Perinuclear leucine-rich repeats and immunoglobulin-like domain proteins (LRIG1-3) as prognostic indicators in astrocytic tumors

The Significant Role of microRNAs in Gliomas Angiogenesis: A Particular Focus on Molecular Mechanisms and Opportunities for Clinical Application

MicroRNAs (miRNAs) are non-coding RNAs with only 20-22 nucleic acids that inhibit gene transcription and translation by binding to mRNA. MiRNAs have a diverse set of target genes and can alter most physiological processes, including cell cycle checkpoints, cell survival, and cell death mechanisms, affecting the growth, development, and invasion of various cancers, including gliomas. So optimum management of miRNA expression is essential for preserving a normal biological environment. Due to their small size, stability, and capability of specifically targeting oncogenes, miRNAs have emerged as a promising marker and new biopharmaceutical targeted therapy for glioma patients. This review focuses on the most common miRNAs associated with gliomagenesis and development by controlling glioma-determining markers such as angiogenesis. We also summarized the recent research about miRNA effects on signaling pathways, their mechanistic role and cellular targets in the development of gliomas angiogenesis. Strategies for miRNA-based therapeutic targets, as well as limitations in clinical applications, are also discussed.

LRIG2 promotes glioblastoma progression by modulating innate antitumor immunity through macrophage infiltration and polarization

Background

Glioblastoma (GBM) is the most common malignant brain tumor with poor clinical outcomes. Immunotherapy has recently been an attractive and promising treatment of extracranial malignancies, however, most of clinical trials for GBM immunotherapy failed due to predominant accumulation of tumor-associated microglia/macrophages (TAMs).

Results

High level of LRIG2/soluble LRIG2 (sLRIG2) expression activates immune-related signaling pathways, which are associated with poor prognosis in GBM patients. LRIG2/sLRIGs promotes CD47 expression and facilitates TAM recruitment. Blockade of CD47–SIRPα interactions and inhibition of sLRIG2 secretion synergistically suppress GBM progression in an orthotropic murine GBM model.

Conclusions

GBM cells with high level LRIG2 escape the phagocytosis by TAM via the CD47-SIRPα axis, highlighting a necessity for an early stage of clinical trial targeting LRIG2 and CD47-SIRPα as a novel treatment for patients with GBM.

Prognostic significance of LRIG2 and LRIG3 proteins in urothelial bladder carcinoma

Bladder carcinoma is the second most frequent cancer in Egyptian males. Leucine-rich and immunoglobulin-like domains (LRIGs) are usually dysregulated in various human tumors. The aim of this study is to explore the immunohistochemical expression of LRIG2 and LRIG3 in urothelial bladder carcinoma (UBC) and their relationship to patients clinicopathological data including survival. The study cohort included 79 UBC cases (14 non muscle invasive (NMI) and 65 muscle invasive (MI)). We assessed the associations of LRIG2 and LRIG3 expression with clinicopathological data, as well as progression-free and overall survival. Most of studied cases (>50%) express LRIG2 and LRIG3. Statistically significant association was observed between positivity for LRIG3 and muscle invasion (P = 0.001), high grade (P = 0.03), and female gender (P = 0.02). Moreover, positive LRIG2 staining was associated with early stage (T2) (P = 0.03), lymphovascular invasion (P = 0.004), and tendency to non-muscle invasive stage (P = 0.07). Grouping of cases according to positivity/negativity of both markers showed that cases with dual positivity for both proteins are associated with muscle invasion (P = 0.001) and paradoxically with prolonged overall survival (P = 0.037). We conclude that although the association of LRIG3 with MI and high-grade tumors, its expression is related to better survival. LRIG3 has the dominant role even if it coexists with LRIG2. The role of LRIG2 remains to be further investigated.

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.

LRIG1, a regulator of stem cell quiescence and a pleiotropic feedback tumor suppressor

LRIG1, leucine-rich repeats and immunoglobulin-like domains protein 1, was discovered more than 20 years ago and has been shown to be downregulated or lost, and to function as a tumor suppressor in several cancers. Another well-reported biological function of LRIG1 is to regulate and help enforce the quiescence of adult stem cells (SCs). In both contexts, LRIG1 regulates SC quiescence and represses tumor growth via, primarily, antagonizing the expression and activities of ERBB and other receptor tyrosine kinases (RTKs). We have recently reported that in treatment-naïve human prostate cancer (PCa), LRIG1 is primarily regulated by androgen receptor (AR) and is prominently overexpressed. In castration-resistant PCa (CRPC), both LRIG1 and AR expression becomes heterogeneous and, frequently, discordant. Importantly, in both androgen-dependent PCa and CRPC models, LRIG1 exhibits tumor-suppressive functions. Moreover, LRIG1 induction inhibits the growth of pre-established AR⁺ and AR⁻ PCa. Here, upon a brief introduction of the LRIG1 and the LRIG family, we provide an updated overview on LRIG1 functions in regulating SC quiescence and repressing tumor development. We further highlight the expression, regulation and functions of LRIG1 in treatment-naïve PCa and CRPC. We conclude by offering the perspectives of identifying novel cancer-specific LRIG1-interacting signaling partners and developing LRIG1-based anti-cancer therapeutics and diagnostic/prognostic biomarkers.

Plasma amino acids indicate glioblastoma with ATRX loss

Glioblastoma (GB) is the most common primary brain tumour in adults. The lack of molecular biomarker, non-specific symptoms and fast growth rate often result in a significant delay in diagnosis. Despite multimodal treatment, the prognosis remains poor. Here, we verified the hypothesis that amino acids (AA) regulating the critical metabolic pathways necessary for maintenance, growth, reproduction, and immunity of an organism, may constitute a favourable target in GB biomarker research. We measured the plasma amino acids levels in 18 GB patients and 15 controls and performed the quantitative and qualitative metabolomic analysis of free AA applying high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). We present both the raw data and the results of our statistical analysis. The majority of AA were lowered in the study group in comparison to the control group. Five of these (arginine, glutamic acid, glutamine, glycine, and histidine) differed significantly (all p < 10^-5 and AUC > 0.9). Plasma levels of leucine and phenylalanine decreased in the case of GB with lost alpha-thalassemia/mental retardation X-linked (ATRX) expression on immunohistochemistry (p = 0.003 and 0.045, respectively). We demonstrated for the first time that certain plasma-free AA levels of GB patients were significantly different from those in healthy volunteers. Target profiling of plasma-free AA, identified utilizing LC-QTOF-MS, may present prognostic value by indicating GB patients with lost ATRX expression. The on-going quest for glioma biomarkers still aims to determine the detailed metabolic profile and evaluate its impact on therapy and prognosis.

Upregulation of microRNA-196a improves cognitive impairment and alleviates neuronal damage in hippocampus tissues of Alzheimer's disease through downregulating LRIG3 expression

PURPOSE

This study is launched to uncover the inner function of microRNA-196a (miR-196a) on cognitive dysfunction and neuronal damage in Alzheimer's disease (AD) rats through regulating the PI3K/Akt signaling pathway.

METHODS

The establishment of AD rat model was performed by a microinjection of Aβ_25-35 . miR-196a and LRIG3 expression was detected, and the putative binding site between them was also determined. The spatial learning and memory capability, the hippocampal neurons ultrastructure as well as the survival, and apoptosis of hippocampal neurons of rats were observed. The expression of apoptosis-associated protein, oxidative stress index, and inflammatory factors as well as the PI3K/Akt pathway-related factors was determined.

RESULTS

Initially, decreased miR-196a and increased LRIG3 were exhibited in hippocampus tissues of AD rats. In addition, restored miR-196a and deleted LRIG3 ameliorated spatial learning and memory capability, suppressed the pathological injury, induced the survival, and suppressed the apoptosis of hippocampal neurons, as well as inhibited oxidative stress injury together with inflammatory injury in AD rats. Furthermore, upregulation of miR-196a activated the PI3/Akt pathway in AD rats.

CONCLUSION

This current study suggests that upregulation of miR-196a and downregulation of LRIG3 improve cognitive impairment and alleviate neuronal damage in hippocampus tissues in AD rats via the modulation of the PI3K/Akt pathway.

LRIG1‑2 and LMO7 immunoreactivity in vulvar squamous cell carcinoma: Association with prognosis in relation to HPV‑DNA and p16INK4a status

The present study was conducted to investigate the possible prognostic value of molecular markers LRIG1‑2 and LIM domain 7 protein (LMO7) in vulvar squamous cell carcinoma (VSCC) and their possible correlation to human papilloma virus (HPV)‑ and p16INK4a‑status of the tumors. Patients diagnosed with VSCC at the University Hospital of Umeå, Sweden, during the years 1990‑2013 were selected. Tumor blocks were retrieved from tissue archives and clinical data were collected from the records of patients. HPV‑PCR analysis, HPV genotyping and immunohistochemistry were performed. In total, 112 patients were included. Forty percent of the tumors were HPV‑positive, 27% were p16INK4a‑positive and 23% were positive for both HPV and p16INK4a (considered HPV‑driven). HPV‑positivity and p16INK4a‑positivity were associated with prolonged disease‑free survival (DFS) in Kaplan‑Meier survival analysis. Leucine‑rich repeats and immunoglobulin‑like domains 1 (LRIG1) immunoreactivity was not significantly associated with survival. High leucine‑rich repeats and immunoglobulin‑like domains 2 (LRIG2) immunoreactivity was associated with a prolonged overall survival (OS) (P=0.001). By analyzing HPV‑negative cases only, it was determined that high LRIG2 immunoreactivity was associated with both favorable OS (P=0.008) and DFS (P=0.031). LRIG2 immunoreactivity was also an independent prognostic factor in multivariate analysis of OS (P=0.002, HR=0.41; 95% CI, 0.24‑0.71). High immunoreactivity with LMO7‑1250 antibody was associated with survival benefits in the whole cohort (OS; P=0.011) although DFS was only prolonged in HPV‑negative and not HPV‑driven tumors (P=0.038 and 0.042, respectively). The present study indicated that LRIG2 and LMO7 may be useful prognostic markers in VSCC, particularly for patients without HPV‑driven tumors or with advanced tumors at diagnosis. In contrast to earlier observations regarding other types of squamous cell carcinoma, LRIG1 was not a significant prognostic factor in VSCC.

LMO7 and LIMCH1 interact with LRIG proteins in lung cancer, with prognostic implications for early-stage disease

OBJECTIVES

The human leucine-rich repeats and immunoglobulin-like domains (LRIG) protein family comprises the integral membrane proteins LRIG1, LRIG2 and LRIG3. LRIG1 is frequently down-regulated in human cancer, and high levels of LRIG1 in tumor tissue are associated with favorable clinical outcomes in several tumor types including non-small cell lung cancer (NSCLC). Mechanistically, LRIG1 negatively regulates receptor tyrosine kinases and functions as a tumor suppressor. However, the details of the molecular mechanisms involved are poorly understood, and even less is known about the functions of LRIG2 and LRIG3. The aim of this study was to further elucidate the functions and molecular interactions of the LRIG proteins.

MATERIALS AND METHODS

A yeast two-hybrid screen was performed using a cytosolic LRIG3 peptide as bait. In transfected human cells, co-immunoprecipitation and co-localization experiments were performed. Proximity ligation assay was performed to investigate interactions between endogenously expressed proteins. Expression levels of LMO7 and LIMCH1 in normal and malignant lung tissue were investigated using qRT-PCR and through in silico analyses of public data sets. Finally, a clinical cohort comprising 355 surgically treated NSCLC cases was immunostained for LMO7.

RESULTS

In the yeast two-hybrid screen, the two paralogous proteins LMO7 and LIMCH1 were identified as interaction partners to LRIG3. LMO7 and LIMCH1 co-localized and co-immunoprecipitated with both LRIG1 and LRIG3. Endogenously expressed LMO7 was in close proximity of both LRIG1 and LRIG3. LMO7 and LIMCH1 were highly expressed in normal lung tissue and down-regulated in malignant lung tissue. LMO7 immunoreactivity was shown to be a negative prognostic factor in LRIG1 positive tumors, predicting poor patient survival.

CONCLUSION

These findings suggest that LMO7 and LIMCH1 physically interact with LRIG proteins and that expression of LMO7 is of clinical importance in NSCLC.

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.

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.

LRIG proteins in glioma: Functional roles, molecular mechanisms, and potential clinical implications

Gliomas are the most common intracranial tumors of the nervous system. These tumors are characterized by unlimited cell proliferation and excessive invasiveness. Despite the advances in diagnostic imaging, microneurosurgical techniques, radiation therapy, and chemotherapy, significant increases in the progression free survival of glioma patients have not been achieved. Improvements in our understanding of the molecular subtypes of gliomas and the underlying alterations in specific signaling pathways may impact both the diagnosis and the treatment strategies for patients with gliomas. Growth factors and their corresponding receptor tyrosine kinases are associated with oncogenesis and development of tumors in numerous human cancer types, including glioma. Leucine-rich repeats and immunoglobulin-like domains (LRIG) are integral membrane proteins which contain three vertebrate members including LRIG1, LRIG2 and LRIG3. They mainly function as regulators of growth factor signaling. Specifically, LRIG1 has been identified as a tumor suppressor in human cancers. In contrast, LRIG2 appears to function as a tumor promoter, while LRIG3 appears to have a function similar to that of LRIG1. In the present review, we summarize the functional roles, molecular mechanisms, and clinical perspectives of LRIG proteins in gliomas and propose that these proteins may be useful in the future as targets for treatment and prognostication in glioma patients.

Expression of LRIG proteins as possible prognostic factors in primary vaginal carcinoma

Background

Primary vaginal carcinoma (PVC) is a rare malignancy. Established prognostic factors include tumour stage and age at diagnosis. The leucine-rich repeats and immunoglobuline-like domains (LRIG)-1 protein functions as a tumour suppressor, but less is known about the functions of LRIG2 and LRIG3. The present study aimed to evaluate the expression of LRIG proteins and analyse their possible associations with clinical characteristics and survival in a cohort of PVC patients.

Methods

We used immunohistochemistry to investigate LRIG1, LRIG2, and LRIG3 expression in tumour samples from a consecutive cohort of 70 PVC patients. The association between LRIG protein expression and clinical characteristics and cancer-specific survival was investigated using univariate and multivariate analyses.

Results

The majority of PVC patients (72%) had >50% LRIG1- and LRIG2-positive cells, and no or low LRIG3-positive cells. HPV status was significantly correlated with LRIG1 expression (p = 0.0047). Having high LRIG1 expression was significantly correlated with superior cancer-specific survival in univariate and multivariate analyses. LRIG2 and LRIG3 expression did not significantly correlate with clinical characteristics or survival.

Conclusion

LRIG1 expression might be of interest as a prognostic marker in PVC patients, whereas the role of LRIG2 and LRIG3 expression remains to be clarified.

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.

Downregulation of LRIG2 expression inhibits angiogenesis of glioma via EGFR/VEGF-A pathway

Active angiogenesis is the basic pathological feature of glioma. Tumor angiogenesis is involved in vascular endothelial cell migration to the tumor tissue and in the formation of tube-like structures. The present study aimed to investigate the role of leucine-rich repeats and immunoglobulin-like domains 2 (LRIG2) in glioma angiogenesis. Glioma (n=50) and normal brain (n=20) tissue samples were collected from patients to detect the expression of LRIG2, epidermal growth factor receptor (EGFR), vascular endothelial growth factor A (VEGF-A), and cluster of differentiation 31 (CD31) using immunohistochemistry. In addition, the association between the expression of LRIG2 in glioma tissue and the microvessel density (MVD) was analyzed. In vitro, the expression of LRIG2 in human glioma U87 and U251 cell lines was knocked down. Subsequently, cell migration and tube formation assays of human umbilical vein endothelial cells (HUVECs) were performed using a coculture system. The protein expression levels of LRIG2, EGFR, phosphorylated-EGFR and VEGF-A were determined using western blotting. The results demonstrated that the expression levels of LRIG2, EGFR, VEGF-A and CD31 were highly upregulated in glioma tissue samples. Furthermore, LRIG2 expression in glioma tissue samples was significantly correlated with the MVD. In vitro, the downregulation of LRIG2 inhibited HUVEC migration and tube formation induced by coculture with glioma cells. The downregulation of LRIG2 resulted in decreased expression of EGFR and VEGF-A. The effects of the LRIG2 knockdown were reversed following EGF treatment. These findings suggest that LRIG2 is a potential target for the inhibition of glioma angiogenesis, which is possibly mediated via the EGFR/VEGF-A signaling pathway.

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.

Overexpression of LRIG1 regulates PTEN via MAPK/MEK signaling pathway in esophageal squamous cell carcinoma

The present study aimed to evaluate the role of leucine-rich repeats and immunoglobulin-like domain protein 1 (LRIG1) in the regulation of phosphatase and tensin homolog (PTEN) expression in esophageal carcinogenesis. LRIG1 was overexpressed in esophageal squamous cell carcinoma (ESCC) cell lines, and the effect of LRIG1 overexpression on the mRNA and protein expression levels of PTEN was evaluated by reverse transcription-quantitative polymerase chain reaction and western blotting. Furthermore, the effects of LRIG1 overexpression on the cell cycle distribution and apoptosis of ESCC cells were examined by flow cytometry. Various cell signaling pathway inhibitors were used to assess the effects of LRIG1 on downstream signaling in ESCC cell lines. In addition, the association between LRIG1 and PTEN expression was examined in 48 samples from patients with ESCC. LRIG1 overexpression was demonstrated to downregulate PTEN expression in ESCC cell lines, and promote their proliferation and inhibit apoptosis. In addition, LRIG1-mediated suppression of PTEN expression was inhibited by the U0126 inhibitor, which suggests that LRIG1 may inhibit the activation of PTEN signaling molecules by triggering the mitogen-activated protein kinase (MAPK)/MAPK kinase 1 (MEK) signaling pathway. In conclusion, the present study demonstrated that overexpression of LRIG1 significantly and adversely affected the survival of ESCC cells, and that the MAPK/MEK signaling pathway may be responsible for the repression of PTEN expression and function.

Cardiac hypertrophy and decreased high-density lipoprotein cholesterol in Lrig3-deficient mice

Genetic factors confer risk for cardiovascular disease. Recently, large genome-wide population studies have shown associations between genomic loci close to LRIG3 and heart failure and plasma high-density lipoprotein (HDL) cholesterol level. Here, we ablated Lrig3 in mice and investigated the importance of Lrig3 for heart function and plasma lipid levels. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to analyze Lrig3 expression in the hearts of wild-type and Lrig3-deficient mice. In addition, molecular, physiological, and functional parameters such as organ weights, heart rate, blood pressure, heart structure and function, gene expression in the heart, and plasma insulin, glucose, and lipid levels were evaluated. The Lrig3-deficient mice were smaller than the wild-type mice but otherwise appeared grossly normal. Lrig3 was expressed at detectable but relatively low levels in adult mouse hearts. At 9 mo of age, ad libitum-fed Lrig3-deficient mice had lower insulin levels than wild-type mice. At 12 mo of age, Lrig3-deficient mice exhibited increased blood pressure, and the Lrig3-deficient female mice displayed signs of cardiac hypertrophy as assessed by echocardiography, heart-to-body weight ratio, and expression of the cardiac hypertrophy marker gene Nppa. Additionally, Lrig3-deficient mice had reduced plasma HDL cholesterol and free glycerol. These findings in mice complement the human epidemiological results and suggest that Lrig3 may influence heart function and plasma lipid levels in mice and humans.

Expression of LRIG1 is Associated With Good Prognosis for Human Non-small Cell Lung Cancer

Somatic mutations, which are associated with a certain rate of response to targeted therapies, are ubiquitously found in human non-small cell lung cancer (NSCLC). However, it is largely unknown which group of patients may benefit from the respective treatments targeting different somatic mutations. Therefore, more effective prognostic and predictive markers are desperately needed for the treatment of NSCLC harboring different somatic mutations. The leucine-rich repeats and immunoglobulin-like domains (LRIG)-1 is a tumor suppressor gene that belongs to the LRIG family. LRIG1 expression has prognostic significance in various human cancers.In this study, we first used the quantitative polymerase chain reaction (qPCR) and immunohistochemical analysis of 36 and 182 NSCLC patient tissues to analyze the LRIG1 expression respectively. To investigate the prognostic value of LRIG1 in NSCLC, we examined the correlation between clinical features and overall survival (OS) with Cox proportional hazard regression. We also compared the sensitivity and specificity of LRIG1 in NSCLC prognosis by logistic regression to further evaluate the prognostic efficiency of LRIG1 in NSCLC.We found that the LRIG1 expression was associated with pathological type, differentiation status, and stage of NSCLC. The result showed that LRIG1 was an independent prognostic factor for OS of NSCLC patients. LRIG1 in combination with other clinicopathological risk factors was a stronger prognostic model than clinicopathological risk factors alone.Thus, the LRIG1 expression potentially offered a significant clinical value in directing personal treatment for NSCLC patients.

LRIG1 inhibits hypoxia-induced vasculogenic mimicry formation via suppression of the EGFR/PI3K/AKT pathway and epithelial-to-mesenchymal transition in human glioma SHG-44 cells

Leucine-rich repeats and immunoglobulin-like domains 1 (LRIG1) is a pan-negative regulator of the epidermal growth factor receptor (EGFR) signaling pathway. The aim of this study was to investigate the underlying mechanism of LRIG1 in the regulation of vasculogenic mimicry (VM) formation in glioma cells. We constructed an enhanced green fluorescent protein plasmid (pEGFP) system, pEGFP-C1-LRIG1, for overexpression of LRIG1, and transfected it into human glioma cell line SHG-44. Under hypoxic conditions induced by CoCl2, we investigated the effects of LRIG1 overexpression on VM formation and VM-dependent malignant behaviors including migration, invasion, and proliferation. Additionally, we explored the effects of LRIG1 on the expression levels of major components of the EGFR/PI3K/AKT pathway as well as E-cadherin and vimentin. We found that LRIG1 overexpression is able to inhibit hypoxia-induced VM formation, migration, invasion, and proliferation. Furthermore, LRIG1 overexpression counteracts hypoxia-induced increase in the expression of phosphorylated EGFR (pEGFR), PI3K (pPI3K), and AKT (pAKT) and reverts hypoxia-induced alteration in E-cadherin and vimentin expression levels. In LRIG1 knockdown SHG-44 cells, however, hypoxia-induced VM formation and alteration in E-cadherin and vimentin expression levels were exacerbated. These results suggest that the inhibitory effects of LRIG1 are most likely mediated by suppression of the EGFR/PI3K/AKT pathway and epithelial-mesenchymal transition (EMT) process. Our findings provide compelling evidence implicating LRIG1 in glioma pathophysiology, suggesting that gene therapy using LRIG1 may serve as a treatment for this disease.

LRIG1 is a prognostic biomarker in non-small cell lung cancer

BACKGROUND

The leucine-rich repeats and immunoglobulin-like domains (LRIG) family of transmembrane proteins are involved in the regulation of cellular signal transduction. LRIG1 is an endogenous inhibitor of receptor tyrosine kinases (RTKs) and an emerging tumor suppressor. In the lung epithelium, the expression of LRIG1 is downregulated by tobacco smoking, and further downregulated in lung squamous cell carcinoma.

MATERIAL AND METHODS

The expression of LRIG proteins were analyzed in 347 cases of non-small cell lung cancer (NSCLC) by immunohistochemistry, and LRIG1 mRNA expression was evaluated in 807 lung cancer samples in silico in the Oncomine database. Potential associations between the expression data and the clinical parameters, including patient survival, were investigated.

RESULTS

Expression of the LRIG1 protein was found to be an independent prognostic factor in NSCLC, whereas expression of LRIG2 or LRIG3 did not correlate with patient survival. The levels of LRIG1 mRNA also correlated with the survival of NSCLC patients.

CONCLUSION

These findings demonstrate that LRIG1 is an independent prognostic factor in patients with NSCLC that could be important in future decision-making algorithms for adjuvant lung cancer treatment.

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.

LRIG2 expression and prognosis in non-small cell lung cancer

The human leucine-rich repeats and immunoglobulin-like domains 2 (LRIG2) protein has been shown to be of prognostic value in several types of human cancer, however, the expression profiles of LRIG2 have not been described in non-small cell lung cancer (NSCLC). The present study evaluated the mRNA expression of LRIG2 in tumor specimens obtained from 39 NSCLC patients by SYBR Green quantitative polymerase chain reaction and the protein expression of LRIG2 in formalin-fixed paraffin sections obtained from 116 NSCLC patients by immunohistochemistry. The correlations between LRIG2 expression and clinicopathological data were analyzed. The patient survival data were collected retrospectively and the possible prognostic value of LRIG2 protein expression was investigated. The results showed that the mRNA expression of LRIG2 was decreased in NSCLC cancer tissues, which was associated with histological subtypes and tumor differentiation status. The protein expression of LRIG2 was only observed in the cytoplasm of the tumor tissue, which conformed to the mRNA expression results. Furthermore, the patients with high LRIG2 cytoplasmic expression showed poor survival times, and the five-year survival rate for patients with high LRIG2 expression was 27.8%, compared with 38.8% for patients with low expression (P=0.034), indicating that LRIG2 expression levels may have a potential role in the pathogenesis of NSCLC, and also a significant prognostic value. Further studies are required to fully elucidate the exact function of LRIG2 in NSCLC.

Immunohistochemical LRIG3 expression in cervical intraepithelial neoplasia and invasive squamous cell cervical cancer: association with expression of tumor markers, hormones, high-risk HPV-infection, smoking and patient outcome

The novel biomarker LRIG3 is a member of the LRIG family (LRIG1-3). While LRIG1 has been associated with favorable prognosis and LRIG2 with poor prognosis in invasive cervical cancer, little is known about the role of LRIG3. The aim of this study was to investigate the expression of LRIG3 in invasive cancer and cervical intraepithelial neoplasia (CIN) for possible correlation with other tumor markers, to hormones and smoking, as a diagnostic adjunct in CIN, and prognostic value in invasive cancer. Cervical biopsies from 129 patients with invasive squamous cell carcinoma and 170 biopsies showing low grade and high grade CIN, or normal epithelium were stained for LRIG3 and 17 additional tumor markers. Among other variables the following were included: smoking habits, hormonal contraceptive use, serum progesterone, serum estradiol, high-risk HPV-infection, menopausal status and ten-year survival. In CIN, high expression of the tumor suppressors retinoblastoma protein, p53, and p16, and Ecadherin (cell-cell interaction), or low expression of CK10, correlated to LRIG3 expression. In addition, progestogenic contraceptive use correlated to high expression of LRIG3. In invasive cancer there was a correlation between expression of the major tumor promoter c-myc and high LRIG3 expression. High LRIG3 expression correlated significantly to presence of high-risk HPV infection in patients with normal epithelium and CIN. There was no correlation between LRIG3 expression and 10-year survival in patients with invasive cell cervical cancer. LRIG3 expression is associated with a number of molecular events in CIN. Expression also correlates to hormonal contraceptive use. The results on expression of other tumor markers suggest that LRIG3 is influenced by or influences a pattern of tumor markers in cancer and precancerous cells. Further studies are needed to elucidate if LRIG3 expression might be clinically useful.

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.

In vivo analysis of Lrig genes reveals redundant and independent functions in the inner ear

Lrig proteins are conserved transmembrane proteins that modulate a variety of signaling pathways from worm to humans. In mammals, there are three family members – Lrig1, Lrig2, and Lrig3 – that are defined by closely related extracellular domains with a similar arrangement of leucine rich repeats and immunoglobulin domains. However, the intracellular domains show little homology. Lrig1 inhibits EGF signaling through internalization and degradation of ErbB receptors. Although Lrig3 can also bind ErbB receptors in vitro, it is unclear whether Lrig2 and Lrig3 exhibit similar functions to Lrig1. To gain insights into Lrig gene functions in vivo, we compared the expression and function of the Lrigs in the inner ear, which offers a sensitive system for detecting effects on morphogenesis and function. We find that all three family members are expressed in the inner ear throughout development, with Lrig1 and Lrig3 restricted to subsets of cells and Lrig2 expressed more broadly. Lrig1 and Lrig3 overlap prominently in the developing vestibular apparatus and simultaneous removal of both genes disrupts inner ear morphogenesis. This suggests that these two family members act redundantly in the otic epithelium. In contrast, although Lrig1 and Lrig2 are frequently co-expressed, Lrig1^−/−;Lrig2^−/− double mutant ears show no enhanced structural abnormalities. At later stages, Lrig1 expression is sustained in non-sensory tissues, whereas Lrig2 levels are enhanced in neurons and sensory epithelia. Consistent with these distinct expression patterns, Lrig1 and Lrig2 mutant mice exhibit different forms of impaired auditory responsiveness. Notably, Lrig1^−/−;Lrig2^−/− double mutant mice display vestibular deficits and suffer from a more severe auditory defect that is accompanied by a cochlear innervation phenotype not present in single mutants. Thus, Lrig genes appear to act both redundantly and independently, with Lrig2 emerging as the most functionally distinct family member.

The mammalian genome encodes three Lrig family members - Lrig1, Lrig2, and Lrig3. Lrig proteins share a characteristic extracellular domain that can bind to a variety of signaling receptors, but the three family members show little homology in the cytoplasmic domain. Lrig1 is a tumor suppressor gene required for normal EGF signaling. Whether Lrig2 and Lrig3 play similar roles is not known. To address this gap in knowledge, we compared the expression and function of Lrigs in the mouse inner ear, which is responsible for hearing and balance. Even subtle changes in the inner ear cause easily detected deficits in hearing and balance, making it an ideal system for analysis of gene function. We find that Lrigs can act both redundantly and independently in the inner ear, with Lrig1 and Lrig3 cooperating to control morphogenesis and Lrig1 and Lrig2 acting independently to ensure proper cochlear function. However, loss of both Lrig1 and Lrig2 causes a more severe auditory response deficit and additionally causes a vestibular defect, suggesting some overlapping activities. Our findings provide new insights into the in vivo functions for the Lrig genes, which play important roles in vertebrate development and disease.

Inhibition of DYRK1A destabilizes EGFR and reduces EGFR-dependent glioblastoma growth

Glioblastomas (GBMs) are very aggressive tumors that are resistant to conventional chemo- and radiotherapy. New molecular therapeutic strategies are required to effectively eliminate the subpopulation of GBM tumor-initiating cells that are responsible for relapse. Since EGFR is altered in 50% of GBMs, it represents one of the most promising targets; however, EGFR kinase inhibitors have produced poor results in clinical assays, with no clear explanation for the observed resistance. We uncovered a fundamental role for the dual-specificity tyrosine phosphorylation-regulated kinase, DYRK1A, in regulating EGFR in GBMs. We found that DYRK1A was highly expressed in these tumors and that its expression was correlated with that of EGFR. Moreover, DYRK1A inhibition promoted EGFR degradation in primary GBM cell lines and neural progenitor cells, sharply reducing the self-renewal capacity of normal and tumorigenic cells. Most importantly, our data suggest that a subset of GBMs depends on high surface EGFR levels, as DYRK1A inhibition compromised their survival and produced a profound decrease in tumor burden. We propose that the recovery of EGFR stability is a key oncogenic event in a large proportion of gliomas and that pharmacological inhibition of DYRK1A could represent a promising therapeutic intervention for EGFR-dependent GBMs.

The soluble form of the tumor suppressor Lrig1 potently inhibits in vivo glioma growth irrespective of EGF receptor status

Background

Deregulated growth factor signaling is a major driving force in the initiation and progression of glioblastoma. The tumor suppressor and stem cell marker Lrig1 is a negative regulator of the epidermal growth factor receptor (EGFR) family. Here, we addressed the therapeutic potential of the soluble form of Lrig1 (sLrig1) in glioblastoma treatment and the mechanism of sLrig1-induced growth inhibition.

Methods

With use of encapsulated cells, recombinant sLrig1 was locally delivered in orthotopic glioblastoma xenografts generated from freshly isolated patient tumors. Tumor growth and mouse survival were evaluated. The efficacy of sLrig1 and the affected downstream signaling was studied in vitro and in vivo in glioma cells displaying variable expression of wild-type and/or a constitutively active EGFR mutant (EGFRvIII).

Results

Continuous interstitial delivery of sLrig1 in genetically diverse patient-derived glioma xenografts led to strong tumor growth inhibition. Glioma cell proliferation in vitro and tumor growth in vivo were potently inhibited by sLrig1, irrespective of EGFR expression levels. Of importance, tumor growth was also suppressed in EGFRvIII-driven glioma. sLrig1 induced cell cycle arrest without changing total receptor level or phosphorylation. Affected downstream effectors included MAP kinase but not AKT signaling. Of importance, local delivery of sLrig1 into established tumors led to a 32% survival advantage in treated mice.

Conclusions

To our knowledge, this is the first report demonstrating that sLrig1 is a potent inhibitor of glioblastoma growth in clinically relevant experimental glioma models and that this effect is largely independent of EGFR status. The potent anti-tumor effect of sLrig1, in combination with cell encapsulation technology for in situ delivery, holds promise for future treatment of glioblastoma.

LRIG1 regulates cadherin-dependent contact inhibition directing epithelial homeostasis and pre-invasive squamous cell carcinoma development

Epidermal growth factor receptor (EGFR) pathway activation is a frequent event in human carcinomas. Mutations in EGFR itself are, however, rare, and the mechanisms regulating EGFR activation remain elusive. Leucine-rich immunoglobulin repeats-1 (LRIG1), an inhibitor of EGFR activity, is one of four genes identified that predict patient survival across solid tumour types including breast, lung, melanoma, glioma, and bladder. We show that deletion of Lrig1 is sufficient to promote murine airway hyperplasia through loss of contact inhibition and that re-expression of LRIG1 in human lung cancer cells inhibits tumourigenesis. LRIG1 regulation of contact inhibition occurs via ternary complex formation with EGFR and E-cadherin with downstream modulation of EGFR activity. We find that LRIG1 LOH is frequent across cancers and its loss is an early event in the development of human squamous carcinomas. Our findings imply that the early stages of squamous carcinoma development are driven by a change in amplitude of EGFR signalling governed by the loss of contact inhibition.

BMP4 reverses multidrug resistance through modulation of BCL-2 and GDNF in glioblastoma

Patients with glioblastoma are commonly treated with chemotherapy. But a significant proportion of patients develop disease progression after an initial response to chemotherapy. Presently, there is no standard of care for such patients. The bone morphogenetic protein 4 (BMP4) has been reported to play a tumor-suppressing role in glioblastoma, but its role in glioblastoma multidrug resistance (MDR) is not clear. We reported that BMP4 can reverse MDR of glioblastoma through the inhibition of B-cell lymphoma 2(BCL-2) and glial cell derived neurotrophic factor (GDNF). We showed that the expression level of BMP4 was lower in glioblastoma compared to normal brain tissue, and also showed that BMP4 expression decreased in multidrug resistance cell line U251/TMZ compared to U251 cells. Our research demonstrated that over-expression of BMP4 can reverse the multidrug resistance. BCL-2 and GDNF were inhibited when BMP4 was over-expressed, and this data were consistent with the negative relationship in human samples; analysis of 40 patient's glioblastoma and brain samples revealed a significant negative correlation between BMP4 and BCL-2, GDNF. When BCL-2 and GDNF were knocked down, the effect of BMP4 in regulating MDR was partially lost. This novel result showed, for the first time, that BMP4 can reverse MDR in glioblastoma, which involved negative inhibition of BCL-2 and GDNF.

A role for LRIG1 in the regulation of malignant glioma aggressiveness

The molecular mechanisms that drive the development and aggressive progression of malignant astrocytic tumors remain obscure. Recently, in the search for endogenous negative regulators of EGF receptor, LRIG1 was cloned and characterized as a putative tumor suppressor gene often downregulated in various human tumors, including astrocytic tumors. Although several studies have implicated the function of LRIG1 in the inhibition of tumorigenesis, its precise role and potential underlying mechanisms remain obscure. Therefore, we generated a full-length expression vector to overexpress LRIG1 in the U251 malignant glioma cell line. Introduction of exogenous LRIG1 into glioma cells inhibited cell proliferation manifested by MTT and soft agar clone assay in vitro and subcutaneously tumor xenografts. On the other hand, LRIG1 overexpression inhibited glioma growth by significantly changing the expression pattern of cyclins, resulting in delayed cell cycle. Employing transwell invasion and wound scratch assay and gelatin zymography, LRIG1 inhibited U-251 MG cell invasion and migration by attenuating MMP2 and MMP9 production. Under ligand-stimulated conditions, p-ERK levels did not change, whereas p-AKT levels were inhibited in cells with LRIG1 upregulation, indicating that LRIG1 exerts more inhibiting effects on the PI3K/AKT pathway. Our findings suggest that LRIG1 restricted glioma aggressiveness by inhibiting cell proliferation, migration and invasion. Restoration of LRIG1 to glioma cells could offer a novel therapeutic strategy.

Expression of LRIG1 and LRIG3 correlates with human papillomavirus status and patient survival in cervical adenocarcinoma

The incidence of cervical adenocarcinoma, which accounts for 10-20% of all cervical cancers, has increased continuously in developed countries during the last two decades, unlike squamous cell cervical carcinoma. This increasing trend, noted particularly among women under the age of 40 years, has occurred despite extensive cytological Pap smear screening. A deeper understanding of the etiology of cervical adenocarcinoma, better preventive measures and reliable prognostic markers are urgently needed. The human leucine-rich repeats and immunoglobulin-like domains (LRIG) gene family includes: LRIG1, LRIG2 and LRIG3. LRIG expression has proven to be of prognostic value in different types of human cancers, including breast cancer, early stage invasive squamous cervical cancer, cutaneous squamous cell carcinoma, oligodendroglioma and astrocytoma. LRIG1 functions as a tumor suppressor, while less is known about the functions of LRIG2 and LRIG3. This study evaluated the expression of the three LRIG proteins in tumor specimens from 86 women with pure cervical adenocarcinoma by immunohistochemistry. Possible correlations between LRIG expression and known prognostic factors, including human papillomavirus (HPV) status, FIGO stage and histology were investigated. Patient survival data were collected retrospectively and the possible prognostic value of LRIG protein expression was investigated. High staining intensity of LRIG1 and high fraction of LRIG3-positive cells were significantly associated with patient survival, and positive correlations were found between LRIG1 and LRIG3 staining intensity and HPV status. Thus, the LRIG proteins may be important determinants of cervical adenocarcinoma progression and their diagnostic and prognostic potential should be studied further.

Downregulation of LRIG1 expression by RNA interference promotes the aggressive properties of glioma cells via EGFR/Akt/c-Myc activation

The LRIG1 [leucine-rich repeats and immunoglobulin-like domains (LRIG)] gene is not universally downregulated in human cancers, and its role in tumorigenesis and the development of glioma has not been well addressed. In this study, we used short hairpin RNA (shRNA)-triggered RNA interference (RNAi) to block LRIG1 gene expression in the GL15 human glioma cell line. Specific downregulation of LRIG1 by shRNA resulted in significantly enhanced capabilities of proliferation, inhibition of apoptosis and invasion in the GL15 cells. LRIG1 repression induced marked activation of epidermal growth factor receptor (EGFR), protein kinase B (Akt) and c-Myc signaling molecules. Our results demonstrated that RNAi against LRIG1 may effectively downregulate LRIG1 gene expression. LRIG1 functions as a tumor suppressor in the pathogenesis of glioma via EGFR/Akt/c-Myc activation.

Immunohistochemical analysis of LRIG proteins in meningiomas: correlation between estrogen receptor status and LRIG expression

The leucine-rich repeats and immunoglobulin-like domains (LRIG) protein family is comprised of three integral membrane proteins: LRIG1, LRIG2, and LRIG3. LRIG1 is a negative regulator of growth factor signaling. The expression and subcellular localization of LRIG proteins have prognostic implications in primary brain tumors, such as oligodendrogliomas and astrocytomas. The expression of LRIG proteins has not previously been studied in meningiomas. In this study, the expression of LRIG1, LRIG2, and LRIG3 was analyzed in 409 meningiomas by immunohistochemistry, and potential associations between LRIG protein expression and tumor grade, gender, progesterone receptor status, and estrogen receptor (ER) status were investigated. The LRIG proteins were most often expressed in the cytoplasm, though LRIG1 also showed prominent nuclear expression. Cytoplasmic expression of LRIG1 and LRIG2 correlated with histological subtypes of meningiomas (p = 0.038 and 0.013, respectively). Nuclear and cytoplasmic expression of LRIG1 was correlated with ER status (p = 0.003 and 0.004, respectively), as was cytoplasmic expression of LRIG2 (p = 0.006). This study is the first to examine the expression of LRIG proteins in meningiomas, and it shows a correlation between ER status and the expression of LRIG1 and LRIG2, which suggests a possible role for LRIG proteins in meningioma pathogenesis.

Expression of EGFR and LRIG proteins in oesophageal carcinoma with emphasis on patient survival and cellular chemosensitivity

BACKGROUND

Leucine-rich and immunoglobulin-like domains 1-3 (LRIG1-3) proteins have been implicated in the regulation of EGFR signalling. In the present study, we investigated the clinical implications of the expression of EGFR and LRIG1-3 in oesophageal carcinoma, as well as the correlation between their expression levels and the chemosensitivity of oesophageal carcinoma cell lines.

PATIENTS AND METHODS

Tumours from 80 patients with oesophageal carcinoma were investigated for the expression of EGFR and LRIG proteins by immunohistochemistry. Oesophageal carcinoma cell lines were investigated for their expression of EGFR and LRIG1, 2, and 3 by quantitative real time RT-PCR and for their sensitivity to commonly used chemotherapeutics by a cytotoxicity assay.

RESULTS AND DISCUSSION

Based on a total score of intensity and expression rates, a trend towards survival difference was found for EGFR (p = 0.09) and LRIG2 (p = 0.18) whereas for LRIG1 and -3 there was no trend towards any association with survival. Correlation analysis revealed a correlation with the clinical expression of EGFR and LRIG3 (p = 0.0007). Significant correlations were found between LRIG1 expression levels and sensitivity to cisplatin (r = -0.74), docetaxel (r = -0.69), and vinorelbine (r = -0.82) in oesophageal carcinoma cell lines. EGFR and the LRIG proteins may be functionally involved in oesophageal carcinoma, but larger materials are needed to fully elucidate the clinical implication.

Effect of over-expressed LRIG3 on cell cycle and survival of glioma cells

This study examined the effects of over-expression of leucine-rich repeats and immunoglobulin-like domains 3 (LRIG3) on the cell cycle and survival of human glioma cell line U87 and U251 and explored the possible mechanisms. The LRIG3 gene was transduced into U87 and U251 cells respectively by using lentivirus and the transduced cells were selected by puromycin. The changes in LRIG3 mRNA and protein levels were measured by RT-PCR and Western blotting. The apoptosis rate was detected by Annexin V-FITC/PI double labeling and the cell cycle was flow cytometrically analyzed. Compared with control cells, LRIG3 mRNA expression in U251 and U87 cells transduced with pLVX-DsRed-LRIG3-Monomer-N1 were increased by 77.6% and 129.7%, and LRIG3 protein expression was raised by 141.3% and 322.7%, respectively. Cell cycle analysis showed that LRIG3 over-expression increased the percentage of cells at G(0)/G(1) phase (P<0.01). Over-expressed LRIG3 could significantly promote the apoptosis of U87 and U251 cells (P<0.05). These findings suggest that the over-expression of LRIG3 could arrest the cell cycle in G(0)/G(1) phase, and promote apoptosis of U87 and U251 cells.

Association of expression of Leucine-rich repeats and immunoglobulin-like domains 2 gene with invasiveness of pituitary adenoma

The Leucine-rich repeats and immunoglobulin-like domains-2 (LRIG2) gene expression in pituitary adenoma and its correlation with tumor invasiveness were studied. The expression of LRIG2 mRNA and protein in human pituitary adenoma obtained surgically was detected by RT-PCR (39 cases) and immunohistochemical staining (30 cases). It was found that LRIG2 was mostly localized at the nucleus of the pituitary adenoma cells. Its expression was significantly higher in the invasive cases than in the non-invasive cases. LRIG2 protein was positive in 14 cases out of 21 cases of invasive adenoma, but only 2 cases were positive in 9 cases of non-invasive adenoma. The positive expression rate of LRIG2 mRNA was 91.3% in invasive cases (total 23 cases) and 62.5% in non-invasive cases (total 16 cases), respectively. LRIG2 gene is overexpressed in invasive pituitary adenoma. It may play an important role in pituitary adenoma invasiveness and further studies are necessary to elucidate the mechanism under this phenomenon.

Correlation between LRIG1 and LRIG2 expressions and expression of 11 tumor markers, with special reference to tumor suppressors, in CIN and normal cervical epithelium

OBJECTIVE

Novel biological markers LRIG1 and LRIG2 have been associated with favorable as well as poor prognosis, respectively, in different cancer types, including cervical cancer. The aim of this study was to investigate possible interactions between these proteins and other tumor markers, and as diagnostic adjuncts in CIN.

METHODS

Cervical biopsies from 171 women, with normal epithelium, and low-grade and high-grade CIN were stained for LRIG1 and LRIG2, and 11 additional tumor markers. The tumor markers were chosen to be relevant in cervical neoplasms. Staining was evaluated semiquantitatively.

RESULTS

Expression of LRIG1 and LRIG2 was found to correlate with increasing CIN grade, as well as with expression of tumor suppressor FHIT, independent of histological grade. In addition, tumor promoter LRIG2 expression correlated negatively with expression of tumor suppressor retinoblastoma protein and positively with IL-10. The latter correlation did not however remain after adjustment for CIN grade. p53 and p16 expressions correlated positively with LRIG1 expression in univariate analyses, but significance did not hold after adjustment for CIN grade.

CONCLUSION

LRIG1 and LRIG2 expressions were seen in precancerous cervical epithelium and found to increase with increasing grade. There was an association between expression of these glycoproteins and FHIT tumor suppressor protein, independently of histological grade.

Effect of silencing LRIG3 gene on the proliferation and apoptosis of bladder cancer T24 cells

This study examined the effect of silencing LRIG3 expression on the proliferation and apoptosis of bladder cancer T24 cells and explored the role of LRIG3 in the tumorigenesis of bladder cancer. Bladder cancer T24 cells were routinely cultured and pSilencer plasmids were employed to construct LRIG3 eukaryotic expression vector of LRIG3-siRNA, i.e., pSilencer-LRIG3-siRNA. After confirmation, the vector was transfected into HEK293 cells to make a replication-deficient adenovirus, pAd-LRIG3-siRNA, which was then introduced into bladder cancer T24 cells. RT-PCR, Western-blotting were performed to detect the levels of LRIG3 mRNA and proteins. Cells number was determined by using MTT test. Hoechst33258 staining, transmission microscopy, flow cytometery were conducted to examine the cell apoptosis. Three groups included a blank control group, a negative control group (containing non-interfering plasmids) and a pAd-LRIG3-siRNA group. Our results showed that the recombinant pAd-LRIG3-siRNA was successfully transfected into the bladder cancer T24 cells. The siRNA formed by the transcription of the recombinant plasmids resulted in significantly reduced expressions of LRIG3 gene and protein and significantly decreased cell proliferation and growth in the pAd-LRIG3-siRNA group as compared with the control group (P<0.01). The siRNA also caused apoptotic changes of some cells, with the apoptosis rate being (17.69±0.75)%, which was significantly different from that of the control group (P<0.01). It was concluded that recombinant pAd-LRIG3-siRNA plasmids could effectively decrease the expression of LRIG3 mRNA and proteins and, to some extent, inhibit the proliferation and promote the apoptosis of bladder cancer T24 cells. Silencing LRIG3 gene might be a novel alternative for the treatment of bladder cancer.

LRIG2 in contrast to LRIG1 predicts poor survival in early-stage squamous cell carcinoma of the uterine cervix

BACKGROUND

The human leucine-rich repeats and immunoglobulin-like domains (LRIG) protein family comprises LRIG1, 2, and 3. LRIG1 negatively regulates growth factor signaling and is a proposed tumor suppressor. In early stage uterine cervical carcinoma, expression of LRIG1 is associated with good survival. Less is known about the function and expression of LRIG2; it has not been studied in cervical carcinoma, previously.

MATERIALS AND METHODS

LRIG2 expression was studied by immunohistochemistry in 129 uterine cervical squamous cell carcinomas and 36 uterine cervical adenocarcinomas. Possible associations between LRIG2 immunoreactivity and patient survival were evaluated.

RESULTS

In early-stage squamous cell carcinoma (stages IB-IIB), high expression of LRIG2 was associated with poor survival (Kaplan-Meier, log-rank, p=0.02). The 10-year survival rate for patients with high expression of LRIG2 was 60%, compared to 87% in patients with low expression (odds ratio 0.22, 95% CI 0.07-0.64). In multivariate analysis including the previously studied tumor suppressor LRIG1 and clinical stage, LRIG2 emerged as an independent prognostic factor (odds ratio 0.22, 95% CI 0.09-0.50). For patients with both high expression of LRIG2 and low expression of LRIG1, the 10-year survival rate was only 26% compared to 66% for the remaining study population. There was no correlation between LRIG2 expression and prognosis in the limited adenocarcinoma series.

DISCUSSION AND CONCLUSION

LRIG2 appears to be a significant predictor of poor prognosis in early-stage squamous cell carcinoma of the uterine cervix. A combination of high LRIG2 expression and low LRIG1 expression identified women with a very poor prognosis.

Vertebrate Lrig3-ErbB interactions occur in vitro but are unlikely to play a role in Lrig3-dependent inner ear morphogenesis

Background

The Lrig genes encode a family of transmembrane proteins that have been implicated in tumorigenesis, psoriasis, neural crest development, and complex tissue morphogenesis. Whether these diverse phenotypes reflect a single underlying cellular mechanism is not known. However, Lrig proteins contain evolutionarily conserved ectodomains harboring both leucine-rich repeats and immunoglobulin domains, suggesting an ability to bind to common partners. Previous studies revealed that Lrig1 binds to and inhibits members of the ErbB family of receptor tyrosine kinases by inducing receptor internalization and degradation. In addition, other receptor tyrosine kinase binding partners have been identified for both Lrig1 and Lrig3, leaving open the question of whether defective ErbB signaling is responsible for the observed mouse phenotypes.

Methodology/Principal Findings

Here, we report that Lrig3, like Lrig1, is able to interact with ErbB receptors in vitro. We examined the in vivo significance of these interactions in the inner ear, where Lrig3 controls semicircular canal formation by determining the timing and extent of Netrin1 expression in the otic vesicle epithelium. We find that ErbB2 and ErbB3 are present in the early otic epithelium, and that Lrig3 acts cell-autonomously here, as would be predicted if Lrig3 regulates ErbB2/B3 activity. However, inhibition of ErbB activation in the chick otic vesicle has no detectable effect on Netrin gene expression or canal morphogenesis.

Conclusions/Significance

Our results suggest that although both Lrig1 and Lrig3 can interact with ErbB receptors in vitro, modulation of Neuregulin signaling is unlikely to contribute to Lrig3-dependent processes of inner ear morphogenesis. These results highlight the similar binding properties of Lrig1 and Lrig3 and underscore the need to determine how these two family members bind to and regulate different receptors to affect diverse aspects of cell behavior in vivo.

Cytoplasmic LRIG2 expression is associated with poor oligodendroglioma patient survival

The three leucine-rich repeats and immunoglobulin-like domains (LRIG) genes encode integral membrane proteins. Of these, LRIG1 negatively regulates growth factor signaling and is implicated as a tumor suppressor in certain malignancies. In astrocytic tumors, the subcellular distribution of LRIG proteins is associated with specific clinicopathological features and patient survival. The role of LRIG proteins in oligodendroglioma has not previously been studied. Here we used immunohistochemistry to analyze the expression of the LRIG proteins in 63 oligodendroglial tumors, and evaluated possible associations between LRIG protein expression and clinicopathological parameters. Notably, cytoplasmic LRIG2 expression was found to be an independent prognostic factor associated with poor oligodendroglioma patient survival. This is the first report of an LRIG protein showing a negative effect on survival, suggesting that LRIG2 might have a function different from that of LRIG1, and possibly contributing to the etiology of oligodendroglioma.

Upregulation of LRIG1 suppresses malignant glioma cell growth by attenuating EGFR activity

Activated epidermal growth factor receptor (EGFR) has emerged as an important therapeutic target for a variety of solid tumors, particularly malignant gliomas. A recently discovered transmembrane glycoprotein, LRIG1, antagonizes the activity of epidermal growth factor receptor family receptor tyrosine kinases and acts as a negative feedback loop of EGFR and proposed tumor suppressors. The aim of this study was to investigate the impact of LRIG1 on the biological features of glioma cells and the possible mechanisms of enhanced apoptosis induced by upregulation of LRIG1. We observed that the expression of LRIG1 was decreased, while the expression of EGFR was increased in the majority of astrocytomas, and the ratio of EGFR/LRIG1 was increased by sixfold in tumors versus corresponding non-neoplastic tissue. Upregulation of LRIG1, followed by a decrease of EGFR on the cytomembrane of the cells, induced cell apoptosis and cell growth inhibition, and further reversed invasion in glioma cell lines and primary glioma cells. Our study now clearly indicates that LRIG1 indeed affects cell fate and biology behaviors of the cells in vitro by inhibiting phosphorylation of downstream MAPK and AKT signaling pathway, and the elevated release level of caspase-8 might contribute to the enhanced apoptosis in LRIG1 transfected glioma cells. Taken together, these findings provide us with an insight into LRIG1 function, and we conclude that LRIG1 evolved in gliomas as a rare feedback negative attenuator of EGFR and could offer a novel therapeutic target to treat patients with malignant gliomas.

Effects of RNAi-mediated gene silencing of LRIG3 expression on cell cycle and survival of glioma cells

The effects of RNAi-mediated gene silencing of LRIG3 expression on cell cycle and survival of human glioma cell line GL15 and the possible mechanisms were explored. The plasmids pGenesil2-LRIG3-shRNA1 and pGenesil2-LRIG3-shRNA2 were transfected into GL15 glioma cells respectively by using Metafectine, and the transfected cells that stably suppressed LRIG3 expression were selected by G418. The control cells were transfected with negative control shRNA. The changes in LRIG3 mRNA and protein levels were measured by RT-PCR and Western blot. The apoptosis rate and cell cycle were analyzed by flow cytometry. As compared with the negative shRNA-transfected GL15 cells, LRIG3 mRNA expression in GL15 cells transfected with pGenesil2-LRIG3-shRNA1 and pGenesil2-LRIG3-shRNA2 was silenced by 52.4%, 63.8%, and LRIG3 protein expression was reduced by 50.9% and 67.4% respectively. The LRIG3-specific siRNA transfected cells had higher proliferation rate than control cells. Cell cycle analysis showed that silencing LRIG3 increased the percentage of G(2)/M phase cells and the proliferation index significantly (P<0.01). Silencing LRIG3 could inhibit the apoptosis of GL15 cells (P<0.05). These findings suggest that the siRNA targeting LRIG3 gene shows a dramatic inhibitory effect on RNA transcription and protein expression, then promoting the proliferation of GL15 cells, arresting GL15 cells in G(2)/M phase, and suppressing apoptosis of GL15 cells.

Cross-repressive interactions between Lrig3 and netrin 1 shape the architecture of the inner ear

The sense of balance depends on the intricate architecture of the inner ear, which contains three semicircular canals used to detect motion of the head in space. Changes in the shape of even one canal cause drastic behavioral deficits, highlighting the need to understand the cellular and molecular events that ensure perfect formation of this precise structure. During development, the canals are sculpted from pouches that grow out of a simple ball of epithelium, the otic vesicle. A key event is the fusion of two opposing epithelial walls in the center of each pouch, thereby creating a hollow canal. During the course of a gene trap mutagenesis screen to find new genes required for canal morphogenesis, we discovered that the Ig superfamily protein Lrig3 is necessary for lateral canal development. We show that this phenotype is due to ectopic expression of the axon guidance molecule netrin 1 (Ntn1), which regulates basal lamina integrity in the fusion plate. Through a series of genetic experiments, we show that mutually antagonistic interactions between Lrig3 and Ntn1 create complementary expression domains that define the future shape of the lateral canal. Remarkably, removal of one copy of Ntn1 from Lrig3 mutants rescues both the circling behavior and the canal malformation. Thus, the Lrig3/Ntn1 feedback loop dictates when and where basement membrane breakdown occurs during canal development, revealing a new mechanism of complex tissue morphogenesis.

Down-regulation of leucine-rich repeats and immunoglobulin-like domain proteins (LRIG1-3) in HP75 pituitary adenoma cell line

Three human leucine-rich repeats and immunoglobulin-like domains (LRIG) genes and proteins, named LRIG1-3, has been previously characterized and it was proposed that they may act as suppressors of tumor growth. The LRIG1 protein can inhibit the growth of tumors of glial cells and the down-regulation of the LRIG1 gene may be involved in the development and progression of the tumor. Real-time reverse transcription-polymerase chain reaction (RT-PCR) is a recently developed technique for quantitative assessment of specific RNA levels. In the current study, it was demonstrated that LRIG1-3 and EGFR mRNA was detected in human pituitary adenoma cell lines and a normal pituitary sample, with differences in the expression levels. Compared to the normal pituitary samples, the expression of LRIG1-3 in HP75 cell line was lower, but the expression of EGFR in HP75 cell line was higher. The results are consistent with LRIG1-3 being tumour suppressor genes, and LRIG genes decreasing the expression of EGFR. The ratio of EGFR/LRIG1 was increased at least 13-fold in HP75 cells compared with the normal pituitary cells, which was also the case for the ratio of EGFR/LRIG2 (14-fold increase in HP75) and EGFR/LRIG3 (11-fold increase in HP75). Further studies were needed to elucidate the explicit role of LRIG genes as negative regulators of oncogenesis in human pituitary adenoma.