Micro-ribonucleic acid-155 is a direct target of Meis1, but not a driver in acute myeloid leukemia

Evaluation of the HOXA9 and MEIS1 genes as a potential biomarker in adult acute myeloid leukemia

Background

Acute myeloid leukemia (AML) is a heterogeneous disorder encompassing a set of hematopoietic tumors that develop when the myeloid precursor cells undergo disproportionate clonal proliferation. Homeobox A 9 (HOXA9) is a pioneer transcription factor in AML pathogenesis along with its cofactor myeloid ecotropic integration site 1 (MEIS1). Our work aimed to evaluate the different expression levels of HOXA9 and MEIS1 genes and their diagnostic and prognostic significance in adult Egyptian patients with de novo AML. The study was carried out on 91 de novo AML Egyptian patients and 41 healthy individuals. Bone marrow samples were obtained from both patients and controls and then tested by reverse transcription-quantitative polymerase chain reaction to assess the mRNA expression in the studied genes.

Results

HOXA9 and MEIS1 gene expression levels were significantly elevated in AML patients compared to controls (p < 0.001). There was a statistically significant positive correlation between HOXA9 and MEIS1 gene expression in AML patients. However, there was no association between HOXA9 and MEIS1 gene expression levels and disease-free survival (DFS) and overall survival (OS) (p = 0.264 and 0.351, respectively).

Conclusion

HOXA9 and MEIS1 genes are highly expressed in Egyptian AML patients, suggesting their interesting pathogenic role in AML. They could be used as markers for the diagnosis of AML, but not for the disease prognosis.

Elucidating the importance and regulation of key enhancers for human MEIS1 expression

Myeloid ecotropic virus insertion site 1 (MEIS1) is essential for normal hematopoiesis and is a critical factor in the pathogenesis of a large subset of acute myeloid leukemia (AML). Despite the clinical relevance of MEIS1, its regulation is largely unknown. To understand the transcriptional regulatory mechanisms contributing to human MEIS1 expression, we created a knock-in green florescent protein (GFP) reporter system at the endogenous MEIS1 locus in a human AML cell line. Using this model, we have delineated and dissected a critical enhancer region of the MEIS1 locus for transcription factor (TF) binding through in silico prediction in combination with oligo pull-down, mass-spectrometry and knockout analysis leading to the identification of FLI1, an E-twenty-six (ETS) transcription factor, as an important regulator of MEIS1 transcription. We further show direct binding of FLI1 to the MEIS1 locus in human AML cell lines as well as enrichment of histone acetylation in MEIS1-high healthy and leukemic cells. We also observe a positive correlation between high FLI1 transcript levels and worse overall survival in AML patients. Our study expands the role of ETS factors in AML and our model constitutes a feasible tool for a more detailed understanding of transcriptional regulatory elements and their interactome.

miR-429 inhibits osteosarcoma progression by targeting HOXA9 through suppressing Wnt/β-catenin signaling pathway

Osteosarcoma (OS) is the most commonly diagnosed malignant cancer of bone that occurs in adolescents and children. Mounting number of studies have indicated that miRNAs are increasingly playing fundamental roles in OS development. Thus, the biological function of miR-429 in OS progression was explored. The results of RT-qPCR revealed that miR-429 was downregulated in OS tissues and OS cell lines (MG-63, U2OS, Saos-2) while homeobox A9 (HOXA9) was markedly increased. Moreover, HOXA9 was confirmed as a direct target of miR-429 by using luciferase reporter assay. It was identified that miR-429 exhibited a suppressive effect on OS progression while HOXA9 showed the oncogenic function in OS progression by using MTT and Transwell assays. More importantly, rescue assays manifested that HOXA9 can partially overturn the suppressive effect of miR-429 on OS. Overexpression of miR-429 inhibited the activation of Wnt/β-catenin signaling pathway. In conclusion, miR-429 suppressed OS progression by targeting HOXA9 through Wnt/β-catenin pathway.

miR-155 Accelerates the Growth of Human Liver Cancer Cells by Activating CDK2 via Targeting H3F3A

miR-155 is associated with the promotion of tumorigenesis. Herein, we indicate that abnormal miR-155 was negatively correlated with the expression of P21WAF1/Cip1. Our results suggest that miR-155 alters the transcriptome and inhibits the expression of H3F3A in liver cancer cells. Therefore, miR-155 inhibits the methylation modification of histone H3 on the 27^th lysine. Notably, on the one hand, miR-155-dependent CTCF loops cause the CDK2 interacting with cyclin E in liver cancer cells; on the other hand, miR-155 promotes the phosphorylation modification of CDK2 by inhibiting H3F3A. Subsequently, miR-155 competitively blocks the binding of RNA polymerase II (RNA Pol II) to the P21WAF1/CIP1 promoter by increasing the phosphorylation of CDK2, inhibiting the transcription and translation of P21WAF1/CIP1. Strikingly, excessive P21WAF1/CIP1 abolishes the cancerous function of miR-155. In conclusion, miR-155 can play a positive role in the development of liver cancer and influence a series of gene expression through epigenetic regulation.

Homeobox gene Meis1 modulates cardiovascular regeneration

Regeneration of cardiomyocytes, endothelial cells and vascular smooth muscle cells (three major lineages of cardiac tissues) following myocardial infarction is the critical step to recover the function of the damaged heart. Myeloid ecotropic viral integration site 1 (Meis1) was first discovered in leukemic mice in 1995 and its biological function has been extensively studied in leukemia, hematopoiesis, the embryonic pattering of body axis, eye development and various genetic diseases, such as restless leg syndrome. It was found that Meis1 is highly associated with Hox genes and their cofactors to exert its regulatory effects on multiple intracellular signaling pathways. Recently with the advent of bioinformatics, biochemical methods and advanced genetic engineering tools, new function of Meis1 has been found to be involved in the cell cycle regulation of cardiomyocytes and endothelial cells. For example, inhibition of Meis1 expression increases the proliferative capacity of neonatal mouse cardiomyocytes, whereas overexpression of Meis1 results in the reduction in the length of cardiomyocyte proliferative window. Interestingly, downregulation of one of the circular RNAs, which acts downstream of Meis1 in the cardiomyocytes, promotes angiogenesis and restores the myocardial blood supply, thus reinforcing better regeneration of the damaged heart. It appears that Meis1 may play double roles in modulating proliferation and regeneration of cardiomyocytes and endothelial cells post-myocardial infarction. In this review, we propose to summarize the major findings of Meis1 in modulating fetal development and adult abnormalities, especially focusing on the recent discoveries of Meis1 in controlling the fate of cardiomyocytes and endothelial cells.