CLEC4E upregulation in gastric cancer: A potential therapeutic target correlating with tumor-associated macrophages

Background

CLEC4E has been reported to promote lung cancer progression. Tumor-associated macrophages (TAMs) play an important role in tumorigenesis. Whether the expression of CLEC4E in TAMs is associated with gastric carcinogenesis remains unclear.

Methods

The TIMER, UALCAN, UCSC Xena, and KM plotter databases are used to examine the expression of CLEC4E and its prognostic significance in gastric cancer (GC). Additionally, GO, KEGG, and GSEA analysis were conducted, and single-cell RNA-seq (scRNA-seq) datasets were utilized. The Coremine medical database was used to predict therapeutic drugs, and molecular docking was performed. Human GC samples were obtained, and co-culture models were constructed to evaluate the effects of CLEC4E in TAMs on tumor growth, migration, and invasion in vitro.

Results

CLEC4E was significantly upregulated in GC, and high CLEC4E expression was associated with poor prognosis. Western blotting and immunostaining showed increased protein levels of CLEC4E in GC. GO, KEGG, and GSEA results indicated that CLEC4E is involved in immune response. Immune infiltration analysis demonstrated that CLEC4E expression positively correlated with multiple immune cell types. scRNA-seq analyses revealed that CLEC4E was predominantly expressed in myeloid cells specifically TAMs, in GC. In vitro experiments confirmed that MFC induced CLEC4E expression in TAMs to mediate tumor progression. Specifically targeting CLEC4E by si-CLEC4E or stigmasterol inhibited cancer cell migration and invasion.

Conclusion

CLEC4E is a potential prognostic biomarker and new therapeutic target for GC that can be specifically targeted by stigmasterol.

Psoriasis and Leprosy: An Arcane Relationship

Purpose

Psoriasis (Ps) and leprosy are chronic inflammatory skin disorders, characterised by enhanced innate and adaptive immunity. Ps and leprosy rarely coexist. The molecular immune mechanism of the Ps and leprosy rarely coexistence is unclear.

Patients and Methods

RNA-sequencing (RNA-seq) was performed on 20 patients with Ps, 5 adults with lepromatous leprosy (L-lep), and 5 patients with tuberculoid leprosy (T-lep) to analyse the differentially expressed genes (DEGs) between them. Moreover, the biological mechanism of Ps and leprosy was explored by Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, Gene Ontology (GO) analysis, Gene Set Enrichment Analysis analysis, and protein-protein interaction (PPI) analyses. Finally, 13 DEGs of 10 skin biopsies of Ps patients, 6 samples of L-lep patients, 6 samples of T-lep patients and 5 healthy controls were confirmed by quantitative real-time polymerase chain reaction (qRT-PCR).

Results

The PPI network was constructed and primarily associated with immune response, IL-17 signalling, and Toll-like receptor pathway between Ps and leprosy. Th17 markers (interleukin (IL)-19, IL-20, IL-36A, IL-36G, IL-22, IL-17A, and lipocalin-2 (LCN2) had higher expression in Ps than in L-lep and T-lep, whereas macrophage biomarkers (CLEC4E and TREM2), SPP1, and dendritic cell (DC)-related hallmarks (ITGAX) and TNF-a had significantly lower expression across Ps and T-lep than in L-lep.

Conclusion

To put it simply, Ps patients with IL-17A, IL-19, IL-20, IL-36A, IL-36G, and IL-22 in conjunction with LCN2 with up-graduated expression might be not susceptible to L-lep. However, high levels of CLEC4E, TREM2, and SPP1 in L-lep patients indicated that they unlikely suffered from Ps.

Clec4e-Receptor Signaling in Myocardial Repair After Ischemia-Reperfusion Injury

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The role of the CLEC4E during myocardial healing after ischemia-reperfusion injury is unknown.

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CLEC4E deletion is associated with reduced cardiac injury, inflammation, and left ventricular structural and functional remodeling.

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CLEC4E is a promising target to modulate myocardial inflammation and enhance repair after ischemia-reperfusion injury.

The bacterial C-type lectin domain family 4 member E (CLEC4E) has an important role in sterile inflammation, but its role in myocardial repair is unknown. Using complementary approaches in porcine, murine, and human samples, we show that CLEC4E expression levels in the myocardium and in blood correlate with the extent of myocardial injury and left ventricular (LV) functional impairment. CLEC4E expression is markedly increased in the vasculature, cardiac myocytes, and infiltrating leukocytes in the ischemic heart. Loss of Clec4e signaling is associated with reduced acute cardiac injury, neutrophil infiltration, and infarct size. Reduced myocardial injury in Clec4e^–/– translates into significantly improved LV structural and functional remodeling at 4 weeks’ follow-up. The early transcriptome of LV tissue from Clec4e^–/– mice versus wild-type mice reveals significant upregulation of transcripts involved in myocardial metabolism, radical scavenging, angiogenesis, and extracellular matrix organization. Therefore, targeting CLEC4E in the early phase of ischemia-reperfusion injury is a promising therapeutic strategy to modulate myocardial inflammation and enhance repair after ischemia-reperfusion injury.

A case-control study on correlation between the single nucleotide polymorphism of CLEC4E and the susceptibility to tuberculosis among Han people in Western China

Background

Tuberculosis (TB) is one of the leading causes of morbidity and mortality in Western China. Preclinical studies have suggested the protective effect of the C-type lectin receptor of family 4 member E (CLEC4E) from TB. Herein, we investigated the association between CLEC4E gene variants and TB susceptibility in a western Chinese Han population.

Methods

We genotyped four single nucleotide polymorphisms (SNPs) rs10841856, rs10770847, rs10770855 and rs4480590 in the CLEC4E gene using the improved multiplex ligation detection reaction (iMLDR) assay in 900 TB cases and 1534 healthy controls.

Results

After stratifying the whole data by sex, it was found that males exhibited mutant allele G of rs10841856 was more strongly associated with increased TB risk after Bonferroni correction (OR = 1.334, 95% CI: 1.142–1.560; P < 0.001 after adjusting for age; p = 0.001 after Bonferroni correction). The genetic model analysis found that rs10841856 was associated with the increased risk of TB among males under the dominant model (OR = 1.557, 95% CI = 1.228–1.984, P < 0.001 after adjusting for age, P < 0.001 after Bonferroni correction). Bioinformatics analysis suggested that rs10841856 might fall in putative functional regions and might be the expression quantitative trait loci (eQTL) for CLEC4E and long noncoding RNA RP11-561P12.5.

Conclusions

Our study revealed that rs10841856 in the CLEC4E gene might be related to increased TB risk, especially the dominant genetic model among male Han individuals from Western China

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06448-2.

CLEC4E (Mincle) genetic variation associates with pulmonary tuberculosis in Guinea-Bissau (West Africa)

Tuberculosis (TB) is the leading cause of death from a single infectious agent. According to the WHO, 85% of cases in 2018 were pulmonary tuberculosis (PTB), making it the most prevalent form of the disease. Although the bacillus responsible for disease, Mycobacterium tuberculosis (MTB), is estimated to infect 1.7 billion people worldwide, only a small portion of those infected (5-10%) will transition into active TB. Because such a small fraction of infected people develop active disease, we hypothesized that underlying host genetic variation associates with developing active pulmonary disease. Variation in CLEC4E has been of interest in previous association studies showing either no effect or protection from PTB. For our study we assessed 60 SNPs in 11 immune genes, including CLEC4E, using a case-control study from Guinea-Bissau. The 289 cases and 322 controls differed in age, sex, and ethnicity all of which were included in adjusted models. Initial association analysis with unadjusted logistic regression revealed putative association with seven SNPs (p < 0.05). All SNPs were then assessed in an adjusted model. Of the six SNPs that remained significant, three of them were assigned to the CLEC4E gene (rs12302046, rs10841847, and rs11046143). Of these, only rs10841847 passed FDR adjustment for multiple testing. Adjusted regression analyses showed that the minor allele at rs10841847 associated with higher risk of developing PTB (OR = 1.55, CI = 1.22-1.96, p-value = 0.00036). Based on these initial association tests, CLEC4E seemed to be the predictor of interest for PTB risk in this population. Haplotype analysis (2-SNP and 3-SNP windows) showed that minor alleles in segments including rs10841847 were the only ones to pass the threshold of global significance, compared to other haplotypes (p-value < 0.05). Linkage disequilibrium patterns showed that rs12302046 is in high LD with rs10841847 (r2 = 0.67), and all other SNPs lost significance when adjusted for rs10841847 effects. These findings indicate that rs10841847 in CLEC4E is the single best predictor of pulmonary tuberculosis risk in our study population. These results provide evidence for the hypothesis that genetic variation of CLEC4E influences risk to TB in Guinea-Bissau.

Polymorphisms in the Pattern Recognition Receptor Mincle Gene (CLEC4E) and Association with Tuberculosis

The mechanisms involved in interactions between Mycobacterium tuberculosis and host innate immune cells determine outcome. Antigen-presenting cells, including macrophages and dendritic cells, express many pattern recognition receptors to identify pathogen-associated molecular patterns, thereby initiating an immune response. A major mycobacterial virulence factor, trehalose-6',6-dimycolate, is recognised by the macrophage-inducible C-type lectin, Mincle, which leads to the activation of the Syk-Card9 signalling pathway in macrophages. Mincle is encoded by CLEC4E, and we investigated polymorphisms in this gene to assess its role in tuberculosis susceptibility. Four tagging single nucleotide polymorphisms (SNPs) (rs10841845, rs10841847, rs10841856 and rs4620776) were genotyped using TaqMan(®) SNP assays in 416 tuberculosis cases and 405 healthy controls. Logistic regression models were used for analysis. No association was detected with any of the SNPs analysed. This research highlights tuberculosis disease complexity where recognition proteins which specifically bind mycobacterial glycolipids cannot be conclusively associated with the disease in genetic studies.

Mycobacterial receptor, Clec4d (CLECSF8, MCL), is coregulated with Mincle and upregulated on mouse myeloid cells following microbial challenge

The C‐type lectin receptor (CTLR), Clec4d (MCL, CLECSF8), is a member of the Dectin‐2 cluster of CTLRs, which also includes the related receptors Mincle and Dectin‐2. Like Mincle, Clec4d recognizes mycobacterial cord factor, trehalose dimycolate, and we recently demonstrated its key role in anti‐mycobacterial immunity in mouse and man. Here, we characterized receptor expression in naïve mice, under inflammatory conditions, and during Mycobacterium bovis BCG infection using newly generated monoclonal antibodies. In naïve mice, Clec4d was predominantly expressed on myeloid cells within the peritoneal cavity, blood, and bone marrow. Unexpectedly, basal expression of Clec4d was very low on leukocytes in the lung. However, receptor expression was significantly upregulated on pulmonary myeloid cells during M. bovis BCG infection. Moreover, Clec4d expression could be strongly induced in vitro and in vivo by various microbial stimuli, including TLR agonists, but not exogenous cytokines. Notably, we show that Clec4d requires association with the signaling adaptor FcRγ and Mincle, but not Dectin‐2, for surface expression. In addition, we provide evidence that Clec4d and Mincle, but not Dectin‐2, are interdependently coregulated during inflammation and infection. These data show that Clec4d is an inducible myeloid‐expressed CTLR in mice, whose expression is tightly linked to that of Mincle.

Mechanism for recognition of an unusual mycobacterial glycolipid by the macrophage receptor mincle

Binding of the macrophage lectin mincle to trehalose dimycolate, a key glycolipid virulence factor on the surface of Mycobacterium tuberculosis and Mycobacterium bovis, initiates responses that can lead both to toxicity and to protection of these pathogens from destruction. Crystallographic structural analysis, site-directed mutagenesis, and binding studies with glycolipid mimics have been used to define an extended binding site in the C-type carbohydrate recognition domain (CRD) of bovine mincle that encompasses both the headgroup and a portion of the attached acyl chains. One glucose residue of the trehalose Glcα1–1Glcα headgroup is liganded to a Ca²⁺ in a manner common to many C-type CRDs, whereas the second glucose residue is accommodated in a novel secondary binding site. The additional contacts in the secondary site lead to a 36-fold higher affinity for trehalose compared with glucose. An adjacent hydrophobic groove, not seen in other C-type CRDs, provides a docking site for one of the acyl chains attached to the trehalose, which can be targeted with small molecule analogs of trehalose dimycolate that bind with 52-fold higher affinity than trehalose. The data demonstrate how mincle bridges between the surfaces of the macrophage and the mycobacterium and suggest the possibility of disrupting this interaction. In addition, the results may provide a basis for design of adjuvants that mimic the ability of mycobacteria to stimulate a response to immunization that can be employed in vaccine development.