Function and mechanism of tumor suppressor gene LRRC4/NGL-2

Membrane-bound transcription factor LRRC4 inhibits glioblastoma cell motility

Membrane-bound transcription factors (MTFs) have been observed in many types of organisms, such as plants, animals and microorganisms. However, the routes of MTF nuclear translocation are not well understood. Here, we reported that LRRC4 is a novel MTF that translocates to the nucleus as a full-length protein via endoplasmic reticulum-Golgi transport, which is different from the previously described nuclear entry mechanism. A ChIP-seq assay showed that LRRC4 target genes were mainly involved in cell motility. We confirmed that LRRC4 bound to the enhancer element of the RAP1GAP gene to activate its transcription and inhibited glioblastoma cell movement by affecting cell contraction and polarization. Furthermore, atomic force microscopy (AFM) confirmed that LRRC4 or RAP1GAP altered cellular biophysical properties, such as the surface morphology, adhesion force and cell stiffness. Thus, we propose that LRRC4 is an MTF with a novel route of nuclear translocation. Our observations demonstrate that LRRC4-null glioblastoma led to disordered RAP1GAP gene expression, which increased cellular movement. Re-expression of LRRC4 enabled it to suppress tumors, and this is a potential for targeted treatment in glioblastoma.

Whole genome sequencing identifies genetic variants associated with neurogenic inflammation in rosacea

Rosacea is a chronic inflammatory skin disorder with high incidence rate. Although genetic predisposition to rosacea is suggested by existing evidence, the genetic basis remains largely unknown. Here we present the integrated results of whole genome sequencing (WGS) in 3 large rosacea families and whole exome sequencing (WES) in 49 additional validation families. We identify single rare deleterious variants of LRRC4, SH3PXD2A and SLC26A8 in large families, respectively. The relevance of SH3PXD2A, SLC26A8 and LRR family genes in rosacea predisposition is underscored by presence of additional variants in independent families. Gene ontology analysis suggests that these genes encode proteins taking part in neural synaptic processes and cell adhesion. In vitro functional analysis shows that mutations in LRRC4, SH3PXD2A and SLC26A8 induce the production of vasoactive neuropeptides in human neural cells. In a mouse model recapitulating a recurrent Lrrc4 mutation from human patients, we find rosacea-like skin inflammation, underpinned by excessive vasoactive intestinal peptide (VIP) release by peripheral neurons. These findings strongly support familial inheritance and neurogenic inflammation in rosacea development and provide mechanistic insight into the etiopathogenesis of the condition.

The transdermal cream of Formestane anti-breast cancer by controlling PI3K-Akt pathway and the tumor immune microenvironment

Background

Treatment of ER+ breast cancer with intramuscular formulation of Formestane (4-OHA) shrinks the tumor within weeks. Since the tedious way of intramuscular administration and side effects are not suited for adjuvant treatment, Formestane was withdrawn from the market. A new transdermal formulation of 4-OHA cream may overcome the defects and retain the effect of shrinking the breast cancer tumor. However, the effects of 4-OHA cream on breast cancer need further confirmatory studies.

Methods

In this work, in vivo, the influence of 4-OHA cream on breast cancer was evaluated using the mode of 7,12-dimethylbenz(a)anthracene (DMBA) induced rat mammary cancer. We explored the common molecule mechanisms of action of 4-OHA cream and its injection formulation on breast cancer through RNA- sequencing-based transcriptome analysis and several biochemical experiments.

Results

The results showed that the cream substantially reduced the entire quantity, size, and volum of tumors in DMBA-treated rats consistent with 4-OHA injection, and indicated that there were comprehensive signals involved in 4-OHA antitumor activity, such as ECM-receptor interaction, focal adhesion, PI3K-Akt signaling pathway, and proteoglycans in cancer. In addition, we observed that both 4-OHA formulations could enhance immune infiltration, especially CD8+ T cells, B cells, natural killer cells, and macrophages infiltration, in the DMBA-induced mammary tumor tissues. The antitumor effects of 4-OHA partly depended on these immune cells.

Conclusion

4-OHA cream could inhibit breast cancer growth as its injection formulation and may provide a new way for neoadjuvant treatment of ER+ breast cancer.

Leucine-rich repeats containing 4 protein (LRRC4) in memory, psychoneurosis, and glioblastoma

ABSTRACT

Leucine-rich repeats containing 4 ( LRRC4 , also named netrin-G ligand 2 [NGL-2]) is a member of the NetrinGs ligands (NGLs) family. As a gene with relatively high and specific expression in brain, it is a member of the leucine-rich repeat superfamily and has been proven to be a suppressor gene for gliomas, thus being involved in gliomagenesis. LRRC4 is the core of microRNA-dependent multi-phase regulatory loops that inhibit the proliferation and invasion of glioblastoma (GB) cells, including LRRC4/NGL2-activator protein 2 (AP2)-microRNA (miR) 182-LRRC4 and LRRC4-miR185-DNA methyltransferase 1 (DNMT1)-LRRC4/specific protein 1 (SP1)-DNMT1-LRRC4. In this review, we demonstrated LRRC4 as a new member of the partitioning-defective protein (PAR) polarity complex that promotes axon differentiation, mediates the formation and plasticity of synapses, and assists information input to the hippocampus and storage of memory. As an important synapse regulator, aberrant expression of LRRC4 has been detected in autism, spinal injury and GBs. LRRC4 is a candidate susceptibility gene for autism and a neuro-protective factor in spinal nerve damage. In GBs, LRRC4 is a novel inhibitor of autophagy, and an inhibitor of protein-protein interactions involving in temozolomide resistance, tumor immune microenvironment, and formation of circular RNA.

LRRC4 mediates the formation of circular RNA CD44 to inhibitGBM cell proliferation

Mounting evidence reveals that dysregulation of circular RNAs (circRNAs) is involved in the development of glioblastoma. Leucine-rich repeat-containing 4 (LRRC4) has been shown to suppress tumors in glioblastoma. However, whether LRRC4 can regulate the formation of circRNA is not yet understood. In this study, LRRC4 was found to interact with SAM68. LRRC4 promoted the generation of circCD44 by inhibiting the binding between SAM68 and CD44 pre-mRNA. Moreover, downregulated expression of circCD44 was found in glioblastoma multiforme (GBM) tissues and GBM primary cells. Re-expression of circCD44 significantly suppressed the proliferation, colony formation, and invasion of GBM cells and inhibited tumor growth in vivo. Mechanistically, circCD44 could regulate the expression of SMAD6 via sponging miR-326 and miR-330-5p involved in the progression of GBM. Thus, the LRRC4/SAM68/circCD44/miR-326/miR-330-5p/SMAD6 signaling axis could be a potential target for GBM treatment.

Methylation and expression levels of microRNA-23b/-24-1/-27b, microRNA-30c-1/-30e, microRNA-301a and let-7g are dysregulated in clear cell renal cell carcinoma

BACKGROUND

Renal cell carcinoma is the most common form of kidney cancer in adults. DNA methylation of regulatory sequences at the genomic level and interaction between microRNAs and the messenger RNAs of target genes at the posttranscriptional level contribute to the dynamic regulation of gene activity. Aberrations in these mechanisms can result in impaired functioning of cell signaling pathways, such as that observed in malignant tumors. We hypothesized that microRNA genes methylation may be associated with renal cancer in patients.

METHODS AND RESULTS

We examined methylation levels of 22 microRNA genes in tumor and normal kidney tissue of 30 patients with TNM Stage III clear cell renal cell carcinoma using a pathway-specific real-time polymerase chain reaction array (EpiTect Methyl II PCR Arrays, Qiagen). MicroRNA expression analysis by quantitative polymerase chain reaction was also performed. Significant differences in methylation levels were found in two genes and in two clusters of microRNA genes. MicroRNA-23b/-24-1/-27b, microRNA -30c-1/-30e and let-7 g was hypermetylated in clear cell renal cell carcinoma tissue, microRNA -301a was hypomethylated in tumor compared with the adjacent normal tissues. Expression of microRNA-301a, microRNA-23b in the clear cell renal cell carcinoma tissues was significantly overexpressed when compared with the adjacent normal tissues and let-7 g was significantly downregulated in tumor.

CONCLUSIONS

Our results may indicate the contribution of microRNA-301a, microRNA-23b and let-7 g in the pathogenesis of renal cancer, but further studies are needed to determine the functional significance of the detected changes.

LRRC4 functions as a neuron-protective role in experimental autoimmune encephalomyelitis

BACKGROUND

Leucine rich repeat containing 4 (LRRC4), also known as netrin-G ligand-2 (NGL-2), belongs to the superfamily of LRR proteins and serves as a receptor for netrin-G2. LRRC4 regulates the formation of excitatory synapses and promotes axon differentiation. Mutations in LRRC4 occur in Autism Spectrum Disorder (ASD) and intellectual disability. Multiple sclerosis (MS) is a chronic neuroinflammatory disease with spinal cords demyelination and neurodegeneration. Here, we sought to investigate whether LRRC4 is involved in spinal cords neuron-associated diseases.

METHODS

LRRC4 was detected in the CNS of experimental autoimmune encephalomyelitis (EAE) mice by the use of real-time PCR and western blotting. LRRC4-/- mice were created and immunized with myelin oligodendrocyte glycoprotein peptide (MOG)35-55. Pathological changes in spinal cords of LRRC4-/- and WT mice 15 days after immunization were examined by using hematoxylin and eosin (H&E), Luxol Fast Blue (LFB) staining and immunohistochemistry. The number of Th1/Th2/Th17/Treg cells in spleens and blood were measured with flow cytometry. Differential gene expression in the spinal cords from WT and LRRC4-/- mice was analyzed by using RNA sequencing (RNA-seq). Adeno-associated virus (AAV) vectors were used to overexpress LRRC4 (AAV-LRRC4) and were injected into EAE mice to assess the therapeutic effect of AAV-LRRC4 ectopic expression on EAE.

RESULTS

We report that LRRC4 is mainly expressed in neuron of spinal cords, and is decreased in the spinal cords of the EAE mice. Knockout of LRRC4 have a disease progression quickened and exacerbated with more severe myelin degeneration and infiltration of leukocytes into the spinal cords. We also first found that Rab7b is high expressed in EAE mice, and the deficiency of LRRC4 induces the elevated NF-κB p65 by up-regulating Rab7b, and up-regulation of IL-6, IFN-γ and down-regulation of TNF-α, results in more severe Th1 immune response in LRRC4-/- mice. Ectopic expression of LRRC4 alleviates the clinical symptoms of EAE mice and protects the neurons from immune damages.

CONCLUSIONS

We identified a neuroprotective role of LRRC4 in the progression of EAE, which may be used as a potential target for auxiliary support therapeutic treatment of MS.

Prognostic value of LRRC4C in Colon and Gastric Cancers correlates with Tumour Microenvironment Immunity

In this study, we aimed to use ESTIMATE and CIBERSORT computational methods to analyse transcriptional information on COAD and STAD in TCGA. We downloaded transcriptome RNA-seq data of 446 patients with colon cancer from TCGA and estimated the amount of immune and stromal components in the COAD samples using CIBERSORT algorithms. We analysed differentially expressed genes in 446 TCGA samples and 585 Series GSE39582 samples, in high- and low-scoring groups, using Cox regression. The expression of LRRC4C, correlated positively with clinicopathological characteristics and negatively with the survival of patients with COAD. Single-gene survival analysis using Gene Expression Profiling Interactive Analysis 2.0 and Kaplan-Meier plotter revealed an association between high levels of LRRC4C expression and poor prognosis in patients with colon and gastric cancers. Gene set enrichment analysis of COAD and STAD samples indicated that genes in groups expressing high and low LRRC4C levels were mainly enriched in immune-related activities and metabolic pathways, respectively. Difference and correlation analyses of the relationship between LRRC4C expression and tumour-infiltrating immune cells, determined using CIBERSORT algorithms, revealed that monocytes, resting mast cells, and M2 macrophages were positively correlated with LRRC4C expression.

Genome-wide association study across pediatric central nervous system tumors implicates shared predisposition and points to 1q25.2 (PAPPA2) and 11p12 (LRRC4C) as novel candidate susceptibility loci

INTRODUCTION

Central nervous system (CNS) tumors constitute the most common form of solid neoplasms in children, but knowledge on genetic predisposition is sparse. In particular, whether susceptibility attributable to common variants is shared across CNS tumor types in children has not been investigated. The purpose of this study was to explore potential common genetic risk variants exhibiting pleiotropic effects across pediatric CNS tumors. We also investigated whether such susceptibility differs between early and late onset of disease.

METHOD

A Danish nationwide genome-wide association study (GWAS) of 1,097 consecutive patients (< 15 years of age) with CNS tumors and a cohort of 4,745 population-based controls.

RESULTS

For both the overall cohort and patients diagnosed after the age of four, the strongest association was rs12064625 which maps to PAPPA2 at 1q25.2 (p = 3.400 × 10^-7 and 9.668 × 10^-8, respectively). PAPPA2 regulates local bioavailability of insulin-like growth factor I (IGF-I). IGF-I is fundamental to CNS development and is involved in tumorigenesis across a wide range of different cancers. For the younger children, the strongest association was provided by rs11036373 mapping to LRRC4C at 11p12 (p = 7.620 × 10^-7), which encoded protein acts as an axon guidance molecule during CNS development and has not formerly been associated with brain tumors.

DISCUSSION

This GWAS indicates shared susceptibility attributable to common variants across pediatric CNS tumor types. Variations in genetic loci with roles in CNS development appear to be involved, possibly via altered IGF-I related pathways.

Differential regulation of LRRC37A2 in gastric cancer by DNA methylation

Gastric cancer (GC) is one of the leading types of fatal cancer worldwide. Epigenetic manipulation of cancer cells is a useful tool to better understand gene expression regulatory mechanisms and contributes to the discovery of novel biomarkers. Our research group recently reported a list of 83 genes that are potentially modulated by DNA methylation in GC cell lines. Herein, we further explored the regulation of one of these genes, LRRC37A2, in clinical samples. LRRC37A2 expression was evaluated by RT-qPCR, and DNA methylation was studied using next-generation bisulphite sequencing in 36 GC and paired adjacent nonneoplastic tissue samples. We showed that both reduced LRRC37A2 mRNA levels and increased LRRC37A2 exon methylation were associated with undifferentiated and poorly differentiated tumours. Moreover, LRRC37A2 gene expression and methylation levels were inversely correlated at the +45 exon CpG site. We suggest that DNA hypermethylation may contribute to reducing LRRC37A2 expression in undifferentiated and poorly differentiated GC. Therefore, our results show how some genes may be useful to stratify patients who are more likely to benefit from epigenetic therapy.Abbreviations: AR: androgen receptor; 5-AZAdC: 5-aza-2'-deoxycytidine; B2M: beta-2-microglobulin; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GC: gastric cancer; GLM: general linear model; LRRC37A2: leucine-rich repeat containing 37 member A2; SD: standard deviation; TFII-I: general transcription factor II-I; TSS: transcription start site; XBP1: X-box binding protein 1.

Exosomes in Immune Regulation

Exosomes, small extracellular vesicles mediate intercellular communication by transferring their cargo including DNA, RNA, proteins and lipids from cell to cell. Notably, in the immune system, they have protective functions. However in cancer, exosomes acquire new, immunosuppressive properties that cause the dysregulation of immune cells and immune escape of tumor cells supporting cancer progression and metastasis. Therefore, current investigations focus on the regulation of exosome levels for immunotherapeutic interventions. In this review, we discuss the role of exosomes in immunomodulation of lymphoid and myeloid cells, and their use as immune stimulatory agents to elicit specific cytotoxic responses against the tumor.

Function of Deptor and its roles in hematological malignancies

Deptor is a protein that interacts with mTOR and that belongs to the mTORC1 and mTORC2 complexes. Deptor is capable of inhibiting the kinase activity of mTOR. It is well known that the mTOR pathway is involved in various signaling pathways that are involved with various biological processes such as cell growth, apoptosis, autophagy, and the ER stress response. Therefore, Deptor, being a natural inhibitor of mTOR, has become very important in its study. Because of this, it is important to research its role regarding the development and progression of human malignancies, especially in hematologic malignancies. Due to its variation in expression in cancer, it has been suggested that Deptor can act as an oncogene or tumor suppressor depending on the cellular or tissue context. This review discusses recent advances in its transcriptional and post-transcriptional regulation of Deptor. As well as the advances regarding the activities of Deptor in hematological malignancies, its possible role as a biomarker, and its possible clinical relevance in these malignancies.

Integrated Analysis of a Competing Endogenous RNA Network Reveals a Prognostic Signature in Kidney Renal Papillary Cell Carcinoma

The kidney renal papillary cell carcinoma (KIRP) is a relatively rare type of renal cell carcinoma (RCC). Currently, most kidney cancer studies primarily focus on RCC, and there has been no investigation to find a robust signature to predict the survival outcome of KIRP patients. In this study, we constructed a competing endogenous RNA (ceRNA) network, including 1,251 lncRNA-miRNA-mRNA interactions. Eight differentially expressed genes (IGF2BP3, PLK1, LINC00200, NCAPG, CENPF, miR-217, GAS6-As1, and LRRC4) based on the TCGA database were selected. The prognostic signature was established by combining the univariate Cox regression method and a stepwise regression method, with its predictive value validated by time-dependent receiver operating characteristic (ROC) curves. In conclusion, we identified eight prognostic signatures with using ceRNA networks. Our study provided a global view and a systematic dissection on KIRP prognosis biomarkers, and the eight identified genes might be used as new and important prognostic factors involved in KIRP pathogenesis.

Leucine-rich repeat containing 4 act as an autophagy inhibitor that restores sensitivity of glioblastoma to temozolomide

Temozolomide (TMZ) insensitivity and resistance are major causes of treatment failure and poor prognosis for GBM patients. Here, we identify LRRC4 as a novel autophagy inhibitor that restores the sensitivity of GBMs to TMZ. LRRC4 was associated with the DEPTOR/mTOR complex, and this interaction resulted in autophagy inhibition. Further investigation demonstrated that the PDZ binding domain of LRRC4 binds to the PDZ domain of DEPTOR. This binding decreases the half-life of DEPTOR via ubiquitination, thus inhibiting GBM cell autophagy and increasing the TMZ treatment response of GBM. Combined LRRC4 expression and TMZ treatment prolonged the survival of mice with tumour xenografts. Furthermore, the levels of LRRC4, DEPTOR and autophagy are clinically relevant for GBM, indicating that LRRC4 is likely to have significant potential as a therapeutic marker and target for TMZ treatment in glioma patients.

LRRC4 Suppresses E-Cadherin-Dependent Collective Cell Invasion and Metastasis in Epithelial Ovarian Cancer

Epithelial ovarian cancer (EOC) is the most malignant gynecological carcinoma and is of a high incidence of death due to detection at late stages when metastasis already occurs. However, the mechanism underlying metastasis of EOC remains unclear. Analysis of the open database and experiments with immunochemistry showed that LRRC4 is lowly expressed in high-grade serous ovarian cancer (HGSC) cells and during EOC metastasis. The 3D cell culture system and the orthotopic ovarian xenograft model infected with LRRC4-containing adeno-associated virus serotype 9 (AAV9) were used to confirm collective invasion and metastasis of cells in vitro and in vivo. Phos-tag SDS-PAGE was used to detect the phosphorylation of LRRC4 and PIK3R1. A number of experiments with methods such as co-immunoprecipitation and immunoblotting were performed to explore the mechanism for the actions of LRRC4 and PIK3R1 in EOC metastasis. An inverse correlation between LRRC4 and E-cadherin expression was detected in the regions of invasion in primary EOC tissues and metastatic ascites. LRRC4 binds to the cSH2 domain of PIK3R1 and inhibits the activity of PIK3R1, without disrupting the physical interactions between PIK3R1 and PIK3CA. LRRC4 inhibits EOC metastasis by targeting E-cadherin-dependent collective cell invasion and does so by inhibiting the PIK3R1-mediated AKT/GSK3β/β-catenin signaling pathway. LRRC4 functions as a tumor suppressor gene to inhibit EOC collective invasion and metastasis in vitro and in vivo and does so by directly binding to the cSH2 domain of PIK3R1 to exert its regulatory function. Our findings provide a potential novel approach for metastasis prognosis and a new strategy for the treatment of EOC.

Identification of Coiled-Coil Domain-Containing Protein 180 and Leucine-Rich Repeat-Containing Protein 4 as Potential Immunohistochemical Markers for Liposarcoma Based on Proteomic Analysis Using Formalin-Fixed, Paraffin-Embedded Tissue

Recent technical improvements in both mass spectrometry and protein extraction have made it possible to use formalin-fixed, paraffin-embedded (FFPE) tissues for proteome analysis. In this study, comparable proteome analysis of FFPE tissues revealed multiple candidate marker molecules for differentiating atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) from lipoma. A total of 181 unique proteins were identified for ALT/WDL. Of the identified proteins, coiled-coil domain-containing protein 180 (CCDC180) and leucine-rich repeat-containing protein 4 (LRRC4) were studied as candidate markers of ALT/WDL. CCDC180 and LRRC4 immunohistochemistry clearly stained tumor cells of ALT/WDL and dedifferentiated liposarcoma and could differentiate them from lipoma with high accuracy. Cell biological methods were used to further examine the expression of the candidate marker molecules in liposarcoma cells. In liposarcoma cells, knockdown of CCDC180 and LRRC4 inhibited cell proliferation. CCDC180 inhibited cell migration, invasion, and apoptosis resistance in WDL cells. Adipogenic differentiation suppressed the expression of CCDC180 and LRRC4 in WDL cells. These results indicated that LRRC4 and CCDC180 are novel immunohistochemical markers for differentiating ALT/WDLs. Their expression was associated with adipocyte differentiation and contributed to malignant potentials of WDL cells. Proteome analysis using a standard stock of FFPE tissues can reveal novel biomarkers for various diseases, which contributes to the progress of molecular pathology.

RHCG and TCAF1 promoter hypermethylation predicts biochemical recurrence in prostate cancer patients treated by radical prostatectomy

PURPOSE

The lack of biomarkers that can distinguish aggressive from indolent prostate cancer has caused substantial overtreatment of clinically insignificant disease. Here, by genome-wide DNA methylome profiling, we sought to identify new biomarkers to improve the accuracy of prostate cancer diagnosis and prognosis.

EXPERIMENTAL DESIGN

Eight novel candidate markers, COL4A6, CYBA, TCAF1 (FAM115A), HLF, LINC01341 (LOC149134), LRRC4, PROM1, and RHCG, were selected from Illumina Infinium HumanMethylation450 BeadChip analysis of 21 tumor (T) and 21 non-malignant (NM) prostate specimens. Diagnostic potential was further investigated by methylation-specific qPCR analysis of 80 NM vs. 228 T tissue samples. Prognostic potential was assessed by Kaplan-Meier, uni- and multivariate Cox regression analysis in 203 Danish radical prostatectomy (RP) patients (cohort 1), and validated in an independent cohort of 286 RP patients from Switzerland and the U.S. (cohort 2).

RESULTS

Hypermethylation of the 8 candidates was highly cancer-specific (area under the curves: 0.79-1.00). Furthermore, high methylation of the 2-gene panel RHCG-TCAF1 was predictive of biochemical recurrence (BCR) in cohort 1, independent of the established clinicopathological parameters Gleason score, pathological tumor stage, and pre-operative PSA (HR (95% confidence interval (CI)): 2.09 (1.26 - 3.46); P = 0.004), and this was successfully validated in cohort 2 (HR (95% CI): 1.81 (1.05 - 3.12); P = 0.032).

CONCLUSION

Methylation of the RHCG-TCAF1 panel adds significant independent prognostic value to established prognostic parameters for prostate cancer and thus may help to guide treatment decisions in the future. Further investigation in large independent cohorts is necessary before translation into clinical utility.

Low expression of miR-381 is a favorite prognosis factor and enhances the chemosensitivity of osteosarcoma

Osteosarcoma (OS) is the most common primary bone malignancy with a poor prognosis for all races and both sexes. In this study, we found that miR-381 is a positive prognosis factor for OS patients that OS patients with a low expression of miR-381 had a longer survival time after surgical intervention, and miR-381 expression promotes MG-63 cell proliferation and cell invasion ability. Our results also showed a strong negative correlation between the expression of miR-381 and LRRC4 (brain relative specific expression gene) in OS tissues. This demonstrated that LRRC4 is a direct target gene of miR-381, and suppressing the expression of miR-381 increases the sensitivity of OS cells to chemotherapeutic drugs through the LRRC4-mediated mTOR pathway. In summary, miR-381 is an important biomarker in directing therapeutic intervention and predicting prognosis in OS patients.

Novel Therapy for Glioblastoma Multiforme by Restoring LRRC4 in Tumor Cells: LRRC4 Inhibits Tumor-Infitrating Regulatory T Cells by Cytokine and Programmed Cell Death 1-Containing Exosomes

Glioblastoma multiforme (GBM) is a heterogeneous malignant brain tumor, the pathological incidence of which induces the accumulation of tumor-infiltrating lymphocytes (TILs). As a tumor suppressor gene, LRRC4 is absent in GBM cells. Here, we report that the recovery of LRRC4 in GBM cells inhibited the infiltration of tumor-infiltrating regulatory T cells (Ti-Treg), promoted the expansion of tumor-infiltrating effector T (Ti-Teff) cells and CD4⁺CCR4⁺ T cells, and enhanced the chemotaxis of CD4⁺CCR4⁺ T cells in the GBM immune microenvironment. LRRC4 was not transferred into TILs from GBM cells through exosomes but mainly exerted its inhibiting function on Ti-Treg cell expansion by directly promoting cytokine secretion. GBM cell-derived exosomes (cytokine-free and programmed cell death 1 containing) also contributed to the modulation of LRRC4 on Ti-Treg, Ti-Teff, and CD4⁺CCR4⁺ T cells. In GBM cells, LRRC4 directly bound to phosphoinositide-dependent protein kinase 1 (PDPK1), phosphorylated IKKβser181, facilitated NF-κB activation, and promoted the secretion of interleukin-6 (IL-6), CCL2, and interferon gamma. In addition, HSP90 was required to maintain the interaction between LRRC4 and PDPK1. However, the inhibition of Ti-Treg cell expansion and promotion of CD4⁺CCR4⁺ T cell chemotaxis by LRRC4 could be blocked by anti-IL-6 antibody or anti-CCL2 antibody, respectively. miR-101 is a suppressor gene in GBM. Our previous studies have shown that EZH2, EED, and DNMT3A are direct targets of miR-101. Here, we showed that miR-101 reversed the hypermethylation of the LRRC4 promoter and induced the re-expression of LRRC4 in GBM cells by directly targeting EZH2, EED, and DNMT3A. Our results reveal a novel mechanism underlying GBM microenvironment and provide a new therapeutic strategy using re-expression of LRRC4 in GBM cells to create a permissive intratumoral environment.

Lapsyn controls branch extension and positioning of astrocyte-like glia in the Drosophila optic lobe

Astrocytes have diverse, remarkably complex shapes in different brain regions. Their branches closely associate with neurons. Despite the importance of this heterogeneous glial cell type for brain development and function, the molecular cues controlling astrocyte branch morphogenesis and positioning during neural circuit assembly remain largely unknown. We found that in the Drosophila visual system, astrocyte-like medulla neuropil glia (mng) variants acquire stereotypic morphologies with columnar and layered branching patterns in a stepwise fashion from mid-metamorphosis onwards. Using knockdown and loss-of-function analyses, we uncovered a previously unrecognized role for the transmembrane leucine-rich repeat protein Lapsyn in regulating mng development. lapsyn is expressed in mng and cell-autonomously required for branch extension into the synaptic neuropil and anchoring of cell bodies at the neuropil border. Lapsyn works in concert with the fibroblast growth factor (FGF) pathway to promote branch morphogenesis, while correct positioning is essential for mng survival mediated by gliotrophic FGF signaling.

How glial cells, such as astrocytes, acquire their characteristic morphology during development is poorly understood. Here the authors describe the morphogenesis of astrocyte-like glia in the Drosophila optic lobe, and through a RNAi screen, they identify a transmembrane LRR protein–Lapsyn–that plays a critical role in this process.

The D Domain of LRRC4 anchors ERK1/2 in the cytoplasm and competitively inhibits MEK/ERK activation in glioma cells

Background

As a well-characterized key player in various signal transduction networks, extracellular-signal-regulated kinase (ERK1/2) has been widely implicated in the development of many malignancies. We previously found that Leucine-rich repeat containing 4 (LRRC4) was a tumor suppressor and a negative regulator of the ERK/MAPK pathway in glioma tumorigenesis. However, the precise molecular role of LRRC4 in ERK signal transmission is unclear.

Methods

The interaction between LRRC4 and ERK1/2 was assessed by co-immunoprecipitation and GST pull-down assays in vivo and in vitro. We also investigated the interaction of LRRC4 and ERK1/2 and the role of the D domain in ERK activation in glioma cells.

Results

Here, we showed that LRRC4 and ERK1/2 interact via the D domain and CD domain, respectively. Following EGF stimuli, the D domain of LRRC4 anchors ERK1/2 in the cytoplasm and abrogates ERK1/2 activation and nuclear translocation. In glioblastoma cells, ectopic LRRC4 expression competitively inhibited the interaction of endogenous mitogen-activated protein kinase (MEK) and ERK1/2. Mutation of the D domain decreased the LRRC4-mediated inhibition of MAPK signaling and its anti-proliferation and anti-invasion roles.

Conclusions

Our results demonstrated that the D domain of LRRC4 anchors ERK1/2 in the cytoplasm and competitively inhibits MEK/ERK activation in glioma cells. These findings identify a new mechanism underlying glioblastoma progression and suggest a novel therapeutic strategy by restoring the activity of LRRC4 to decrease MAPK cascade activation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-016-0355-1) contains supplementary material, which is available to authorized users.

Cofunctional Subpathways Were Regulated by Transcription Factor with Common Motif, Common Family, or Common Tissue

Dissecting the characteristics of the transcription factor (TF) regulatory subpathway is helpful for understanding the TF underlying regulatory function in complex biological systems. To gain insight into the influence of TFs on their regulatory subpathways, we constructed a global TF-subpathways network (TSN) to analyze systematically the regulatory effect of common-motif, common-family, or common-tissue TFs on subpathways. We performed cluster analysis to show that the common-motif, common-family, or common-tissue TFs that regulated the same pathway classes tended to cluster together and contribute to the same biological function that led to disease initiation and progression. We analyzed the Jaccard coefficient to show that the functional consistency of subpathways regulated by the TF pairs with common motif, common family, or common tissue was significantly greater than the random TF pairs at the subpathway level, pathway level, and pathway class level. For example, HNF4A (hepatocyte nuclear factor 4, alpha) and NR1I3 (nuclear receptor subfamily 1, group I, member 3) were a pair of TFs with common motif, common family, and common tissue. They were involved in drug metabolism pathways and were liver-specific factors required for physiological transcription. In short, we inferred that the cofunctional subpathways were regulated by common-motif, common-family, or common-tissue TFs.