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Background The Foxo3 gene, belonging to the forkhead family, is one of the classes of transcription factors characterized by a forkhead DNA-binding domain, which usually considered being a cancer suppressor gene. Circ-Foxo3 is a circular structure which connects the 3’end to the 5’end. Scholars detected that circ-Foxo3 could compete with Foxo3 for binding to some miRNAs. Methods In this study, we will test the expression of Foxo3 and circ-Foxo3 in de novo acute myeloid leukemia (AML) patients to explore the relationship between Foxo3 gene and circ-Foxo3 . All the de novo AML samples and normal control samples was measured by real-time quantitative PCR. A receiver operating characteristic curve was conducted to differentiate AML patients from control people. Association of Foxo3 expression and overall survival was conducted by Kaplan-Meier survival analysis. Results We found that the expression of Foxo3 gene in de novo patients was significantly lower than control samples ( P  = 0.009). Meanwhile, circ-Foxo3 also expressed lower in de novo AML patients than in control samples ( P  = 0.040). In different classifications, this trend could be observed more remarkably. In non-M3 patients, the Foxo3 high patients’ survival time was longer than Foxo3 low patients ( P  = 0.002). Besides, in non-favorable risk groups, patients with low expression of Foxo3 had longer survival time than Foxo3 high patients ( P  = 0.004). Furthermore, in normal Karyotypic patients, the overall survival time of patients with high-expressed Foxo3 was significantly longer than those with low expression ( P  = 0.034). Besides, Pearson analysis was also conducted between these two genes in AML patients. Results revealed that they were positively correlated (R = 0.63, P  < 0.001). Conclusion In conclusion, we found that low expression of circ-Foxo3 and Foxo3 were frequent in AML patients, and patients with high expression of Foxo3 often had a trend of better prognosis.

Although mechanistic studies clarifying the molecular underpinnings of AML have facilitated the development of several novel targeted therapeutics, most AML patients still relapse. Thus, overcoming the inherent and acquired resistance to current therapies remains an unsolved clinical problem. While current diagnostic modalities are primarily defined by gross morphology, cytogenetics, and to an extent, by deep targeted gene sequencing, there is an ongoing demand to identify newer diagnostic, therapeutic and prognostic biomarkers for AML. Recent interest in exploring the role of circular RNA (circRNA) in elucidating AML biology and therapy resistance has been promising. This review discerns the circular RNAs’ evolving role on the same scientific premise and attempts to identify its potential in managing AML.

Background: Acute myeloid leukemia (AML) is one of the most common malignant and aggressive hematologic tumors, and its pathogenesis is associated with abnormal post-transcriptional regulation. Unbalanced competitive endogenous RNA (ceRNA) promotes tumorigenesis and progression, and greatly contributes to tumor risk classification and prognosis. However, the comprehensive analysis of the circular RNA (circRNA)-long non-coding RNA (lncRNA)-miRNA-mRNA ceRNA network in the prognosis of AML is still rarely reported. Method: We obtained transcriptome data of AML and normal samples from The Cancer Genome Atlas (TCGA), Genotype-tissue Expression (GTEx), and Gene Expression Omnibus (GEO) databases, and identified differentially expressed (DE) mRNAs, lncRNAs, and circRNAs. Then, the targeting relationships among lncRNA-miRNA, circRNA-miRNA, and miRNA-mRNA were predicted, and the survival related hub mRNAs were further screened by univariate and multivariate Cox proportional hazard regression. Finally, the AML prognostic circRNA-lncRNA-miRNA-mRNA ceRNA regulatory network was established. Results: We identified prognostic 6 hub mRNAs (TM6SF1, ZMAT1, MANSC1, PYCARD, SLC38A1, and LRRC4) through Cox regression model, and divided the AML samples into high and low risk groups according to the risk score obtained by multivariate Cox regression. Survival analysis verified that the survival rate of the high-risk group was significantly reduced (p < 0.0001). The prognostic ceRNA network of 6 circRNAs, 32 lncRNAs, 8 miRNAs, and 6 mRNAs was established according to the targeting relationship between 6 hub mRNAs and other RNAs. Conclusion: In this study, ceRNA network jointly participated by circRNAs and lncRNAs was established for the first time. It comprehensively elucidated the post-transcriptional regulatory mechanism of AML, and identified novel AML prognostic biomarkers, which has important guiding significance for the clinical diagnosis, treatment, and further scientific research of AML.

Background Drug resistance and immune escape continue to contribute to poor prognosis in AML. Increasing evidence suggests that exosomes play a crucial role in AML immune microenvironment. Methods Sanger sequencing, RNase R and fluorescence in situ hybridization were performed to confirm the existence of circ_0006896. The role of circ_0006896 in the progression of AML was assessed by in vitro and in vivo functional experiments. Flow cytometry, RT-qPCR and adoptive T cell-transfer immunotherapy were conducted to assess the function of exosomal circ_0006896 in CD8 + T cell dysfunction. RNA pull-down assay, mass spectrometry, immunofluorescence, co-immunoprecipitation and western blot were performed to identify and confirm the circ_0006896 interacting proteins. Results CircRNA expression patterns in exosomes differ significantly between AML and controls compared to lncRNAs or mRNAs. A new crucial exosomal circRNA, circ_0006896, is upregulated in both AML cells and exosomes and correlates with the prognosis and relapse of AML. In vitro and in vivo studies suggest that circ_0006896 significantly promotes AML cell proliferation, reduces chemotherapy sensitivity, and more importantly, impairs the efficacy of adoptive T cell-transfer immunotherapy. Mechanistically, circ_0006896 physically interacts with the catalytic domain of histone deacetylase HDAC1, decreasing histone H3 acetylation, and impairing the transcription of genes involved in arachidonic acid metabolism, ultimately inhibiting lipid peroxidation and ferroptosis in AML cells. Exosomal circ_0006896 disrupts CD8 + T cell function by interacting with HDAC1, impairing LEF1 transcription and subsequently decreasing the expression of cytotoxic molecules IFN-γ and Granzyme B. Conclusions We demonstrate a self-driven progression mediated by exosomal circRNAs and CD8 + T cells, highlighting the potential of targeting circRNAs in AML immunotherapy.

Acute myeloid leukemia (AML) is a hematological malignancy with a high relapse rate and a poor survival rate. The circular RNA circPVT1 and myocyte enhancer factor 2A (MEF2A) have unique functions in the progression of AML; however, the underlying mechanisms and clinical significance remain to be clarified. Bioinformatics and database analyses were used to assess the transcription factors and target genes of circPVT1. Dual-luciferase reporter gene and argonaute 2-RNA immunoprecipitation assays were used to verify the targeted relationships. The expression levels of related genes and proteins were detected by reverse transcription-quantitative PCR and western blotting. Cell viability and apoptosis were detected by Cell Counting Kit-8 assay and flow cytometry, respectively. The results revealed that circPVT1 was highly expressed in AML samples and cell lines, and that MEF2A regulated the expression of circPVT1. MEF2A overexpression promoted cell viability and epithelial-mesenchymal transition (EMT), and inhibited cell apoptosis. In addition, circPVT1 was revealed to target the regulation of microRNA (miR)-455-3p, and miR-455-3p targeted the regulation of MCL1 expression, thus indicating that circPVT1 promoted MCL1 expression through its interaction with miR-455-3p. Furthermore, cells were transfected with the small interfering RNA-(si)-circPVT1, miR-455-3p inhibitor or si-MCL1, and si-circPVT1 and si-MCL1 inhibited the viability and EMT of NB4 and HL-60 cells. However, the miR-455-3p inhibitor had the opposite effect on cells. In conclusion, MEF2A may act as a transcription factor of circPVT1 to promote the malignant process of AML, and knockdown of circPVT1 could inhibit the viability and EMT of AML cells through the miR-455-3p/MCL1 axis.

Circular RNAs (circRNAs) are abundantly expressed in the haematopoietic compartment, but knowledge on their diversity among blood cell types is still limited. Nevertheless, emerging data indicate an array of circRNA functions exerted through interactions with other RNAs and proteins, by translation into peptides, and circRNA involvement as regulatory molecules in many biological processes and cancer mechanisms. Interestingly, the role of specific circRNAs in leukemogenesis has been disclosed by a few studies, mostly in acute myeloid leukemia. In this study, circRNA expression in B-cells, T-cells and monocytes of healthy subjects is described, including putative new circRNA genes. Expression comparison considered 6,228 circRNAs and highlighted cell population-specific expression and exon usage patterns. Differential expression has been confirmed by qRT-PCR for circRNAs specific of B-cells (circPAX5, circAFF3, circIL4R, and circSETBP1) or T-cells (circIKZF1, circTNIK, circTXK, and circFBXW7), and for circRNAs from intronic (circBCL2) and intergenic regions that were overexpressed in lymphocytes. Starting from this resource of circRNA expression in mature blood cell populations, targeted examination identified striking and generalized upregulated expression of circPAX5, circPVT1 and circHIPK3 in pediatric B-precursor acute lymphoblastic leukemia, and disclosed circRNAs with variable expression across cytogenetic subtypes.

AML is a complex disease caused by multiple molecular mechanisms. As an important regulatory molecule, the role of circRNA in AML is not fully understood. By performing high-throughput sequencing on clinical samples, we systematically identified the differences in circRNA expression and distribution between AML and healthy donor samples. One circular RNA, circAFF2, was found to be significantly upregulated in AML patients. Functional studies showed that knockdown of circAFF2 could significantly inhibit the proliferation of AML cells and promote their apoptosis. Overexpression of circAFF2 can have opposite effects. In vivo experiments showed that transplantation of AML cells with circAFF2 knockdown slowed the proliferation and infiltration and prolonged the survival time of mice compared to controls. Further studies showed that circAFF2 can promote the degradation of PML mRNA by binding to the 3’UTR of PML mRNA, thereby affecting the proliferation and apoptosis of AML cells. In conclusion, our work demonstrates that circAFF2 can bind to PML mRNA to regulate AML cell function, providing new insights into the mechanism of AML development and potential targets for clinical diagnosis and treatment.

Background Circular RNAs (circRNAs) constitute a family of transcripts with unique structures and have been confirmed to be critical in tumorigenesis and to be potential biomarkers or therapeutic targets. However, only a few circRNAs have been functionally characterized in pediatric acute myeloid leukemia (AML). Methods Here, we investigated the expression pattern of circRNAs in pediatric AML using a circRNA microarray. The characteristics, potential diagnostic value, and prognostic significance of circRNF220 were evaluated. A series of functional experiments were performed to investigate the role of circRNF220 in primary pediatric AML cells. Then we investigated the aberrant transcriptional networks regulated by circRNF220 in primary AML cells by RNA-seq. Furthermore, biotin RNA pulldown assays were implemented to verify the relationship between circRNF220 and miR-30a. Results We identified a circRNA, circRNF220, which was specifically abundant in and accumulated in the peripheral blood and bone marrow of pediatric patients with AML. It could distinguish AML from ALL and other hematological malignancies with high sensitivity and specificity. Significantly, circRNF220 expression independently predicted prognosis, while high expression of circRNF220 was an unfavorable prognostic marker for relapse. Furthermore, we characterized the function of circRNF220 and found that circRNF220 knockdown specifically inhibited proliferation and promoted apoptosis in AML cell lines and primary cells. Mechanistically, circRNF220 may act as an endogenous sponge of miR-30a to sequester miR-30a and inhibit its activity, which increases the expression of its targets MYSM1 and IER2 and implicated in AML relapse. Conclusions Collectively, these findings demonstrated that circRNF220 could be highly efficient and specific for the accurate diagnosis of pediatric AML, with implications for relapse prediction.

Purpose Circular RNA (circRNA) is a type of novel non-coding RNA with close involvement in the tumorigenesis and treatment response of leukemias. This study aimed to screen and validate candidate circRNAs that estimate disease risk and response to induction therapy of pediatric acute myeloid leukemia (AML). Methods Bone marrow samples were obtained from 4 complete response (CR) pediatric AML patients, 4 non-CR pediatric AML patients, and 4 controls to screen differentially expressed circRNAs (DECs) through microarray analyses. Ten candidate circRNAs were selected and validated in 40 pediatric AML patients and 10 controls through reverse transcription-quantitative polymerase chain reaction. Results Microarray assay discovered 378 upregulated DECs and 688 downregulated DECs in pediatric AML patients vs. controls; 832 upregulated DECs and 950 downregulated DECs in CR AML patients vs. non-CR AML patients. Then cross-analysis identified 441 DECs that both related to pediatric AML risk and CR achievement. Further validation of ten candidate circRNAs in larger sample-sized populations showed that circ_0032891, circ_0076995, circ_0014352, circ_0047663, circ_0007444, circ_0001684, circ_0000544, and circ_0005354 were related to pediatric AML risk; circ_0032891, circ_0076995, circ_0014352, circ_0047663, circ_0007444, circ_0001684, and circ_0000544 were related to CR achievement in pediatric AML patients. Regarding the correlation of candidate circRNAs with survival profile, only circ_0032891, circ_0076995, and circ_0000544 forecasted event-free survival; circ_0076995 and circ_0001684 estimated overall survival in pediatric AML patients. Conclusion CircRNA profile is intensively implicated in the disease risk and treatment response of pediatric AML, especially that circ_0032891, circ_0000544, circ_0076995, and circ_0001684 are related to pediatric AML risk, CR achievement, and survival.

Non coding RNAs (ncRNAs) have emerged as regulators of human carcinogenesis by affecting the expression of key tumor suppressor genes and oncogenes. They are divided into short and long ncRNAs, according to their length. Circular RNAs (circRNAs) are included in the second group and were recently discovered as being originated by back-splicing, joining either single or multiple exons, or exons with retained introns. The human Plasmacytoma Variant Translocation 1 ( PVT1 ) gene maps on the long arm of chromosome 8 (8q24) and encodes for 52 ncRNAs variants, including 26 linear and 26 circular isoforms, and 6 microRNAs. PVT1 genomic locus is 54 Kb downstream to MYC and several interactions have been described among these two genes, including a feedback regulatory mechanism. MYC -independent functions of PVT1 / circPVT1 have been also reported, especially in the regulation of immune responses. We here review and discuss the role of both PVT1 and circPVT1 in the hematopoietic system. No information is currently available concerning their transforming ability in hematopoietic cells. However, present literature supports their cooperation with a more aggressive and/or undifferentiated cell phenotype, thus contributing to cancer progression. PVT1 / circPVT1 upregulation through genomic amplification or rearrangements and/or increased transcription, provides a proliferative advantage to malignant cells in acute myeloid leukemia, acute promyelocytic leukemia, Burkitt lymphoma, multiple myeloma (linear PVT1 ) and acute lymphoblastic leukemia ( circPVT1 ). In addition, PVT1 and circPVT1 regulate immune responses: the overexpression of the linear form in myeloid derived suppressor cells induced immune tolerance in preclinical tumor models and circPVT1 showed immunosuppressive properties in myeloid and lymphoid cell subsets. Overall, these recent data on PVT1 and circPVT1 functions in hematological malignancies and immune responses reflect two faces of the same coin: involvement in cancer progression by promoting a more aggressive phenotype of malignant cells and negative regulation of the immune system as a novel potential therapy-resistance mechanism.