Downregulation of MTSS1 in acute myeloid leukemia is associated with a poor prognosis, chemotherapy resistance, and disease aggressiveness

Arid4a Suppresses Breast Tumor Metastasis by Enhancing MTSS1 Expression via mRNA Stability

BACKGROUND

Tumor metastasis is one of the main causes of death in cancer patients; however, the mechanism controlling metastasis is unclear. The posttranscriptional regulation of metastasis-related genes mediated by AT-rich interactive domain-containing protein 4A (Arid4a), an RNA-binding protein (RBP), has not been elucidated.

METHODS

Bioinformatic analysis, qRT-PCR, immunohistochemistry, and immunoblotting were employed to determine the expression of Arid4a in breast tumor tissues and its association with the survival of cancer patients. In vitro and in vivo cellular experiments were used to assess the function of Arid4a in breast tumor metastasis. PCR array, RNA immunoprecipitation (RIP), luciferase, mRNA stability, RIP-ChIP, and EMSA were conducted to elucidate the potential mechanism of Arid4a.

RESULTS

Reduced expression of Arid4a in breast tumor samples was detected via bioinformatic analyses and experimental methods. Low Arid4a expression was significantly correlated with poor prognosis in breast cancer patients. Gain-of-function and silencing experiments confirmed the inhibitory effect of Arid4a on tumor metastasis in vitro and in vivo. Mechanistically, Arid4a preferentially stabilizes metastasis-suppressing transcripts, including metastasis suppressor 1 (MTSS1), tissue inhibitor of metalloproteinase 2 (TIMP2), retinoblastoma 1 (Rb1), and phosphatase and tensin homolog (PTEN), through binding to a conserved structural RNA element localized in the 3' untranslated region (3'UTR). The Arid domain of Arid4a is required for its mRNA stabilization and metastasis inhibition. Notably, the expression of Arid4a and metastasis-suppressing genes was positively correlated in human breast tumor tissues.

CONCLUSIONS

Arid4a was confirmed to suppress breast tumor metastasis progression by stabilizing the transcripts of tumor metastasis-suppressing genes, suggesting that Arid4a might be a potential therapeutic target for breast cancer treatment.

MTSS1: beyond the integration of actin and membrane dynamics

MTSS1 is a ubiquitously expressed intracellular protein known mainly for its involvement in basic cellular processes, such as the regulation of actin organization and membrane architecture. MTSS1 has attracted much attention for its role as a tumor suppressor, being absent or expressed at reduced levels in advanced and metastasizing cancers. Occasionally, MTSS1 is, instead, upregulated in metastasis and, in some cases, even in primary tumors. In addition to these well-established functions of MTSS1 linked to its I-BAR- and WH2-domains, the protein is involved in modulating cell-cell contacts, cell differentiation, lipid metabolism, and vesicle formation and acts as a scaffolding protein for several E3 ubiquitin ligases. MTSS1 is classified as a housekeeping protein and is never mutated despite the several pathologic phenotypes linked to its dysregulation. Despite MTSS1's involvement in fundamental signaling pathways, MTSS1 gene ablation is not ubiquitously lethal, although it affects embryonic development. Due to MTSS1´s involvement in many seemingly disparate processes, with many cases lacking mechanistic explanations, we found it timely to review the recent data on MTSS1's role at the cellular level, as well as in health and disease, to direct further studies on this interesting multifunctional protein.

The mechanisms behind the dual role of long non-coding RNA (lncRNA) metastasis suppressor-1 in human tumors: Shedding light on the molecular mechanisms

When the expression levels of metastasis suppressor-1 (MTSS1) were discovered to be downregulated in a metastatic cancer cell line in 2002, it was proposed that MTSS1 functioned as a suppressor of metastasis. The 755 amino acid long protein MTSS1 connects to actin and organizes the cytoskeleton. Its gene is located on human chromosome 8q24. The suppressor of metastasis in metastatic cancer was first found to be MTSS1. Subsequent reports revealed that MTSS1 is linked to the prevention of metastasis in a variety of cancer types, including hematopoietic cancers like diffuse large B cell lymphoma and esophageal, pancreatic, and stomach cancers. Remarkably, conflicting results have also been documented. For instance, it has been reported that MTSS1 expression levels are elevated in a subset of melanomas, hepatocellular carcinoma associated with hepatitis B, head and neck squamous cell carcinoma, and lung squamous cell carcinoma. This article provides an overview of the pathological effects of lncRNA MTSS1 dysregulation in cancer. In order to facilitate the development of MTSS1-based therapeutic targeting, we also shed light on the current understanding of MTS1.

Identification of colon cancer subtypes based on multi-omics data-construction of methylation markers for immunotherapy

Background

Being the most widely used biomarker for immunotherapy, the microsatellite status has limitations in identifying all patients who benefit in clinical practice. It is essential to identify additional biomarkers to guide immunotherapy. Aberrant DNA methylation is consistently associated with changes in the anti-tumor immune response, which can promote tumor progression. This study aims to explore immunotherapy biomarkers for colon cancers from the perspective of DNA methylation.

Methods

The related data (RNA sequencing data and DNA methylation data) were obtained from The Cancer Genome Atlas (TCGA) and UCSC XENA database. Methylation-driven genes (MDGs) were identified through the Pearson correlation analysis. Unsupervised consensus clustering was conducted using these MDGs to identify distinct clusters of colon cancers. Subsequently, we evaluated the immune status and predicted the efficacy of immunotherapy by tumor immune dysfunction and exclusion (Tide) score. Finally, The Quantitative Differentially Methylated Regions (QDMR) software was used to identify the specific DNA methylation markers within particular clusters.

Results

A total of 282 MDGs were identified by integrating the DNA methylation and RNA-seq data. Consensus clustering using the K-means algorithm revealed that the optimal number of clusters was 4. It was revealed that the composition of the tumor immune microenvironment (TIME) in Cluster 1 was significantly different from others, and it exhibited a higher level of tumor mutation burdens (TMB) and stronger anti-tumor immune activity. Furthermore, we identified three specific hypermethylation genes that defined Cluster 1 (PCDH20, APCDD1, COCH). Receiver operating characteristic (ROC) curves demonstrated that these specific markers could effectively distinguish Cluster 1 from other clusters, with an AUC of 0.947 (95% CI 0.903-0.990). Finally, we selected clinical samples for immunohistochemical validation.

Conclusion

In conclusion, through the analysis of DNA methylation, consensus clustering of colon cancer could effectively identify the cluster that benefit from immunotherapy along with specific methylation biomarkers.

MTSS1 is downregulated in nasopharyngeal carcinoma (NPC) which disrupts adherens junctions leading to enhanced cell migration and invasion

Loss of cell-cell adhesions is the indispensable first step for cancer cells to depart from the primary tumor mass to metastasize. Metastasis suppressor 1 (MTSS1) is frequently lost in metastatic tissues, correlating to advanced tumor stages and poor prognosis across a variety of cancers. Here we explore the anti-metastatic mechanisms of MTSS1, which have not been well understood. We found that MTSS1 is downregulated in NPC tissues. Lower levels of MTSS1 expression correlate to worse prognosis. We show that MTSS1 suppresses NPC cell migration and invasion in vitro through cytoskeletal remodeling at cell-cell borders and assembly of E-cadherin/β-catenin/F-actin in adherens junctions. The I-BAR domain of MTSS1 was both necessary and sufficient to restore this formation of E-cadherin/β-catenin/F-actin-mediated cell adherens junctions.

Microbiota composition and its impact on DNA methylation in colorectal cancer

Colorectal cancer is a complex disease resulting from the interaction of genetics, epigenetics, and environmental factors. DNA methylation is frequently found in tumor suppressor genes to promote cancer development. Several factors are associated with changes in the DNA methylation pattern, and recently, the gastrointestinal microbiota could be associated with this epigenetic change. The predominant phyla in gut microbiota are Firmicutes and Bacteroidetes; however, an enrichment of Bacteroides fragilis, Fusobacterium nucleatum, and Streptococcus bovis, among others, has been reported in colorectal cancer, although the composition could be influenced by several factors, including diet, age, sex, and cancer stage. Fusobacterium nucleatum, a gram-negative anaerobic bacillus, is mainly associated with colorectal cancer patients positive for the CpG island methylator phenotype, although hypermethylation in genes such as MLH1, CDKN2A, MTSS1, RBM38, PKD1, PTPRT, and EYA4 has also been described. Moreover, Hungatella hathewayi, a gram-positive, rod-shaped bacterium, is related to hypermethylation in SOX11, THBD, SFRP2, GATA5, ESR1, EYA4, CDX2, and APC genes. The underlying epigenetic mechanism is unclear, although it could be implicated in the regulation of DNA methyltransferases, enzymes that catalyze the transfer of a methyl group on cytosine of CpG sites. Since DNA methylation is a reversible event, changes in gut microbiota could modulate the gene expression through DNA methylation and improve the colorectal cancer prognosis.

Association of rs35006907 Polymorphism with Risk of Dilated Cardiomyopathy in Han Chinese Population

Background

Several investigations have demonstrated the association of MTSS1 with left ventricular (LV) structure and function. A recently published study has even revealed that rs35006907 was associated with both MTSS1 expression and the risk of dilated cardiomyopathy (DCM).

Objective

Our study intended to investigate the relationship between rs35006907 and the risk of DCM in the Han Chinese population.

Methods

A total of 529 DCM and 600 healthy controls were recruited. We conducted genotyping for rs35006907 in all participants. Gene association studies were performed to assess the association between rs35006907 and the risk of DCM. A series of functional assays including western blot, realtime PCR and firefly luciferase reporter gene assays were conducted to illuminate the underlying mechanism.

Results

We found that rs35006907-A allele was significantly associated with reduced risk of DCM in additive (p= 0.004; OR=0.78; 95% CI=0.66-0.93) and recessive models (p= 0.0005; OR=0.56; 95%CI=0.41-0.78) when compared with the rs35006907-C allele. There were significant differences in the left ventricular end-diastolic diameter (LVEDD) and left ventricular ejection fraction (LVEF) between rs35006907-CC/AC and AA genotypes. Furthermore, the variant rs35006907-A allele presented lower reporter gene activity, reduced mRNA and protein expression levels when compared with the C allele.

Conclusions

Our findings demonstrated that rs35006907-C allele increased the risk of DCM in Han Chinese population. Besides, rs35006907-C displayed higher reporter gene activity and increased MTSS1 expression in human samples.

Abemaciclib drives the therapeutic differentiation of acute myeloid leukaemia stem cells

Self-renewal and differentiation arrest are two features of leukaemia stem cells (LSCs) responsible for the high relapse rate of acute myeloid leukaemia (AML). To screen drugs to overcome differentiation blockade for AML, we conducted screening of 2040 small molecules from a library of United States Food and Drug Administration-approved drugs and found that the cyclin-dependent kinase (CDK)4/6 inhibitor, abemaciclib, exerts high anti-leukaemic activity. Abemaciclib significantly suppressed proliferation and promoted the differentiation of LSCs in vitro. Abemaciclib also efficiently induced differentiation and impaired self-renewal of LSCs, thus reducing the leukaemic cell burden and improving survival in various preclinical animal models, including patient-derived xenografts. Importantly, abemaciclib strongly enhanced anti-tumour effects in combination with venetoclax, a B-cell lymphoma 2 (Bcl-2) inhibitor. This treatment combination led to a marked decrease in LSC-enriched populations and resulted in a synergistic anti-leukaemic effect. Target screening revealed that in addition to CDK4/6, abemaciclib bound to and inhibited CDK9, consequently attenuating the protein levels of global p-Ser2 RNA Polymerase II (Pol II) carboxy terminal domain (CTD), Myc, Bcl-2, and myeloid cell leukaemia-1 (Mcl-1), which was important for the anti-AML effect of abemaciclib. Collectively, these data provide a strong rationale for the clinical evaluation of abemaciclib to induce LSC differentiation and treat highly aggressive AML as well as other advanced haematological malignancies.

Actin-rich lamellipodia-like protrusions contribute to the integrity of epithelial cell-cell junctions

Metastasis-suppressor 1 (MTSS1) is a membrane-interacting scaffolding protein that regulates the integrity of epithelial cell-cell junctions and functions as a tumor suppressor in a wide range of carcinomas. MTSS1 binds phosphoinositide-rich membranes through its I-BAR domain, and is capable of sensing and generating negative membrane curvature in vitro. However, the mechanisms by which MTSS1 localizes to intercellular junctions in epithelial cells, and contributes to their integrity and maintenance have remained elusive. By carrying out electron microscopy and live-cell imaging on cultured Madin-Darby canine kidney (MDCK) cell monolayers, we provide evidence that adherens junctions of epithelial cells harbor lamellipodia-like, dynamic actin-driven membrane folds, which exhibit high negative membrane curvature at their distal edges. BioID proteomics and imaging experiments demonstrated that MTSS1 associates with an Arp2/3 complex activator, the WAVE-2 complex, in dynamic actin-rich protrusions at cell-cell junctions. Inhibition of Arp2/3 or WAVE-2 suppressed actin filament assembly at adherens junctions, decreased the dynamics of junctional membrane protrusions, and led to defects in epithelial integrity. Together, these results support a model in which membrane-associated MTSS1, together with the WAVE-2 and Arp2/3 complexes, promotes the formation of dynamic lamellipodia-like actin protrusions that contribute to the integrity of cell-cell junctions in epithelial monolayers.

TMBIM5 is the Ca2+ /H+ antiporter of mammalian mitochondria

Mitochondrial Ca2+ ions are crucial regulators of bioenergetics and cell death pathways. Mitochondrial Ca2+ content and cytosolic Ca2+ homeostasis strictly depend on Ca2+ transporters. In recent decades, the major players responsible for mitochondrial Ca2+ uptake and release have been identified, except the mitochondrial Ca2+ /H+ exchanger (CHE). Originally identified as the mitochondrial K+ /H+ exchanger, LETM1 was also considered as a candidate for the mitochondrial CHE. Defining the mitochondrial interactome of LETM1, we identify TMBIM5/MICS1, the only mitochondrial member of the TMBIM family, and validate the physical interaction of TMBIM5 and LETM1. Cell-based and cell-free biochemical assays demonstrate the absence or greatly reduced Na+ -independent mitochondrial Ca2+ release in TMBIM5 knockout or pH-sensing site mutants, respectively, and pH-dependent Ca2+ transport by recombinant TMBIM5. Taken together, we demonstrate that TMBIM5, but not LETM1, is the long-sought mitochondrial CHE, involved in setting and regulating the mitochondrial proton gradient. This finding provides the final piece of the puzzle of mitochondrial Ca2+ transporters and opens the door to exploring its importance in health and disease, and to developing drugs modulating Ca2+ exchange.

Gene expression changes contribute to stemness and therapy resistance of relapsed acute myeloid leukemia: roles of SOCS2, CALCRL, MTSS1, and KDM6A

Relapse is associated with therapy resistance and is a major cause of death in acute myeloid leukemia (AML). It is thought to result from the accretion of therapy-refractory leukemic stem cells. Genetic and transcriptional changes that are recurrently gained at relapse are likely to contribute to the increased stemness and decreased therapy responsiveness at this disease stage. Despite the recent approval of several targeted drugs, chemotherapy with cytosine arabinoside and anthracyclines is still the mainstay of AML therapy. Accordingly, a number of studies have investigated genetic and gene expression changes between diagnosis and relapse of patients subjected to such treatment. Genetic alterations recurrently acquired at relapse were identified, but were restricted to small proportions of patients, and their functional characterization is still largely pending. In contrast, the expression of a substantial number of genes was altered consistently between diagnosis and recurrence of AML. Recent studies corroborated the roles of the upregulation of SOCS2 and CALCRL and of the downregulation of MTSS1 and KDM6A in therapy resistance and/or stemness of AML. These findings spur the assumption that functional investigations of genes consistently altered at recurrence of AML have the potential to promote the development of novel targeted drugs that may help to improve the outcome of this currently often fatal disease.