Ectopic Activation of Fgf8 in Dental Mesenchyme Causes Incisor Agenesis and Molar Microdontia.

Putatively, tooth agenesis was attributed to the initiation failure of tooth germs, though little is known about the histological and molecular alterations. To address if constitutively active FGF signaling is associated with tooth agenesis, we activated Fgf8 in dental mesenchyme with Osr-cre knock-in allele in mice (Osr2-creKI; Rosa26R-Fgf8) and found incisor agenesis and molar microdontia. The cell survival assay showed tremendous apoptosis in both the Osr2-creKI; Rosa26R-Fgf8 incisor epithelium and mesenchyme, which initiated incisor regression from cap stage. In situ hybridization displayed vanished Shh transcription, and immunostaining exhibited reduced Runx2 expression and enlarged mesenchymal Lef1 domain in Osr2-creKI; Rosa26R-Fgf8 incisors, both of which were suggested to enhance apoptosis. In contrast, Osr2-creKI; Rosa26R-Fgf8 molar germs displayed mildly suppressed Shh transcription, and the increased expression of Ectodin, Runx2 and Lef1. Although mildly smaller than WT controls prenatally, the Osr2-creKI; Rosa26R-Fgf8 molar germs produced a miniature tooth with impaired mineralization after a 6-week sub-renal culture. Intriguingly, the implanted Osr2-creKI; Rosa26R-Fgf8 molar germs exhibited delayed odontoblast differentiation and accelerated ameloblast maturation. Collectively, the ectopically activated Fgf8 in dental mesenchyme caused incisor agenesis by triggering incisor regression and postnatal molar microdontia. Our findings reported tooth agenesis resulting from the regression from the early bell stage and implicated a correlation between tooth agenesis and microdontia.

Exosomes derived from mouse vibrissa dermal papilla cells promote hair follicle regeneration during wound healing by activating Wnt/ß-catenin signaling pathway.

Hair follicle (HF) regeneration during wound healing continues to present a significant clinical challenge. Dermal papilla cell-derived exosomes (DPC-Exos) hold immense potential for inducing HF neogenesis. However, the accurate role and underlying mechanisms of DPC-Exos in HF regeneration in wound healing remain to be fully explained. This study, represents the first analysis into the effects of DPC-Exos on fibroblasts during wound healing. Our findings demonstrated that DPC-Exos could stimulate the proliferation and migration of fibroblasts, more importantly, enhance the hair-inducing capacity of fibroblasts. Fibroblasts treated with DPC-Exos were capable of inducing HF neogenesis in nude mice when combined with neonatal mice epidermal cells. In addition, DPC-Exos accelerated wound re-epithelialization and promoted HF regeneration during the healing process. Treatment with DPC-Exos led to increased expression levels of the Wnt pathway transcription factors ß-catenin and Lef1 in both fibroblasts and the dermis of skin wounds. Specifically, the application of a Wnt pathway inhibitor reduced the effects of DPC-Exos on fibroblasts and wound healing. Accordingly, these results offer evidence that DPC-Exos promote HF regeneration during wound healing by enhancing the hair-inducing capacity of fibroblasts and activating the Wnt/ß-catenin signaling pathway. This suggests that DPC-Exos may represent a promising therapeutic strategy for achieving regenerative wound healing.

Epigenetic alterations affecting hematopoietic regulatory networks as drivers of mixed myeloid/lymphoid leukemia.

Leukemias with ambiguous lineage comprise several loosely defined entities, often without a clear mechanistic basis. Here, we extensively profile the epigenome and transcriptome of a subgroup of such leukemias with CpG Island Methylator Phenotype. These leukemias exhibit comparable hybrid myeloid/lymphoid epigenetic landscapes, yet heterogeneous genetic alterations, suggesting they are defined by their shared epigenetic profile rather than common genetic lesions. Gene expression enrichment reveals similarity with early T-cell precursor acute lymphoblastic leukemia and a lymphoid progenitor cell of origin. In line with this, integration of differential DNA methylation and gene expression shows widespread silencing of myeloid transcription factors. Moreover, binding sites for hematopoietic transcription factors, including CEBPA, SPI1 and LEF1, are uniquely inaccessible in these leukemias. Hypermethylation also results in loss of CTCF binding, accompanied by changes in chromatin interactions involving key transcription factors. In conclusion, epigenetic dysregulation, and not genetic lesions, explains the mixed phenotype of this group of leukemias with ambiguous lineage. The data collected here constitute a useful and comprehensive epigenomic reference for subsequent studies of acute myeloid leukemias, T-cell acute lymphoblastic leukemias and mixed-phenotype leukemias.

Low-level laser activates Wnt/ß-catenin signaling pathway-promoting hair follicle stem cell regeneration and wound healing: Upregulate the expression of key downstream gene Lef 1.

BACKGROUND: The objective of this study is to investigate the mechanism by which low-level laser stimulation promotes the proliferation of intraepithelial hair follicle stem cells (HFSCs) in wounds. This research aims to expand the applications of laser treatment, enhance wound repair methods, and establish a theoretical and experimental foundation for achieving accelerated wound healing. METHODS: The experimental approach involved irradiating a cell model with low-level laser to assess the proliferation of HFSCs and examine alterations in the expression of proteins related to the Wnt/ß-catenin signaling pathway. A mouse back wound model was established to investigate the effects of low-level laser irradiation on wound healing rate, wound microenvironment, and the proliferation of HFSCs in relation to the Wnt/ß-catenin signaling pathway. RESULTS: The research findings indicate that low-level laser light effectively activates the Wnt signaling pathway, leading to the increased accumulation of core protein ß-catenin and the upregulation of key downstream gene Lef 1. Consequently, this regulatory mechanism facilitates various downstream biological effects, including the notable promotion of HFSC proliferation and differentiation into skin appendages and epithelial tissues. As a result, the process of wound healing is significantly accelerated. CONCLUSION: Low levels of laser activates the Wnt signalling pathway, promotes the regeneration of hair follicle stem cells and accelerates wound healing.

Bromuconazole exposure induces cardiac dysfunction by upregulating the expression LEF1.

With the wide application of bromuconazole (BRO), a kind of triazole fungicide, the environmental problems caused by BRO have been paid more and more attention. In this study, adult male zebrafish were exposed to environmental related concentration and the maximum non-lethal concentration for zebrafish larvae (0,50 ng/L and 7.5 mg/L) for 7 days, respectively. Zebrafish exposed to BRO exhibited a significant reduction in body length and an increase in fatness index, indicating adverse physiological changes. Notably, the exposed zebrafish showed enlarged heart ventricular volumes and thinner heart walls. Transcriptome analysis of heart samples showed that BRO exposure mainly affected pathways related to cardiac energy metabolism. In addition, the amount of ATP in the heart tissue was correspondingly reduced, and the expression levels of genes related to controlling ion balance and myosin synthesis in the heart were also altered. The study extended its findings to the rat cardiomyocytes (H9C2), where similar cardiotoxic effects including changes in transcription of genes related to energy metabolism and heart function were also observed, suggesting a potential universal mechanism of BRO-induced cardiotoxicity. In a doxorubicin (DOX) induced larval zebrafish heart failure model, the expression of lymphoid enhancer-binding factor 1(LEF1), a key gene in the Wnt/ß-catenin signaling pathway, was significantly increased in larval zebrafish and adult fish heart tissues and cardiomyocytes, suggesting that LEF1 might play an important role in BRO-induced cardiotoxicity. Taken together, BRO exposure could interfere with cardiac function and metabolic capacity by abnormal activation the expression of LEF1. The study emphasized the urgent need for monitoring and regulating BRO due to its harmful effects on the hearts of aquatic organisms.

TCF1-LEF1 co-expression identifies a multipotent progenitor cell (TH2-MPP) across human allergic diseases.

Repetitive exposure to antigen in chronic infection and cancer drives T cell exhaustion, limiting adaptive immunity. In contrast, aberrant, sustained T cell responses can persist over decades in human allergic disease. To understand these divergent outcomes, we employed bioinformatic, immunophenotyping and functional approaches with human diseased tissues, identifying an abundant population of type 2 helper T (TH2) cells with co-expression of TCF7 and LEF1, and features of chronic activation. These cells, which we termed TH2-multipotent progenitors (TH2-MPP) could self-renew and differentiate into cytokine-producing effector cells, regulatory T (Treg) cells and follicular helper T (TFH) cells. Single-cell T-cell-receptor lineage tracing confirmed lineage relationships between TH2-MPP, TH2 effectors, Treg cells and TFH cells. TH2-MPP persisted despite in vivo IL-4 receptor blockade, while thymic stromal lymphopoietin (TSLP) drove selective expansion of progenitor cells and rendered them insensitive to glucocorticoid-induced apoptosis in vitro. Together, our data identify TH2-MPP as an aberrant T cell population with the potential to sustain type 2 inflammation and support the paradigm that chronic T cell responses can be coordinated over time by progenitor cells.

Utility of LEF1 to differentiate desmoid fibromatosis from its histologic mimics.

Diagnosis of desmoid-type fibromatosis (DF) may be challenging on biopsy due to morphologic overlap with reactive fibrosis (scar) and other uniform spindle cell neoplasms. Evaluation of nuclear ß-catenin, a surrogate of Wnt pathway activation, is often difficult in DF due to weak nuclear expression and high background membranous/cytoplasmic staining. Lymphoid enhancer-factor 1 (LEF1) is a recently characterized effector partner of ß-catenin which activates the transcription of target genes. We investigated the performance of LEF1 and ß-catenin immunohistochemistry in a retrospective series of 156 soft tissue tumors, including 35 DF, 3 superficial fibromatosis, and 121 histologic mimics (19 soft tissue perineurioma, 8 colorectal perineurioma, 4 intraneural perineurioma, 26 scars, 23 nodular fasciitis, 6 low-grade fibromyxoid sarcomas, 6 angioleiomyomas, 5 neurofibromas, 5 dermatofibrosarcoma protuberans, 3 low-grade myofibroblastic sarcomas, 3 synovial sarcomas, 3 inflammatory myofibroblastic tumors, 2 schwannomas, and 1 each of Gardner-associated fibroma, radiation-associated spindle cell sarcoma, sclerotic fibroma, dermatofibroma, and glomus tumor). LEF1 expression was not only seen in 33/35 (94%) of DF but also observed in 19/23 (82%) nodular fasciitis, 7/19 (37%) soft tissue perineurioma, 2/3 (66%) synovial sarcoma, and 6/26 (23%) scar, as well as in 1 radiation-associated spindle cell sarcoma. The sensitivity and specificity of LEF1 IHC for diagnosis of DF were 94% and 70%, respectively. By comparison, ß-catenin offered similar sensitivity, 94%, but 88% specificity. Positivity for LEF1 and ß-catenin in combination showed sensitivity of 89%, lower than the sensitivity of ß-catenin alone (94%); however, the combination of both LEF1 and ß-catenin improved specificity (96%) compared to the specificity of ß-catenin alone (88%). Although LEF1 has imperfect specificity in isolation, this stain has diagnostic utility when used in combination with ß-catenin.

Targeting LEF1-mediated epithelial-mesenchymal transition reverses lenvatinib resistance in hepatocellular carcinoma.

Acquired resistance is a significant hindrance to clinical application of lenvatinib in unresectable hepatocellular carcinoma (HCC). Further in-depth investigation of resistance mechanisms can help to develop additional therapeutic strategies to overcome or delay resistance. In our study, two lenvatinib-resistant (LR) HCC cell lines were established by treatment with gradient increasing concentration of lenvatinib, named Hep3B-LR and HepG2-LR. Interestingly, continuous lenvatinib treatment reinforced epithelial-mesenchymal transition (EMT), cell migration, and cell invasion. Gene set enrichment analysis (GSEA) enrichment analysis of RNA-sequencing from Hep3B-LR and corresponding parental cells revealed that activation of Wnt signaling pathway was involved in this adaptive process. Active ß-catenin and its downstream target lymphoid enhancer binding factor 1 (LEF1) were significantly elevated in LR HCC cells, which promoted lenvatinib resistance through mediating EMT-related genes. Data analysis based on Gene Expression Omnibus (GEO) and the Cancer Genome Atlas Program (TCGA) databases suggests that LEF1, as a key regulator of EMT, was a novel molecular target linked to lenvatinib resistance and poor prognosis in HCC. Using a small-molecule specific inhibitor ICG001 and knocking down LEF1 showed that targeting LEF1 restored the sensitivity of LR HCC cells to lenvatinib. Our results uncover upregulation of LEF1 confers lenvatinib resistance by facilitating EMT, cell migration, and invasion of LR HCC cells, indicating that LEF1 is a novel therapeutic target for overcoming acquired lenvatinib resistance.

Downregulation of TCF7 and LEF1 is a key determinant of tumor-infiltrating regulatory T-cell function.

Forkhead box P3 (Foxp3)-expressing regulatory T (Treg) cells play essential roles in immune homeostasis but also contribute to establish a favorable environment for tumor growth by suppressing anti-tumor immune responses. It is thus necessary to specifically target tumor-infiltrating Treg cells to minimize effects on immune homeostasis in cancer immunotherapy. However, molecular features that distinguish tumor-infiltrating Treg cells from those in secondary lymphoid organs remain unknown. Here we characterize distinct features of tumor-infiltrating Treg cells by global analyses of the transcriptome and chromatin landscape. They exhibited activated phenotypes with enhanced Foxp3-dependent transcriptional regulation, yet being distinct from activated Treg cells in secondary lymphoid organs. Such differences may be attributed to the extensive clonal expansion of tumor-infiltrating Treg cells. Moreover, we found that TCF7 and LEF1 were specifically downregulated in tumor-infiltrating Treg cells both in mice and humans. These factors and Foxp3 co-occupied Treg suppressive function-related gene loci in secondary lymphoid organ Treg cells, whereas the absence of TCF7 and LEF1 accompanied altered gene expression and chromatin status at these gene loci in tumor-infiltrating Treg cells. Functionally, overexpression of TCF7 and LEF1 in Treg cells inhibited the enhancement of Treg suppressive function upon activation. Our results thus show the downregulation of TCF7 and LEF1 as markers of highly suppressive Treg cells in tumors and suggest that their absence controls the augmentation of Treg suppressive function in tumors. These molecules may be potential targets for novel cancer immunotherapy with minimum effects on immune homeostasis.

Stabilization of Epithelial ß-Catenin Compromises Mammary Cell Fate Acquisition and Branching Morphogenesis.

The Wnt/ß-catenin pathway plays a critical role in cell fate specification, morphogenesis, and stem cell activation across diverse tissues, including the skin. In mammals, the embryonic surface epithelium gives rise to the epidermis as well as the associated appendages including hair follicles and mammary glands, both of which depend on epithelial Wnt/ß-catenin activity for initiation of their development. Later on, Wnts are thought to enhance mammary gland growth and branching, whereas in hair follicles, they are essential for hair shaft formation. In this study, we report a strong downregulation of epithelial Wnt/ß-catenin activity as the mammary bud progresses to branching. We show that forced activation of epithelial ß-catenin severely compromises embryonic mammary gland branching. However, the phenotype of conditional Lef1-deficient embryos implies that a low level of Wnt/ß-catenin activity is necessary for mammary cell survival. Transcriptomic profiling suggests that sustained high ß-catenin activity leads to maintenance of mammary bud gene signature at the expense of outgrowth/branching gene signature. In addition, it leads to upregulation of epidermal differentiation genes. Strikingly, we find a partial switch to hair follicle fate early on upon stabilization of ß-catenin, suggesting that the level of epithelial Wnt/ß-catenin signaling activity may contribute to the choice between skin appendage identities.

Efficient delivery of the lncRNA LEF1-AS1 through the antibody LAIR-1 (CD305)-modified Zn-Adenine targets articular inflammation to enhance the treatment of rheumatoid arthritis.

BACKGROUNDS: Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease characterized by synovial hyperplasia. Maintaining a balance between the proliferation and apoptosis of rheumatoid arthritis synovial fibroblasts (RASFs) is crucial for preventing the erosion of bone and cartilage and, ultimately, mitigating the progression of RA. We found that the lncRNA LEF1-AS1 was expressed at low levels in the RASFs and inhibited their abnormal proliferation by targeting PIK3R2 protein and regulating the PI3K/AKT signal pathway through its interaction with miR-30-5p. In this study, we fabricated a nano-drug delivery system for LEF1-AS1 using Zn-Adenine nanoparticles (NPs) as a novel therapeutic strategy against RA. METHODS: The expression levels of LEF1-AS1, miR-30-5p, PIK3R2, p-PI3K, and p-AKT were detected in the primary RASFs and a human fibroblast-like synovial cell line (HFLS). Zn-Adenine nanoparticles (NPs) were functionalized with anti-CD305 antibody to construct (Zn-Adenine)@Ab. These NPs were then loaded with LEF1-AS1 to form (Zn-Adenine)@Ab@lncRNA LEF1-AS1. Finally, the (Zn-Adenine)@Ab@lncRNA LEF1-AS1 NPs were locally injected into a rat model with collagen-induced arthritis (CIA). The arthritic injuries in each group were evaluated by HE staining and other methods. RESULTS: LEF1-AS1 was expressed at low levels in the primary RASFs. High expression levels of LEF1-AS1 were detected in the HFLS cells, which corresponded to a significant downregulation of miR-30-5p. In addition, the expression level of PIK3R2 was significantly increased, and that of p-PI3K and p-AKT were significantly downregulated in these cells. The (Zn-Adenine)@Ab@lncRNA LEF1-AS1 NPs significantly inhibited the proliferation of RASFs and decreased the production of inflammatory cytokines (IL-1ß, IL-6, TNF-α). Intra-articular injection (IAI) of (Zn-Adenine)@Ab@lncRNA LEF1-AS1 NPs significantly alleviated cartilage destruction and joint injury in the CIA-modeled rats. CONCLUSIONS: LEF1-AS1 interacts with miR-30-5p to inhibit the abnormal proliferation of RASFs by regulating the PI3K/AKT signal pathway. The (Zn-Adenine)@Ab NPs achieved targeted delivery of the loaded LEF1-AS1 into the RASFs, which improved the cellular internalization rate and therapeutic effects. Thus, LEF1-AS1 is a potential target for the treatment of RA.

A distinct isoform of lymphoid enhancer binding factor 1 (LEF1) epigenetically restricts EBV reactivation to maintain viral latency.

As a human tumor virus, EBV is present as a latent infection in its associated malignancies where genetic and epigenetic changes have been shown to impede cellular differentiation and viral reactivation. We reported previously that levels of the Wnt signaling effector, lymphoid enhancer binding factor 1 (LEF1) increased following EBV epithelial infection and an epigenetic reprogramming event was maintained even after loss of the viral genome. Elevated LEF1 levels are also observed in nasopharyngeal carcinoma and Burkitt lymphoma. To determine the role played by LEF1 in the EBV life cycle, we used in silico analysis of EBV type 1 and 2 genomes to identify over 20 Wnt-response elements, which suggests that LEF1 may bind directly to the EBV genome and regulate the viral life cycle. Using CUT&RUN-seq, LEF1 was shown to bind the latent EBV genome at various sites encoding viral lytic products that included the immediate early transactivator BZLF1 and viral primase BSLF1 genes. The LEF1 gene encodes various long and short protein isoforms. siRNA depletion of specific LEF1 isoforms revealed that the alternative-promoter derived isoform with an N-terminal truncation (ΔN LEF1) transcriptionally repressed lytic genes associated with LEF1 binding. In addition, forced expression of the ΔN LEF1 isoform antagonized EBV reactivation. As LEF1 repression requires histone deacetylase activity through either recruitment of or direct intrinsic histone deacetylase activity, siRNA depletion of LEF1 resulted in increased histone 3 lysine 9 and lysine 27 acetylation at LEF1 binding sites and across the EBV genome. Taken together, these results indicate a novel role for LEF1 in maintaining EBV latency and restriction viral reactivation via repressive chromatin remodeling of critical lytic cycle factors.

Mechanism of LEF1-AS1 regulating HUVEC cells by targeting miR-489-3p/S100A11 axis.

Background: The venous malformation is the most common congenital vascular malformation and exhibits the characteristics of local invasion and lifelong progressive development. Long noncoding RNA (lncRNA) regulates endothelial cells, vascular smooth muscle cells, macrophages, vascular inflammation, and metabolism and also affects the development of venous malformations. This study aimed to elucidate the role of the lncRNA LEF1-AS1 in the development of venous malformations and examine the interaction among LEF1-AS1, miR-489-3p, and S100A11 in HUVEC cells. Methods: Venous malformation tissues, corresponding normal venous tissues, and HUVEC cells were used. Agilent human lncRNA microarray gene chip was used to screen differential genes, RNA expression was detected using quantitative reverse transcription PCR, and protein expression was detected using Western blotting. The proliferation, migration, and angiogenesis of HUVEC cells were assessed using CCK8, transwell, and in vitro angiogenesis tests. Results: A total of 1,651 lncRNAs were screened using gene chip analysis, of which 1015 were upregulated and 636 were downregulated. The lncRNA LEF1-AS1 was upregulated with an obvious difference multiple, and the fold-change value was 11.03273. The results of the analysis performed using the StarBase bioinformatics prediction website showed that LEF1-AS1 and miR-489-3p possessed complementary binding sites and that miR-489-3p and S100A11 also had complementary binding sites. The findings of tissue experiments revealed that the expressions of LEF1-AS1 and S100A11 were higher in tissues with venous malformations than in normal tissues, whereas the expression of miR-489-3p was lower in venous malformations than in normal tissues. Cell culture experiments indicated that LEF1-AS1 promoted the proliferation, migration, and angiogenesis of HUVEC cells. In these cells, LEF1-AS1 targeted miR-489-3p, which in turn targeted S100A11. LEF1-AS1 acted as a competitive endogenous RNA and promoted the expression of S100A11 by competitively binding to miR-489-3p and enhancing the proliferation, migration, and angiogenesis of HUVEC cells. Thus, LEF1-AS1 participated in the occurrence and development of venous malformation. Conclusions: The expression of LEF1-AS1 was upregulated in venous malformations, and the expression of S100A11 was increased by the adsorption of miR-489-3p to venous endothelial cells, thus enhancing the proliferation, migration, and angiogenesis of HUVEC cells. In conclusion, LEF1-AS1 is involved in the occurrence and development of venous malformations by regulating the miR-489-3p/S100A11 axis, which provides valuable insights into the pathogenesis of this disease and opens new avenues for its treatment.

LEF1 isoforms regulate cellular senescence and aging.

The study of aging and its mechanisms, such as cellular senescence, has provided valuable insights into age-related pathologies, thus contributing to their prevention and treatment. The current abundance of high-throughput data combined with the surge of robust analysis algorithms has facilitated novel ways of identifying underlying pathways that may drive these pathologies. For the purpose of identifying key regulators of lung aging, we performed comparative analyses of transcriptional profiles of aged versus young human subjects and mice, focusing on the common age-related changes in the transcriptional regulation in lung macrophages, T cells, and B immune cells. Importantly, we validated our findings in cell culture assays and human lung samples. Our analysis identified lymphoid enhancer binding factor 1 (LEF1) as an important age-associated regulator of gene expression in all three cell types across different tissues and species. Follow-up experiments showed that the differential expression of long and short LEF1 isoforms is a key regulatory mechanism of cellular senescence. Further examination of lung tissue from patients with idiopathic pulmonary fibrosis, an age-related disease with strong ties to cellular senescence, revealed a stark dysregulation of LEF1. Collectively, our results suggest that LEF1 is a key factor of aging, and its differential regulation is associated with human and murine cellular senescence.

Constant small-cell changes and variable LEF1 expression in DUSP22-rearranged primary cutaneous anaplastic large-cell lymphoma: Analysis of the repeated biopsies of three patients.

DUSP22-rearranged primary cutaneous anaplastic large-cell lymphoma (pcALCL) has a biphasic histological pattern defined by large dermal atypical lymphocytes and epidermotropic small lymphocytes resembling pagetoid reticulosis, but the positivity rate of the biphasic pattern in DUSP22-rearranged pcALCL is unknown. Immunohistochemically, LEF1 expression in >75% of tumor cells is associated with DUSP22-rearrangement (DUSP22-R) in systemic ALCL. However, whether this association applies to pcALCL remains unclear. To analyze these pathological clues for screening DUSP22-R, we reviewed 11 skin biopsies from three patients with DUSP22-rearranged pcALCL. All specimens showed a biphasic pattern, of which three showed nonpagetoid infiltration of the epidermis. In all lesions, small-cell changes of tumor cells were observed not only within the epidermis but also under the epidermis. LEF1 positivity rates varied by lesion (range: 30%-90%, mean: 59.6%) with only three patients expressing LEF1 in more than 75% of tumor cells. In conclusion, the biphasic pattern was a constant finding in DUSP22-rearranged pcALCL, but it was not always pagetoid reticulosis-like. The recognition of small-cell change outside the epidermis may be helpful in diagnosing DUSP22-rearranged pcALCL. However, LEF1 expression was variable and its diagnostic usefulness may be limited.

Carcinogenesis promotion in oral squamous cell carcinoma: KDM4A complex-mediated gene transcriptional suppression by LEF1.

Oral squamous cell carcinoma (OSCC) is the most prevalent cancer of the mouth, characterised by rapid progression and poor prognosis. Hence, an urgent need exists for the development of predictive targets for early diagnosis, prognosis determination, and clinical therapy. Dysregulation of lymphoid enhancer-binding factor 1 (LEF1), an important transcription factor involved in the Wnt-ß-catenin pathway, contributes to the poor prognosis of OSCC. Herein, we aimed to explore the correlation between LEF1 and histone lysine demethylase 4 A (KDM4A). Results show that the KDM4A complex is recruited by LEF1 and specifically binds the LATS2 promoter region, thereby inhibiting its expression, and consequently promoting cell proliferation and impeding apoptosis in OSCC. We also established NOD/SCID mouse xenograft models using CAL-27 cells to conduct an in vivo analysis of the roles of LEF1 and KDM4A in tumour growth, and our findings show that cells stably suppressing LEF1 or KDM4A have markedly decreased tumour-initiating capacity. Overall, the results of this study demonstrate that LEF1 plays a pivotal role in OSCC development and has potential to serve as a target for early diagnosis and treatment of OSCC.

PRAME and LEF1 in Combined Deep Penetrating Nevus and Combined Blue Nevus: Utility and Pitfalls.

ABSTRACT: Deep penetrating nevi (DPN), particularly those showing combined features, or combined deep penetrating nevi (CDPN), may show histopathological resemblance to blue nevus (BN) and melanoma. Preferentially Expressed Antigen in MElanoma (PRAME) is a marker that helps distinguish melanoma from benign melanocytic lesions. Lymphoid enhancer-binding factor 1 (LEF1) has been proposed to be used in conjunction with ß-catenin for diagnosis of DPN. The immunohistochemical expression of PRAME and LEF1 was evaluated in 10 DPN (including 6 CDPN and 2 DPN-like proliferations with atypical features), 16 BN (including combined and cellular BN), and 2 melanomas with features of DPN or BN. PRAME was negative in most DPN (n = 10/10, n = 9/10, one case with discrepancy between readers) and all BN (n = 16/16), while the 2 melanomas included were positive (n = 2/2). All DPN were positive for LEF1 (n = 9/9) while only a subset of BN were positive (n = 6/16, P = 0.0028; n = 5/16, P = 0.001, per both readers). LEF1 seemed to be easier to interpret than ß-catenin because of its nuclear pattern of expression. The expression of LEF1 in the regular nevus component of combined BN presents a potential pitfall in practice because it may lead to misinterpretation of LEF1 as positive in the BN component of the lesion. However, a subset (approximately one-third) of combined BN seemed to show true LEF1 expression. Taking into account pitfalls in interpretation, the combinatorial panel of PRAME and LEF1, in addition to conventional histopathological features, may be useful to distinguish CDPN from combined BN and other benign and malignant mimics.

PD1 is transcriptionally regulated by LEF1 in mature T cells.

The role of programmed cell death 1 (PD1) in cancer immune evasion is of considerable importance, prompting the development of monoclonal antibodies that specifically target PD-1 to enhance the immune system for cancer therapy. Nevertheless, the efficacy of PD1/programmed cell death-Ligand 1 (PD-L1) blocking antibodies is limited to certain patients or tumor types. Although researchers have demonstrated the influence of PD-1 on the positive selection of T cells, its effect on the T-cell repertoire remains uncertain. Lymphoid enhancer binding factor 1 (LEF1) has been known to play a critical role as a transcription factor in the development and maturation of T cells. Despite the greater focus on the study of its homologous protein, T cell factor 1 (TCF1), we discovered that LEF1 had a positive regulatory effect on the transcription of PD1 in mature T cells, including CD4+ T cells, CD8+ T cells, and Treg cells. This finding was observed in LEF1 knockout and LEF1-stimulated mice models. Additionally, we confirmed the direct regulation of PD1 by LEF1 in tumor-infiltrating lymphocytes through tumor-implantation experiments. The direct regulation of PD1 by LEF1 was further validated in the LEF1 knockout cell line. The results of our study provide novel perspectives on the regulation of PD1 in immune responses and investigate potential approaches for clinical anti-PD1 therapy.

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. ß-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 ß-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.