LRIG1 modulates aggressiveness of head and neck cancers by regulating EGFR-MAPK-SPHK1 signaling and extracellular matrix remodeling

Dysregulation and antimetastatic function of circLRIG1 modulated by miR-214-3p/LRIG1 axis in bladder carcinoma

CircLRIG1, a newly discovered circRNA, has yet to have its potential function and biological processes reported. This study explored the role of circLRIG1 in the development and progression of bladder carcinoma and its potential molecular mechanisms. Techniques such as qRT-PCR, Western blot, various cellular assays, and in vivo models were used to investigate mRNA and protein levels, cell behavior, molecular interactions, and tumor growth. The results showed that both circLRIG1 and LRIG1 were significantly reduced in bladder carcinoma tissues and cell lines. Low circLRIG1 expression was associated with poor patient prognosis. Overexpressing circLRIG1 inhibited bladder carcinoma cell growth, migration, and invasion, promoted apoptosis, and decreased tumor growth and metastasis in vivo. Importantly, circLRIG1 was found to sponge miR-214-3p, enhancing LRIG1 expression, and its overexpression also modulated protein levels of E-cadherin, N-cadherin, Vimentin, and LRIG1. Similar effects were observed with LRIG1 overexpression. Notably, a positive correlation was found between circLRIG1 and LRIG1 expression in bladder carcinoma tissues. Additionally, the tumor-suppressing effect of circLRIG1 was reversed by overexpressing miR-214-3p or silencing LRIG1. The study concludes that circLRIG1 suppresses bladder carcinoma progression by enhancing LRIG1 expression via sponging miR-214-3p, providing a potential strategy for early diagnosis and treatment of bladder carcinoma.

Role of prognostic gene DKK1 in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is one of the most common squamous cell carcinomas of the head and neck. The morbidity and mortality rates of OSCC have increased in recent years. However, the pathogenesis of this disease remains unknown. The present study aimed to identify predictive biomarkers and therapeutic targets for OSCC. Bioinformatics screening of differentially expressed genes in OSCC was performed based on data from The Cancer Genome Atlas and Gene Expression Omnibus databases. Dickkopf Wnt signaling pathway inhibitor 1 (DKK1) was identified to be associated with survival, tumor immunity and DNA repair in OSCC. Furthermore, the effects of DKK1 were evaluated by the knockdown of DKK1 in two OSCC cell lines. The proliferation, clonogenicity, migration and invasion of the cells were assessed in vitro using Cell Counting Kit-8, colony formation, wound healing and Transwell assays, respectively, and were found to be inhibited by DKK1 knockdown. The present study suggests that DKK1 may be used in the prognosis of patients with OSCC and that targeting DKK1 is a potential strategy for OSCC therapy.

Aberrant promoter methylation contributes to LRIG1 silencing in basal/triple-negative breast cancer

BACKGROUND

LRIG1, the founding member of the LRIG (leucine-rich repeat and immunoglobulin-like domain) family of transmembrane proteins, is a negative regulator of receptor tyrosine kinases and a tumour suppressor. Decreased LRIG1 expression is consistently observed in cancer, across diverse tumour types, and is linked to poor patient prognosis. However, mechanisms by which LRIG1 is repressed are not fully understood. Silencing of LRIG1 through promoter CpG island methylation has been reported in colorectal and cervical cancer but studies in breast cancer remain limited.

METHODS

In silico analysis of human breast cancer patient data were used to demonstrate a correlation between DNA methylation and LRIG1 silencing in basal/triple-negative breast cancer, and its impact on patient survival. LRIG1 gene expression, protein abundance, and methylation enrichment were examined by quantitative reverse-transcription PCR, immunoblotting, and methylation immunoprecipitation, respectively, in breast cancer cell lines in vitro. We examined the impact of global demethylation on LRIG1 expression and methylation enrichment using 5-aza-2'-deoxycytidine. We also examined the effects of targeted demethylation of the LRIG1 CpG island, and transcriptional activation of LRIG1 expression, using the RNA guided deadCas9 transactivation system.

RESULTS

Across breast cancer subtypes, LRIG1 expression is lowest in the basal/triple-negative subtype so we investigated whether differential methylation may contribute to this. Indeed, we find that LRIG1 CpG island methylation is most prominent in basal/triple-negative cell lines and patient samples. Use of the global demethylating agent 5-aza-2'-deoxycytidine decreases methylation leading to increased LRIG1 transcript expression in basal/triple-negative cell lines, while having no effect on LRIG1 expression in luminal/ER-positive cell lines. Using a CRISPR/deadCas9 (dCas9)-based targeting approach, we demonstrate that TET1-mediated demethylation (Tet1-dCas9) along with VP64-mediated transcriptional activation (VP64-dCas9) at the CpG island, increased endogenous LRIG1 expression in basal/triple-negative breast cancer cells, without transcriptional upregulation at predicted off-target sites. Activation of LRIG1 by the dCas9 transactivation system significantly increased LRIG1 protein abundance, reduced site-specific methylation, and reduced cancer cell viability. Our findings suggest that CRISPR-mediated targeted activation may be a feasible way to restore LRIG1 expression in cancer.

CONCLUSIONS

Our study contributes novel insight into mechanisms which repress LRIG1 in triple-negative breast cancer and demonstrates for the first time that targeted de-repression of LRIG1 in cancer cells is possible. Understanding the epigenetic mechanisms associated with repression of tumour suppressor genes holds potential for the advancement of therapeutic approaches.

Effect of PAIP1 on the metastatic potential and prognostic significance in oral squamous cell carcinoma

Poly Adenylate Binding Protein Interacting protein 1 (PAIP1) plays a critical role in translation initiation and is associated with the several cancer types. However, its function and clinical significance have not yet been described in oral squamous cell carcinoma (OSCC) and its associated features like lymph node metastasis (LNM). Here, we used the data available from Gene Expression Omnibus (GEO), The Cancer Genome Atlas (TCGA), and Clinical Proteomic Tumor Analysis Consortium (CPTAC) to analyze PAIP1 expression in oral cancer. The publicly available data suggests that PAIP1 mRNA and protein levels were increased in OSCC. The high PAIP1 expression was more evident in samples with advanced stage, LNM, and worse pattern of invasion. Moreover, the in vitro experiments revealed that PAIP1 knockdown attenuated colony forming, the aggressiveness of OSCC cell lines, decreasing MMP9 activity and SRC phosphorylation. Importantly, we found a correlation between PAIP1 and pSRC through the analysis of the IHC scores and CPTAC data in patient samples. Our findings suggest that PAIP1 could be an independent prognostic factor in OSCC with LNM and a suitable therapeutic target to improve OSCC patient outcomes.

Integrative Multi-Omics Analysis Reveals Candidate Biomarkers for Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is one of the most common types of cancer worldwide. Due to the lack of early detection and treatment, the survival rate of OSCC remains poor and the incidence of OSCC has not decreased during the past decades. To explore potential biomarkers and therapeutic targets for OSCC, we analyzed differentially expressed genes (DEGs) associated with OSCC using RNA sequencing technology. Methylation-regulated and differentially expressed genes (MeDEGs) of OSCC were further identified via an integrative approach by examining publicly available methylomic datasets together with our transcriptomic data. Protein-protein interaction (PPI) networks of MeDEGs were constructed and highly connected hub MeDEGs were identified from these PPI networks. Subsequently, expression and survival analyses of hub genes were performed using The Cancer Genome Atlas (TCGA) database and the Gene Expression Profiling Interactive Analysis (GEPIA) online tool. A total of 56 upregulated MeDEGs and 170 downregulated MeDEGs were identified in OSCC. Eleven hub genes with high degree of connectivity were picked out from the PPI networks constructed by those MeDEGs. Among them, the expression level of four hub genes (CTLA4, CDSN, ACTN2, and MYH11) were found to be significantly changed in the head and neck squamous carcinoma (HNSC) patients. Three hypomethylated hub genes (CTLA4, GPR29, and TNFSF11) and one hypermethylated hub gene (ISL1) were found to be significantly associated with overall survival (OS) of HNSC patients. Therefore, these hub genes may serve as potential DNA methylation biomarkers and therapeutic targets of OSCC.

High Expression of Interferon Pathway Genes CXCL10 and STAT2 Is Associated with Activated T-Cell Signature and Better Outcome of Oral Cancer Patients

To improve the survival rate of cancer patients, biomarkers for both early diagnosis and patient stratification for appropriate therapeutics play crucial roles in precision oncology. Investigation of altered gene expression and the relevant molecular pathways in cancer cells are helpful for discovering such biomarkers. In this study, we explore the potential prognostic biomarkers for oral cancer patients through systematically analyzing five oral cancer transcriptomic data sets (TCGA, GSE23558, GSE30784, GSE37991, and GSE138206). Gene Set Enrichment Analysis (GSEA) was individually applied to each data set and the upregulated Hallmark molecular pathways of each data set were intersected to generate 13 common pathways including interferon-α/γ pathways. Among the 5 oral cancer data sets, 43 interferon pathway genes were commonly upregulated and 17 genes exhibited prognostic values in TCGA cohort. After validating in another oral cancer cohort (GSE65858), high expressions of C-X-C motif chemokine ligand 10 (CXCL10) and Signal transducer and activator of transcription 2 (STAT2) were confirmed to be good prognostic biomarkers. GSEA of oral cancers stratified by CXCL10/STAT2 expression showed that activation of T-cell pathways and increased tumor infiltration scores of Type 1 T helper (Th1) and CD8+ T cells were associated with high CXCL10/STAT2 expression. These results suggest that high CXCL10/STAT2 expression can predict a favorable outcome in oral cancer patients.

Understanding the role of potential pathways and its components including hypoxia and immune system in case of oral cancer

There are a few biological functions or phenomenon which are universally associated with majority of the cancers and hypoxia and immune systems are among them. Hypoxia often occurs in most of the cancers which helps the cells in adapting different responses with respect to the normal cells which may be the activation of signaling pathways which regulate proliferation, angiogenesis, and cell death. Similar to it, immune signaling pathways are known to play critical roles in cancers. Moreover, there are a number of genes which are known to be associated with these hypoxia and immune system and appear to direct affect the tumor growth and propagations. Cancer is among the leading cause of death and oral cancer is the tenth-leading cause due to cancer death. In this study, we were mainly interested to understand the impact of alteration in the expression of hypoxia and immune system-related genes and their contribution to head and neck squamous cell carcinoma. Moreover, we have collected the genes associated with hypoxia and immune system from the literatures. In this work, we have performed meta-analysis of the gene and microRNA expression and mutational datasets obtained from public database for different grades of tumor in case of oral cancer. Based on our results, we conclude that the critical pathways which dominantly enriched are associated with metabolism, cell cycle, immune system and based on the survival analysis of the hypoxic genes, we observe that the potential genes associated with head and neck squamous cell carcinoma and its progression are STC2, PGK1, P4HA1, HK1, SPIB, ANXA5, SERPINE1, HGF, PFKM, TGFB1, L1CAM, ELK4, EHF, and CDK2.

Tumor microenvironment in head and neck squamous cell carcinoma: Functions and regulatory mechanisms

The tumor microenvironment has been recently reported to play a pivotal role in sustaining tumor cells survival and protecting them from immunotherapy and chemotherapy-induced death. It remains largely unknown how the specific signaling pathway exerts the tumor microenvironment in head and neck squamous cell carcinoma though previous studies have elucidated the regulatory mechanisms involve in tumor immune microenvironment, stromal cells, tumor angiogenesis and cancer stem cell. These components are responsible for tumor progression as well as anti-cancer therapy resistance, leading to rapid tumor growth and treatment failure. In this review, we focus on discussing the interaction between tumor cells and the surrounding components for better understanding of anti-cancer treatment ineffectiveness and its underlying molecular mechanisms.

LRIG proteins regulate lipid metabolism via BMP signaling and affect the risk of type 2 diabetes

Leucine-rich repeats and immunoglobulin-like domains (LRIG) proteins have been implicated as regulators of growth factor signaling; however, the possible redundancy among mammalian LRIG1, LRIG2, and LRIG3 has hindered detailed elucidation of their physiological functions. Here, we show that Lrig-null mouse embryonic fibroblasts (MEFs) are deficient in adipogenesis and bone morphogenetic protein (BMP) signaling. In contrast, transforming growth factor-beta (TGF-β) and receptor tyrosine kinase (RTK) signaling appeared unaltered in Lrig-null cells. The BMP signaling defect was rescued by ectopic expression of LRIG1 or LRIG3 but not by expression of LRIG2. Caenorhabditis elegans with mutant LRIG/sma-10 variants also exhibited a lipid storage defect. Human LRIG1 variants were strongly associated with increased body mass index (BMI) yet protected against type 2 diabetes; these effects were likely mediated by altered adipocyte morphology. These results demonstrate that LRIG proteins function as evolutionarily conserved regulators of lipid metabolism and BMP signaling and have implications for human disease.

SphK1-targeted miR-6784 inhibits functions of skin squamous cell carcinoma cells

Sphingosine kinase 1 (SphK1) is overexpressed in skin squamous cell carcinoma (SCC). It has emerged as a novel therapeutic oncotarget. The current study identified a novel SphK1-targeting microRNA, microRNA-6784 (miR-6784). Here, we show that miR-6784 is located at the cytoplasm of A431 skin SCC cells. It directly binds to SphK1 mRNA. Ectopic overexpression of miR-6784 inhibited SphK1 3’-untranslated region (UTR) luciferase activity and downregulated its expression. Moreover, miR-6784 overexpression caused ceramide accumulation in skin SCC cells. Functional studies in established (A431 and SCC9) and primary skin SCC cells revealed that miR-6784 overexpression inhibited cell viability, proliferation, migration, and invasion. It also simultaneously provoked apoptosis activation. Conversely, miR-6784 silencing by antagomiR-6784 induced SphK1 elevation and augmented A431 cell proliferation, migration, and invasion. miR-6784 overexpression-induced anti-A431 cell activity was inhibited by the expression of an UTR-null SphK1 construct. CRISPR/Cas9-induced SphK1 knockout inhibited A431 cell growth. Importantly, miR-6784 was completely ineffective when treating SphK1-knockout A431 cells. Collectively, miR-6784 silences SphK1 and inhibits skin SCC cell progression.

LRIG1 expression and colorectal cancer prognosis

BACKGROUND

To make the right treatment decisions about colorectal cancer (CRC) patients reliable predictive and prognostic data are needed. However, in many cases this data is not enough. Some studies suggest that LRIG1 gene (leucine-rich repeats and immunoglobulin-like domains1) has prognostic implications in different kinds of cancers.

METHODS

One hundred and two patients with colorectal cancer were retrospectively analyzed for LRIG1 expression at both mRNA and protein levels. SYBR Green Real-Time RT-PCR technique was used for mRNA expression analyses and Glyceraldehyde-3-Phosphate Dehydrogenase gene (GAPDH) was considered as a reference gene for data normalization. LRIG1 protein expression was analyzed using Immunohistochemistry. Additionally, appropriate statistic analyses were used to assess the expression of LRIG1 in test and control groups. The prognostic significance of LRIG1 expression was analyzed using the univariate and multivariate analyses.

RESULTS

The data revealed that the expression of LRIG1 in both mRNA and protein levels was down regulated in colorectal tumor tissues (P < 0.01) but is not clinically relevant prognostic indicator in CRC.

CONCLUSIONS

Therefore, it is suggested that LRIG1 expression analyses may not be considered as an important issue when making informed and individualized clinical decisions regarding the management of colorectal cancer patients.

Overexpression of wild type or a Q311E mutant MB21D2 promotes a pro-oncogenic phenotype in HNSCC

Cadherin‐mediated cell–cell contacts regulated by intracellular binders play critical roles in tissue homeostasis and tumorigenesis. Here, we screened mutational profiles of 312 annotated genes involved in cadherin binding in human squamous cell carcinomas and found MB21D2 to carry a unique recurrent Q311E mutation. MB21D2 overexpression was also frequently found in head and neck cancer (HNSCC) and was associated with poor clinical outcomes. Cell‐based characterizations revealed pro‐oncogenic roles for MB21D2 wild‐type (WT) and its Q311E mutant (Q311E) in cell proliferation, colony formation, sphere growth, and migration/invasion by promoting epithelial–mesenchymal transition. Conversely, MB21D2 knockdown in MB21D2‐overexpressing cells resulted in cell growth arrest and apoptosis. Xenograft tumor models with Q311E‐expressing cells formed larger and more aggressive lesions, compared to models with WT‐MB21D2‐expressing cells or an empty vector. Transcriptome and protein interactome analyses revealed enrichment of KRAS signaling by MB21D2 expression. Immunoblotting confirmed RAS elevation, along with upregulation/phosphorylation of PI3K, AKT, and CREB. Blocking RAS signaling in MB21D2‐expressing cells by manumycin significantly reduced cell growth and survival. Our study thus defined RAS signaling‐dependent pro‐oncogenic roles for MB21D2 overexpression and Q311E MB21D2 expression in HNSCC development.

Osimertinib and dihydroartemisinin: a novel drug combination targeting head and neck squamous cell carcinoma

Background

Recurrent and metastatic head and neck squamous cell carcinoma (HNSCC) has a dismal prognosis with limited progression-free survival and overall survival, even when treated with different combinations of chemotherapy, targeted therapies and immunotherapy. We explored in vitro and in vivo the effect of the epidermal growth factor receptor (EGFR) inhibitor, osimertinib, alone and in combination with dihydroartemisinin (DHA) in HNSCC.

Methods

The combination of osimertinib with DHA was tested in the FaDu and CAL27 HNSCC cell lines. Tumor cell proliferation assays were conducted in cultured cells and mouse xenografts. Western blotting analysis of related signal pathways was performed to investigate the molecular mechanisms of the inhibitory effect of DHA and the combination. Other compounds, which inhibit signal transducer and activator of transcription 3 (STAT3), Src-family kinases (SFKs), sphingosine kinase 1 (SPHK1), or the receptor tyrosine kinase (RTK) AXL were also combined with osimertinib in vitro.

Results

Osimertinib exerted synergistic cytotoxicity toward FaDu and CAL27 HNSCC cells when combined with DHA. DHA reversed the osimertinib-induced STAT3 and Src phosphorylation. The double combination inhibited AXL expression. The anticancer potential of osimertinib plus DHA combination was validated in vivo on FaDu and CAL27 xenografts in mice without notable side effects.

Conclusions

The results illustrate that the combinatory therapy of osimertinib and DHA, as a repurposing anticancer drug, could be a novel therapeutic strategy for recurrent and/or metastatic HNSCC patients. The findings strongly indicate that a clinical trial is warranted to confirm the benefit of the combination.

A conserved major facilitator superfamily member orchestrates a subset of O-glycosylation to aid macrophage tissue invasion

Aberrant display of the truncated core1 O-glycan T-antigen is a common feature of human cancer cells that correlates with metastasis. Here we show that T-antigen in Drosophila melanogaster macrophages is involved in their developmentally programmed tissue invasion. Higher macrophage T-antigen levels require an atypical major facilitator superfamily (MFS) member that we named Minerva which enables macrophage dissemination and invasion. We characterize for the first time the T and Tn glycoform O-glycoproteome of the Drosophila melanogaster embryo, and determine that Minerva increases the presence of T-antigen on proteins in pathways previously linked to cancer, most strongly on the sulfhydryl oxidase Qsox1 which we show is required for macrophage tissue entry. Minerva's vertebrate ortholog, MFSD1, rescues the minerva mutant's migration and T-antigen glycosylation defects. We thus identify a key conserved regulator that orchestrates O-glycosylation on a protein subset to activate a program governing migration steps important for both development and cancer metastasis.

Novel K6-K14 keratin fusion enhances cancer stemness and aggressiveness in oral squamous cell carcinoma

Keratin intermediate filament (IF) is one component of cellular architectures, which provides necessary mechanical support to conquer environmental stresses. Recent findings reveal its involvement in mechano-transduction and the associated stem cell reprogramming, suggesting the possible roles in cancer development. Here, we report t(12;17)(q13.13;q21.2) chromosomal rearrangement as the most common fusion event in OSCC, resulting in a variety of inter-keratin fusions. Junction site mapping verified 9 in-frame K6-K14 variants, three of which were correlated with lymph node invasion, late tumor stages (T3/T4) and shorter disease-free survival times. When expressed in OSCC cells, those fusion variants disturbed wild-type K14 organization through direct interaction or aggregate formation, leading to perinuclear structure loss and nuclear deformation. Protein array analyses showed the ability of K6-K14 variant 7 (K6-K14/V7) to upregulate TGF-β and G-CSF signaling, which contributed to cell stemness, drug tolerance, and cell aggressiveness. Notably, K6-K14/V7-expressing cells easily adapted to a soft 3-D culture condition in vitro and formed larger, less differentiated tumors in vivo. In addition to the anti-mechanical-stress activity, our data uncover oncogenic functionality of novel keratin filaments caused by gene fusions during OSCC development.

Identification of key pathways regulated by a set of competitive long non-coding RNAs in oral squamous cell carcinoma

Objective

The aim of this study was to identify important pathways regulated by a set of long non-coding RNAs (lncRNAs) in oral squamous cell carcinoma (OSCC).

Methods

A lncRNA-mediated competitive endogenous RNA network (LMCN) was constructed using information on microRNA (miRNA)–mRNA interactions and lncRNA–miRNA intersections from the E-GEOD-37991 transcription profiling data in the ArrayExpress database. A random walk with restart ranking algorithm was then applied to evaluate the influences of protein-coding genes regulated by competitive lncRNAs. Pathway enrichment scores were calculated based on the propagation scores of protein-coding genes. Finally, permutation tests were used to estimate the significance of the pathways.

Results

We obtained lncRNA–mRNA interactions based on miRNAs common to both miRNA–mRNA interactions and lncRNA–miRNA intersections, and used interactions with a z-score > 0.7 to construct a LMCN. Ten lncRNAs were identified as source nodes in the LMCN, and nine pathways with enrichment scores >0.8, including ‘Cell cycle’, ‘Endocytosis’, and ‘Pathways in cancer’, were significantly enriched by these source nodes.

Conclusions

Nine significant pathways regulated by a set of competitive lncRNAs were identified in OSCC, which may play important roles in the development of OSCC via the cell cycle and endocytosis.

TRH site-specific methylation in oral and oropharyngeal squamous cell carcinoma

Background

The incidence of oral squamous cell carcinoma (OSCC) continues to increase each year. Clinical examination and biopsy usually detect OSCC at an advanced stage that is difficult to treat, leading to poor prognosis. DNA methylation pattern is tissue specific and has emerged as a biomarker for the detection of cancers of tissue origin. Herein, we aimed to discover a novel site-specific methylation marker for OSCC.

Methods

We selected OSCC datasets analyzed using the IlluminaHumanMethylation27 BeadChip from the Gene Expression Omnibus repository of the National Center for Biotechnology Information using a bioinformatics approach. From 27,578 CG dinucleotide (CpG) sites, the CpG site with the highest difference in methylation level between healthy and cancerous cells was selected for further validation. A total of 18 mucosal tissue samples were collected from nine healthy controls and nine from OSCC subjects and subjected to microdissection for cell purification, followed by DNA extraction, bisulfite conversion, and pyrosequencing. Additionally, epithelial cells were collected from 2 cohorts including oral rinse from healthy controls, oral rinse and oral swab from OSCC subjects and oral rinse from oropharyngeal squamous cell carcinoma (SCC) were examined for their methylation status using real-time polymerase chain reaction (PCR).

Results

Among the 27,578 differentially methylated CpG sites, cg01009664 of the thyrotropin-releasing hormone (TRH) gene showed the greatest difference in methylation level between healthy and cancerous cells. Validation of the TRH gene using pyrosequencing revealed a methylation percentage of 7% ± 3.43% in healthy cells in contrast to 63% ± 19.81% in cancerous cells. Screening of epithelial cells using real-time PCR showed that the DNA methylation level was significantly higher in oral swab and rinse samples collected from OSCC and oropharyngeal SCC subjects than those from healthy controls (p < 0.001). In addition, when using a cutoff at 3.31 ng/μL, the TRH methylation biomarker was able to distinguish OSCC and oropharyngeal SCC subjects from healthy controls with high level of area under the curve, sensitivity and specificity.

Conclusion

We demonstrated cg01009664 of TRH as a potential biomarker for OSCC and oropharyngeal SCC screening using oral rinse and swab techniques.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4706-x) contains supplementary material, which is available to authorized users.

LRIG2 promotes the proliferation and cell cycle progression of glioblastoma cells in vitro and in vivo through enhancing PDGFRβ signaling

The leucine-rich repeats and immunoglobulin-like domains (LRIG) gene family, comprising LRIG1, 2 and 3, encodes integral membrane proteins. It has been well established that LRIG1 negatively regulates multiple growth factor signaling pathways and is considered to be a tumor suppressor; however, the biological functions of LRIG2 remain largely unexplored. It was previously demonstrated that LRIG2 positively regulates epidermal growth factor receptor (EGFR) signaling, the most common aberrant receptor tyrosine kinase (RTK) signaling in glioblastoma multiforme (GBM), which promotes GBM growth. In the present study, the effect of LRIG2 on the proliferation of GBM cells was further addressed, as well as the possible mechanisms underlying the regulatory effect of LRIG2 on platelet-derived growth factor receptor β (PDGFRβ) signaling, another common oncogenic RTK signaling pathway in GBM. First, the expression levels of endogenous LRIG2 and PDGFRβ were found to vary notably in human GBM, and the LRIG2 expression level was positively correlated with the expression level of PDGFRβ. Furthermore, to the best of our knowledge, this is the first study to demonstrate that LRIG2 promoted the PDGF-BB-induced proliferation of GBM cells in vitro and in vivo through regulating the PDGFRβ signaling-mediated cell cycle progression. Mechanistically, LRIG2 has the ability to physically interact with PDGFRβ, promoting the total expression and the activation of PDGFRβ, and enhancing its downstream signaling pathways of Akt and signal transducer and activator of transcription 3 and the effectors of key regulators of cell cycle progression, resulting in increased GBM cell proliferation. Collectively, these data indicated that LRIG2 may serve as a tumor promoter gene in gliomagenesis by positively regulating PDGFRβ signaling, another important oncogenic RTK signaling pathway, in addition to the previously reported EGFR signaling in GBM modulated by LRIG2, and validated LRIG2 as a promising therapeutic target for the treatment of GBM characterized by multiple aberrant RTK signaling.

cIAP1 regulates the EGFR/Snai2 axis in triple-negative breast cancer cells

Inhibitor of apoptosis (IAP) proteins constitute a family of conserved molecules that regulate both apoptosis and receptor signaling. They are often deregulated in cancer cells and represent potential targets for therapy. In our work, we investigated the effect of IAP inhibition in vivo to identify novel downstream genes expressed in an IAP-dependent manner that could contribute to cancer aggressiveness. To this end, immunocompromised mice engrafted subcutaneously with the triple-negative breast cancer MDA-MB231 cell line were treated with SM83, a Smac mimetic that acts as a pan-IAP inhibitor, and tumor nodules were profiled for gene expression. SM83 reduced the expression of Snai2, an epithelial-to-mesenchymal transition factor often associated with increased stem-like properties and metastatic potential especially in breast cancer cells. By testing several breast cancer cell lines, we demonstrated that Snai2 downregulation prevents cell motility and that its expression is promoted by cIAP1. In fact, the chemical or genetic inhibition of cIAP1 blocked epidermal growth factor receptor (EGFR)-dependent activation of the mitogen-activated protein kinase (MAPK) pathway and caused the reduction of Snai2 transcription levels. In a number of breast cancer cell lines, cIAP1 depletion also resulted in a reduction of EGFR protein levels which derived from the decrease of its gene transcription, though, paradoxically, the silencing of cIAP1 promoted EGFR protein stability rather than its degradation. Finally, we provided evidence that IAP inhibition displays an anti-tumor and anti-metastasis effect in vivo. In conclusion, our work indicates that IAP-targeted therapy could contribute to EGFR inhibition and to the reduction of its downstream mediators. This approach could be particularly effective in tumors characterized by high levels of EGFR and Snai2, such as triple-negative breast cancer.

Downregulation of leucine-rich repeats and immunoglobulin-like domains 1 by microRNA-20a modulates gastric cancer multidrug resistance

Multidrug resistance (MDR) significantly restricts the clinical efficacy of gastric cancer (GC) chemotherapy, and it is critical to search novel targets to predict and overcome MDR. Leucine‐rich repeats and immunoglobulin‐like domains 1 (LRIG1) has been proved to be correlated with drug resistance in several cancers. The present study revealed that LRIG1 was overexpressed in chemosensitive GC tissues and decreased expression of LRIG1 predicted poor survival in GC patients. We observed that upregulation of LRIG1 enhanced chemosensitivity in GC cells. Interestingly, miR‐20a, which was overexpressed in GC MDR cell lines and tissues, was identified to regulate LRIG1 expression by directly targeting its 3′ untranslated region. We also found that inhibition of miR‐20a suppressed GC MDR, and upregulation showed opposite effects. Moreover, we demonstrated that the miR‐20a/LRIG1 axis regulated GC cell MDR through epidermal growth factor receptor (EGFR)‐mediated PI3K/AKT and MAPK/ERK signaling pathways. Finally, LRIG1 expression in human GC tissues is inversely correlated with miR‐20a and EGFR. Taken together, the newly identified miR‐20a/LRIG1/EGFR link provides insight into the MDR process of GC, and targeting this axis represents a novel potential therapeutic strategy to block GC chemoresistance.

LRIG1 negatively regulates RET mutants and is downregulated in thyroid cancer

Papillary thyroid carcinoma (PTC) and medullary thyroid carcinoma (MTC) are characterized by genomic rearrangements and point mutations in the proto-oncogene RET. Leucine-rich repeats and immunoglobulin-like domains 1 (LRIG1) is a suppressor of various receptor tyrosine kinases, including RET. LRIG1 expression levels are associated with patient survival in many cancer types. In the present study, we investigated whether the oncogenic RET mutants RET2A (C634R) and RET2B (M918T) were regulated by LRIG1, and the possible effects of LRIG1 expression in thyroid cancer were investigated in three different clinical cohorts and in a RET2B-driven mouse model of MTC. LRIG1 was shown to physically interact with both RET2A and RET2B and to restrict their ligand-independent activation. LRIG1 mRNA levels were downregulated in PTC and MTC compared to normal thyroid gland tissue. There was no apparent association between LRIG1 RNA or protein expression levels and patient survival in the studied cohorts. The transgenic RET2B mice developed pre-cancerous medullary thyroid lesions at a high frequency (36%); however, no overt cancers were observed. There was no significant difference in the incidence of pre-cancerous lesions between Lrig1 wild-type and Lrig1-deficient RET2B mice. In conclusion, the findings that LRIG1 is a negative regulator of RET2A and RET2B and is also downregulated in PTC and MTC may suggest that LRIG1 functions as a thyroid tumor suppressor.

Lrig1 is a haploinsufficient tumor suppressor gene in malignant glioma

Recently, a genome-wide association study showed that a single nucleotide polymorphism (SNP) —rs11706832—in intron 2 of the human LRIG1 (Leucine-rich repeats and immunoglobulin-like domains 1) gene is associated with susceptibility to glioma. However, the mechanism by which rs11706832 affects glioma risk remains unknown; additionally, it is unknown whether the expression levels of LRIG1 are a relevant determinant of gliomagenesis. Here, we investigated the role of Lrig1 in platelet-derived growth factor (PDGF)-induced experimental glioma in mice by introducing mono-allelic and bi-allelic deletions of Lrig1 followed by inducing gliomagenesis via intracranial retroviral transduction of PDGFB in neural progenitor cells. Lrig1 was expressed in PDGFB-induced gliomas in wild-type mice as assessed using in situ hybridization. Intriguingly, Lrig1-heterozygous mice developed higher grade gliomas than did wild-type mice (grade IV vs. grade II/III, p = 0.002). Reciprocally, the ectopic expression of LRIG1 in the TB107 high-grade human glioma (glioblastoma, grade IV) cell line decreased the invasion of orthotopic tumors in immunocompromised mice in vivo and reduced cell migration in vitro. Concomitantly, the activity of the receptor tyrosine kinase MET was downregulated, which partially explained the reduction in cell migration. In summary, Lrig1 is a haploinsufficient suppressor of PDGFB-driven glioma, possibly in part via negative regulation of MET-driven cell migration and invasion. Thus, for the first time, changes in physiological Lrig1 expression have been linked to gliomagenesis, whereby the SNP rs11706832 may affect glioma risk by regulating LRIG1 expression.

AMACR overexpression acts as a negative prognostic factor in oral squamous cell carcinoma

Background: Alpha-methylacyl-CoA racemase (AMACR) is a key enzyme responsible for the metabolism of branched-chain fatty acids. It has been found to be an important prognostic factor in numerous types of cancers. This study was aimed to investigate the expression of AMACR and its prognostic significance in patients with oral squamous cell carcinoma (SCC). Methods: Analysis of publicly available microarray data of oral SCC revealed that AMACR was significantly upregulated in tumor tissue compared with normal mucosa. We further assessed the protein expression of AMACR in 164 patients with oral SCC by immunohistochemistry. The prognostic impact of AMACR expression and its association with various clinicopathological parameters were statistically analyzed. Results: AMACR overexpression was significantly associated with advanced tumor status (P=0.001), advanced nodal status (P=0.036), increased vascular invasion (P=0.026) and increased perineural invasion (P=0.004). Patients with high expression level of AMACR had significantly worse disease-specific survival (DSS), distant metastasis-free survival (DMFS) and local recurrence-free survival (LRFS) (all P<0.0001). In multivariate analysis, AMACR overexpression was also an independent negative prognostic factor for DSS (hazard ratio [HR]: 4.410, 95% confidence interval [CI]: 2.285-8.511, P<0.001), DMFS (HR: 5.157, 95% CI: 2.756-9.651, P<0.001) and LRFS (HR: 4.462, 95% CI: 2.429-8.198, P<0.001). Conclusions: High expression of AMACR was not only a key adverse prognostic factor but also a potential therapeutic target in oral SCC.

Role and mechanism of action of LRIG1 in ovarian cancer cell line and VP16 drug-resistant cell line

We investigated the role of leucine-rich repeats and immunoglobulin-like domains (LRIG)-1 in ovarian cancer cell line and VP16 drug-resistant cell line to explore the possible mechanism of action. Human ovarian cancer cell line SKOV3 and the VP16 drug-resistant cell line SKOV3/VP16 were used to investigate whether LRIG1 affects the sensitivity of SKOV3 to drugs. RT-qPCR was used to detect the difference in LRIG1 expression between drug-resistant and wild-type cell lines. siRNA LRIG1 was designed and transfected to silence LRIG1 to investigate the mechanism by which LRIG1 affects the sensitivity of SKOV3 to drugs. Wild-type cells were transfected with SKOV3. The cells were divided into 3 groups (VP16, NC + VP16 and siRNA LRIG1 + VP16 treatment group). VP16 (IC₅₀ value) was added 24 h after transfection. The CCK-8 method was used to detect the proliferation of each group at multiple time points (0, 24, 48 and 72 h). A colony-forming assay was used to detect cell proliferation and flow cytometry was used to detect cell apoptosis. The expression of LRIG1 was lower in the drug resistant cell line than that of the wild-type cell line. The expression of LRIG1 significantly decreased with the increase of VP16 concentration (P<0.05). The apoptotic rate was decreased but there was an increase on cell clones in the siLRIG1 + VP16-treated group as compared to VP16- and NC+ VP16-treated groups (P<0.05). The LRIG1 gene affects the sensitivity of SKOV3 cells to drug in a dose-related manner, indicating that the reduced expression of LRIG1 can inhibit cell apoptosis.

MicroRNA-590-3p enhances the radioresistance in glioblastoma cells by targeting LRIG1

microRNA (miR)-590 has been found to serve potential roles in cancer development; however, the expression and function of miR-590 in human gliomas remains to be elucidated. The present study aimed to investigate the expression of miR-590 in human glioma tissues and radioresistant human glioblastoma cells (U251R), and to determine the effect and related molecular mechanism of miR-590-3p on the radiosensitivity of U251R cells in vitro. The results from reverse transcription-quantitative polymerase chain reaction indicated that miR-590-3p was upregulated in human glioma tissues and radioresistant human glioblastoma cells, and that miR-590-3p expression was higher in high grade than in low grade gliomas. In vitro experiments revealed that the miR-590-3p inhibitor enhanced the radiosensitivity of U251R cells by suppressing cell viability, decreasing colony formation capacity and increasing cell apoptosis rate, as demonstrated by MTT, colony formation and flow cytometry analyses. A luciferase reporter assay demonstrated that leucine-rich repeats and immunoglobulin-like domains protein 1 (LRIG1) was a direct target of miR-590-3p. Furthermore, it was demonstrated that the effect of miR-590-3p suppression on cell viability, colony formation capacity and cell apoptosis rate was attenuated by the knockdown of LRIG1 in the U251R cells. In conclusion, the present study revealed that miR-590-3p was upregulated in human glioma tissues and radioresistant human glioblastoma cells, and miR-590-3p contributes to the radioresistance of human glioblastoma cells by directly targeting LRIG1. These findings may provide potential therapeutic strategies to prevent radioresistance in human gliomas.

Expression and influence of Notch signaling in oral squamous cell carcinoma

Notch signaling dysregulation plays an important role in altering cancer cell behaviors; however, its role in oral squamous cell carcinoma (OSCC) remains controversial. This study aimed to investigate the role of Notch signaling related genes in human OSCC using a meta-analysis of Gene Expression Omnibus database (GEO-publicly available gene expression microarray data) and to examine the role of Notch signaling in OSCC behaviors. The meta-analysis included 13 GEO datasets and was performed by combining effect sizes in a random effect model. The results demonstrated that in OSCC dysregulated genes participated in the metabolic process and protein binding as determined by gene ontology analysis. Enriched pathway analysis demonstrated the majority of the dysregulated genes were involved in pathway categories as follow; pathway in cancers, small cell lung cancer, extracellular matrix-receptor interaction, focal adhesion, and cell cycle progression. Interestingly, the enriched pathway analysis also demonstrated that OSCC samples exhibited an upregulation of genes in Notch signaling pathway, namely JAG1, JAG2, ADAM17, NCSTN, PSEN1, NCOR2, NUMB, DVL3, HDAC1, and HDAC2. Furthermore, Notch signaling inhibition by a γ-secretase inhibitor significantly decreased OSCC cell proliferation in vitro, corresponding with a decrease in C-FOS mRNA expression. The study demonstrated that Notch signaling is dysregulated in human OSCC and plays a role in cell proliferation. (J Oral Sci 58, 283-294, 2016).

Harnessing LRIG1-mediated inhibition of receptor tyrosine kinases for cancer therapy

Leucine-rich repeats and immunoglobulin-like domains containing protein 1 (LRIG1) is an endogenous feedback regulator of receptor tyrosine kinases (RTKs) and was recently shown to inhibit growth of different types of malignancies. Additionally, this multifaceted RTK inhibitor was reported to be a tumor suppressor, a stem cell regulator, and a modulator of different cellular phenotypes. This mini-review provides a concise and up-to-date summary about the known functions of LRIG1 and its related family members, with a special emphasis on underlying molecular mechanisms and the opportunities for harnessing its therapeutic potential against cancer.

Parathyroid Hormone-Like Hormone is a Poor Prognosis Marker of Head and Neck Cancer and Promotes Cell Growth via RUNX2 Regulation

Parathyroid Hormone-Like Hormone (PTHLH) is an autocrine/paracrine ligand that is up-regulated in head and neck squamous cell carcinoma (HNSCC). However, the cellular function and regulatory mechanism in HNSCC remains obscure. We investigated the clinical significance of PTHLH in HNSCC patients, and verified the role of RUNX2/PTHLH axis, which is stimulated HNSCC cell growth. In patients, PTHLH is a poor prognosis marker. PTHLH expression lead to increasing the cell proliferation potential through an autocrine/paracrine role and elevating blood calcium level in Nod-SCID mice. In public HNSCC microarray cohorts, PTHLH is found to be co-expressed with RUNX2. Physiologically, PTHLH is regulated by RUNX2 and also acting as key calcium regulator. However, elevations of calcium concentration also increased the RUNX2 expression. PTHLH, calcium, and RUNX2 form a positive feedback loop in HNSCC. Furthermore, ectopic RUNX2 expression also increased PTHLH expression and promoted proliferation potential through PTHLH expression. Using cDNA microarray analysis, we found PTHLH also stimulated expression of cell cycle regulators, namely CCNA2, CCNE2, and CDC25A in HNSCC cells, and these genes are also up-regulated in HNSCC patients. In summary, our results reveal that PTHLH expression is a poor prognosis marker in HNSCC patients, and RUNX2-PTHLH axis contributes to HNSCC tumor growth.

Antiglioma effects of N6-isopentenyladenosine, an endogenous isoprenoid end product, through the downregulation of epidermal growth factor receptor

Malignant gliomas are highly dependent on the isoprenoid pathway for the synthesis of lipid moieties critical for cell proliferation. The isoprenoid derivative N6-isopentenyladenosine (iPA) displays pleiotropic biological effects, including a direct anti-tumor activity in several tumor models. The antiglioma effects of iPA was then explored in U87MG cells both in vitro and grafted in mice and the related molecular mechanism confirmed in primary derived patients' glioma cells. iPA powerfully inhibited tumor cell growth and induced caspase-dependent apoptosis through a mechanism involving a marked accumulation of the pro-apoptotic BIM protein and inhibition of EGFR. Indeed, activating AMPK following conversion into its iPAMP active form, iPA stimulated EGFR phosphorylation and ubiquitination along a proteasome-mediated pathway which was responsible for receptor degradation and its downstream signaling pathways inhibition, including the STAT3, ERK and AKT cascade. The inhibition of AMPK by compound C prevented iPA-mediated phosphorylation of EGFR, known to precede receptor loss. As expected the block of EGFR degradation, by exposure to the proteasome inhibitor MG132, significantly reduced iPA-induced cell death. Given the importance of receptor degradation in iPA-mediated cytotoxicity, we also documented that the EGFR expression levels in a panel of primary glioma cells confers them a high sensitivity to iPA treatment. In conclusion our study provides the first evidence of iPA antiglioma effect. Indeed, as glioma is driven by aberrant signaling of growth factor receptors, particularly the EGFR, iPA, alone or in association with EGFR targeted therapies, might be a promising therapeutic tool to achieve a potent anti-tumoral effect.

Over-expression of LRIG1 suppresses biological function of pituitary adenoma via attenuation of PI3K/AKT and Ras/Raf/ERK pathways in vivo and in vitro

Pituitary adenomas (PAs) are well known as a common intracranial benign tumor, and a portion of PAs are refractory to current therapeutic methods. ErbB receptors family signaling pathway regulates the expression of PAs activation associated gene. Inhibition of epidermal growth factor receptor (EGFR) can inhibit proliferation of PAs. Leucine-rich repeats and immunoglobulin-like domains protein 1 ( LRIG1), a negative mediated gene of ErbB receptors family, plays a role in many tumors. However, there are seldom researches about the functional role of LRIG1 in PAs. The aim of this study is to explore the potential effect of LRIG1 and its regulating mechanism in PAs. First, we investigated the role of LRIG1 in cell migration, invasion of PAs with transfected LRIG1 or control. Then, we explored its impact on cell proliferation and apoptosis of PAs in vivo. To study the regulating mechanism of LRIG1, we examined the expression of molecular factor of PI3K/AKT and Ras/Raf/ERK pathway using Western blotting in vitro and RT-PCR in vitro and in vivo. It was found that LRIG1 over-expression inhibited cell migration, invasion and proliferation, and promoted apoptosis of PAs in vivo and in vitro. Furthermore, LRIG1 suppressed the expression of signaling of PI3K/AKT and Ras/Raf/ERK pathways in PAs. LRIG1, as a negative mediated gene of tumor, can inhibit biological function of PAs via inhibiting PI3K/AKT and Ras/Raf/ERK pathways, and it might be a new target for gene therapy of PAs.

LDOC1 silenced by cigarette exposure and involved in oral neoplastic transformation

Previously, we identified global epigenetic aberrations in smoking-associated oral squamous cell carcinoma (OSCC). We hypothesized that cigarette exposure triggers OSCC through alteration of the methylome of oral cells. Here we report that cigarette smoke condensate (CSC) significantly changes the genomic 5-methyldeoxycytidine content and nuclear accumulation of DNA methyltransferase 1 (DNMT1) and DNMT3A in human untransformed oral cells. By using integrated analysis of cDNA and methylation arrays of the smoking-associated dysplastic oral cell line and OSCC tumors, respectively, we identified four epigenetic targets—UCHL1, GPX3, LXN, and LDOC1—which may be silenced by cigarette. Results of quantitative methylation-specific PCR showed that among these four genes, LDOC1 promoter was the most sensitive to CSC. LDOC1 promoter hypermethylation and gene silencing followed 3 weeks of CSC treatment. LDOC1 knockdown led to a proliferative response and acquired clonogenicity of untransformed oral cells. Immunohistochemistry showed that LDOC1 was downregulated in 53.3% (8/15) and 57.1% (20/35) of premalignant oral tissues and early stage OSCCs, respectively, whereas 76.5% (13/17) of normal oral tissues showed high LDOC1 expression. Furthermore, the microarray data showed that LDOC1 expression had decreased in the lung tissues of current smokers compared with that in those of never smokers and had significantly decreased in the lung tumors of smokers compared with that in normal lung tissues. Our data suggest that CSC-induced promoter methylation may contribute to LDOC1 downregulation, thereby conferring oncogenic features to oral cells. These findings also imply a tumor suppressor role of LDOC1 in smoking-related malignancies such as OSCC and lung cancer.

Emerging role of sphingosine-1-phosphate signaling in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is the sixth most frequent cancer type, with an annual incidence of approximately half a million people worldwide. It has a high recurrence rate and an extremely low survival rate. This is due to limited availability of effective therapies to reduce the rate of recurrence, resulting in high morbidity and mortality of patients with advanced stages of the disease. HNSCC often develops resistance to chemotherapy and targeted drug therapy. Thus, to overcome the problem of drug resistance, there is a need to explore novel drug targets. Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid involved in inflammation, tumor progression, and angiogenesis. S1P is synthesized intracellularly by two sphingosine kinases (SphKs). It can be exported to the extracellular space, where it can activate a family of G-protein-coupled receptors. Alternatively, S1P can act as an intracellular second messenger. SphK1 regulates tumor progression, invasion, metastasis, and chemoresistance in HNSCC. SphK1 expression is highly elevated in advanced stage HNSCC tumors and correlates with poor survival. In this article, we review current knowledge regarding the role of S1P receptors and enzymes of S1P metabolism in HNSCC carcinogenesis. Furthermore, we summarize the current perspectives on therapeutic approaches for targeting S1P pathway for treating HNSCC.

LRIG1 opposes epithelial-to-mesenchymal transition and inhibits invasion of basal-like breast cancer cells

LRIG1, a member of the LRIG family of transmembrane leucine rich repeat-containing proteins, is a negative regulator of receptor tyrosine kinase signaling and a tumor suppressor. LRIG1 expression is broadly decreased in human cancer and in breast cancer, low expression of LRIG1 has been linked to decreased relapse-free survival. Recently, low expression of LRIG1 was revealed to be an independent risk factor for breast cancer metastasis and death. These findings suggest that LRIG1 may oppose breast cancer cell motility and invasion, cellular processes which are fundamental to metastasis. However, very little is known of LRIG1 function in this regard. In this study, we demonstrate that LRIG1 is down-regulated during epithelial to mesenchymal transition (EMT) of human mammary epithelial cells, suggesting that LRIG1 expression may represent a barrier to EMT. Indeed, depletion of endogenous LRIG1 in human mammary epithelial cells expands the stem cell population, augments mammosphere formation and accelerates EMT. Conversely, expression of LRIG1 in highly invasive Basal B breast cancer cells provokes a mesenchymal to epithelial transition accompanied by a dramatic suppression of tumorsphere formation and a striking loss of invasive growth in three-dimensional culture. LRIG1 expression perturbs multiple signaling pathways and represses markers and effectors of the mesenchymal state. Furthermore, LRIG1 expression in MDA-MB-231 breast cancer cells significantly slows their growth as tumors, providing the first in vivo evidence that LRIG1 functions as a growth suppressor in breast cancer.

LRIG1, a 3p tumor suppressor, represses EGFR signaling and is a novel epigenetic silenced gene in colorectal cancer

Downregulation of LRIG1 was found in many types of cancer. However, data concerning the possible mechanism of LRIG1 reduction in cancers were not reported yet. To analyze the regulation and function of LRIG1 in colorectal cancer (CRC), 6 cell lines, 46 paired tissues from primary CRC cases were employed in this study. In CRC cell lines, under-expression of LRIG1 was correlated with promoter region hypermethylation, and restoration of LRIG1 was induced by 5-Aza-2'-deoxyazacytidine treatment. Subsequently, we ectopically expressed LRIG1 in LRIG1 low-expressing HCT-116 cells and suppressed LRIG1 in LRIG1 high-expressing LoVo cells. We found that over-expression of LRIG1 inhibits cell proliferation and colony formation and tumor growth, while knockdown of LRIG1 promotes cell proliferation and colony formation. Decreased and increased EGFR/AKT signaling pathway may partially explain the lower and higher rates of proliferation in CRC cells transfected with LRIG1 cDNA or shRNA. In clinical samples, we compared the methylation, mRNA and protein expression of LRIG1 in samples of CRC tissues. A significant increase in LRIG1 methylation was identified in CRC specimens compared to adjacent normal tissues and that it was negatively correlated with its mRNA and protein expression. In conclusion, LRIG1 is frequently methylated in human CRC and consequent mRNA and protein downregulation may contribute to tumor growth by activating EGFR/AKT signaling.

PGTools: A Software Suite for Proteogenomic Data Analysis and Visualization

We describe PGTools, an open source software suite for analysis and visualization of proteogenomic data. PGTools comprises applications, libraries, customized databases, and visualization tools for analysis of mass-spectrometry data using combined proteomic and genomic backgrounds. A single command is sufficient to search databases, calculate false discovery rates, group and annotate proteins, generate peptide databases from RNA-Seq transcripts, identify altered proteins associated with cancer, and visualize genome scale peptide data sets using sophisticated visualization tools. We experimentally confirm a subset of proteogenomic peptides in human PANC-1 cells and demonstrate the utility of PGTools using a colorectal cancer data set that led to the identification of 203 novel protein coding regions missed by conventional proteomic approaches. PGTools should be equally useful for individual proteogenomic investigations as well as international initiatives such as chromosome-centric Human Proteome Project (C-HPP). PGTools is available at http://qcmg.org/bioinformatics/PGTools.

Adenovirus-mediated LRIG1 expression enhances the chemosensitivity of bladder cancer cells to cisplatin

Cisplatin (cis-diaminodichloroplatinum, CDDP) is one of the most effective chemotherapeutic agents that has been widely used in the treatment of many malignancies, including muscle invasive bladder cancer. However, development of CDDP resistance in cancer cells is a major obstacle to the effective treatment of bladder cancer. Therefore, the development of chemosensitizers to overcome the acquired resistance to chemotherapeutic agents is crucial. Previous studies have confirmed that the epidermal growth factor receptor (EGFR) and its signaling pathways are important in the chemoresistance of cancer cells against CDDP‑induced cell apoptosis. In a preliminary study we showed that leucine-rich repeats and immunoglobulin-like domains 1 (LRIG1) is the natural ligand of EGFR, and that the extracellular leucine-rich repeat (LRR) domain and immunoglobulin-like domains of LRIG1 were able to bind to the extracellular domain of EGFR, resulting in the downregulation of EGFR expression. Based on these findings, we hypothesized that LRIG1 may enhance the chemosensitivity of bladder cancer cells to CDDP. In the present study, LRIG1 was overexpressed by the adenovirus vector to determine the effect of LRIG1 on chemosensitivity in the T24 bladder cancer cell line and explored the possible mechanisms. The results showed that CDDP inhibited the growth of the T24 cell line and induced activation of EGFR. Overexpression of LRIG1 increased the inhibitory effect of CDDP on the T24 cell line, which may be associated with inactivation of the EGFR signaling pathway, followed by the decrease of Bcl-2 expression and a concomitantly induced expression of Bax. Based on these results, we concluded that the upregulation of LRIG1 expression inhibited the EGFR signaling pathway, activated the mitochondrial pathway of apoptosis and eventually increased the sensitivity of bladder cancer cells to CDDP.

LRIG and cancer prognosis

BACKGROUND

Optimal treatment decisions for cancer patients require reliable prognostic and predictive information. However, this information is inadequate in many cases. Several recent studies suggest that the leucine-rich repeats and immunoglobulin-like domains (LRIG) genes, transcripts, and proteins have prognostic implications in various cancer types.

MATERIAL AND METHODS

Relevant literature was identified on PubMed using the key words lrig1, lrig2, and lrig3. LRIG mRNA expression in cancer versus normal tissues was investigated using the Oncomine database.

RESULTS

The three human LRIG genes, LRIG1, LRIG2, and LRIG3, encode single-pass transmembrane proteins. LRIG1 is a negative regulator of growth factor signaling that has been shown to function as a tumor suppressor in vitro and in vivo in mice. The functions of LRIG2 and LRIG3 are less well defined. LRIG gene and protein expression are commonly dysregulated in human cancer. In early stage breast cancer, LRIG1 copy number was recently shown to predict early and late relapse in addition to overall survival; in nasopharyngeal carcinoma, loss of LRIG1 is also associated with poor survival. LRIG gene and protein expression have prognostic value in breast cancer, uterine cervical cancer, head-and-neck cancer, glioma, non-small cell lung cancer, prostate cancer, and cutaneous squamous cell carcinoma. In general, expression of LRIG1 and LRIG3 is associated with good survival, whereas expression of LRIG2 is associated with poor survival. Additionally, LRIG1 regulates cellular sensitivity to anti-cancer drugs, which indicates a possible role as a predictive marker.

CONCLUSIONS

LRIG gene statuses and mRNA and protein expression are clinically relevant prognostic indicators in several types of human cancer. We propose that LRIG analyses could become important when making informed and individualized clinical decisions regarding the management of cancer patients.

LRIG1 enhances chemosensitivity by modulating BCL-2 expression and receptor tyrosine kinase signaling in glioma cells

PURPOSE

Leucine-rich repeats and immunoglobulin-like domains 1 (LRIG1) are an inhibitor of receptor tyrosine kinases (RTKs) that was discovered in recent years, and many studies showed that LRIG1 is a tumor suppressor gene and may be related to tumor drug resistance. In this study, we explored whether LRIG1 protein expression can improve the chemosensitivity of glioma cells and what was its mechanism.

MATERIALS AND METHODS

We collected 93 cases of glioma tissues and detected the expression of LRIG1 and BCL-2. We constructed a multidrug resistance cell line U251/multidrug resistance (MDR) and examined the change of LRIG1 and BCL-2 at mRNA and protein expression levels. LRIG1 expression was upregulated in U251/MDR cells and we detected the change of multidrug resistance. Meanwhile, we changed the expression of LRIG1 and BCL-2 and explored the relationship between LRIG1 and BCL-2. Finally, we also explored the relationship between LRIG1 and RTKs.

RESULTS

LRIG1 was negatively correlated with BCL-2 expression in glioma tissue and U251/MDR cells, and upregulation of LRIG1 can enhance chemosensitivity and inhibit BCL-2 expression. Furthermore, LRIG1 was negatively correlated with RTKs in U251/MDR cells.

CONCLUSION

These results demonstrated that LRIG1 can improve chemosensitivity by modulating BCL-2 expression and RTK signaling in glioma cells.

LRIG1 as a potential novel marker for neoplastic transformation in ocular surface squamous neoplasia

The leucine rich repeats and immunoglobulin-like protein 1 (LRIG1) is a newly discovered negative regulator of epidermal growth factor receptor (EGFR) and a proposed tumor suppressor. It is not universally downregulated in human cancers, and its role in neoplastic transformation and tumorigenesis is not well-documented. In this study, we show the expression of LRIG1 as a novel potential marker for neoplastic transformation in ocular-surface squamous neoplasia (OSSN). The following two groups were included in this study: 1) benign group (3 cases; 1 with papilloma and 2 with dysplasia) and 2) malignant group (3 cases with squamous cell carcinoma (SCC)). In both groups, immunofluorescence analysis was firstly performed for keratins 4, 12, 13, and 15 to characterize the state of differentiation, and for Ki67 to evaluate the proliferation activity. Subsequently, LRIG1 and EGFR expression was analyzed. Either keratin 4 and/or 13, both non-keratinized epithelial cell markers, were generally expressed in both groups, except for 1 severe SCC case. Keratin 15, an undifferentiated basal cell marker, was more strongly expressed in the malignant cases than in the benign cases. The Ki67 index was significantly higher (P<0.002) in the malignant group (33.2%) than in the benign group (10.9%). LRIG1 expression was limited to basal epithelial cells in normal corneal epithelial tissue. Interestingly, LRIG1 was expressed throughout the epithelium in all the benign cases. In contrast, its expression was limited or totally disappeared in the malignant cases. Inversely, EGFR staining was faintly expressed in the benign cases, yet strongly expressed in the malignant cases. Malignant tissue with proliferative potential presented EGFR overexpression and inverse downregulation of LRIG1, consistent with LRIG1 being a suppressor of neoplastic transformation by counteracting the tumor growth property of EGFR. Our findings indicate that downregulation of LRIG1 is possibly a novel potential marker of transformation and tumorigenesis in OSSN cases.

Expression of LRIG1 is associated with good prognosis and human papillomavirus status in oropharyngeal cancer

Background:

The incidence of human papillomavirus (HPV)-associated oropharyngeal cancer has increased rapidly during the past decades. HPV is typically associated with a favourable outcome; however, a need exists for new and more effective prognostic and predictive markers for this disease. Leucine-rich repeats and immunoglobulin-like domains (LRIG)-1 is a tumour suppressor protein that belongs to the LRIG family. LRIG1 expression has prognostic significance in various human cancers, including cervical cancer, where HPV is a key aetiological agent.

Methods:

The prognostic value of LRIG1 and LRIG2 immunoreactivity was investigated in tumour specimens from a Swedish cohort of patients with tonsillar and base of tongue oropharyngeal cancers, including 278 patients.

Results:

LRIG1 immunoreactivity correlated with disease-free survival and overall survival in univariate and multivariate analyses. Notably, patients with HPV-positive tumours with high LRIG1 staining intensity or a high percentage of LRIG1-positive cells showed a very good prognosis. Furthermore, LRIG1 expression correlated with HPV status, whereas LRIG2 expression inversely correlated with HPV status.

Conclusions:

Taken together, the results suggest that LRIG1 immunoreactivity could be a clinically important prognostic marker in HPV-associated oropharyngeal cancer.

The LRIG family: enigmatic regulators of growth factor receptor signaling

The leucine-rich repeats and immunoglobulin-like domains (LRIG) family of transmembrane proteins contains three vertebrate members (LRIG1, LRIG2 and LRIG3) and one member each in flies (Lambik) and worms (Sma-10). LRIGs have stepped into the spotlight as essential regulators of growth factor receptors, including receptor tyrosine and serine/threonine kinases. LRIGs have been found to both negatively (LRIG1 and LRIG3) and positively (Sma-10 and LRIG3) regulate growth factor receptor expression and signaling, although the precise molecular mechanisms by which LRIGs function are not yet understood. The most is known about LRIG1, which was recently demonstrated to be a tumor suppressor. Indeed, in vivo experiments reinforce the essential link between LRIG1 and repression of its targets for tissue homeostasis. LRIG1 has also been identified as a stem cell marker and regulator of stem cell quiescence in a variety of tissues, discussed within. Comparably, less is known about LRIG2 and LRIG3, although studies to date suggest that their functions are largely distinct from that of LRIG1 and that they likely do not serve as growth/tumor suppressors. Finally, the translational applications of expressing soluble forms of LRIG1 in LRIG1-deficient tumors are being explored and hold tremendous promise.

Leucine-rich repeat and immunoglobulin domain-containing protein-1 (Lrig1) negative regulatory action toward ErbB receptor tyrosine kinases is opposed by leucine-rich repeat and immunoglobulin domain-containing protein 3 (Lrig3)

Lrig1 is the founding member of the Lrig family of transmembrane leucine-rich repeat proteins, which also includes Lrig2 and Lrig3. Lrig1 is a negative regulator of oncogenic receptor tyrosine kinases, including ErbB and Met receptors, and promotes receptor degradation. Lrig1 has recently emerged as both a tumor suppressor and a key regulator of epidermal and epithelial stem cell quiescence. Despite this, little is known of the mechanisms by which Lrig1 is regulated. Lrig3 was recently reported to increase ErbB receptor expression suggesting that it may function in a manner opposite to Lrig1. In this study, we explore the interaction between Lrig1 and Lrig3 and demonstrate that Lrig1 and Lrig3 functionally oppose one another. Lrig3 opposes Lrig1 negative regulatory activity and stabilizes ErbB receptors. Conversely, Lrig1 destabilizes Lrig3, limiting Lrig3's positive effects on receptors and identifying Lrig3 as a new target of Lrig1. These studies provide new insight into the regulation of Lrig1 and uncover a complex cross-talk between Lrig1 and Lrig3.