m6A RNA methylation regulators predict prognosis and indicate characteristics of tumour microenvironment infiltration in acute myeloid leukaemia

Patients with acute myeloid leukaemia (AML) have poor prognoses and low overall survival (OS) rates owing to its heterogeneity and the complexity of its tumour microenvironment (TME). N6-methyladenosine (m6A) modification plays a key role in the initiation and progression of haematopoietic malignancies. However, the underlying function of m6A regulators in AML remains elusive. This study thoroughly analysed the m6A modification features of 177 AML patients based on 22 m6A regulators. Utilizing unsupervised clustering, we determined three distinct m6A modification patterns related to different biological functions, TME cell-infiltrating characteristics and clinical outcomes. Additionally, a risk score was constructed based on six m6A regulators-associated prognostic signatures and was validated as an independent and valuable prognostic factor for AML. Patients with a low-risk score exhibited better survival than those with a high-risk score. Many m6A regulators were aberrantly expressed in AML, among which METTL14, YTHDC2, ZC3H13 and RBM15 were observed to be associated with the OS of AML. In addition, these four m6A regulators were found to be noticeably related to the immune checkpoint inhibitor (ICI) treatments. Finally, we verified the expression levels of these four m6A regulators in AML and healthy samples and three groups of AML patients with different risk categories. Collectively, our study indicates that the m6A modification pattern is involved in TME immune-infiltrating characteristics and prognosis in AML. A better understanding of the m6A modification pattern will help enhance our knowledge of the molecular mechanisms of AML and develop potential prognosis prediction indicators and more effective immunotherapeutic strategies

Asymmetric Stratification-Induced Polarity Loss and Coordinated Individual Cell Movements Drive Directional Migration of Vertebrate Epithelium.

Collective migration is essential for development, wound repair, and cancer metastasis. For most collective systems, "leader cells" determine both the direction and the power of the migration. It has remained unclear, however, how the highly polarized vertebrate epithelium migrates directionally during branching morphogenesis. We show here that, unlike in other systems, front-rear polarity of the mammary epithelium is set up by preferential cell proliferation in the front in response to the FGF10 gradient. This leads to frontal stratification, loss of apicobasal polarity, and leader cell formation. Leader cells are a dynamic population and move faster and more directionally toward the FGF10 signal than do follower cells, partly because of their intraepithelial protrusions toward the signal. Together, our data show that directional migration of the mammary epithelium is a unique multistep process and that, despite sharing remarkable cellular and molecular similarities, vertebrate and invertebrate epithelial branching are fundamentally distinct processes

Asymmetric Stratification-Induced Polarity Loss and Coordinated Individual Cell Movements Drive Directional Migration of Vertebrate Epithelium.

Collective migration is essential for development, wound repair, and cancer metastasis. For most collective systems, "leader cells" determine both the direction and the power of the migration. It has remained unclear, however, how the highly polarized vertebrate epithelium migrates directionally during branching morphogenesis. We show here that, unlike in other systems, front-rear polarity of the mammary epithelium is set up by preferential cell proliferation in the front in response to the FGF10 gradient. This leads to frontal stratification, loss of apicobasal polarity, and leader cell formation. Leader cells are a dynamic population and move faster and more directionally toward the FGF10 signal than do follower cells, partly because of their intraepithelial protrusions toward the signal. Together, our data show that directional migration of the mammary epithelium is a unique multistep process and that, despite sharing remarkable cellular and molecular similarities, vertebrate and invertebrate epithelial branching are fundamentally distinct processes

Secreted insulin-like growth factor binding protein 5 functions as a tumor suppressor and chemosensitizer through inhibiting insulin-like growth factor 1 receptor/protein kinase B pathway in acute myeloid leukemia

Background: In addition to being secreted into the intercellular spaces by exocytosis, insulin-like growth factor binding protein 5 (IGFBP5) may also remain in the cytosol or be transported to the nucleus. Depending on the different cellular context and subcellular distribution, IGFBP5 can act as a tumor suppressor or promoter through insulin-like growth factor -dependent or -independent mechanisms. Yet, little is known about the impacts of IGFBP5 on acute myeloid leukemia (AML) and its underlying mechanism. Methods: Here we investigated the roles of IGFBP5 in human AML by using recombinant human IGFBP5 (rhIGFBP5) protein and U937 and THP1 cell lines which stably and ectopically expressed IGFBP5 or mutant IGFBP5 (mtIGFBP5) with the lack of secretory signal peptide. Cell counting kit-8 and flow cytometry assay were conducted to assess the cell viability, cell apoptosis and cell cycle distribution. Cytotoxicity assay was used to detect the chemosensitivity. Leukemia xenograft model and hematoxylin-eosin staining were performed to evaluate AML progression and extramedullary infiltration in vivo. Results: In silico analysis demonstrated a positive association between IGFBP5 expression and overall survival of the AML patients. Both IGFBP5 overexpression and extrinsic rhIGFBP5 suppressed the growth of THP1 and U937 cells by inducing cell apoptosis and arresting G1/S transition and promoted the chemosensitivity of U937 and THP1 cells to daunorubicin and cytarabine. However, overexpression of mtIGFBP5 failed to demonstrate these properties. An in vivo xenograft mouse model of U937 cells also indicated that overexpression of IGFBP5 rather than mtIGFBP5 alleviated AML progression and extramedullary infiltration. Mechanistically, these biological consequences depended on the inactivation of insulin-like growth factor 1 receptor -mediated phosphatidylinositol-3-kinase/protein kinase B pathway. Conclusions: Our findings revealed secreted rather than intracellular IGFBP5 as a tumor-suppressor and chemosensitizer in AML. Upregulation of serum IGFBP5 by overexpression or addition of extrinsic rhIGFBP5 may serve as a suitable therapeutic approach for AML

Deletion of Mettl3 in mesenchymal stem cells promotes acute myeloid leukemia resistance to chemotherapy

Abstract Acute myeloid leukemia (AML) cell survival and chemoresistance are influenced by the existence of bone marrow mesenchymal stem cells (BMMSCs); however, the pathways by which BMMSCs contribute to these processes remain unclear. We earlier revealed that methyltransferase-like 3 (METTL3) expression is significantly reduced in AML BMMSCs and that METTL3 mediates BMMSC adipogenesis to promote chemoresistance in human AML cell lines in vitro. In this investigation, we evaluated the METTL3 function in vivo. Mice exhibiting a conditional removal of Mettl3 in BMMSCs were developed by mating Prrx1-Cre ERT2 ;Mettl3 fl/+ mice with Mettl3 fl/fl mice using the CRISPR-Cas9 system. The Mettl3 deletion increased bone marrow adiposity, enhanced disease progression in the transplantation-induced MLL-AF9 AML mouse model, and chemoresistance to cytarabine. The removal of Mettl3 in BMMSCs resulted in a significant increase in BMMSC adipogenesis. This effect was attributed to the downregulation of AKT1 expression, an AKT serine/threonine kinase 1, in an m6A-dependent manner. The development of chemoresistance in AML is linked to the promoted adipogenesis of BMMSCs. We conclude that METTL3 expression in BMMSCs has a critical function in limiting AML progression and chemoresistance, providing a basis for the progression of therapeutic approaches for AML