many cellular pathways, including those involved in chemical detoxification and liver tumor development. In this study, we used deep sequencing approaches with an Illumina HiSeq platform to differentially profile microRNA expression patterns in livers from wild type C57BL/6J mice following CAR activation with the mouse CAR-specific ligand activator, 1,4-bis-[2-(3,5,-dichloropyridyloxy)] benzene (TCPOBOP). Bioinformatic analyses and pathway evaluations were performed leading to the identification of 51 miRNAs whose expression levels were significantly altered by TCPOBOP treatment, including mmu-miR-802-5p and miR-485-3p. Ingenuity Pathway Analysis of the differentially expressed microRNAs revealed altered effector pathways, including those involved in liver cell growth and proliferation. A functional network among CAR targeted genes and the affected microRNAs was constructed to illustrate how CAR modulation of microRNA expression may potentially mediate its biological role in mouse hepatocyte proliferation. This article is part of a Special Issue entitled: Xenobiotic nuclear receptors: New Tricks for An Old Dog, edited by Dr. Wen Xie.

Leukemia Stem Cell-Released Microvesicles Promote the Survival and Migration of Myeloid Leukemia Cells and These Effects Can Be Inhibited by MicroRNA34a Overexpression

Leukemia stem cells (LSCs) play the major role in relapse of acute myeloid leukemia (AML). Recent evidence indicates that microvesicles (MVs) released from cancer stem cells can promote tumor growth and invasion. In this study, we investigated whether LSCs-released MVs (LMVs) can regulate the malignance of AML cells and whether overexpression of tumor suppressive microRNA (miR), miR34a, is able to interrupt this process. LSCs were transfected with miRNA control (miRCtrl) or miR34a mimic for producing LMVs, respectively, defined as LMVs^miRCtrl and LMVs^miR34a. The effect of miR34a transfection on LSC proliferation and the effects of LMVs^miRCtrl or LMVs^miR34a on the proliferation, migration, and apoptosis of AML cells (after LSC depletion) were determined. The levels of miR34a targets, caspase-3 and T cell immunoglobulin mucin-3 (Tim-3), were analyzed. Results showed that (1) LMVs^miRCtrl promoted proliferation and migration and inhibited apoptosis of AML cells, which were associated with miR34a deficit; (2) transfection of miR34a mimic inhibited LSC proliferation and increased miR34a level in LMVs^miR34a; (3) LMVs^miR34a produced opposite effects as compared with LMVs^miRCtrl, which were associated with the changes of caspase-3 and Tim-3 levels. In summary, LMVs support AML cell malignance and modulating miR34a could offer a new approach for the management of AML.

Transcription factor CCAAT/enhancer binding protein alpha up-regulates microRNA let-7a-1 in lung cancer cells by direct binding

AIMS

The transcription factor CCAAT/enhancer binding protein α (C/EBPα) and microRNA (miRNA) let-7a-1 act as tumor suppressors in many types of cancers including lung cancer. In the present study, we aim to investigate whether let-7a-1 is a novel important target of C/EBPα in lung cancer cells.

METHODS

The DNA sequence of the 2.1 kb let-7a-1 promoter was analyzed with MatInspector 4.1 (http://www.genomatix.de). Human lung cancer cell lines A549 and H1299, and human cervical cancer cell line Hela were used for transfection. Total RNA was extracted from cells using Trizol reagent and pri-let-7a-1 mRNA expression was measured using quantitative real-time polymerase chain reaction. Western blotting was performed to detect C/EBPα protein expression. To test whether C/EBP-α could up-regulate the expression level of let-7a at transcription level, dual-luciferase reporter gene assay was carried out. To determine whether C/EBPα could bind let-7a-1 promoter, electrophoretic mobility shift assay was employed. To further confirm the direct targeting let-7a-1 promoter by C/EBPα, chromatin immunoprecipitation was used.

RESULTS

Both C/EBPα and let-7a-1 were down-regulated in lung cancer A549 and H1299 cells, but up-regulated in Hela cells. Transfection and reporter gene assay showed that C/EBPα increased the expression of let-7a-1 at transcription level. Bioinformatics assay identified four putative C/EBP elements within let-7a-1 promoter. Dual-luciferase reporter gene, electrophoretic mobility shift assay and chromatin immunoprecipitation assays demonstrated that these four elements mediated the up-regulation effect of C/EBPα on let-7a-1.

CONCLUSIONS

The present study reveals that decreased C/EBPα contributes to the down-regulation of miRNA let-7a-1 in lung cancer cells.