PD-L2 mediates tobacco smoking-induced recruitment of regulatory T cells via the RGMB/NFκB/CCL20 cascade.

Programmed cell death ligand 2 (PD-L2), a ligand for the receptor programmed cell death 1 (PD-1), has an identity of 34% with its twin ligand PD-L1 and exhibits higher binding affinity with PD-1 than PD-L1. However, the role of PD-L2 in non-small cell lung cancer (NSCLC) progression, especially tobacco-induced cancer progression, has not been fully understood. Here, we found that PD-L2 promoted tumor growth in murine models with recruitment of regulatory T cells (Tregs). In patients with NSCLC, PD-L2 expression level in tumor samples was higher than in counterpart normal controls and was positively associated with patients' response to anti-PD-1 treatment. Mechanismly, PD-L2 bound its receptor Repulsive guidance molecule B (RGMB) on cancer cells and activated extracellular signal-regulated kinase (Erk) and nuclear factor κB (NFκB), leading to increased production of chemokine CCL20, which recruited Tregs and contributed to NSCLC progression. Consistently, knockdown of RGMB or NFκB p65 inhibited PD-L2-induced CCL20 production, and silencing of PD-L2 repressed Treg recruitment by NSCLC cells. Furthermore, cigarette smoke and carcinogen benzo(a)pyrene (BaP) upregulated PD-L2 in lung epithelial cells via aryl hydrocarbon receptor (AhR)-mediated transcription activation, whose deficiency markedly suppressed BaP-induced PD-L2 upregulation. These results suggest that PD-L2 mediates tobacco-induced recruitment of Tregs via the RGMB/NFκB/CCL20 cascade, and targeting this pathway might have therapeutic potentials in NSCLC.

RGMb impacts partial epithelial-mesenchymal transition and BMP2-Induced ID mRNA expression independent of PD-L2 in nonsmall cell lung cancer cells.

PD-1/PD-ligand-axis immunotherapy-mediated activation of T-cells for cancer cell elimination is a promising treatment of nonsmall cell lung cancer (NSCLC). However, the effect of immunotherapy on intracellular signaling pathways in cancer cells still needs further delineation. Repulsive Guidance Molecule b (RGMb), a regulator of Bone Morphogenetic Proteins (BMPs) signaling, interacts with the PD-ligand, PD-L2, at cancer cell membranes. Accordingly, a clarification of the functions of RGMb and its relation to PD-L2 might provide insight into NSCLC cell signaling responses to PD-1/PD-ligand-axis immunotherapy. In this study, the functions of RGMb and PD-L2 were examined using the two NSCLC cell lines HCC827 and A549. CRISPR/Cas9 was used to decrease the expression of RGMb and PD-L2, while lentiviral vectors were used to increase their expression. Downstream effects were examined by RT-qPCR and immunoassays. Ectopic expression of RGMb impacted BMP2-induced expression of ID1 and ID2 messenger RNA (mRNA) independently of PD-L2, while RGMb depletion by CRISPR/Cas9 did not affect the BMP2-mediated induction of ID1, ID2, and ID3 mRNA. However, depletion of RGMb resulted in a partial epithelial-mesenchymal transition (EMT) gene expression profile in HCC827 cells, which was not mimicked by PD-L2 depletion. The results show that RGMb is a coregulator of BMP signaling and hence, ID mRNA expression and that RGMb can control the EMT balance in NSCLC cells. However, RGMb appears to exert these functions independently of PD-L2, and accordingly, the PD-1/PD-ligand axis for immune surveillance in NSCLC cells.

Circ_0000419 acts as a tumor suppressor in gastric cancer development via regulating miR-300/RGMB axis.

OBJECTIVE: Dysregulated circular RNAs (circRNAs) have been verified to function in the development of gastric cancer (GC). The current study was designed to investigate the role of circ_0000419 in GC progression, and the potential mechanistic pathway. METHODS: Relative expression of circ_0000419, microRNA-300 (miR-300) and Repulsive Guidance Molecule B (RGMB) was analyzed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assay. Cell metastasis, including migration and invasion, was assessed by wound healing and Transwell assays. Glucose consumption and lactate production were examined using kits. The association between miR-300 and circ_0000419 or RGMB was validated by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assays. Role of circ_0000419 in vivo was determined by xenograft experiment. RESULTS: Circ_0000419 and RGMB were downregulated, while miR-300 was upregulated in GC tissues and cells. Gain of circ_0000419 inhibited migration, invasion and glycolysis in GC cells, which was attenuated by introduction of miR-300 or silencing of RGMB. Circ_0000419 sponged miR-300, and RGMB was direct target of miR-300. Circ_0000419 overexpression could block GC tumor growth in vivo. CONCLUSION: Circ_0000419 inhibited GC cell migration, invasion and glycolysis through regulation of miR-300/RGMB axis, at least in part, affording a molecular target for GC treatment.

LncRNA RGMB-AS1 facilitates pancreatic cancer cell proliferation and migration but inhibits cell apoptosis via miR-574-3p/PIM3 axis.

Pancreatic cancer (PC) is among the most notorious malignancies worldwide. Long noncoding RNA (lncRNA) repulsive guidance molecule bone morphogenetic protein (BMP) coreceptor b antisense RNA 1 (RGMB-AS1) was an oncogene in glioma. However, the RGMB-AS1 function in PC remains largely unknown. Herein, quantitative real-time polymerase chain reaction was performed to analyze the expression of RGMB-AS1. We determined RGMB-AS1 influence on PC cell malignant behaviors via functional assays. Besides, we applied subcellular fractionation and fluorescence in situ hybridization (FISH) assays to confirm the cellular distribution of RGMB-AS1 in PC cells. We used mechanism assays to detect the regulatory axis of RGMB-AS1 in PC cells. Briefly, the level of RGMB-AS1 expression in PC cells was abnormally high. RGMB-AS1 knockdown impeded PC cell proliferation and migration, but induced cell apoptosis, and RGMB-AS1 overexpression led the opposite consequences. RGMB-AS1 acted as a competing endogenous RNA (ceRNA) to sequester miR-574-3p and thereby regulated Pim-3 proto-oncogene, serine/threonine kinase (PIM3) expression. Conclusively, our work revealed the cancer-promoting function of RGMB-AS1 in PC and that the regulatory mechanism of the RGMB-AS1/miR-574-3p/PIM3 axis might contribute to novel biomarker development in PC treatment.NEW & NOTEWORTHY RGMB-AS1 promotes PC cell proliferation, elevates PC cell migration capacity, inhibits PC cell apoptosis, and promotes PC cell proliferation and migration but inhibits cell apoptosis via targeting miR-574-3p. PIM3 is directly targeted by miR-574-3p.

RGMb protects against acute kidney injury by inhibiting tubular cell necroptosis via an MLKL-dependent mechanism.

Tubular cell necrosis is a key histological feature of acute kidney injury (AKI). Necroptosis is a type of programed necrosis, which is executed by mixed lineage kinase domain-like protein (MLKL) upon its binding to the plasma membrane. Emerging evidence indicates that necroptosis plays a critical role in the development of AKI. However, it is unclear whether renal tubular cells undergo necroptosis in vivo and how the necroptotic pathway is regulated during AKI. Repulsive guidance molecule (RGM)-b is a member of the RGM family. Our previous study demonstrated that RGMb is highly expressed in kidney tubular epithelial cells, but its biological role in the kidney has not been well characterized. In the present study, we found that RGMb reduced membrane-associated MLKL levels and inhibited necroptosis in cultured cells. During ischemia/reperfusion injury (IRI) or oxalate nephropathy, MLKL was induced to express on the apical membrane of proximal tubular (PT) cells. Specific knockout of Rgmb in tubular cells (Rgmb cKO) increased MLKL expression at the apical membrane of PT cells and induced more tubular cell death and more severe renal dysfunction compared with wild-type mice. Treatment with the necroptosis inhibitor Necrostatin-1 or GSK'963 reduced MLKL expression on the apical membrane of PT cells and ameliorated renal function impairment after IRI in both wild-type and Rgmb cKO mice. Taken together, our results suggest that proximal tubular cell necroptosis plays an important role in AKI, and that RGMb protects against AKI by inhibiting MLKL membrane association and necroptosis in proximal tubular cells.

Emerging evidence for cell-autonomous axon guidance.

Current models of axon guidance within the central nervous system (CNS) involve the presentation of environmental cues to navigating growth cones. The surrounding and target tissues present a variety of ligands that either restrict or promote growth, thus providing pathfinding instructions to developing axons. Recent findings show that RGMb, a GPI anchored extracellular protein present on retinal ganglion cells, down-regulates Wnt3a signaling by lowering LRP5 levels at the membrane surface. When RGMb is phosphorylated by the extracellular tyrosine kinase VLK, phosphorylated RGMb (p-RGMb) is internalized and carries LRP5 towards intracellular compartments. In the eye, a dorsal-high ventral-low gradient of VLK generates a dorsal-low ventral-high gradient of LRP5 that modulates Wnt3a signaling. These molecules, which are all expressed by individual RGCs, generate Wnt-signal gradients along the dorso-ventral axis of the retina, resulting in differential axon growth which in turn regulates proper retino-tectal/collicular map formation. This pathway represents a regulatory mechanism whereby extracellular phosphorylation generates what may be the first example of a unique self-guiding mechanism that affects neuronal-target connections independent of paracrine signals from the surrounding target tissue.

Repulsive Guidance Molecule b (RGMb) Is Dispensable for Normal Gonadal Function in Mice.

Bone morphogenetic protein (BMP) signaling plays an important role in spermatogenesis and follicle development. Our previous studies have shown that repulsive guidance molecule b (RGMb, also known as Dragon) is a coreceptor that enhances BMP2 and BMP4 signaling in several cell types and that RGMb is expressed in spermatocytes and spermatids in the testis and in oocytes of the secondary follicles in the ovary. Here, we demonstrated that specific deletion of Rgmb in germ cells in the testis and ovary did not alter Smad1/5/8 phosphorylation, gonadal structures, and fertility. In addition, ovaries from postnatal global Rgmb knockout mice showed similar structures to the wild-type ovaries. Our results suggest that RGMb is not essential for normal gonadal function.

LncRNA RGMB-AS1 inhibits HMOX1 ubiquitination and NAA10 activation to induce ferroptosis in non-small cell lung cancer.

Ferroptosis, an iron-dependent regulated cell death caused by excessive lipid peroxide accumulation, has emerged as a promising therapeutic target in various cancers, including non-small cell lung cancer (NSCLC). In this study, we identified the long non-coding RNA RGMB-AS1 as a key regulator of ferroptosis in NSCLC. Mechanistically, RGMB-AS1 interacted with heme oxygenase 1 (HMOX1) and prevented its ubiquitination by the E3 ligase TRC8, leading to increased HMOX1 stability and enhanced ferroptosis. Additionally, RGMB-AS1 bound to the 82-87 amino acid region of N-alpha-acetyltransferase 10 (NAA10), stimulating its acetyltransferase activity and promoting the conversion of acetyl-CoA to HMG-CoA, further contributing to ferroptosis. The RGMB-AS1-HMOX1 and RGMB-AS1-NAA10 axes synergistically inhibited NSCLC growth both in vitro and in vivo. Clinically, low RGMB-AS1 expression was associated with advanced tumor stage and poor overall survival in NSCLC patients. Furthermore, adeno-associated virus-mediated RGMB-AS1 overexpression significantly suppressed tumor growth in mouse xenograft models. Our findings uncover a novel lncRNA-mediated regulatory mechanism of ferroptosis and highlight the potential of RGMB-AS1 as a prognostic biomarker and therapeutic target in NSCLC.

Immunoregulatory effects of RGMb in gut inflammation.

Graft-versus-host disease (GvHD) is a major complication after allogeneic hematopoietic cell transplantation (HCT). Current strategies to prevent GvHD with immunosuppressive drugs carry significant morbidity and may affect the graft-versus-tumor (GVT) effect. Inflammatory bowel disease (IBD) is an intestinal inflammatory condition that affects more than 2 million people in the United States. Current strategies to prevent colitis with immunosuppressive drugs carry significant morbidity. Recently, Repulsive Guidance Molecule b (RGMb) has been identified as part of a signaling hub with neogenin and BMP receptors in mice and humans. In addition, RGMb binds BMP-2/4 in mice and humans as well as PD-L2 in mice. RGMb is expressed in the gut epithelium and by antigen presenting cells, and we found significantly increased expression in mouse small intestine after total body irradiation HCT conditioning. We hypothesized that RGMb may play a role in GvHD and IBD pathogenesis by contributing to mucosal inflammation. Using major-mismatched HCT mouse models, treatment with an anti-RGMb monoclonal antibody (mAb) that blocks the interaction with BMP-2/4 and neogenin prevented GvHD and improved survival compared to isotype control (75% versus 30% survival at 60 days after transplantation). The GVT effect was retained in tumor models. Using an inflammatory bowel disease dextran sulfate sodium model, treatment with anti-RGMb blocking monoclonal antibody but not isotype control prevented colitis and improved survival compared to control (73% versus 33% at 21 days after treatment) restoring gut homeostasis. Anti-RGMb mAb (9D1) treatment decreased IFN-γ and significantly increased IL-5 and IL-10 in the gut of the treated mice compared to the isotype control treated mice.

Long non-coding RNA RGMB-AS1 represses nasopharyngeal carcinoma progression via binding to forkhead box A1.

Long non-coding RNA RGMB-AS1 (RGMB antisense RNA 1) plays a crucial role in tumor progression. However, its underlying mechanism in nasopharyngeal carcinoma (NPC) remains unclear. In this study, we analyzed the clinical significance of lncRNA RGMB-AS1 as a possible potential marker in NPC, and investigated the effect and mechanism of lncRNA RGMB-AS1 on proliferation, migration and epithelial mesenchymal transformation (EMT) of NPC by directly binding Forkhead box A1 (FOXA1) in vitro and in vivo. In conclusion, LncRNA RGMB-AS1 inhibits malignant behaviors and EMT by regulating FOXA1, and lncRNA RGMB-AS1 may be an important indicator of clinical prognosis.

LncRNA RGMB-AS1 up-regulates ANKRD1 Through Competitively Sponging miR-3614-5p to Promote OSA Cell Proliferation and Invasion.

BACKGROUND: Osteosarcoma (OSA) is associated with unfavorable prognosis. The overall survival rate for patients with OSA recurrence or metastasis is only about 20%. Long non-coding RNAs (lncRNAs) significantly function in gene expression and the progression of various cancers including OSA. METHODS: The expression of repulsive guidance molecule BMP co-receptor b antisense RNA 1 (RGMB-AS1) was detected in OSA cells via qRT-PCR. Western blot assay exposed the protein level of ankyrin repeat domain 1 (ANKRD1). The function assays showed the role of RGMB-AS1, miR-3614-5p, ANKRD1 on OSA cell proliferation and invasion. Subcellular Fraction assay was conducted to detect RGMB-AS1 localization. Rescue assays manifested the mechanism of RGMB-AS1/miR-3614-5p/ANKRD1 axis in OSA cells. RESULTS: FOXA1-activated RGMB-AS1 positively regulated OSA cell progression including proliferation and invasion but negatively modulated apoptosis. miR-3614-5p interacted with RGMB-AS1 and functioned as the tumor suppressor in OSA cells. ANKRD1 was targeted by miR-3614-5p and was negatively interacted by miR-3614-5p. RGMB-AS1 and ANKRD1 competitively bound with miR-3614-5p. The suppression of silencing RGMB-AS1 on OSA cell progression was rescued by ANKRD1 overexpression or miR-3614-5p down-regulation. CONCLUSIONS: FOXA1-activated RGMB-AS1 promoted cell proliferation and invasion in OSA via miR-3614-5p/ANKRD1 pathway.

Repulsive Guidance Molecule b Deficiency Induces Gut Microbiota Dysbiosis and Increases the Susceptibility to Intestinal Inflammation in Mice.

Imbalance of gut microbiota can induce or aggravate intestinal inflammation. To enhance our understanding of the molecular mechanisms of gut microbiota and inflammatory bowel disease (IBD), we studied the role of repulsive guidance molecule b (RGMb) in gut microbiota and colitis in mice. We generated Rgmb knockout mice and inducible Rgmb knockout mice and induced colitis using dextran sulfate sodium (DSS) in these mice. 16S ribosomal RNA (rRNA) high-throughput sequencing was performed to acquire the gut microbiota composition and abundance. We found that Rgmb deficiency significantly altered the diversity of gut microbiota and also induced dysbiosis. In sharp contrast to the balanced distribution of various bacteria in control mice, Prevotellaceae was almost exhausted in Rgmb-deficient mice under both basal and inflammatory conditions. Correlation analysis indicated that Prevotellaceae was negatively associated with inflammation in Rgmb-deficient mice with colitis. Similar results were obtained at the early inflammatory stage of colitis associated colon cancer (CAC). Taken together, our results reveal that Rgmb deficiency leads to dysbiosis of predominant gut microbiota under basal and inflammatory conditions. Rgmb-deficiency-mediated Prevotellaceae loss may render mice more susceptible to intestinal inflammation. Therefore, RGMb may be a novel potential target for reconstruction of the gut microbiota for the treatment of IBD.

RGMB-AS1/miR-4428/PBX1 axis drives the progression of cervical cancer.

BACKGROUND: RGMB antisense RNA 1 (RGMB-AS1) is a member of long non-coding RNAs (lncRNAs) and relates to the carcinogenesis of numerous cancers. Nonetheless, its performance and mechanism in cervical cancer (CC) is unclear. METHODS: The expressions of RGMB-AS1, microRNA-4428 (miR-4428), PBX homeobox 1 (PBX1) were analyzed by quantitative real-time PCR (qRT-PCR). Nuclear-cytoplasmic fractionation was used to locate RGMB-AS1. Cell counting kit-8 (CCK-8), EdU, TUNEL, Western blot and transwell assays were performed to assess RGMB-AS1 function in proliferation, apoptosis, and invasion in vitro. Interplays involving miR-4428, RGMB-AS1 and PBX1 were verified applying luciferase reporter, RNA pull-down and RNA immunoprecipitation (RIP). RESULTS: RGMB-AS1 level was high in CC specimens and cells. RGMB-AS1 encouraged proliferation, and invasion, and depressed apoptosis in CC cells. Further, miR-4428 was screened as a targeted for RGMB-AS1, and RGMB-AS1 performed the competitive endogenous RNA (ceRNA) role to release PBX1 from miR-4428. Correlation analysis based on clinical specimens confirmed positive association between RGMB-AS1 and PBX1 and negative association of miR-4428 with RGMB-AS1 and PBX1. Rescue experiments indicated that PBX1 overexpression counteracted RGMB-AS1 silence-caused inhibition on CC development. CONCLUSIONS: RGMB-AS1 regulated miR-4428/PBX1 axis to aggravate CC development, indicating that targeting RGMB-AS1 could be a potent way for developing the novel therapeutic methods for CC patients.

Long Noncoding RNA RGMB-AS1 Acts as a microRNA-574 Sponge Thereby Enhancing the Aggressiveness of Gastric Cancer via HDAC4 Upregulation.

PURPOSE: The long noncoding RNA RGMB-AS1 plays an important part in the genesis and progression of multiple human cancers. Nonetheless, little is known regarding its expression, roles, and mechanisms of action in gastric cancer (GC). This study was aimed at investigating the relationship between RGMB-AS1 and GC and illustrating the mechanisms of action of RGMB-AS1 therein. METHODS: RGMB-AS1 expression in GC was measured via reverse-transcription quantitative PCR. A series of experiments including Cell Counting Kit-8 assay, flow-cytometric analysis of apoptosis, Transwell migration and invasion assays, and in vivo tumorigenesis experiment were conducted to test the effects of RGMB-AS1 on the malignant phenotype of GC cells. The molecular events behind the oncogenic actions of RGMB-AS1 in GC were elucidated through subcellular fractionation, RNA immunoprecipitation assay, bioinformatics analysis and luciferase reporter assay. RESULTS: RGMB-AS1 upregulation was confirmed in GC tissues and cell lines. Higher RGMB-AS1 expression was associated with adverse clinical parameters and negatively correlated with patient overall survival. RGMB-AS1 knockdown inhibited GC cell proliferation, facilitated apoptosis, and reduced migration and invasion in vitro. Further experiments revealed that RGMB-AS1 knockdown decreased the tumor growth of GC cells in vivo. Mechanistically, RGMB-AS1 functioned as a competing endogenous RNA upregulating histone deacetylase 4 (HDAC4) by sponging microRNA-574 (miR-574). Rescue experiments indicated that miR-574 inhibition and HDAC4 reintroduction reversed the effects of the RGMB-AS1 knockdown on GC cells. CONCLUSION: The RGMB-AS1-miR-574-HDAC4 regulatory network contributes to the malignancy of GC, thereby offering a novel target for the diagnosis, prognosis, and/or treatment of GC.

miR-93-5p enhances migration and invasion by targeting RGMB in squamous cell carcinoma of the head and neck.

Invasion and metastasis represent the primary causes of therapeutic failure in patients diagnosed with squamous cell carcinoma of the head and neck (SCCHN). Therefore, disease prediction and inhibition of invasion and metastasis are critical for enhancing the survival of patients with SCCHN. Our previous study revealed that increased expression of miR-93-5p is associated with poor prognosis in SCCHN; however, the mechanism underlying the oncogenic functions of miR-93-5p in SCCHN migration and invasion remains unclear. Using qPCR analyses, transwell assays, and scratch tests, we demonstrated that expression of ectopic miR-93-5p induced the migration and invasion of SCCHN, and this was accompanied by corresponding alterations in biomarkers and transcription factors specific for epithelial-mesenchymal transition (EMT). Luciferase reporter assays were used to demonstrate that miR-93-5p directly targeted the 3' UTR of RGMB, and we further found that the tumor-promoting functions of miR-93-5p were partly mediated by targeting RGMB, whose downregulation also promoted the migration and invasion of SCCHN. Overall, our results indicate that miR-93-5p acts as an oncogene in the regulation of migration and invasion by suppressing RGMB in SCCHN. These findings provide novel evidence that miR-93-5p may serve as a valuable predictive biomarker and potential intervention target in patients with SCCHN.

LncRNA RGMB-AS1 Promotes Glioma Growth and Invasion Through miR-1200/HOXB2 Axis.

BACKGROUND: Dysfunction of long noncoding RNA (lncRNA) is associated with tumorigenesis of various malignancies, including glioma. LncRNA RGMB-AS1 (RGMB antisense RNA 1) has been reported to participate in initiation and progression of several cancers, such as lung cancer, hepatocellular carcinoma and laryngeal squamous cell carcinoma. Nevertheless, whether RGMB-AS1 regulates glioma development is not investigated. In this study, we aimed to determine its roles in glioma. METHODS: qRT-PCR and Western blotting were used to measure gene expression. CCK8 and colony formation assays were utilized to analyze proliferation. Transwell assay was used to determine cell migration and invasion. Luciferase reporter assay was used to validate the interactions among RGMB-AS1, miR-1200 and HOXB2. RESULTS: RGMB-AS1 was upregulated in glioma tissues and associated with glioma grade and patients' prognosis. Moreover, RGMB-AS1 silencing significantly inhibited the proliferation, migration and invasion of glioma cells. RGMB-AS1 downregulation led to more tumor cells arrested in the quiescent state. Mechanistically, we found that RGMB-AS1 was a molecular sponge for miR-1200. MiR-1200 level was inhibited by RGMB-AS1. And RGMB-AS1 promoted HOXB2 expression via sponging miR-1200. Restoration of HOXB2 effectively rescued the abilities of proliferation, migration and invasion in RGMB-AS1-depleted glioma cells. CONCLUSION: Collectively, our work clarified that RGMB-AS1/miR-1200/HOXB2 signaling exerts an essential role in regulating glioma progression.

Variation in the repulsive guidance molecule family in human populations.

Repulsive guidance molecules, RGMA, RGMB, and RGMC, are related proteins discovered independently through different experimental paradigms. They are encoded by single copy genes in mammalian and other vertebrate genomes, and are ~50% identical in amino acid sequence. The importance of RGM actions in human physiology has not been realized, as most research has focused on non-human models, although mutations in RGMC are the cause of the severe iron storage disorder, juvenile hemochromatosis. Here I show that repositories of human genomic and population genetic data can be used as starting points for discovery and for developing new testable hypotheses about each of these paralogs in human biology and disease susceptibility. Information was extracted, aggregated, and analyzed from the Ensembl and UCSC Genome Browsers, the Exome Aggregation Consortium, the Genotype-Tissue Expression project portal, the cBio portal for Cancer Genomics, and the National Cancer Institute Genomic Data Commons data site. Results identify extensive variation in gene expression patterns, substantial alternative RNA splicing, and possible missense alterations and other modifications in the coding regions of each of the three genes, with many putative mutations being detected in individuals with different types of cancers. Moreover, selected amino acid substitutions are highly prevalent in the world population, with minor allele frequencies of up to 37% for RGMA and up to 8% for RGMB. These results indicate that protein sequence variation is common in the human RGM family, and raises the possibility that individual variants will have a significant population impact on human physiology and/or disease predisposition.

LncRNA RGMB-AS1 promotes laryngeal squamous cell carcinoma cells progression via sponging miR-22/NLRP3 axis.

Long non-coding RNA RGMB-AS1 (lncRNA RGMB-AS1) was reported to play important roles in human cancer progression. However, the roles of lncRNA RGMB-AS1 in laryngeal squamous cell carcinoma (LSCC) remain unclear. In our research, lncRNA RGMB-AS1 was shown to be upregulated in LSCC tissues. High RGMB-AS1 expression was closely associated with advanced clinical features and poor prognosis. Silencing of lncRNA RGMB-AS1 suppressed LSCC cells proliferation and invasion in vitro and inhibited tumor growth in vivo. In mechanism, lncRNA RGMB-AS1 could sponge miR-22 to upregulate the expression of NLRP3. Additionally, we verified that the suppression of LSCC progression induced by lncRNA RGMB-AS1 reduction required the activity of miR-22. Altogether, these findings elucidated that lncRNA RGMB-AS1 could exert as an oncogenic factor through modulating miR-22/NLRP3 pathway, suggesting a potential novel target for the treatment of LSCC.

The clinical significance and biological function of lncRNA RGMB-AS1 in hepatocellular carcinoma.

LncRNA RGMB-AS1 has been suggested to play significant roles in lung cancer progression. However, it remains unknown whether lncRNA RGMB-AS1 is involved in the development and progression of hepatocellular carcinoma. In our results, lncRNA RGMB-AS1 was low-expressed in hepatocellular carcinoma tissues and cell lines, and associated with clinical stage, tumor size and metastasis. Survival analysis indicated that lncRNA RGMB-AS1 high was an independent favorable prognostic factor for hepatocellular carcinoma patients. Gain-of-function studies showed up-regulated lncRNA RGMB-AS1 expression suppressed hepatocellular carcinoma cells proliferation, migration and invasion, and promoted cells apoptosis. There was a positively association between lncRNA RGMB-AS1 and RGMB in hepatocellular carcinoma tissues, and up-regulated lncRNA RGMB-AS1 expression increased RGMB mRNA and protein expressions in hepatocellular carcinoma cells. In conclusion, lncRNA RGMB-AS1 serves an anti-oncogenic role in hepatocellular carcinoma.

B7-DC (PD-L2) costimulation of CD4+ T-helper 1 response via RGMb.

The role of B7-DC in T-cell responses remains controversial because both coinhibitory and costimulatory functions have been reported in various experimental systems in vitro and in vivo. In addition to interacting with the coinhibitory receptor PD-1, B7-DC has also been shown to bind repulsive guidance molecule b (RGMb). The functional consequences of the B7-DC/RGMb interaction, however, remain unclear. More than a decade ago, we reported that replacement of a murine B7-DC mutant lysine with serine (K113S) at positive 113 resulted in a loss of binding capacity to PD-1. Nevertheless, K113S remained costimulatory for T cells in vitro, implicating a dual functionality for B7-DC in T-cell responses. Here we show that recombinant K113S protein interacts with RGMb with a similar affinity to wild-type B7-DC. More importantly, K113S costimulates CD4+ T-cell responses via RGMb and promotes Th1 polarization. RGMb is expressed on the surface of naive mouse T cells, macrophages, neutrophils and dendritic cells. Finally, K113S/RGMb costimulation suppresses Th2-mediated asthma and ameliorates small airway inflammation and lung pathology in an experimental mouse model. Our findings indicate that RGMb is a costimulatory receptor for B7-DC. These findings from the K113S variant provide not only a possible explanation for the B7-DC-triggered contradictory effects on T-cell responses, but also a novel approach to investigate the B7-DC/PD-1/RGMb axis. Recombinant K113S or its derivatives could potentially be developed as an agonist for RGMb to costimulate the Th1 response without triggering PD-1-mediated T-cell inhibition.