A novel role for Lef-1, a central transcription mediator of Wnt signaling, in leukemogenesis

Mutant IDH1 cooperates with NPM1c or FLT3ITD to drive distinct myeloid diseases and molecular outcomes

In human acute myeloid leukemia (AML), mutations of isocitrate dehydrogenase-1 (IDH1) often co-occur with NPM1 mutations, and less frequently with FLT3 mutations. To investigate whether the effects of IDH1 mutation differ according to the specific co-occurring mutation, we generated two strains of double knock-in mutant mice. Idh1R132H combined with Npm1c induced overt AML, whereas Idh1R132H plus Flt3ITD resulted in Flt3ITD-driven myelo- or lymphoproliferation that was minimally affected by Idh1R132H and rarely generated AML. Gene expression profiling revealed differences between Idh1R132H;Npm1c cells and Idh1R132H;Flt3ITD cells and suggested altered heme metabolism and immune responses in the former. The profile of Idh1R132H;Npm1c cells corresponded to that of human IDH-mutated AML cells, particularly those resistant to inhibitors of mutant IDH. Compared to treatment with a menin inhibitor, IDH1-targeted therapy of Idh1R132H;Npm1c AML-bearing mice was less efficacious in improving cell differentiation and extending survival. The differential cooperation of Idh1R132H with Npm1c vs. Flt3ITD may have implications for the devising of subtype-specific treatments for human AML.

Superficial Wnt-Activated Melanocytic Nevi/Melanocytomas With a Junctional Component: A Case Series

ABSTRACT

The conventional morphological characteristics of Wnt-activated deep penetrating/plexiform melanocytomas/nevi (DPN) are those of large spindled or epithelioid melanocytes with distinctive voluminous amphophilic cytoplasm, fine pigmented granules, and surrounding melanophages. The central molecular hallmark is the activation of the Wnt-pathway predominantly driven by mutations in the beta-catenin ( CTNNB1 ) gene. Although typically lacking a junctional component, a lesser-known superficial variant with a junctional component has been identified, which could potentially lead to diagnostic challenges. This study presents a cohort of 11 such cases displaying a junctional component of DPN from 10 patients (5 women and 5 men; age range: 27-78 years; median age: 51 years). The nevi were distributed as follows: 1 conjunctival, 1 scalp, 2 lower limb, and 6 truncal lesions. Eight cases were combined with a conventional nevus, 2 cases displayed pure DPN cytology exhibiting only a junctional element, and 9 cases exhibited some degree of lentiginous architecture. All cases demonstrated a low mitotic index (<1 mitosis/mm 2 ). Immunohistochemistry revealed positive BRAF V600E staining in 8 cases (8/11), whereas all cases tested (11/11) were PRAME negative. Nuclear beta-catenin and LEF1 staining was consistently strong and diffuse with DPN cytology (11/11), along with robust cyclin D1 staining in all cases tested (11/11). By contrast, all 9 conventional nevi showed an absence of nuclear beta-catenin staining (0/9) and weaker, mosaic-type LEF1 and cyclin D1 staining was observed. This study emphasizes the diagnostic challenge these nevi can pose in the absence of a conventional, deeper DPN component, which can potentially be misdiagnosed as melanoma.

The evolving roles of Wnt signaling in stem cell proliferation and differentiation, the development of human diseases, and therapeutic opportunities

The evolutionarily conserved Wnt signaling pathway plays a central role in development and adult tissue homeostasis across species. Wnt proteins are secreted, lipid-modified signaling molecules that activate the canonical (β-catenin dependent) and non-canonical (β-catenin independent) Wnt signaling pathways. Cellular behaviors such as proliferation, differentiation, maturation, and proper body-axis specification are carried out by the canonical pathway, which is the best characterized of the known Wnt signaling paths. Wnt signaling has emerged as an important factor in stem cell biology and is known to affect the self-renewal of stem cells in various tissues. This includes but is not limited to embryonic, hematopoietic, mesenchymal, gut, neural, and epidermal stem cells. Wnt signaling has also been implicated in tumor cells that exhibit stem cell-like properties. Wnt signaling is crucial for bone formation and presents a potential target for the development of therapeutics for bone disorders. Not surprisingly, aberrant Wnt signaling is also associated with a wide variety of diseases, including cancer. Mutations of Wnt pathway members in cancer can lead to unchecked cell proliferation, epithelial-mesenchymal transition, and metastasis. Altogether, advances in the understanding of dysregulated Wnt signaling in disease have paved the way for the development of novel therapeutics that target components of the Wnt pathway. Beginning with a brief overview of the mechanisms of canonical and non-canonical Wnt, this review aims to summarize the current knowledge of Wnt signaling in stem cells, aberrations to the Wnt pathway associated with diseases, and novel therapeutics targeting the Wnt pathway in preclinical and clinical studies.

Emerging roles of MITF as a crucial regulator of immunity

Microphthalmia-associated transcription factor (MITF), a basic helix-loop-helix leucine zipper transcription factor (bHLH-Zip), has been identified as a melanocyte-specific transcription factor and plays a critical role in melanocyte survival, differentiation, function, proliferation and pigmentation. Although numerous studies have explained the roles of MITF in melanocytes and in melanoma development, the function of MITF in the hematopoietic or immune system-beyond its function in melanin-producing cells-is not yet fully understood. However, there is convincing and increasing evidence suggesting that MITF may play multiple important roles in immune-related cells. Therefore, this review is focused on recent advances in elucidating novel functions of MITF in cancer progression and immune responses to cancer. In particular, we highlight the role of MITF as a central modulator in the regulation of immune responses, as elucidated in recent studies.

ZMIZ2 facilitates hepatocellular carcinoma progression via LEF1 mediated activation of Wnt/β-catenin pathway

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignancies with a high lethality rate. ZMIZ2 is a transcriptional co-activator implicated in various human diseases. However, the role and molecular mechanism of ZMIZ2 in HCC remains to be elucidated.

METHODS

The expression and prognostic value of ZMIZ2 in HCC was excavated from public databases and explored by bioinformatic analysis. Then the expression of ZMIZ2 and related genes was further validated by quantitative RT-PCR, western blotting, and immunohistochemistry. Loss and gain-of-function experiments were performed in vitro and in vivo to investigate the function of ZMIZ2 in HCC. In addition, transcriptome sequencing and immunoprecipitation was conducted to explore the potential molecular mechanisms of ZMIZ2.

RESULTS

ZMIZ2 was highly expressed in HCC and associated with poor prognosis. Silencing ZMIZ2 significantly inhibited HCC cell proliferation, cell cycle process, migration, and invasion in vitro, and also inhibited the progression of HCC in vivo. Additionally, ZMIZ2 expression was correlated with immune cell infiltration in HCC samples. Somatic mutation analysis showed that ZMIZ2 and TP53 mutations jointly affected the progression of HCC. Mechanistically, ZMIZ2 interacted with LEF1 to regulate malignant progression of HCC by activating the Wnt/β-catenin pathway.

CONCLUSION

ZMIZ2 was overexpressed in HCC and associated with poor prognosis. The overexpression of ZMIZ2 was corelated with malignant phenotype, and it facilitated HCC progression via LEF1-mediated activation of the Wnt/β-catenin pathway. Furthermore, ZMIZ2 could be served as a prognostic biomarker and a new therapeutic target for HCC.

Gene-Environment Analyses Reveal Novel Genetic Candidates with Prenatal Tobacco Exposure in Relation to Risk for Childhood Acute Lymphoblastic Leukemia

BACKGROUND

Associations between maternal tobacco exposure during pregnancy and childhood acute lymphoblastic leukemia (ALL) have yielded mixed results. This may be due to biases in self-reported smoking or other differences in individual-level risk factors. We utilized a biological marker of maternal tobacco exposure to evaluate the association between maternal tobacco exposure during pregnancy, genetics, and subsequent childhood ALL risk in two large population-based studies of childhood ALL in California.

METHODS

Maternal exposure to tobacco smoke was assessed with a validated methylation marker (cg05575921) of the aryl hydrocarbon receptor repressor (AHRR) gene in newborn dried blood spots. We adjusted for sex, birthweight, gestational age, mode of delivery, year of birth, AHRR quantitative trait locus (mQTL) rs77111113, and a polygenetic risk score for childhood ALL. We additionally adjusted for principal components in a gene-environment interaction testing method that incorporates gene-only and environment-only effects along with interactions.

RESULTS

AHRR hypomethylation overall was not associated with childhood ALL. In gene-environment interaction testing, several genetic variants displayed significant interaction with AHRR hypomethylation and childhood ALL.

CONCLUSIONS

Our results suggest that novel candidates in PTPRK and DPP6 may play a role in tobacco-related leukemogenesis. Further research is necessary to better understand the effects of tobacco and these variants on childhood ALL risk.

IMPACT

Despite the lack of an overall "main effect," tobacco exposure during pregnancy affects childhood ALL risk depending on specific genetic variants.

Effects of S-Adenosylhomocysteine Hydrolase Downregulation on Wnt Signaling Pathway in SW480 Cells

S-adenosylhomocysteine hydrolase (AHCY) deficiency results mainly in hypermethioninemia, developmental delay, and is potentially fatal. In order to shed new light on molecular aspects of AHCY deficiency, in particular any changes at transcriptome level, we enabled knockdown of AHCY expression in the colon cancer cell line SW480 to simulate the environment occurring in AHCY deficient individuals. The SW480 cell line is well known for elevated AHCY expression, and thereby represents a suitable model system, in particular as AHCY expression is regulated by MYC, which, on the other hand, is involved in Wnt signaling and the regulation of Wnt-related genes, such as the β-catenin co-transcription factor LEF1 (lymphoid enhancer-binding factor 1). We selected LEF1 as a potential target to investigate its association with S-adenosylhomocysteine hydrolase deficiency. This decision was prompted by our analysis of RNA-Seq data, which revealed significant changes in the expression of genes related to the Wnt signaling pathway and genes involved in processes responsible for epithelial-mesenchymal transition (EMT) and cell proliferation. Notably, LEF1 emerged as a common factor in these processes, showing increased expression both on mRNA and protein levels. Additionally, we show alterations in interconnected signaling pathways linked to LEF1, causing gene expression changes with broad effects on cell cycle regulation, tumor microenvironment, and implications to cell invasion and metastasis. In summary, we provide a new link between AHCY deficiency and LEF1 serving as a mediator of changes to the Wnt signaling pathway, thereby indicating potential connections of AHCY expression and cancer cell phenotype, as Wnt signaling is frequently associated with cancer development, including colorectal cancer (CRC).

OTUD7B Activates Wnt Signaling Pathway through the Interaction with LEF1

The Wnt signaling pathway plays a critical role in regulating normal cellular processes, including proliferation, differentiation, and apoptosis. Dysregulation of Wnt signaling has been implicated in various human diseases, including cancer. β-catenin and LEF1 are key mediators of Wnt signaling, and their dysregulation is a hallmark of many cancer types. In this study, we aimed to identify the deubiquitinases (DUBs) that regulate the Wnt signaling pathway through the essential component LEF1. Screening candidate DUBs from the human DUB library, we discovered that OTUD7B interacts with LEF1 and activates Wnt signaling. OTUD7B and LEF1 interact with each other through the UBA and HMG domains, respectively. Furthermore, OTUD7B promotes the nuclear localization of LEF1, leading to an increased interaction with β-catenin in the nucleus while not noticeably affecting ubiquitination on LEF1. Using qPCR array analysis, we found that OTUD7B overexpression leads to an upregulation of 75% of the tested Wnt target genes compared to the control. These findings suggest that OTUD7B may serve as a potential therapeutic target in human diseases, including cancers where Wnt signaling is frequently dysregulated.

Dual inhibition of EZH2 and G9A/GLP histone methyltransferases by HKMTI-1-005 promotes differentiation of acute myeloid leukemia cells

All-trans-retinoic acid (ATRA)-based differentiation therapy of acute promyelocytic leukemia (APL) represents one of the most clinically effective examples of precision medicine and the first example of targeted oncoprotein degradation. The success of ATRA in APL, however, remains to be translated to non-APL acute myeloid leukemia (AML). We previously showed that aberrant histone modifications, including histone H3 lysine 4 (H3K4) and lysine 27 (H3K27) methylation, were associated with this lack of response and that epigenetic therapy with small molecule inhibitors of the H3K4 demethylase LSD1/KDM1A could reprogram AML cells to respond to ATRA. Serving as the enzymatic component of Polycomb Repressive Complex 2, EZH2/KMT6A methyltransferase plays a critical role in normal hematopoiesis by affecting the balance between self-renewal and differentiation. The canonical function of EZH2 is methylation of H3K27, although important non-canonical roles have recently been described. EZH2 mutation or deregulated expression has been conclusively demonstrated in the pathogenesis of AML and response to treatment, thus making it an attractive therapeutic target. In this study, we therefore investigated whether inhibition of EZH2 might also improve the response of non-APL AML cells to ATRA-based therapy. We focused on GSK-343, a pyridone-containing S-adenosyl-L-methionine cofactor-competitive EZH2 inhibitor that is representative of its class, and HKMTI-1-005, a substrate-competitive dual inhibitor targeting EZH2 and the closely related G9A/GLP H3K9 methyltransferases. We found that treatment with HKMTI-1-005 phenocopied EZH2 knockdown and was more effective in inducing differentiation than GSK-343, despite the efficacy of GSK-343 in terms of abolishing H3K27 trimethylation. Furthermore, transcriptomic analysis revealed that in contrast to treatment with GSK-343, HKMTI-1-005 upregulated the expression of differentiation pathway genes with and without ATRA, while downregulating genes associated with a hematopoietic stem cell phenotype. These results pointed to a non-canonical role for EZH2, which was supported by the finding that EZH2 associates with the master regulator of myeloid differentiation, RARα, in an ATRA-dependent manner that was enhanced by HKMTI-1-005, possibly playing a role in co-regulator complex exchange during transcriptional activation. In summary, our results strongly suggest that addition of HKMTI-1-005 to ATRA is a new therapeutic approach against AML that warrants further investigation.

LEF1 Drives a Central Memory Program and Supports Antitumor Activity of Natural Killer T Cells

Vα24-invariant natural killer T cells (NKT) possess innate antitumor properties that can be exploited for cancer immunotherapy. We have shown previously that the CD62L+ central memory-like subset of these cells drives the in vivo antitumor activity of NKTs, but molecular mediators of NKT central memory differentiation remain unknown. Here, we demonstrate that relative to CD62L- cells, CD62L+ NKTs express a higher level of the gene encoding the Wnt/β-catenin transcription factor lymphoid enhancer binding factor 1 (LEF1) and maintain active Wnt/β-catenin signaling. CRISPR/Cas9-mediated LEF1 knockout reduced CD62L+ frequency after antigenic stimulation, whereas Wnt/β-catenin activator Wnt3a ligand increased CD62L+ frequency. LEF1 overexpression promoted NKT expansion and limited exhaustion following serial tumor challenge and was sufficient to induce a central memory-like transcriptional program in NKTs. In mice, NKTs expressing a GD2-specific chimeric-antigen receptor (CAR) with LEF1 demonstrated superior control of neuroblastoma xenograft tumors compared with control CAR-NKTs. These results identify LEF1 as a transcriptional activator of the NKT central memory program and advance development of NKT cell-based immunotherapy. See related Spotlight by Van Kaer, p. 144.

Characterization of chromatin accessibility patterns in different mouse cell types using machine learning methods at single-cell resolution

Chromatin accessibility is a generic property of the eukaryotic genome, which refers to the degree of physical compaction of chromatin. Recent studies have shown that chromatin accessibility is cell type dependent, indicating chromatin heterogeneity across cell lines and tissues. The identification of markers used to distinguish cell types at the chromosome level is important to understand cell function and classify cell types. In the present study, we investigated transcriptionally active chromosome segments identified by sci-ATAC-seq at single-cell resolution, including 69,015 cells belonging to 77 different cell types. Each cell was represented by existence status on 20,783 genes that were obtained from 436,206 active chromosome segments. The gene features were deeply analyzed by Boruta, resulting in 3897 genes, which were ranked in a list by Monte Carlo feature selection. Such list was further analyzed by incremental feature selection (IFS) method, yielding essential genes, classification rules and an efficient random forest (RF) classifier. To improve the performance of the optimal RF classifier, its features were further processed by autoencoder, light gradient boosting machine and IFS method. The final RF classifier with MCC of 0.838 was constructed. Some marker genes such as H2-Dmb2, which are specifically expressed in antigen-presenting cells (e.g., dendritic cells or macrophages), and Tenm2, which are specifically expressed in T cells, were identified in this study. Our analysis revealed numerous potential epigenetic modification patterns that are unique to particular cell types, thereby advancing knowledge of the critical functions of chromatin accessibility in cell processes.

MiR-34a-5p promotes autophagy and apoptosis of ovarian granulosa cells via the Hippo-YAP signaling pathway by targeting LEF1 in chicken

Follicular atresia is a natural physiological phenomenon in poultry reproduction. It is well known that follicular atresia is caused by both autophagy and apoptosis of granulosa cells. In current experiment, we evaluated the function of miR-34a-5p on autophagy and apoptosis in chicken follicular atresia. First, the follicular atresia model of chicken was successfully constructed by subcutaneous injection of tamoxifen (TMX), and found the expression of miR-34a-5p in the atresia follicles obviously increased. Then, we confirmed that miR-34a-5p accelerates autophagy and apoptosis of chicken granulose cells in vitro, and miR-34a-5p could induce apoptosis by mediating autophagy. Mechanistically, lymphoid enhancer binding factor 1 (LEF1) was deemed as a target gene for miR-34a-5p. On the contrary, LEF1 overexpression attenuated the autophagy and apoptosis of chicken granular cells. In addition, it was confirmed that the miR-34a-5p/LEF1 axis plays a regulatory role in chicken granulosa cells by mediating the Hippo-YAP signaling pathway. Taken together, this study demonstrated that miR-34a-5p contributes to autophagy and apoptosis of chicken follicular granulosa cells by targeting LEF1 to mediate the Hippo-YAP signaling pathway.

MicroRNA-621 functions as a metastasis suppressor in colorectal cancer by directly targeting LEF1 and suppressing Wnt/β-catenin signaling

AIMS

Colorectal liver metastasis (CRLM) is the leading death-causing among colorectal cancer (CRC) patients. Recently, a novel tumor-related microRNA, miR-621, has been identified as a tumor suppressor in diverse tumor types, but its role in CRLM remains unclear and requires further investigation.

MAIN METHODS

To elucidate novel regulators of CRLM progression, we used a well-established CRLM animal model. After serially transplanting human colon carcinoma cell lines Caco-2 into the liver, we obtained liver metastatic variants that exhibited a strong ability for invasion and metastasis. High-throughput sequencing was conducted on these newly established cell lines. After comparison and prediction between the two cell lines: parental Caco-2 (hereafter referred to as F0) and F3, miR-621 was identified as a candidate regulator for lymphoid enhancer-binding factor 1 (LEF1) expression. Further validation was achieved with dual-luciferase reporter assay.

KEY FINDINGS

The gain- and loss-of-function validation showed that miR-621 inhibits cell viability, cell cycle progression, colony formation, and proliferation in vitro. Meanwhile, miR-621 could reverse EMT malignant phenotype. LEF1, an important downstream mediator of activated Wnt/β-catenin signaling pathway, was validated as the direct functional target of miR-621. miR-621 interacts directly with the LEF1 3'-UTR and post-transcriptionally suppresses LEF1 expression. Moreover, LEF1 overexpression reversed the effect of miR-621. LEF1 silencing counteracted miR-621 down-regulation-induced effects. Further in vivo experiments revealed that miR-621 over-expression suppressed CRLM, but LEF1 abrogated the inhibitory effect of miR-621.

SIGNIFICANCE

MiR-621 is a vital tumor suppressor in CRC and could be a promising anti-cancer therapeutic target.

E Protein Transcription Factors as Suppressors of T Lymphocyte Acute Lymphoblastic Leukemia

T Lymphocyte Acute Lymphoblastic Leukemia (ALL) is an aggressive disease arising from transformation of T lymphocytes during their development. The mutation spectrum of T-ALL has revealed critical regulators of the growth and differentiation of normal and leukemic T lymphocytes. Approximately, 60% of T-ALLs show aberrant expression of the hematopoietic stem cell-associated helix-loop-helix transcription factors TAL1 and LYL1. TAL1 and LYL1 function in multiprotein complexes that regulate gene expression in T-ALL but they also antagonize the function of the E protein homodimers that are critical regulators of T cell development. Mice lacking E2A, or ectopically expressing TAL1, LYL1, or other inhibitors of E protein function in T cell progenitors, also succumb to an aggressive T-ALL-like disease highlighting that E proteins promote T cell development and suppress leukemogenesis. In this review, we discuss the role of E2A in T cell development and how alterations in E protein function underlie leukemogenesis. We focus on the role of TAL1 and LYL1 and the genes that are dysregulated in E2a^-/- T cell progenitors that contribute to human T-ALL. These studies reveal novel mechanisms of transformation and provide insights into potential therapeutic targets for intervention in this disease.

LEF1 Enhances the Progression of Colonic Adenocarcinoma via Remodeling the Cell Motility Associated Structures

Lymphoid enhancer-binding factor 1 (LEF1) is a key transcription factor mediating the Wnt signaling pathway. LEF1 is a regulator that is closely associated with tumor malignancy and is usually upregulated in cancers, including colonic adenocarcinoma. The underlying molecular mechanisms of LEF1 regulation for colonic adenocarcinoma progression remain unknown. To explore it, the LEF1 expression in caco2 cells was inhibited using an shRNA approach. The results showed that downregulation of LEF1 inhibited the malignancy and motility associated microstructures, such as polymerization of F-actin, β-tubulin, and Lamin B1 in caco2 cells. LEF1 inhibition suppressed the expression of epithelial/endothelial-mesenchymal transition (EMT) relevant genes. Overall, the current results demonstrated that LEF1 plays a pivotal role in maintaining the malignancy of colonic adenocarcinoma by remodeling motility correlated microstructures and suppressing the expression of EMT-relevant genes. Our study provided evidence of the roles LEF1 played in colonic adenocarcinoma progression, and suggest LEF1 as a potential target for colonic adenocarcinoma therapy.

Downregulation of LEF1 Impairs Myeloma Cell Growth Through Modulating CYLD/NF-κB Signaling

Aberrant expression of lymphoid enhancer-binding factor-1 (LEF1) has been identified in various hematological malignancies including multiple myeloma (MM). However, the exact role of LEF1 in MM remains largely unknown. Here, we showed that knockdown of LEF1 could apparently impair the proliferation, induce apoptosis and promote the ROS production in MM cell lines, suggesting that LEF1 might be involved in maintaining MM cell growth and survival. Moreover, we observed that the mRNA level of the deubiquitinase cylindromatosis (CYLD), a well-recognized tumor suppressor in MM, was significantly increased following LEF1 depletion in myeloma cells. Further study showed that LEF1 could directly associate with the promoter of CYLD gene and thus repress its transcription in MM cells. Intriguingly, LEF1 depletion-mediated CYLD upregulation was sufficient to negatively modulate NF-κB signaling pathway in MM cells. Moreover, the decrease in NF-κB activity following LEF1 knockdown could be largely rescued when CYLD was silenced in MM cells. Taken together, our study provided the compelling evidence to show that LEF1 may augment the proliferation and survival of MM cells through direct repression of CYLD transcription and subsequent activation of NF-κB signaling pathway, corroborating that LEF1 may become a potential therapeutic target against MM.

Bone marrow mesenchymal stromal cells in chronic myelomonocytic leukaemia: overactivated WNT/β-catenin signalling by parallel RNA sequencing and dysfunctional phenotypes

Sophisticated cross-talk between bone marrow mesenchymal stromal cells (BM MSCs) and haematopoietic/leukaemic stem cells in patients with myelodysplastic syndromes (MDS) and myeloid leukaemia have been emphasized in previous reports. However, mesenchymal elements in patients with chronic myelomonocytic leukaemia (CMML) were poorly investigated. By utilizing a parallel RNA-sequencing method, we investigated the transcriptional profile and functional defects of primary BM MSCs from patients with CMML for the first time. Within a 24-patient cohort, transcriptional and functional analysis reveals a prominent enrichment of WNT/β-catenin signalling and multiple biology processes. Deregulated expression of WNT/β-catnin factors CTNNB1, CMYC, LEF1, and FRZB is associated with impaired proliferation, senescence phenotype, and abnormal secretion in CMML MSCs. The impaired ability to support healthy CD34⁺ haematopoietic stem and progenitor cells (HSPCs) correlates with activation of WNT/β-catenin signalling in CMML MSCs. Furthermore, we observed an association between WNT/β-catenin factors and treatment response to hypomethylating agents (HMAs) in a cohort of patients with MDS/myeloproliferative neoplasms (MPNs). Taken together, our study provides evidence for transcriptional and functional abnormalities in CMML MSCs, and suggests potential prognostic value of evaluating WNT/β-catenin signalling in patients with CMML.

Prognostic evidence of LEF1 isoforms in childhood acute lymphoblastic leukemia

INTRODUCTION

The lymphoid enhancer factor 1 (LEF1) is a DNA-binding transcription factor that functions in the Wnt signaling pathway. Increased LEF1 activity is associated with progression of several types of cancer including leukemia. Here, we investigated LEF1 isoform expression and genomic variations in acute lymphoblastic leukemia (ALL).

METHODS

LEF1 isoform expression was evaluated by quantitative real-time PCR in 87 newly diagnosed childhood ALL patients and controls. Moreover, Western blot analysis was performed for detection of LEF1 expression and the hotspot region of LEF1 was screened by deep sequencing.

RESULTS

The LEF1 mRNA expression of B cell ALL patients was higher than the controls (LEF1-total P = .011, LEF1-long P = .026). Moreover, B-ALL samples showing higher total LEF1 expression had significantly shorter relapse-free survival (P = .008) and overall survival (P = .011). Although full-length LEF1 expression was similar to the controls in T-ALL, 50% (n = 15) of the ALL patients had increased full-length LEF1 protein expression. Imbalance between short- and full-length LEF1 isoforms may lead to cell survival in ALL. Beside the LEF1 activation, LEF1 gene variations were rarely observed in our cohort.

CONCLUSION

The results indicate that the Wnt pathway may have a pathogenic function in a group of ALL patients and high LEF1-total expression might be a marker for shorter relapse-free survival time in B cell ALL.

High expression of LEF1 correlates with poor prognosis in solid tumors, but not blood tumors: a meta-analysis

BACKGROUND

Previously published studies have indicated that lymphoid enhancer-binding factor 1 (LEF1) expression could be recognized as a valuable biomarker to evaluate clinical outcome for various types of malignant cancer, but the results remained controversial. Therefore, we conducted this meta-analysis to pool the published estimates and discuss the relationship of LEF1 expression with cancer prognosis.

METHODS

Five electronic databases Pubmed, Web of Science, Embase, CNKI, and Wanfang were systematically searched for eligible literatures. Hazard ratios (HRs) and 95% confidence intervals (CIs) from the included studies were combined to estimate the effect of LEF1 expression on cancer patients' survival.

RESULTS

Eleven original studies met the criteria and were enrolled for analysis. The results indicated that compared with patients in low LEF1 expression group, patients in high LEF1 expression group tended to have shorter overall survival (HR = 1.74, 95% CI: 1.06-2.86, P=0.029), especially for patients with solid tumors (HR = 2.39, 95% CI: 1.86-3.08, P=0.000).

CONCLUSIONS

Individual evidence about the prognostic value of LEF1 expression in human cancers was limited. Our meta-analysis supported the suggestion that elevated LEF1 expression could function as a promising biomarker to predict the clinical outcomes for malignant cancers, especially solid tumors. More high-quality clinical studies are warranted to highlight the prognostic value of LEF1 expression in human cancers.

Lymphoid enhancer-binding factor 1 (LEF-1): a favorable prognostic factor in adult acute myeloid leukemia in Egyptian patients

Background

Canonical wingless-type (Wnt) signaling is a crucial pathway involved in normal hematopoiesis and the self-renewal process of hematopoietic stem cells. Deregulation of this pathway has been associated with different subtypes of leukemia. Lymphoid enhancer-binding factor 1 (LEF-1) is a major transcription factor of this pathway and plays a pivotal role in lymphoid differentiation and granulopoiesis. High LEF-1 expression has been reported as a prognostic marker in several types of adult hematological malignancies. We aimed to assess the prognostic utility of LEF-1 expression in adult de novo acute myeloid leukemia (AML) Egyptian patients in continuation of our previous work. LEF-1 expression was analyzed by real-time polymerase chain reaction (PCR) in 30 adults with newly diagnosed AML and remeasured at day 28 after induction therapy with the assessment of remission status.

Results

Patients were classified according to median expression level into high and low LEF-1 expression groups. LEF-1 levels were dramatically decreased following successful induction therapy. Also, high LEF-1 expression patients had a better response to therapy with better overall survival. ROC curve analysis of LEF-1 expression yielded a cutoff value of < 10.11 log10 (sensitivity of 90.48% and specificity of 100%) for predicting poor outcome. Univariate logistic regression analysis showed that for every log10 increase in the LEF-1 expression level, the chance of the patient to achieve hematological remission was increased by 2.29 folds.

Conclusion

Our study showed preliminary results that overexpression of LEF-1 is a favorable prognostic factor in newly diagnosed adult AML patients. The prognostic value of LEF-1 could suggest its utility for further risk classifications of AML and potentiality for being a target for therapy.

B-ALL Complexity: Is Targeted Therapy Still A Valuable Approach for Pediatric Patients?

Simple Summary

B-ALL is the more frequent childhood malignancy. Even though significant improvements in patients’ survival, some pediatric B-ALL have still poor prognosis and novel strategies are needed. Recently, new genetic abnormalities and altered signaling pathways have been described, defining novel B-ALL subtypes.Innovative targeted therapeutic drugs may potentially show a great impact on the treatment of B-ALL subtypes, offering an important chance to block multiple signaling pathways and potentially improving the clinical management of B-ALL younger patients, especially for the new identified subtypes that lack efficient chemotherapeutic protocols. In this review, we shed light on the up-to-date knowledge of the novel childhood B-ALL subtypes and the altered signaling pathways that could become new druggable targets.

Abstract

B-cell acute lymphoblastic leukemia (B-ALL) is a hematologic malignancy that arises from the clonal expansion of transformed B-cell precursors and predominately affects childhood. Even though significant progresses have been made in the treatment of B-ALL, pediatric patients’ outcome has to be furtherly increased and alternative targeted treatment strategies are required for younger patients. Over the last decade, novel approaches have been used to understand the genomic landscape and the complexity of the molecular biology of pediatric B-ALL, mainly next generation sequencing, offering important insights into new B-ALL subtypes, altered pathways, and therapeutic targets that may lead to improved risk stratification and treatments. Here, we will highlight the up-to-date knowledge of the novel B-ALL subtypes in childhood, with particular emphasis on altered signaling pathways. In addition, we will discuss the targeted therapies that showed promising results for the treatment of the different B-ALL subtypes.

LEF1 Induces DHRS2 Gene Expression in Human Acute Leukemia Jurkat T-Cells

Objective

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive disease resulting from the accumulation of genetic changes that affect the development of T-cells. The precise role of lymphoid enhancer-binding factor 1 (LEF1) in T-ALL has been controversial since both overexpression and inactivating LEF1 mutations have been reported to date. Here, we investigate the potential gene targets of LEF1 in the Jurkat human T-cell leukemia cell line.

Materials and Methods

We used small interfering RNA (siRNA) technology to knock down LEF1 in Jurkat cells and then compared the gene expression levels in the LEF1 knockdown cells with non-targeting siRNA-transfected and non-transfected cells by employing microarray analysis.

Results

We identified DHRS2, a tumor suppressor gene, as the most significantly downregulated gene in LEF1 knockdown cells, and we further confirmed its downregulation by real-time quantitative polymerase chain reaction (qRT-PCR) in mRNA and at protein level by western blotting.

Conclusion

Our results revealed that DHRS2 is positively regulated by LEF1 in Jurkat cells, which indicates the capability of LEF1 as a tumor suppressor and, together with previous reports, suggests that LEF1 exhibits a regulatory role in T-ALL via not only its oncogenic targets but also tumor suppressor genes.

Deciphering the role of Wnt signaling in acute myeloid leukemia prognosis: how alterations in DNA methylation come into play in patients' prognosis

Acute myeloid leukemia (AML) is a malignant clonal disorder affecting myeloid differentiation through mechanisms that include epigenetic dysregulation. Abnormal changes in DNA methylation and gene expression profiles of pathways involved in hematopoietic development, such as Wnt/β-catenin, contribute to the transformation, development, and maintenance of leukemic cells. This review summarizes the alterations of Wnt signaling-related genes at the epigenetic and transcriptional level and their implications for AML prognosis. Among the implications of epigenetic alterations in AML, methylation of Wnt antagonists is related to poor prognosis, whereas their upregulation has been associated with a better clinical outcome. Furthermore, Wnt target genes c-Myc and LEF-1 present distinct implications. LEF-1 expression positively influences the patient overall survival. c-Myc upregulation has been associated with treatment resistance in AML, although c-Myc expression is not exclusively dependent of Wnt signaling. Understanding the signaling abnormalities could help us to further understand leukemogenesis, improve the current risk stratification for AML patients, and even serve to propose novel therapeutic targets.

Wnt Signaling in Leukemia and Its Bone Marrow Microenvironment

Leukemia is an aggressive hematologic neoplastic disease. Therapy-resistant leukemic stem cells (LSCs) may contribute to the relapse of the disease. LSCs are thought to be protected in the leukemia microenvironment, mainly consisting of mesenchymal stem/stromal cells (MSC), endothelial cells, and osteoblasts. Canonical and noncanonical Wnt pathways play a critical role in the maintenance of normal hematopoietic stem cells (HSC) and LSCs. In this review, we summarize recent findings on the role of Wnt signaling in leukemia and its microenvironment and provide information on the currently available strategies for targeting Wnt signaling.

Quercetin Inhibits Lef1 and Resensitizes Docetaxel-Resistant Breast Cancer Cells

Drug resistance is a major problem for breast cancer patients. Docetaxel is an anti-mitotic agent that serves as first line of treatment in metastatic breast cancer, however it is susceptible to cellular drug resistance. Drug-resistant cells are able to spread during treatment, leading to treatment failure and eventually metastasis, which remains the main cause for cancer-associated death. In previous studies, we used single-cell technologies and identified a set of genes that exhibit increased expression in drug-resistant cells, and they are mainly regulated by Lef1. Furthermore, upregulating Lef1 in parental cells caused them to become drug resistant. Therefore, we hypothesized that inhibiting Lef1 could resensitize cells to docetaxel. Here, we confirmed that Lef1 inhibition, especially on treatment with the small molecule quercetin, decreased the expression of Lef1 and resensitized cells to docetaxel. Our results demonstrate that Lef1 inhibition also downregulated ABCG2, Vim, and Cav1 expression and equally decreased Smad-dependent TGF-β signaling pathway activation. Likewise, these two molecules worked in a synergetic manner, greatly reducing the viability of drug-resistant cells. Prior studies in phase I clinical trials have already shown that quercetin can be safely administered to patients. Therefore, the use of quercetin as an adjuvant treatment in addition to docetaxel for the treatment of breast cancer may be a promising therapeutic approach.

The Role Played by Wnt/β-Catenin Signaling Pathway in Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is an aggressive hematologic neoplastic disorder that arises from the clonal expansion of transformed T-cell or B-cell precursors. Thanks to progress in chemotherapy protocols, ALL outcome has significantly improved. However, drug-resistance remains an unresolved issue in the treatment of ALL and toxic effects limit dose escalation of current chemotherapeutics. Therefore, the identification of novel targeted therapies to support conventional chemotherapy is required. The Wnt/β-catenin pathway is a conserved signaling axis involved in several physiological processes such as development, differentiation, and adult tissue homeostasis. As a result, deregulation of this cascade is closely related to initiation and progression of various types of cancers, including hematological malignancies. In particular, deregulation of this signaling network is involved in the transformation of healthy HSCs in leukemic stem cells (LSCs), as well as cancer cell multi-drug-resistance. This review highlights the recent findings on the role of Wnt/β-catenin in hematopoietic malignancies and provides information on the current status of Wnt/β-catenin inhibitors with respect to their therapeutic potential in the treatment of ALL.

Targeting Wnt/β-catenin and PI3K/Akt/mTOR pathways in T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological disorder that results from the clonal transformation of T-cell precursors. Phosphatidylinositol 3-kinase (PI3K)/Akt/mechanistic target of rapamycin (mTOR) and canonical Wnt/β-catenin signaling pathways play a crucial role in T-cell development and in self-renewal of healthy and leukemic stem cells. Notably, β-catenin is a transcriptional regulator of several genes involved in cancer cell proliferation and survival. In this way, aberrations of components belonging to the aforementioned networks contribute to T-ALL pathogenesis. For this reason, inhibition of both pathways could represent an innovative strategy in this hematological malignancy. Here, we show that combined targeting of Wnt/β-catenin pathway through ICG-001, a CBP/β-catenin transcription inhibitor, and of the PI3K/Akt/mTOR axis through ZSTK-474, a PI3K inhibitor, downregulated proliferation, survival, and clonogenic activity of T-ALL cells. ICG-001 and ZSTK-474 displayed cytotoxic effects, and, when combined together, induced a significant increase in apoptotic cells. This induction of apoptosis was associated with the downregulation of Wnt/β-catenin and PI3K/Akt/mTOR pathways. All these findings were confirmed under hypoxic conditions that mimic the bone marrow niche where leukemic stem cells are believed to reside. Taken together, our findings highlight potentially promising treatment consisting of cotargeting Wnt/β-catenin and PI3K/Akt/mTOR pathways in T-ALL settings.

Prognostic Impact of Lymphoid Enhancer Factor 1 Expression and Serum Galectin.3 in Egyptian AML Patients

BACKGROUND

Deregulation of the Wnt signaling pathway had a role in haematological malignancies. Previous studies reported that lymphoid enhancer factor 1 (LEF1) expression and serum Galectin-3 level could affect clinical parameters and outcome in acute myeloid leukemia patients, but as far as we know, no study has addressed their combined effect on AML patients.

AIM

We studied the expression of LEF1 by real-time qPCR and measured serum level of Gal.3 by ELISA technique in peripheral blood of 69 AML patients and correlated it with different clinicopathological criteria of patients, response, PFS and OS.

RESULTS

We found high expression (LEF1high) was associated with better OS (p = 0.02) and EFS (p = 0.019) compared to LEF1low, low serum Gal.3 level had better OS (p = 0.014) and EFS (p = 0.02) compared to high serum Gal.3 level. LEF1high less likely to carry a FLT3-ITD (p = 0.047) compared to LEF1low patient, also LEF1high characterized by favorable risk (p = 0.02) than LEF1low patients. While patients with higher Gal-3 levels characterized by poor risk (p = 0.02) than lower Gal.3 lels, also more likely to carry a FLT3-ITD with borderline significance (p = 0.054). Combined LEF1high/Gal.3 low patients had lower baseline blast percentages (p = 0.02), favorable risk (p = 0.01), less likely to carry FLT3-ITD (p = 0.02), higher CR rate (p = 0.055), shorter time to CR (0.001) than other groups. Among high Gal.3 level group, LEF1highexpression improved OS and EFS (20 and 15 months respectively) vs LEF1low expression (13 and 8 months respectively).

CONCLUSION

We conclude that high LEF1 expression was a favorable prognostic marker which can define AML patient risk and outcome independent from assessing the serum galectin.3 level.

Wnt Signalling in Acute Myeloid Leukaemia

Acute myeloid leukaemia (AML) is a group of malignant diseases of the haematopoietic system. AML occurs as the result of mutations in haematopoietic stem/progenitor cells, which upregulate Wnt signalling through a variety of mechanisms. Other mechanisms of Wnt activation in AML have been described such as Wnt antagonist inactivation through promoter methylation. Wnt signalling is necessary for the maintenance of leukaemic stem cells. Several molecules involved in or modulating Wnt signalling have a prognostic value in AML. These include: β-catenin, LEF-1, phosphorylated-GSK3β, PSMD2, PPARD, XPNPEP, sFRP2, RUNX1, AXIN2, PCDH17, CXXC5, LLGL1 and PTK7. Targeting Wnt signalling for tumour eradication is an approach that is being explored in haematological and solid tumours. A number of preclinical studies confirms its feasibility, albeit, so far no reliable clinical trial data are available to prove its utility and efficacy.

Nuclear factor of activated T-cells, NFATC1, governs FLT3ITD-driven hematopoietic stem cell transformation and a poor prognosis in AML

Background

Acute myeloid leukemia (AML) patients with a high allelic burden of an internal tandem duplication (ITD)-mutated FMS-like Tyrosine Kinase-3 (FLT3) have a dismal outcome. FLT3^ITD triggers the proliferation of the quiescent hematopoietic stem cell (HSC) pool but fails to directly transform HSCs. While the inflammatory transcription factor nuclear factor of activated T-cells 2 (NFAT2, NFATC1) is overexpressed in AML, it is unknown whether it plays a role in FLT3^ITD-induced HSC transformation.

Methods

We generated a triple transgenic mouse model, in which tamoxifen-inducible Cre-recombinase targets expression of a constitutively nuclear transcription factor NFATC1 to FLT3^ITD positive HSC. Emerging genotypes were phenotypically, biochemically, and also transcriptionally characterized using RNA sequencing. We also retrospectively analyzed the overall survival of AML patients with different NFATC1 expression status.

Results

We find that NFATC1 governs FLT3^ITD-driven precursor cell expansion and transformation, causing a fully penetrant lethal AML. FLT3^ITD/NFATC1-AML is re-transplantable in secondary recipients and shows primary resistance to the FLT3^ITD-kinase inhibitor quizartinib. Mechanistically, NFATC1 rewires FLT3^ITD-dependent signaling output in HSC, involving augmented K-RAS signaling and a selective de novo recruitment of key HSC-transforming signaling pathways such as the Hedgehog- and WNT/B-Catenin signaling pathways. In human AML, NFATC1 overexpression is associated with poor overall survival.

Conclusions

NFATC1 expression causes FLT3^ITD-induced transcriptome changes, which are associated with HSC transformation, quizartinib resistance, and a poor prognosis in AML.

Electronic supplementary material

The online version of this article (10.1186/s13045-019-0765-y) contains supplementary material, which is available to authorized users.

LEF1-AS1, long non-coding RNA, inhibits proliferation in myeloid malignancy

LEF1 antisense RNA 1 (LEF1‐AS1) is an antisense long non‐coding RNA encoded in the lymphoid enhancer‐binding factor 1 (LEF1) locus. LEF1‐AS1 is a conserved transcript dysregulated in hematopoiesis. This study aimed to functionally characterize the role of this transcript in myeloid malignancy and explore a possible regulatory effect of LEF1‐AS1 upon LEF1. We show that LEF1‐AS1 is highly expressed in normal hematopoietic stem cells but barely detectable in myeloid malignant cell lines. Additionally, bone marrow cells from myelodysplastic syndrome (n=12) and acute myeloid malignancy patients (n=28) expressed significantly reduced levels of LEF1‐AS1 compared to healthy controls (n=15). Artificial LEF1‐AS1 over‐expression inhibited proliferation in HL60 and led to an upregulation of tumor suppressors p21 and p27, and reduced ERK1/2 activation. Unexpectedly, no underlying modulation of LEF1 was detected. Ectopic expression of LEF1‐AS1 also inhibited proliferation in HELA, a cell line lacking endogenous expression of LEF1, supporting a LEF1‐independent mechanism. Additionally, transient over‐expression of LEF1‐AS1 in AML patient cells also led to reduced proliferation and colony formation capacity. We used a mass spectrometry‐based proteomics approach. Proteomic quantification identified the modulation of an important metabolic regulator, Fumarase, and concomitant accumulation of the metabolite fumarate.

Lymphoid enhancer-binding factor-1 promotes stemness and poor differentiation of hepatocellular carcinoma by directly activating the NOTCH pathway

The poorly differentiated hepatocellular carcinoma (HCC) cells are usually characterized by immature hepatic progenitor cell-like properties, such as enhanced self-renewal ability, resistance to chemotherapeutic drugs, and a loss of mature hepatocyte proteins. However, the molecular mechanisms governing this process still remain unclear. In this study, we found the lymphoid enhancer-binding factor-1 (LEF1), a transcriptional factor, was frequently overexpressed in HCCs, which was significantly associated with poor prognosis and tumor cell differentiation. Functional studies have found that LEF1 enhanced cell growth, foci formation, colony formation in soft agar, and tumor formation in nude mice. Different from its canonical roles in the WNT signaling pathway, we found that LEF1 could activate the critical members (e.g., NOTCH1 and NOTCH2) of the NOTCH signaling pathway through directly binding to their promoter regions. Further studies have found that LEF1 could enhance the self-renewal ability, drug resistance, dedifferentiation, and invasion of HCC cells. The oncogenic functions and the effects of LEF1 on cancer stemness could be effectively inhibited by NOTCH inhibitor. Further characterization of LEF1 may lead to the development of novel therapeutic strategies for HCC treatment.

LEF-1 drives aberrant β-catenin nuclear localization in myeloid leukemia cells

Canonical Wnt/β-catenin signaling is frequently dysregulated in myeloid leukemias and is implicated in leukemogenesis. Nuclear-localized β-catenin is indicative of active Wnt signaling and is frequently observed in acute myeloid leukemia (AML) patients; however, some patients exhibit little or no nuclear β-catenin even where cytosolic β-catenin is abundant. Control of the subcellular localization of β-catenin therefore represents an additional mechanism regulating Wnt signaling in hematopoietic cells. To investigate the factors mediating the nuclear-localization of β-catenin, we carried out the first nuclear/cytoplasmic proteomic analysis of the β-catenin interactome in myeloid leukemia cells and identified putative novel β-catenin interactors. Comparison of interacting factors between Wnt-responsive cells (high nuclear β-catenin) versus Wnt-unresponsive cells (low nuclear β-catenin) suggested the transcriptional partner, LEF-1, could direct the nuclear-localization of β-catenin. The relative levels of nuclear LEF-1 and β-catenin were tightly correlated in both cell lines and in primary AML blasts. Furthermore, LEF-1 knockdown perturbed β-catenin nuclear-localization and transcriptional activation in Wnt-responsive cells. Conversely, LEF-1 overexpression was able to promote both nuclear-localization and β-catenin-dependent transcriptional responses in previously Wnt-unresponsive cells. This is the first β-catenin interactome study in hematopoietic cells and reveals LEF-1 as a mediator of nuclear β- catenin level in human myeloid leukemia.

Targeting nuclear β-catenin as therapy for post-myeloproliferative neoplasm secondary AML

Transformation of post-myeloproliferative neoplasms into secondary (s) AML exhibit poor clinical outcome. In addition to increased JAK-STAT and PI3K-AKT signaling, post-MPN sAML blast progenitor cells (BPCs) demonstrate increased nuclear β-catenin levels and TCF7L2 (TCF4) transcriptional activity. Knockdown of β-catenin or treatment with BC2059 that disrupts binding of β-catenin to TBL1X (TBL1) depleted nuclear β-catenin levels. This induced apoptosis of not only JAKi-sensitive but also JAKi-persister/resistant post-MPN sAML BPCs, associated with attenuation of TCF4 transcriptional targets MYC, BCL-2, and Survivin. Co-targeting of β-catenin and JAK1/2 inhibitor ruxolitinib (rux) synergistically induced lethality in post-MPN sAML BPCs and improved survival of mice engrafted with human sAML BPCs. Notably, co-treatment with BET protein degrader ARV-771 and BC2059 also synergistically induced apoptosis and improved survival of mice engrafted with JAKi-sensitive or JAKi-persister/resistant post-MPN sAML cells. These preclinical findings highlight potentially promising anti-post-MPN sAML activity of the combination of β-catenin and BETP antagonists against post-MPN sAML BPCs.

Identification of LEF1 as a Susceptibility Locus for Kawasaki Disease in Patients Younger than 6 Months of Age

Kawasaki disease (KD) is an acute febrile vasculitis predominately affecting infants and children. The dominant incidence age of KD is from 6 months to 5 years of age, and the incidence is unusual in those younger than 6 months and older than 5 years of age. We tried to identify genetic variants specifically associated with KD in patients younger than 6 months or older than 5 years of age. We performed an age-stratified genome-wide association study using the Illumina HumanOmni1-Quad BeadChip data (296 cases vs. 1,000 controls) and a replication study (1,360 cases vs. 3,553 controls) in the Korean population. Among 26 candidate single nucleotide polymorphisms (SNPs) tested in replication study, only a rare nonsynonymous SNP (rs4365796: c.1106C＞T, p.Thr369Met) in the lymphoid enhancer binding factor 1 (LEF1) gene was very significantly associated with KD in patients younger than 6 months of age (odds ratio [OR], 3.07; p_combined = 1.10 × 10^-5), whereas no association of the same SNP was observed in any other age group of KD patients. The same SNP (rs4365796) in the LEF1 gene showed the same direction of risk effect in Japanese KD patients younger than 6 months of age, although the effect was not statistically significant (OR, 1.42; p = 0.397). This result indicates that the LEF1 gene may play an important role as a susceptibility gene specifically affecting KD patients younger than 6 months of age.

Role of human oocyte-enriched factors in somatic cell reprograming

Cellular reprograming paves the way for creating functional patient-specific tissues to eliminate immune rejection responses by applying the same genetic profile. However, the epigenetic memory of a cell remains a challenge facing the current reprograming methods and does not allow transcription factors to bind properly. Because somatic cells can be reprogramed by transferring their nuclear contents into oocytes, introducing specific oocyte factors into differentiated cells is considered a promising approach for mimicking the reprograming process that occurs during fertilization. Mammalian metaphase II oocyte possesses a superior capacity to epigenetically reprogram somatic cell nuclei towards an embryonic stem cell-like state than the current factor-based reprograming approaches. This may be due to the presence of specific factors that are lacking in the current factor-based reprograming approaches. In this review, we focus on studies identifying human oocyte-enriched factors aiming to understand the molecular mechanisms mediating cellular reprograming. We describe the role of oocyte-enriched factors in metabolic switch, chromatin remodelling, and global epigenetic transformation. This is critical for improving the quality of resulting reprogramed cells, which is crucial for therapeutic applications.

Early mortality in acute promyelocytic leukemia: Potential predictors

Acute promyelocytic leukemia (APL) is a rare leukemia characterized by the balanced reciprocal translocation between the promyelocytic leukemia gene on chromosome 15 and the retinoic acid receptor α (RARα) gene on chromosome 17, and accounts for 10-15% of newly diagnosed acute myeloid leukemia each year. The combined use of all-trans retinoic acid and arsenic trioxide (ATO) as primary therapy has markedly improved the survival rate of patients with APL. Mortality in the first 30 days following therapy remains a major contribution to treatment failure. In the present study, published data was reviewed with a focus on the factors associated with early mortality. When treated with ATO as a primary treatment, the fms-like tyrosine kinase-internal tandem deletion has no impact on early mortality. Low lymphoid enhancer binding factor-1 expression may be a reliable marker for early mortality and the target of therapy if it could be proven by further studies. Cluster of differentiation (CD)56+ and CD34+/CD2+ may be candidates to select high-risk patients. The risk of early mortality in APL still cannot be predicted via the cell surface makers, despite multiple studies on their prognostic significance. Typically, a complex translocation did not alter the survival rate in patients with APL; however, if an abnormal karyotype [e.g., Ide(17), ZBTB16/RARα and STAT5B/RARα] appeared singularly or as part of a complex mutation, there is a high possibility of early mortality if clinicians are unable to identify or monitor it.

Gene expression profiling of hematologic malignant cell lines resistant to oncolytic virus treatment

Pexa-Vec (pexastimogene devacirpvec; JX-594) has emerged as an attractive tool in oncolytic virotherapy. Pexa-Vec demonstrates oncolytic and immunotherapeutic mechanisms of action. But the determinants of resistance to Pexa-Vec are mostly unknown. We treated hemoatologic malignant cells with Pexa-Vec and examined the gene-expression pattern of sensitive and resistant cells. Human myeloid malignant cell lines (RPMI-8226, IM-9, K562, THP-1) and lymphoid cancer cell lines (MOLT4, CCRF-CEM, Ramos, U937) were treated with Pexa-Vec. Pexa-Vec was cytotoxic on myeloid cell lines in a dose-dependent manner, and fluorescent imaging and qPCR revealed that Pexa-Vec expression was low in RAMOS than IM-9 after 24 hrs and 48 hrs of infection. Gene expression profiles between two groups were analyzed by microarray. Genes with at least 2-fold increase or decrease in their expression were identified. A total of 660 genes were up-regulated and 776 genes were down-regulated in lymphoid cancer cell lines. The up- and down-regulated genes were categorized into 319 functional gene clusters. We identified the top 10 up-regulated genes in lymphoid cells. Among them three human genes (LEF1, STAMBPL1, and SLFN11) strongly correlated with viral replication. Up-regulation of PVRIG, LPP, CECR1, Arhgef6, IRX3, IGFBP2, CD1d were related to resistant to Pexa-Vec. In conclusion, lymphoid malignant cells are resistant to Pexa-Vec and displayed up-regulated genes associated with resistance to oncolytic viral therapy. These data provide potential targets to overcome resistance, and suggest that molecular assays may be useful in selecting patients for further clinical trials with Pexa-Vec.

LEF1 reduces tumor progression and induces myodifferentiation in a subset of rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children and show characteristics of skeletal muscle differentiation. The two major RMS subtypes in children are alveolar (ARMS) and embryonal RMS (ERMS). We demonstrate that approximately 50% of ARMS and ERMS overexpress the LEF1/TCF transcription factor LEF1 when compared to normal skeletal muscle and that LEF1 can restrain aggressiveness especially of ARMS cells. LEF1 knockdown experiments in cell lines reveal that depending on the cellular context, LEF1 can induce pro-apoptotic signals. LEF1 can also suppress proliferation, migration and invasiveness of RMS cells both in vitro and in vivo. Furthermore, LEF1 can induce myodifferentiation of the tumor cells. This may involve regulation of other LEF1/TCF factors i.e. TCF1, whereas β-catenin activity plays a subordinate role. Together these data suggest that LEF1 rather has tumor suppressive functions and attenuates aggressiveness in a subset of RMS.

Neuroblastoma pathogenesis: deregulation of embryonic neural crest development

Neuroblastoma (NB) is an aggressive pediatric cancer that originates from neural crest tissues of the sympathetic nervous system. NB is highly heterogeneous both from a clinical and a molecular perspective. Clinically, this cancer represents a wide range of phenotypes ranging from spontaneous regression of 4S disease to unremitting treatment-refractory progression and death of high-risk metastatic disease. At a cellular level, the heterogeneous behavior of NB likely arises from an arrest and deregulation of normal neural crest development. In the present review, we summarize our current knowledge of neural crest development as it relates to pathways promoting 'stemness' and how deregulation may contribute to the development of tumor-initiating CSCs. There is an emerging consensus that such tumor subpopulations contribute to the evolution of drug resistance, metastasis and relapse in other equally aggressive malignancies. As relapsed, refractory disease remains the primary cause of death for neuroblastoma, the identification and targeting of CSCs or other primary drivers of tumor progression remains a critical, clinically significant goal for neuroblastoma. We will critically review recent and past evidence in the literature supporting the concept of CSCs as drivers of neuroblastoma pathogenesis.

LEF1 is preferentially expressed in the tubal-peritoneal junctions and is a reliable marker of tubal intraepithelial lesions

Recently it has been reported that serous tubal intraepithelial carcinoma (STIC), the likely precursor of ovarian/extra-uterine high-grade serous carcinoma, are frequently located in the vicinity of tubal-peritoneal junctions, consistent with the cancer-prone features of many epithelial transitional regions. To test if p53 (aka TP53)-signatures and secretory cell outgrowths (SCOUTs) also localize to tubal-peritoneal junctions, we examined these lesions in the fallopian tubes of patients undergoing salpingo-oophorectomy for sporadic high-grade serous carcinomas or as a prophylactic procedure for carriers of familial BRCA1 or 2 mutations. STICs were located closest to the tubal-peritoneal junctions with an average distance of 1.31 mm, while SCOUTs were not detected in the fimbriated end of the fallopian tube. As many epithelial transitional regions contain stem cells, we also determined the expression of stem cell markers in the normal fallopian tube, tubal intraepithelial lesions and high-grade serous carcinomas. Of those, LEF1 was consistently expressed in the tubal-peritoneal junctions and all lesions, independent of p53 status. All SCOUTs demonstrated strong nuclear expression of β-catenin consistent with the LEF1 participation in the canonical WNT pathway. However, β-catenin was preferentially located in the cytoplasm of cells comprising STICs and p53 signatures, suggesting WNT-independent function of LEF1 in those lesions. Both frequency of LEF1 expression and β-catenin nuclear expression correlated with the worst 5-year patient survival, supporting important role of both proteins in high-grade serous carcinoma. Taken together, our findings suggest the existence of stem cell niche within the tubal-peritoneal junctions. Furthermore, they support the notion that the pathogenesis of SCOUTs is distinct from that of STICs and p53 signatures. The location and discrete patterns of LEF1 and β-catenin expression may serve as highly sensitive and reliable ancillary markers for the detection and differential diagnosis of tubal intraepithelial lesions.

Wnt signaling pathway protein LEF1 in cancer, as a biomarker for prognosis and a target for treatment

Transcription factors are regulatory proteins that either activate or repress the transcription of genes via binding to DNA regulatory sequences and regulating recruitment of transcriptional complexes. Lymphoid enhancer-binding factor 1 (LEF1), a member of the T-cell Factor (TCF)/LEF1 family of high-mobility group transcription factors, is a downstream mediator of the Wnt/β-catenin signaling pathway, but can also modulate gene transcription independently. LEF1 is essential in stem cell maintenance and organ development, especially in its role in epithelial-mesenchymal transition (EMT) by activating the transcription of hallmark EMT effectors including N-Cadherin, Vimentin, and Snail. Aberrant expression of LEF1 is implicated in tumorigenesis and cancer cell proliferation, migration, and invasion. LEF1's activity in particular cancer cell types, such as chronic lymphocytic leukemia (CLL), Burkitt lymphoma (BL), acute lymphoblastic leukemia (ALL), oral squamous cell carcinoma (OSCC), and colorectal cancer (CRC), makes it a valuable biomarker in predicting patient prognosis. Additionally, due to aberrant LEF1 activity resulting in cancer progression, knockdown and inhibition treatments designed to target LEF1 have proven effective in alleviating cancer growth, migration, and invasion in CLL, CRC, glioblastoma multiforme (GBM), and renal cell carcinoma (RCC). In prostate cancer cells, LEF1 promotes androgen receptor expression and activity in an androgen-independent manner, ultimately increasing prostate cancer growth regardless of androgen ablation therapy. In this review, we review LEF1 regulation, its role in tumorigenesis in several cancer types, and its clinical value as a biomarker for predicting prognoses and as a target for treatment.

The expressions of metadherin and LEF-1 in mucosa-associated lymphoid tissue lymphoma of ocular adnexal

AIM

To investigate the expressions of metadherin (astrocyte elevated gene-1, AEG-1) and lymphoid enhancer-binding factor-1 (LEF-1) in ocular adnexal mucosa-associated lymphoid tissue (MALT) lymphoma.

METHODS

The expressions of AEG-1 and LEF-1 were detected on specimens harvested from patients suffering from MALT lymphoma and lymphadenosis of ocular adnexal in Ophthalmology Department, Affiliated Hospital of Qingdao University from 2000 to 2015 by immunohistochemical and polymerase chain reaction (PCR) analysis.

RESULTS

AEG-1 and LEF-1 expressions in MALT lymphoma was respectively higher than that in lymphadenosis, both by immunohistochemical and PCR analysis (P<0.05). Diversity of AEG-1 and LEF-1 expressions in different Ann Arbor clinical stages showed a statistically significant result (P<0.05). A positive relevance between AEG-1 and LEF-1 was observed in MALT ocular adnexal lymphoma (r=0.435, P=0.016).

CONCLUSION

The over expressions of AEG-1 and LEF-1 at the level of protein and mRNA participates in the tumorigenesis of ocular adnexal MALT lymphoma. They should act as a new biological marker for pathological diagnosis in the future.

Isolation and characterization of lymphoid enhancer factor-1-positive deciduous dental pulp stem-like cells after transfection with a piggyBac vector containing LEF1 promoter-driven selection markers

OBJECTIVE

Lymphoid enhancer-binding factor-1 (LEF1) is a 48-kD nuclear protein that is expressed in pre-B and T cells. LEF1 is also an important member of the Wnt/β-catenin signaling pathway that plays important roles in the self-renewal and differentiation of embryonic stem cells. We speculated that LEF1 might function in the stem cells from human exfoliated deciduous teeth (SHED). In this study, we attempted to isolate such LEF1-positive cells from human deciduous dental pulp cells (HDDPCs) by genetic engineering technology, using the human LEF1 promoter.

DESIGN

A piggyBac transposon plasmid (pTA-LEN) was introduced into HDDPCs, using the Neon^® transfection system. After G418 selection, the emerging colonies were assessed for EGFP-derived fluorescence by fluorescence microscopy. Reverse transcription polymerase chain reaction (RT-PCR) analysis was performed using RNA isolated from these colonies to examine stem cell-specific transcript expression. Osteoblastic or neuronal differentiation was induced by cultivating the LEF1-positive cells with differentiation-inducing medium.

RESULTS

RT-PCR analysis confirmed the expression of several stem cell markers, including OCT3/4, SOX2, REX1, and NANOG, in LEF1-positive HDDPCs, which could be differentiated into osteoblasts and neuronal cells.

CONCLUSIONS

The isolated LEF1-positive HDDPCs exhibited the properties of stem cells, suggesting that LEF1 might serve as a marker for SHED.

Cellular transformation of human mammary epithelial cells by SATB2

Breast tumors are heterogeneous and carry a small population of progenitor cells that can produce various subtypes of breast cancer. SATB2 (special AT-rich binding protein-2) is a newly identified transcription factor and epigenetic regulator. It is highly expressed in embryonic stem cells, but not in adult tissues, and regulates pluripotency-maintaining factors. However, the molecular mechanisms by which SATB2 induces transformation of human mammary epithelial cells (HMECs) leading to malignant phenotype are unknown. The main goal of this paper is to examine the molecular mechanisms by which SATB2 induces cellular transformation of HMECs into cells that are capable of self-renewal. SATB2-transformed HMECs gain the phenotype of breast progenitor cells by expressing markers of stem cells, pluripotency-maintaining factor, and epithelial to mesenchymal transition. SATB2 is highly expressed in human breast cancer cell lines, primary mammary tissues and cancer stem cells (CSCs), but not in HMECs and normal breast tissues. Chromatin Immunoprecipitation assays demonstrate that SATB2 can directly bind to promoters of Bcl-2, c-Myc, Nanog, Klf4, and XIAP, suggesting a role of SATB2 in regulation of pluripotency, cell survival and proliferation. Furthermore, inhibition of SATB2 by shRNA in breast cancer cell lines and CSCs attenuates cell proliferation and EMT phenotype. Our results suggest that SATB2 induces dedifferentiation/transformation of mature HMECs into progenitor-like cells.

High LEF1 expression predicts adverse prognosis in chronic lymphocytic leukemia and may be targeted by ethacrynic acid

Aberrant activation of lymphoid enhancer-binding factor-1 (LEF1) has been identified in several cancers, including chronic lymphocytic leukemia (CLL). As a key transcription factor of the Wnt/β-catenin pathway, LEF1 helps to regulate important genes involved in tumor cell death mechanisms. In this study, we determined LEF1 gene expression levels in CLL (n = 197) and monoclonal B-cell lymphocytosis (MBL) (n = 6) patients through real-time RT-PCR. LEF1 was significantly up-regulated in both MBL and CLL patients compared with normal B cells. Treatment-free survival (TFS) time and overall survival (OS) time were much longer in CLL patients with low LEF1 expression than in those with high LEF1 levels. Furthermore, Wnt inhibitor ethacrynic acid (EA) induced both apoptosis and necroptosis in primary CLL cells. EA also enhanced the cytotoxicity of both fludarabine and cyclophosphamide against CLL cells in vitro. Finally, we demonstrated that EA functions by inhibiting the recruitment of LEF1 to DNA promoters and restoring cylindromatosis (CYLD) expression in CLL cells. Our results showed, for the first time, that high LEF1 expression is associated with poor survival for CLL patients. Combined with other chemotherapeutic drugs, EA may be a promising therapeutic agent for CLL.

Hematopoietic and Leukemic Stem Cells Have Distinct Dependence on Tcf1 and Lef1 Transcription Factors

Hematopoietic and leukemic stem cells (HSCs and LSCs) have self-renewal ability to maintain normal hematopoiesis and leukemia propagation, respectively. Tcf1 and Lef1 transcription factors are expressed in HSCs, and targeting both factors modestly expanded the size of the HSC pool due to diminished HSC quiescence. Functional defects of Tcf1/Lef1-deficient HSCs in multi-lineage blood reconstitution was only evident under competitive conditions or when subjected to repeated regenerative stress. These are mechanistically due to direct positive regulation of Egr and Tcf3 by Tcf1 and Lef1, and significantly, forced expression of Egr1 in Tcf1/Lef1-deficient HSCs restored HSC quiescence. In a preclinical CML model, loss of Tcf1/Lef1 did not show strong impact on leukemia initiation and progression. However, when transplanted into secondary recipients, Tcf1/Lef1-deficient LSCs failed to propagate CML. By induced deletion of Tcf1 and Lef1 in pre-established CML, we further demonstrated an intrinsic requirement for these factors in LSC self-renewal. When combined with imatinib therapy, genetic targeting of Tcf1 and Lef1 potently diminished LSCs and conferred better protection to the CML recipients. LSCs are therefore more sensitive to loss of Tcf1 and Lef1 than HSCs in their self-renewal capacity. The differential requirements in HSCs and LSCs thus identify Tcf1 and Lef1 transcription factors as novel therapeutic targets in treating hematological malignancies, and inhibition of Tcf1/Lef1-regulated transcriptional programs may thus provide a therapeutic window to eliminate LSCs with minimal side effect on normal HSC functions.