Identification of serum miR-34a as a potential biomarker in acute myeloid leukemia

Histone lysine demethylase KDM5B facilitates proliferation and suppresses apoptosis in human acute myeloid leukemia cells through the miR-140-3p/BCL2 axis

The histone lysine demethylase KDM5B is frequently up-regulated in various human cancer cells. However, its expression and functional role in human acute myeloid leukemia (AML) cells remain unclear. Here, we found that the expression level of KDM5B is high in primary human AML cells. We have demonstrated that knocking down KDM5B leads to apoptosis and impairs proliferation in primary human AML and some human AML cell lines. We further identified miR-140-3p as a downstream target gene of KDM5B. KDM5B expression was inversely correlated with the miR-140-3p level in primary human AML cells. Molecular studies showed that silencing KDM5B enhanced H3K4 trimethylation (H3K4me3) at the promoter of miR-140-3p, leading to high expression of miR-140-3p, which in turn inhibited B-cell CLL/lymphoma 2 (BCL2) expression. Finally, we demonstrate that the defective proliferation induced by KDM5B knockdown (KD) can be rescued with the miR-140-3p inhibitor or enhanced by combining KDM5B KD with a BCL2 inhibitor. Altogether, our data support the conclusion that KDM5B promotes tumorigenesis in human AML cells through the miR-140-3p/BCL2 axis. Targeting the KDM5B/miR-140-3p/BCL2 pathway may hold therapeutic promise for treating human AML.

The Promising Role of Non-Coding RNAs as Biomarkers and Therapeutic Targets for Leukemia

Early-stage leukemia identification is crucial for effective disease management and leads to an improvement in the survival of leukemia patients. Approaches based on cutting-edge biomarkers with excellent accuracy in body liquids provide patients with the possibility of early diagnosis with high sensitivity and specificity. Non-coding RNAs have recently received a great deal of interest as possible biomarkers in leukemia due to their participation in crucial oncogenic processes such as proliferation, differentiation, invasion, apoptosis, and their availability in body fluids. Recent studies have revealed a strong correlation between leukemia and the deregulated non-coding RNAs. On this basis, these RNAs are also great therapeutic targets. Based on these advantages, we tried to review the role of non-coding RNAs in leukemia. Here, the significance of several non-coding RNA types in leukemia is highlighted, and their potential roles as diagnostic, prognostic, and therapeutic targets are covered.

Is the AURKB Gene Involved in Aml Cell Proliferation Since It is Targeted by miR-34a-5p and let-7b-5p?

ABSTRACT Objective: The production of normal blood cells in the bone marrow is interrupted in AML, which is characterized by the proliferation and accumulation of leukemic blasts. Therefore, patients experience anemia and thrombocytopenia. When gene expression of Aurora kinases, which is reported to be highly expressed in AML, decreases, it may be possible to alleviate the clinical findings in AML. In this study, it was aimed to examine the relationship of AURKB with important miRNAs that have the potential to regulate gene expression. Method: HL60 and NB4 cells were transfected with important tumor suppressor miRNAs miR-34a-5p and let-7b-5p mimics. Then, its effects on proliferation were examined with WST-8 technique and its effects on AURKB gene expression were examined with qRT-PCR. Results: It was determined that these miRNAs negatively regulated proliferation in both AML cell lines and downregulated the expression level of the Aurora kinase B (AURKB) gene in the miRNA transfected group compared to the control group. Conclusion: In conclusion, it was determined that miR-34a-5p and let-7b-5p could regulate AURKB expression in AML cells. Therefore, it was thought that these miRNAs may have an important potential as a therapeutic biomarker in preventing excessive cell division and poor prognosis in AML.

Identification of a Novel Long Non-coding RNA, lnc-ATMIN-4:2, and its Clinicopathological and Prognostic Significance in Advanced Gastric Cancer

BACKGROUND/AIM

Long non-coding RNAs (lncRNAs) are emerging as significant regulators of gene expression and a novel promising biomarker for cancer diagnosis and prognosis. This study identified a novel, differentially expressed lncRNA in advanced gastric cancer (AGC), Inc-ATMIN-4:2, and evaluated its clinicopathological and prognostic significance.

PATIENTS AND METHODS

Whole transcriptome sequencing was performed to identify differentially expressed lncRNAs in AGC tissue samples. We also analyzed lnc-ATMIN-4:2 expression in 317 patients with AGC using RNA in situ hybridization.

RESULTS

High (>30 dots) lnc-ATMIN-4:2 expression significantly correlated with younger age, poorly differentiated histology, diffuse type, deeper invasion depth, perineural invasion, lymph node metastasis, and higher stage group. In addition, high lnc-ATMIN-4:2 expression was significantly associated with worse overall survival in patients with AGC.

CONCLUSION

This study elucidated the significance of lncRNAs in AGC and indicated the value of lnc-ATMIN-4:2 expression as a predictive biomarker for the overall survival of patients with AGC.

MicroRNAs Regulate TASK-1 and Are Linked to Myocardial Dilatation in Atrial Fibrillation

Background

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia. However, underlying molecular mechanisms are insufficiently understood. Previous studies suggested that microRNA (miRNA) dependent gene regulation plays an important role in the initiation and maintenance of AF. The 2‐pore‐domain potassium channel TASK‐1 (tandem of P domains in a weak inward rectifying K⁺ channel–related acid sensitive K⁺ channel 1) is an atrial‐specific ion channel that is upregulated in AF. Inhibition of TASK‐1 current prolongs the atrial action potential duration to similar levels as in patients with sinus rhythm. Here, we hypothesize that miRNAs might be responsible for the regulation of KCNK3 that encodes for TASK‐1.

Methods and Results

We selected miRNAs potentially regulating KCNK3 and studied their expression in atrial tissue samples obtained from patients with sinus rhythm, paroxysmal AF, or permanent/chronic AF. MiRNAs differentially expressed in AF were further investigated for their ability to regulate KCNK3 mRNA and TASK‐1 protein expression in human induced pluripotent stem cells, transfected with miRNA mimics or inhibitors. Thereby, we observed that miR‐34a increases TASK‐1 expression and current and further decreases the resting membrane potential of Xenopus laevis oocytes, heterologously expressing hTASK‐1. Finally, we investigated associations between miRNA expression in atrial tissues and clinical parameters of our patient cohort. A cluster containing AF stage, left ventricular end‐diastolic diameter, left ventricular end‐systolic diameter, left atrial diameter, atrial COL1A2 (collagen alpha‐2(I) chain), and TASK‐1 protein level was associated with increased expression of miR‐25, miR‐21, miR‐34a, miR‐23a, miR‐124, miR‐1, and miR‐29b as well as decreased expression of miR‐9 and miR‐485.

Conclusions

These results suggest an important pathophysiological involvement of miRNAs in the regulation of atrial expression of the TASK‐1 potassium channel in patients with atrial cardiomyopathy.

Simvastatin regulates the proliferation, apoptosis, migration and invasion of human acute myeloid leukemia cells via miR-19a-3p/HIF-1α axis

Statins are mainly used to lower plasma cholesterol level. In addition, the anti-leukemia effect of statins has been reported, but the mechanism remains unclear.

This study aimed to explore the bioregulation of simvastatin and its mechanism in acute leukemia cell lines. Cell viability was detected by CCK-8 analysis. Apoptosis was detected through flow cytometry. Cell invasion and migration both were observed by transwell and wound healing separately. RT-qPCR and Western blot were used for determination of genes and proteins. We found that that simvastatin could regulate the biological functions of acute myeloid leukemia (AML) cells, including its proliferation, migration, invasion and apoptosis, which may be carried out by down-regulating miR-19a-3p. Overexpression of miR-19a-3p had the opposite effect in AML cells, suggesting simvastatin-inhibited AML by reducing miR-19a-3p expression. Following researches showed that HIF-1α was directly regulated by the target of miR-19a-3p. Simvastatin could reverse the adverse effects caused by miR-19a-3p mimics. Conversely, the increased expression of Mcl-1, the inhibition of caspase-3 could promote the growth of AML cells. In conclusion, simvastatin could inhibit the proliferation, migration, invasion and promote apoptosis in AML cells through miR-19a-3p/HIF-1α axis.

Tumor suppressors in acute myeloid leukemia

Acute myeloid leukemia (AML) is a very heterogeneous type of blood cancer, which presents with a high rate of mortality especially in elderly patients. Better understanding of critical players, such as molecules with tumor suppressive properties, may help to fine-tune disease classification and thereby treatment modalities for this detrimental disease. Here, we summarize well-known and established tumor suppressors as well as emerging tumor suppressors, including transcription factors (TCFs) and other transcriptional regulators, such as epigenetic modulators. In addition, we look into the versatile field of miRNAs also interfering with tumorigenesis and progression, which offer new possibilities in AML diagnosis, prognosis, and therapy.

The Potential Diagnostic Accuracy of Circulating MicroRNAs for Leukemia: A Meta-Analysis

Background:

Leukemia is a common malignant disease in the human blood system. Many researchers have proposed circulating microRNAs as biomarkers for the diagnosis of leukemia. We conducted a meta-analysis to evaluate the diagnostic accuracy of circulating miRNAs in the diagnosis of leukemia.

Methods:

A comprehensive literature search (updated to October 13, 2020) in PubMed, EMBASE, Web of Science, Cochrane Library, Wanfang database and China National Knowledge Infrastructure (CNKI) was performed to identify eligible studies. The sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and area under the curve (AUC) for diagnosing leukemia were pooled for both overall and subgroup analysis. The meta-regression and subgroup analysis were performed to explore heterogeneity and Deeks’ funnel plot was used to assess publication bias.

Results:

49 studies from 22 publications with a total of 3,489 leukemia patients and 2,756 healthy controls were included in this meta-analysis. The overall sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio and area under the curve were 0.83, 0.92, 10.8, 0.18, 59 and 0.94, respectively. Subgroup analysis shows that the microRNA clusters of plasma type could carry out a better diagnostic accuracy of leukemia patients. In addition, publication bias was not found.

Conclusions:

Circulating microRNAs can be used as a promising noninvasive biomarker in the early diagnosis of leukemia.

Identification of Acute Myeloid Leukemia Bone Marrow Circulating MicroRNAs

BACKGROUND

In addition to their roles in different biological processes, microRNAs in the tumor microenvironment appear to be potential diagnostic and prognostic biomarkers for various malignant diseases, including acute myeloid leukemia (AML). To date, no screening of circulating miRNAs has been carried out in the bone marrow compartment of AML. Accordingly, we investigated the circulating miRNA profile in AML bone marrow at diagnosis (AMLD) and first complete remission post treatment (AMLPT) in comparison to healthy donors (HD).

METHODS

Circulating miRNAs were isolated from AML bone marrow aspirations, and a low-density TaqMan miRNA array was performed to identify deregulated miRNAs followed by quantitative RT-PCR to validate the results. Bioinformatic analysis was conducted to evaluate the diagnostic and prognostic accuracy of the highly and significantly identified deregulated miRNA(s) as potential candidate biomarker(s).

RESULTS

We found several deregulated miRNAs between the AMLD vs. HD vs. AMLPT groups, which were involved in tumor progression and immune suppression pathways. We also identified significant diagnostic and prognostic signatures with the ability to predict AML patient treatment response.

CONCLUSIONS

This study provides a possible role of enriched circulating bone marrow miRNAs in the initiation and progression of AML and highlights new markers for prognosis and treatment monitoring.

Tanshinone IIA regulates human AML cell proliferation, cell cycle, and apoptosis through miR-497-5p/AKT3 axis

Background

The roots of Salvia miltiorrhiza are used in traditional Chinese medicine (TCM) and have high medicinal value. Tanshinone IIA (Tan IIA) is the active ingredient of Salvia miltiorrhiza which can inhibit the growth of acute leukemia cell lines in vitro, although the mechanism remains unclear.

Methods

CCK-8 assays and BrdU stain were used to evaluate cell proliferation ability. Western blot analysis was used to detect protein expression. miR-497-5p expression level was detected by using qRT-PCR, and Annexin V-FITC/propidium iodide (PI) was used to detect cell apoptosis.

Results

Here we reported that Tan IIA could inhibit cell proliferation, induce cell cycle arrest, and promote cell apoptosis in acute myeloid leukemia (AML) cells. Thus, Tan IIA had the anti-cancer activity in AML cell lines, which was likely mediated by up-regulation of miR-497-5p expression. Our data further showed that in AML cells, the same effects were observed with overexpression of miR-497-5p by a miR-497-5p mimic. We demonstrated that Tan IIA could inhibit the expression of AKT3 by up-regulating the expression of miR-497-5p. We subsequently identified that AKT3 was the direct target of miR-497-5p, and that treatment with Tan IIA obviously reversed the effect of treatment with an miR-497-5p inhibitor under harsh conditions. In turn, PCNA expression was increased and cleaved Caspase-3 was suppressed, which contributed to the growth of AML cells.

Conclusions

Our results showed that Tan IIA could inhibit cell proliferation in AML cells through miR-497-5p-mediated AKT3 downregulation pathway.

Regulatory and immunomodulatory role of miR-34a in T cell immunity

miRNAs are a class of non-coding RNAs and very conserve molecules that negatively regulate the expression of many genes by targeting the 3' UTR of mRNAs. miRNAs are involved in the modulation of T-cell biology during the earliest and last stages and key controllers of T-cell differentiation and function. The miR-34a, as a major hub of the regulatory network of T cells, plays an important role in T cell activation. miR-34a is widely expressed in immune cells (dendritic cells, macrophages, mast cells, B cells, and T cells) and regulates their development, function, and survival. This miRNA, by targeting over 30 genes across different cellular pathways controls immune response. miR-34a expression is controlled by p53 in transcription level. As well as, miR-34a by activating dendritic cells mediates innate immune response and increases tumor-infiltrating CD8 expression T lymphocytes. In various types of cancers and autoimmune diseases, miR-34a can regulate T cell function and become a possible significant target of microRNA-based therapy. Therefore, in this review, we focus on miR-34a-related regulatory mechanisms in T cell function and understanding mechanisms and molecules involved in this network.

Role of non-coding RNA networks in leukemia progression, metastasis and drug resistance

Early-stage detection of leukemia is a critical determinant for successful treatment of the disease and can increase the survival rate of leukemia patients. The factors limiting the current screening approaches to leukemia include low sensitivity and specificity, high costs, and a low participation rate. An approach based on novel and innovative biomarkers with high accuracy from peripheral blood offers a comfortable and appealing alternative to patients, potentially leading to a higher participation rate.

Recently, non-coding RNAs due to their involvement in vital oncogenic processes such as differentiation, proliferation, migration, angiogenesis and apoptosis have attracted much attention as potential diagnostic and prognostic biomarkers in leukemia. Emerging lines of evidence have shown that the mutational spectrum and dysregulated expression of non-coding RNA genes are closely associated with the development and progression of various cancers, including leukemia. In this review, we highlight the expression and functional roles of different types of non-coding RNAs in leukemia and discuss their potential clinical applications as diagnostic or prognostic biomarkers and therapeutic targets.

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.

MicroRNAs: pivotal regulators in acute myeloid leukemia

MicroRNAs are a class of small non-coding RNAs that are 19-22 nucleotides in length and regulate a variety of biological processes at the post-transcriptional level. MicroRNA dysregulation disrupts normal biological processes, resulting in tumorigenesis. Acute myeloid leukemia is an invasive hematological malignancy characterized by the abnormal proliferation and differentiation of immature myeloid cells. Due to the low 5-year survival rate, there is an urgent need to discover novel diagnostic markers and therapeutic targets. In recent years, microRNAs have been shown to play important roles in hematological malignancies by acting as tumor suppressors and oncogenes. MicroRNAs have the potential to be a breakthrough in the diagnosis and treatment of acute myeloid leukemia. In this review, we summarize the biology of microRNAs and discuss the relationships between microRNA dysregulation and acute myeloid leukemia in the following aspects: signaling pathways, the abnormal biological behavior of acute myeloid leukemia cells, the clinical application of microRNAs and competing endogenous RNA regulatory networks.

High serum extracellular vesicle miR-10b expression predicts poor prognosis in patients with acute myeloid leukemia

BACKGROUND

Increasing evidence have demonstrated that serum extracellular vesicle microRNAs (EV-miRNAs) are promising noninvasive biomarkers for various cancer types.

OBJECTIVE

In this study, we aimed to investigate and evaluate the potential clinical significance of serum EV-miR-10b for acute myeloid leukemia (AML).

METHODS

Blood samples were collected from a cohort of 95 de novo AML patients and 80 healthy individuals. Of all AML patients, 51 patients were considered as cytogenetic normal AML (CN-AML). Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) was performed to measure the expression levels of serum EV-miR-10b.

RESULTS

The extracellular vesicles we extracted from the serum samples were positive for EV/exosome markers including TSG101, CD63, Flotillin-1 and CD9. The expression levels of serum EV-miR-10b were significantly higher in AML/CN-AML patients than healthy controls. In addition, serum EV-miR-10b expression was strongly correlated with aggressive clinical characteristics. Moreover, receiver operating characteristic analysis showed serum EV-miR-10b yielded an area under the curve of 0.875, with 77.89% specificity and 82.50% sensitivity in identifying AML patients from normal controls. Furthermore, AML patients with higher serum EV-miR-10b expression had significantly shorter survival and serum EV-miR-10b was demonstrated to be an independent prognostic marker for overall survival in AML.

CONCLUSIONS

Taken together, serum EV-miR-10b might serve as a promising biomarker for predicting the prognosis of AML.

LncRNA ANRIL promotes cell proliferation, migration and invasion during acute myeloid leukemia pathogenesis via negatively regulating miR-34a

OBJECTIVE

LncRNA ANRIL (antisense non-coding RNA in the INK4 locus) was highly expressed in acute myeloid leukemia (AML) patients to promote AML pathogenesis. In this study, we aimed to investigate the roles and molecular events of ANRIL associated with AML progression.

METHODS

Expression patterns of ANRIL and miR-34a in the bone marrow (BM) samples and cell lines were determined using qRT-PCR. Cell proliferation, apoptosis, migration and invasion of cells with ANRIL knockdown or miR-34a overexpression were assessed by CCK-8, EdU staining, flow cytometry and Transwell assays, respectively. The dual-luciferase reporter assay was employed to validate the relationship between miR-34a and Histone deacetylase 1 (HDAC1). The binding of E2 F1 (E2 F transcription factor 1) with gene promoter was analyzed by ChIP. Furthermore, the tumorigenicity of AML was determined by xenograft transplantation in nude mice.

RESULTS

ANRIL was up-regulated both in the BM samples from AML patients and cell lines (HL-60 and THP-1), of which expression was negatively correlated with miR-34a expression. ANRIL knockdown inhibited cell proliferation, migration and invasion but promoted apoptosis of AML cells, while overexpression of miR-34a exerted opposite effects. miR-34a was verified as a downstream gene targeted by ANRIL. Moreover, HDAC1 was a direct target of miR-34a, and HDAC1 overexpression impaired the recruitment of E2 F1 to ASPP2 (apoptosis stimulating proteins of p53) gene promoter. ANRIL knockdown significantly inhibited the tumorigenesis of AML.

CONCLUSION

ANRIL promotes AML development through HDAC1-mediated epigenetic suppression of ASPP2 via negatively regulating miR-34a, which might serve as a therapeutic target for AML treatment.

MiR-340 Is a Biomarker for Selecting Treatment Between Chemotherapy and Allogeneic Transplantation in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) requires refined risk stratification tools to drive decisions concerning effective therapeutic strategies. Here, genome-wide screening was carried out for identifying miRNA molecules capable of predicting treatment outcome in AML patients based on the TCGA dataset. We identified miR-340 as a prognostic factor for selecting treatment between chemotherapy and allogeneic transplantation (allo-HSCT). In multivariable analyses, low miR-340 expression independently predicted reduced OS (HR = 2.07, P = 0.004) and EFS (HR = 1.909, P = 0.01) independent of other well-known prognostic factors. Meanwhile, allo-HSCT overcome deleterious outcomes related to low miR-340. Cases administered allo-HSCT showed markedly improved OS (HR = 0.316, P < 0.0001) and EFS (HR = 0.391, P = 0.002) in comparison with those receiving chemotherapy in the low miR-340 group. Gene expression assessment revealed that elevated miR-340 amounts were negatively correlated with HOXA/HOXB cluster levels, as well as the amounts of the HOX cofactor MEIS1. Strikingly, in silico analysis pointing to HOXA10, HOXB2, and MEIS1 as miR-340 targets. The miR-340 expression may help identify cases requiring strategies for selecting the optimal therapeutic option between chemotherapy and allo-HCST. AML cases showing low miR-340 levels should be strongly considered for early allo-HSCT treatment.

MicroRNA-31 is a potential biomarker for screening B-lymphoblastic leukemia in children

The present study aimed to investigate the expression and significance of microRNA-31 (miR-31) in children with acute B-lymphoblastic leukemia (B-ALL). Bone marrow specimens and peripheral blood were collected from children with B-ALL (n=38) and healthy controls (n=18). Total RNA was extracted and the expression levels of miR-31 were measured using quantitative PCR. In addition, a receiver operating characteristic curve was generated, and the area under the curve (AUC) was calculated to evaluate the diagnostic value of miR-31 for the development of B-ALL. miR-31 expression was significantly lower in the B-ALL group compared with in the control group (P<0.05). Additionally, the expression levels of miR-31 in the B-ALL group before treatment were markedly lower than in the B-ALL group after treatment, and miR-31 expression was significantly lower after 30 days of treatment compared with after 12 weeks of treatment. Furthermore, miR-31 expression in the group of children ≥10 years of age was higher than that in the group of children <10 years of age. Furthermore, the expression levels of miR-31 were higher in the low-risk group compared with in the medium- and high-risk groups (P<0.05). When the cutoff value was set at 1.8, the AUC of miR-31 for B-ALL diagnosis was 0.915 (95% CI, 0.828-1.000; P<0.0001), with a sensitivity and specificity of 80.8 and 100%, respectively. In conclusion, miR-31 may exert an anticancer role in B-ALL in children and may be a potential marker to assist in diagnosis and prognostic prediction.

MicroRNA-21 promotes proliferation in acute myeloid leukemia by targeting Krüppel-like factor 5

Abnormal expression of microRNA (miR)-21 has been reported in various types of cancers. However, the role and mechanism of miR-21 remain to be elucidated in acute myeloid leukemia (AML). In the present study, it was observed that miR-21 was upregulated and Krüppel-like factor 5 (KLF5) was downregulated in AML cells compared with normal bone marrow cells. Dual luciferase reporter assays revealed that KLF5 was a direct target of miR-21. Indeed, miR-21 overexpression resulted in a downregulation of KLF5 expression, while miR-21 inhibition had the opposite effect in AML cells. In addition, miR-21 overexpression promoted the proliferation of AML cells in vitro. Notably, using a mouse xenograft model, miR-21 overexpression was demonstrated to result in enhanced tumor growth and suppressed KLF5 expression in the xenograft tumors in vivo. In conclusion, the present results indicated that miR-21 promoted proliferation through directly regulating KLF5 expression in AML cells. miR-21 may thus serve as an oncogene in AML, providing a potential target for AML therapy.

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.

Roles of MicroRNA-34a in Epithelial to Mesenchymal Transition, Competing Endogenous RNA Sponging and Its Therapeutic Potential

MicroRNA-34a (miR-34a), a tumor suppressor, has been reported to be dysregulated in various human cancers. MiR-34a is involves in certain epithelial-mesenchymal transition (EMT)-associated signal pathways to repress tumorigenesis, cancer progression, and metastasis. Due to the particularity of miR-34 family in tumor-associated EMT, the significance of miR-34a is being increasingly recognized. Competing endogenous RNA (ceRNA) is a novel concept involving mRNA, circular RNA, pseudogene transcript, and long noncoding RNA regulating each other’s expressions using microRNA response elements to compete for the binding of microRNAs. Studies showed that miR-34a is efficient for cancer therapy. Here, we provide an overview of the function of miR-34a in tumor-associated EMT. ceRNA hypothesis plays an important role in miR-34a regulation in EMT, cancer progression, and metastasis. Its potential roles and challenges as a microRNA therapeutic candidate are discussed. As the negative effect on cancer progression, miR-34a should play crucial roles in clinical diagnosis and cancer therapy.

microRNA-628 inhibits the proliferation of acute myeloid leukemia cells by directly targeting IGF-1R

Background

A variety of microRNAs (miRNAs) are aberrantly expressed in acute myeloid leukemia (AML), and these dysregulated miRNAs perform crucial roles in tumorigenesis and progression of AML. miR-628-3p (miR-628), one of the miRNAs dysregulated in multiple types of human cancers, exerts antitumor roles in different cancer types. However, no specific study has explored the expression pattern and role of miR-628 in AML.

Materials and methods

In this study, RT-qPCR was performed to detect miR-628 expression in AML tissues and cell lines. CCK-8 assay, flow cytometry analysis and xenograft tumor experiment was carried out to determine the functions of miR-628 in AML cells. The possible mechanism underlying the activity of miR-628 in AML cells was also explored using a series of experiments.

Results

Our results revealed the downregulated expression of miR-628 in patients with AML and AML cell lines. Ectopic expression of miR-628 resulted in the inhibition of AML cell proliferation and induction of cell cycle arrest and apoptosis in vitro and attenuation of tumor growth in vivo. Insulin-like growth factor 1 receptor (IGF-1R) was identified as a direct target gene of miR-628 in AML cells. IGF-1R expression was upregulated in patients with AML and upregulation of IGF-1R expression inversely correlated with miR-628 level. Furthermore, IGF-1R knockdown imitated the tumor suppressive effect of miR-628 in AML cells. Restoration of IGF-1R expression abrogated the effects of miR-628 on the proliferation, cycle status, and apoptosis rate of AML cells. miR-628 inhibited the activation of phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/protein kinase B (Akt) pathway in AML cells both in vitro and in vivo through the inhibition of IGF-1R expression.

Conclusion

Our results demonstrate that miR-628 exhibits antitumor effects in AML through the direct targeting of IGF-1R and regulation of PI3K/Akt pathway, suggestive of its potential role as a therapeutic target in patients with this aggressive hematological malignant tumor.

miR‑1271‑5p inhibits cell proliferation and induces apoptosis in acute myeloid leukemia by targeting ZIC2

MicroRNAs (miRNAs) have been demonstrated to regulate the progression of numerous types of cancer, including acute myeloid leukemia (AML). Previous studies demonstrated that miR‑1271‑5p functions as a tumor suppressor; however, the roles of miR‑1271‑5p in AML remain unknown. In the present study, miR‑1271‑5p was significantly downregulated in AML tissues compared with normal tissues by reverse transcription‑quantitative polymerase chain reaction analysis. Furthermore, the expression levels of miR‑1271‑5p in patients with AML may function as a prognostic marker. In addition, overexpression of miR‑1271‑5p significantly suppressed the proliferation and induced apoptosis of AML cells by Cell Counting kit‑8 and fluorescence activated cell sorter assays; miR‑1271‑5p downregulation exhibited opposing effects. Additionally, transcription factor ZIC2 may be a direct target of miR‑1271‑5p in AML cells, which was demonstrated by a luciferase reporter assay and RNA pulldown assay. Overexpression of miR‑1271‑5p significantly reduced the mRNA and protein expression levels of ZIC2 in AML193 and OCI‑AML2 cells by reverse transcription‑quantitative polymerase chain reaction analysis and western blotting. Furthermore, an inverse correlation between miR‑1271‑5p and ZIC2 expression in AML samples was observed. In summary, ZIC2 was upregulated in AML tissues, and restoration of ZIC2 expression was able to promote the proliferation and reduce the apoptosis of AML cells transfected with miR‑1271‑5p mimics. The results of the present study demonstrated that miR‑1271‑5p inhibited the progression of AML by targeting ZIC2.

MiRNA Dysregulation in Childhood Hematological Cancer

For decades, cancer biology focused largely on the protein-encoding genes that have clear roles in tumor development or progression: cell-cycle control, apoptotic evasion, genome instability, drug resistance, or signaling pathways that stimulate growth, angiogenesis, or metastasis. MicroRNAs (miRNAs), however, represent one of the more abundant classes of cell modulators in multicellular organisms and largely contribute to regulating gene expression. Many of the ~2500 miRNAs discovered to date in humans regulate vital biological processes, and their aberrant expression results in pathological and malignant outcomes. In this review, we highlight what has been learned about the roles of miRNAs in some of the most common human pediatric leukemias and lymphomas, along with their value as diagnostic/prognostic factors.