LRIG1 Research Articles

Abstract C119: Exploring the functional role of LRIG1 and WWOX tumor suppressors in breast cancer disparities

Abstract Breast cancer is the most commonly diagnosed cancer among women in the US. Despite a lower rate of breast cancer incidence, Black women in the US suffer higher rates of mortality compared to White women. This disparity poses a major clinical issue for Black women in the US, and we are particularly interested in understanding how molecular and environmental mechanisms may be contributing to these disproportionate outcomes. Our previous study found that in a cohort of women from Baltimore, Maryland (110 Black, 75 White), higher neighborhood deprivation was associated with decreased gene body methylation and gene expression of two tumor suppressor genes, LRIG1 and WWOX. These findings were unique to the tumor, which potentially points to ancestry-specific somatic mutations that may impact gene and protein expression for LRIG1 and WWOX. The goal of this project is to determine gene and protein differences in LRIG1 and WWOX by population group in women with and without breast cancer as it relates to neighborhood-level socioeconomic deprivation. We hypothesize that LRIG1 and WWOX exhibit decreased gene and protein expression in Black women compared to White women. Using the same diverse cohort from Baltimore, Maryland, we identified and conducted DNA genotyping on clinically relevant mutations of LRIG1 and WWOX using amplification by PCR and detection by fluorescent reporters. We found that the genotype frequencies in two single nucleotide polymorphisms (SNPs) for LRIG1, rs1403626 (P=6.3e-1) and rs2306272 (P=0.005967), differ significantly between population groups in these breast tissue samples, an interesting finding that matches our previous predictions. We also identified a dose-dependent relationship between LRIG1 gene expression and rs1403626 SNP genotypes. Additional patient genotyping will be conducted to determine relationships between LRIG1 and WWOX SNPs, differences in DNA methylation, and correlations with neighborhood deprivation measures. To interrogate the impact on protein expression, we will construct LRIG1 and WWOX knockdown mutants in estrogen receptor (ER)-positive and ER-negative commercially available breast cancer cell lines derived from Black and White patients, and determine the functional consequences of LRIG1 and WWOX loss by immunofluorescence and western blot, including how this may differ by population group. These studies will give us a better understanding of how the expression of tumor suppressor genes may contribute to the higher susceptibility of Black women developing more aggressive breast tumors. Citation Format: Angel H. Pajimola, Brittany Jenkins-Lord. Exploring the functional role of LRIG1 and WWOX tumor suppressors in breast cancer disparities [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr C119.

Preservation of 5-Hydroxymethylcytosine Levels in LRIG1 across Genomic DNA and Cell-Free DNA in Glioma Patients.

Cell-free DNA (cfDNA) has recently emerged as a promising minimally invasive diagnostic biomarker for various cancers. In this study, our aim was to identify cfDNA biomarkers by investigating genes that displayed significant differences between glioma patients and their corresponding controls. To accomplish this, we utilized publicly available data from the Gene Expression Omnibus, focusing on 5-hydroxymethylcytosine (5hmC) profiles in both cfDNA and genomic DNA (gDNA) from glioma patients and healthy individuals. The intersection of gene lists derived from these comparative analyses unveiled LRIG1 and ZNF703 as the two genes with elevated 5hmC levels in both the cfDNA of glioma patients and gDNA of glioma tissue compared to their respective controls. The gene expression data revealed both genes were upregulated in glioma tissue compared to normal brain tissue. Integration of 5hmC data revealed a strong positive correlation in the glioma tissue group between 5hmC and the gene expression of the LRIG1 gene. Furthermore, exploration using the AmiCa web tool indicated that LRIG1 gene expression was elevated compared to 17 other cancers included in the database, emphasizing its potential as a distinctive biomarker across multiple cancer types.

Neighborhood Deprivation and DNA Methylation and Expression of Cancer Genes in Breast Tumors

The biological processes that underlie the association of neighborhood environment with chronic diseases, such as cancer, remain poorly understood. To determine whether differences in breast tissue DNA methylation are associated with neighborhood deprivation among Black and White women with breast cancer. This cross-sectional study collected breast tissue from women undergoing surgery for breast cancer between January 1, 1993, and December 31, 2003. Participants were recruited through the University of Maryland Medical Center, with additional collection sites at Baltimore-area hospitals. Data analysis was performed from March 1 through December 1, 2022. Year 2000 census tract-level socioeconomic deprivation measured via neighborhood deprivation index (NDI) as a standardized score, with Black and White race being ascertained through self-report. The primary outcome was tissue DNA methylation using genome-wide measurements. The secondary outcome was tissue gene expression. Participants included 185 women with breast cancer (110 Black [59.5%], 75 White [40.5%]). Mean (SD) age at surgery was 56.0 (14.1) years. Neighborhood deprivation was higher for Black women than for White women (Mean [SD] NDI, 2.96 [3.03] for Black women and -0.54 [1.91] for White women; difference, -3.50; 95% CI, -4.22 to -2.79; P < .001). In unstratified analysis, 8 hypomethylated CpG sites were identified as associated with the NDI, including sites in 2 tumor suppressor genes, LRIG1 and WWOX. Moreover, expression of the 2 genes inversely correlated with neighborhood deprivation. In the race-stratified analysis, the negative correlation between the LRIG1 gene body CpG site cg26131019 and the NDI remained significant in Black women. A neighborhood deprivation-associated decrease in gene expression was also observed for LRIG1 and WWOX in tumors from Black women. In this study, high neighborhood deprivation was associated with differences in tissue DNA methylation and gene expression among Black women. These findings suggest that continued investment in public health interventions and policy changes at the neighborhood level may help to remedy biological alterations that could make minoritized populations more susceptible to chronic diseases.

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

BackgroundLRIG1, 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.MethodsIn 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.ResultsAcross 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.ConclusionsOur 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.

Lrig1 and Lrig3 cooperate to control Ret receptor signaling, sensory axonal growth and epidermal innervation.

Negative feedback loops represent a regulatory mechanism that guarantees that signaling thresholds are compatible with a physiological response. Previously, we established that Lrig1 acts through this mechanism to inhibit Ret activity. However, it is unclear whether other Lrig family members play similar roles. Here, we show that Lrig1 and Lrig3 are co-expressed in Ret-positive mouse dorsal root ganglion (DRG) neurons. Lrig3, like Lrig1, interacts with Ret and inhibits GDNF/Ret signaling. Treatment of DRG neurons with GDNF ligands induces a significant increase in the expression of Lrig1 and Lrig3. Our findings show that, whereas a single deletion of either Lrig1 or Lrig3 fails to promote Ret-mediated axonal growth, haploinsufficiency of Lrig1 in Lrig3 mutants significantly potentiates Ret signaling and axonal growth of DRG neurons in response to GDNF ligands. We observe that Lrig1 and Lrig3 act redundantly to ensure proper cutaneous innervation of nonpeptidergic axons and behavioral sensitivity to cold, which correlates with a significant increase in the expression of the cold-responsive channel TrpA1. Together, our findings provide insights into the in vivo functions through which Lrig genes control morphology, connectivity and function in sensory neurons.

Member Domain 3 (LRIG3) Activates Hypoxia-Inducible Factor-1 α/Vascular Endothelial Growth Factor (HIF-1α/VEGF) Pathway to Inhibit the Growth of Bone Marrow Mesenchymal Stem Cells in Glioma

Member domain 3 (LRIG3) of the LRIG gene family is down-regulated in several cancers. However, its role in bone marrow mesenchymal stem cells (BMSCs) in gliomas and the related mechanisms is unknown. The qRT-PCR assessed LRIG3 mRNA level. Rat BMSCs were randomly assigned into glioma group (BMSCs cultured in glioma microenvironment); LRIG3 overexpression group; and si-LRIG3 inhibitor group followed by analysis of LRIG3 expression, cell proliferation, PCNA and Ki-67 apoptosis, TNF-α; and HIF-1α/VEGF mRNA level. LRIG3 mRNA expression was decreased in gliomas patients (P &lt; 0.05). BMSCs cultured in glioma microenvironment showed decreased LRIG3, increased cell proliferation, decreased PCNA, Ki-67 and TNF-α secretion as well as elevated HIF-1α and VEGF level (P &lt; 0.05). Transfection of LRIG3 siRNA further promoted the above changes. Conversely, LRIG3 plasmid transfection significantly promoted its expression in glioma BMSCs (P &lt; 0.05), inhibited cell proliferation, promoted PCNA, Ki-67, and TNF-α secretion, and increased HIF-1α and VEGF level (P &lt; 0.05). LRIG3 in rat BMSCs cultured in the glioma microenvironment is decreased. Down-regulation of LRIG3 inhibits TNF-α secretion by activating HIF-1α/VEGF pathway regulating BMSCs proliferation and apoptosis.

LRIG1 expression and colorectal cancer prognosis

BackgroundTo 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.MethodsOne 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.ResultsThe 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.ConclusionsTherefore, 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.

Novel Somatic Genetic Variants as Predictors of Resistance to EGFR-Targeted Therapies in Metastatic Colorectal Cancer Patients.

Background: About 40% of RAS/BRAF wild-type metastatic colorectal cancer (mCRC) patients undergoing anti-EGFR-based therapy have poor outcomes. Treatment failure is not only associated with poorer prognosis but higher healthcare costs. Our aim was to identify novel somatic genetic variants in the primary tumor and assess their effect on anti-EGFR response. Patients and Methods: Tumor (somatic) and blood (germline) DNA samples were obtained from two well-defined cohorts of mCRC patients, those sensitive and those resistant to EGFR blockade. Genetic variant screening of 43 EGFR-related genes was performed using targeted next-generation sequencing (NGS). Relevant clinical data were collected through chart review to assess genetic results. Results: Among 61 patients, 38 were sensitive and 23 were resistant to treatment. We identified eight somatic variants that predicted non-response. Three were located in insulin-related genes (I668N and E1218K in IGF1R, T1156M in IRS2) and three in genes belonging to the LRIG family (T152T in LRIG1, S697L in LRIG2 and V812M in LRIG3). The remaining two variants were found in NRAS (G115Efs*46) and PDGFRA (T301T). We did not identify any somatic variants related to good response. Conclusions: This study provides evidence that novel somatic genetic variants along the EGFR-triggered pathway could modulate the response to anti-EGFR drugs in mCRC patients. It also highlights the influence of insulin-related genes and LRIG genes on anti-EGFR efficacy. Our findings could help characterize patients who are resistant to anti-EGFR blockade despite harboring RAS/BRAF wild-type tumors.

LRIG1 gene copy number analysis by ddPCR and correlations to clinical factors in breast cancer

BackgroundLeucine-rich repeats and immunoglobulin-like domains 1 (LRIG1) copy number alterations and unbalanced gene recombination events have been reported to occur in breast cancer. Importantly, LRIG1 loss was recently shown to predict early and late relapse in stage I-II breast cancer.MethodsWe developed droplet digital PCR (ddPCR) assays for the determination of relative LRIG1 copy numbers and used these assays to analyze LRIG1 in twelve healthy individuals, 34 breast tumor samples previously analyzed by fluorescence in situ hybridization (FISH), and 423 breast tumor cytosols.ResultsFour of the LRIG1/reference gene assays were found to be precise and robust, showing copy number ratios close to 1 (mean, 0.984; standard deviation, +/− 0.031) among the healthy control population. The correlation between the ddPCR assays and previous FISH results was low, possibly because of the different normalization strategies used. One in 34 breast tumors (2.9%) showed an unbalanced LRIG1 recombination event. LRIG1 copy number ratios were associated with the breast cancer subtype, steroid receptor status, ERBB2 status, tumor grade, and nodal status. Both LRIG1 loss and gain were associated with unfavorable metastasis-free survival; however, they did not remain significant prognostic factors after adjustment for common risk factors in the Cox regression analysis. Furthermore, LRIG1 loss was not significantly associated with survival in stage I and II cases.ConclusionsAlthough LRIG1 gene aberrations may be important determinants of breast cancer biology, and prognostic markers, the results of this study do not verify an important role for LRIG1 copy number analyses in predicting the risk of relapse in early-stage breast cancer.

The Expression Analysis of Intestinal Cancer Stem Cell Marker Lgr5 in Colorectal Cancer Patients and the Correlation with Histopathological Markers.

Cancer stem cells (CSCs) have frequently been utilized in the cell characterization and identified responsible for tumor development, metastasis, recurrence, and chemoresistance. CSC surface markers function in cancer cell signaling and are indicated as potential biomarkers for cancer diagnosis and prognosis. As well, dysregulation of cancer-related signaling pathways could promote CSC development and progression. Our aim was to evaluate the expression of colorectal CSC markers and their correlation with cancer proliferation and angiogenesis. In this case-control study, total RNA was extracted from a total of 74 colorectal tumors and 74 adjacent normal tissue biopsies. Then, using a quantitative real-time PCR, the relative expression levels of Lgr5 and Lrig1 were measured in all malignant and healthy samples. Also, immunohistochemical (IHC) staining of tumor tissues was performed for Ki-67 (proliferation) and CD34 (angiogenesis) markers, and the immunoexpression staining scores were obtained. The diagnostic value of the genes was evaluated using receiver operating characteristic (ROC) curve. Possible correlation between CSC markers and immunohistochemical markers in CRC was analyzed by Pearson's correlation test and linear regression. The expression level of Lgr5 in tumor samples showed a significant increase compared with normal samples (p < 0.001) with a fold change of 2.54 (± 0.182). However, there was no significant difference in the relative expression of Lrig1 gene in tissue samples of healthy subjects and patients. The analysis of the ROC showed an AUC of 0.92 for Lgr5 and sensitivity 80% and specificity 96%. Further analysis revealed a significant correlation between mRNA levels of Lgr5 and immunoexpression of Ki-67 (r2 = 0.680, p < 0.001). The high expression levels of Lgr5 found in tumor tissues were correlated with histological parameters, indicating a significant role in CRC development and diagnosis.

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.

Abstract 5539: The phenotypic characterization of Lrig null mouse embryonic fibroblasts

Abstract The LRIG gene family consists of LRIG1, LRIG2 and LRIG3. The most studied of these is LRIG1, which is a tumor suppressor gene. The LRIG1 protein is downregulated in various types of cancer and it negatively regulates receptor tyrosine kinases including the EGF- and PDGF-receptors. Lrig1 also regulates stem cell homeostasis in mouse skin and intestine. The functions of LRIG2 and LRIG3 are less known, but some findings imply that they might antagonize LRIG1. Intriguingly, the sole LRIG homolog in C. elegans, Sma-10, positively regulates BMP signaling. Thus, it is not known to what degree the LRIG proteins have the same, overlapping, or opposing functions, and the molecular mechanisms involved are poorly characterized. To elucidate the functions of the three LRIG proteins we generated a series of wildtype and LRIG-null (Lrig1-/-;Lrig2-/-;Lrig3-/-) mouse embryonic fibroblast (MEF) lines. These cell lines were created from homozygous Lrig1flox/flox;Lrig2flox/flox;Lrig3flox/flox mouse embryos. The FLOXed Lrig genes were then deleted with CRE-recombinase, thereby creating Lrig-null MEFs. ddPCR analysis showed that the Lrig-null MEF lines were contaminated with less than 1% of cells carrying wildtype Lrig3 alleles. Lrig-null MEFs showed a higher proliferation rate and migrated more in trans-well chambers than the wildtype cells. These cell lines will also be useful to investigate the importance of Lrig proteins for other cellular functions such as, signal transduction, lipidomics, transcriptomics, secretomics, metabolomics, and oxidative stress sensitivity. We also transduced the Lrig-null cells with individual inducible Lrig-genes thus creating a powerful system for the examination of the biology of the specific Lrig proteins. Citation Format: Carl Herdenberg, Håkan Hedman. The phenotypic characterization of Lrig null mouse embryonic fibroblasts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5539. doi:10.1158/1538-7445.AM2017-5539

Notch1 targeted regulation of mir-224/LRIG2 signaling for the proliferation and apoptosis of cervical cancer cells.

In the present study, we explored the participation of Notch1 targeted regulation of mir-224/LRIG2 gene signal pathway in proliferation and apoptosis of cervical cancer cells. Forty-nine cases of cervical cancer lesion samples from cervical cancer patients treated in our hospital from February 2013 to February 2015 were chosen as subjects (the observation group), and cervical samples of healthy women (42 cases) during the same period were used as the control group. We determined the mRNA and protein expression of Notch1, mir-224, and LRIG2 genes. We also analyzed the mutual relationship between Notch1 gene expression and cervical cancer. The Notch1 genes in the cervical cancer cells (HeLa) were silenced and overexpressed to measure cancer apoptosis with flow cytometry. After obstruction of the Notch1 signal pathway, the mRNA and protein expression in the mir-224 and LRIG2 genes was also measured. It was found that in comparison to the control group, Notch1 gene expression in the observation group was significantly higher (p<0.05), cell growth was suppressed in Notch1 silent cell strains but accelerated in overexpressed Notch1 cells. The silencing of Notch1 genes can lead to the reduction of mir-224/LRIG gene and protein levels, while overexpression of the Notch1 genes increased the mir-224/LRIG gene and protein levels. In conclusion, the Notch1 gene is positively related to cervical cancer and can promote the occurrence of the disease. The potential mechanism shows that Notch1 gene can regulate cervical cancer cell proliferation by regulating the mir-224/LRIG2 signal pathway.

LRIGs: A Prognostically Significant Family with Emerging Therapeutic Competence against Cancers.

The human leucine-rich repeats and immunoglobulin like domains (LRIG) are evolutionary conserved family of single-pass transmembrane proteins. LRIG gene family includes three members, LRIG1 (formerly LIG1), LRIG2 and LRIG3, all of which are differentially expressed in human tissues and have long been proposed to be tumor suppressors. However, recently accumulated evidence on LRIG protein expression in human cancer appears to be inconsistent with this belief, as LRIG proteins have been found to be upregulated in certain tumors. Moreover, LRIG3 has been shown to act in an opposite manner to LRIG1 and LRIG1, in turn, has been shown to attenuate LRIG3 activity by its proteolytic degradation. These remarkable observations underline and reveal the previously unappreciated complexity of LRIG family dynamics. In the current review, the role of LRIG proteins in various human cancers is summarized and their differential regulation and expression is brought to light in order to understand how these proteins are involved in the genesis and progression of human cancers. Moreover, this is the first compilation that highlights the therapeutic potential of LRIG1 and suggests the same to be undertaken for LRIG2 and LRIG3. By virtue of their potential in prognosis of several cancer types, as well as their role as probable therapeutic proteins or in enhancing the receptiveness of the cancer cells to anti-tumor agents, it is strongly proposed that LRIG analysis should be undertaken and consequently be employed as a part of potential cancer treatment strategies.

Inhibition of subcutaneously implanted human pituitary tumor cells in nude mice by LRIG1.

The aim of this study was to explore the inhibition of subcutaneously implanted human pituitary tumor cells in nude mice by LRIG1 and its mechanism. For this study, athymic nude mice were injected with either normal pituitary tumor RC-4B/C cells or LRIG1-transfected RC-4B/C cells. We then calculated the volume inhibition rate of the tumors, as well as the apoptosis index of tumor cells and the expression of Ras, Raf, AKt, and ERK mRNA in tumor cells. Tumor cell morphological and structural changes were also observed under electron microscope. Our data showed that subcutaneous tumor growth was slowed or even halted in LRIG1-transfected tumors. The tumor volumes were significantly different between the two groups of mice (χ2 = 2.14, P < 0.05). The tumor apoptosis index was found to be 8.72% in the control group and 39.7% in LRIG1-transfected mice (χ2 = 7.59, P < 0.05). The levels of Ras, Raf, and AKt mRNA in LRIG1-transfected RC-4B/C cells were significantly reduced after transfection (P < 0.01). Transfected subcutaneous tumor cells appeared to be in early or late apoptosis under an electron microscope, while only a few subcutaneous tumor cells appeared to be undergoing apoptosis in the control group. In conclusion, the LRIG1 gene is able to inhibit proliferation and promote apoptosis in subcutaneously implanted human pituitary tumors in nude mice. The mechanism of LRIG1 may involve the inhibition of the PI3K/ Akt and Ras/Raf/ERK signal transduction pathways.

Overexpression of LRIG1 gene enhances chemosensitvity of human bladder cancer T24 cell line to cisplatin

Objective To investigate the effects and mechanisms of LRIG1 overexpression on chemosensitivity of human bladder cancer T24 cell line to cisplatin. Methods Human bladder cancer T24 cell line was used in the experiment since December 2012. Firstly, human bladder cancer T24 cells which were capable of highly expressing exogenous LRIG1 gene were established and identified. The T24 cells were divided into 3 groups: experimental group (transfected with Ad–Surp–LRIGl), control group (transfected with Adeno–SP–EGFP), blank control group (untransfected). Secondly, experiments of CDDP–induced apoptosis were divided into 4 groups: control group (untreated), CDDP group (treated with CDDP), CDDP/Adeno–SP–EGFP group (treated with CDDP/Adeno–SP–EGFP and CDDP), CDDP/Ad–Surp–LRIG1 group (treated with CDDP/Ad–Surp–LRIG1 and CDDP). The expression of mRNA and protein of LRIG1 and EGFR were detected by RT–PCR and Western blot. The effect of LRIG1 and/or CDDP on the expression of EGFR and pEGFR of T24 cells were measured by Western blot. The cellular sensitivity to CDDP was evaluated by cell counting Kit–8 (CCK–8). The cells apoptosis rates were examined by flow cytometry. Results The mRNA expression of LRIG1 and EGFR in experimental group, control group and blank control group were (2.79±0.15) and (0.65±0.05), (0.76±0.09) and (1.98±0.07), (0.66±0.05) and (2.05±0.04); the protein expression of LRIG1 and EGFR in experimental group, control group and blank control group were(1.98±0.12) and (0.92±0.05), (0.88±0.07) and (2.51±0.07), (1.00±0.08) and (2.42±0.09). The differences were significant between experimental group and the other groups(P 0.05). The IC50 values in CDDP group, CDDP/Adeno–SP–EGFP group and CDDP/Ad–Surp–LRIGl group were (30.96±0.57) μg/ml, (31.55±0.48) μg/ml and (14.09±0.31) μg/ml. The difference were significant between CDDP/Ad–Surp–LRIGl group and the other groups(P 0.05). The apoptosis rate in CDDP/Ad–Surp–LRIGl group [(69.77±2.14)%] was significantly higher than that in CDDP/Adeno–SP–EGFP group [(48.15±1.53)%], CDDP group [(46.82±1.23)%] and control group [(3.17±0.21)%] (P 0.05). The expression of total EGFR protein and nuclear pEGFR protein in control group、CDDP group、CDDP/Adeno–SP–EGFP group, CDDP/Ad–Surp–LRIGl group were (2.52±0.11) and (1.76±0.08), (1.22±0.05) and (2.75±0.15), (1.25±0.05) and (2.82±0.13), (0.32±0.02) and (1.08±0.04). The differences between CDDP group and control group, CDDP/Adeno–SP–EGFP group and CDDP/Ad–Surp–LRIGl group were significant(P 0.05). Conclusions LRIG1 promotes the cisplatin–induced apoptosis of T24 cells and enhances the sensitivity to cisplatin by down–regulating the expression of EGFR and pEGFR. Key words: Leucine–rich repeats and immunoglobulin–like domains–1 gene; Cis–diaminodichloroplatinum; Bladder neoplasm; Apoptosis

Biodegradable polymeric gene delivering nanoscale hybrid micelles enhance the suppression effect of LRIG1 in breast cancer

Biodegradable polymeric gene delivering nanoscale hybrid micelles enhance the suppression effect of LRIG1 in breast cancer.

Loss of LRIG1 locus increases risk of early and late relapse of stage I/II breast cancer.

Gains and losses at chromosome 3p12-21 are common in breast tumors and associated with patient outcomes. We hypothesized that the LRIG1 gene at 3p14.1, whose product functions in ErbB-family member degradation, is a critical tumor modifier at this locus. We analyzed 971 stage I/II breast tumors using Affymetrix Oncoscan molecular inversion probe arrays that include 12 probes located within LRIG1. Copy number results were validated against gene expression data available in the public database. By partitioning the LRIG1 probes nearest exon 12/13, we confirm a breakpoint in the gene and show that gains and losses in the subregions differ by tumor and patient characteristics including race/ethnicity. In analyses adjusted for known prognostic factors, loss of LRIG1 was independently associated with risk of any relapse (HR, 1.90; 95% CI, 1.32-2.73), relapse≥5 years (HR, 2.39; 95% CI, 1.31-4.36), and death (HR, 1.55; 95% CI, 1.11-2.16). Analyses of copy number across chromosome 3, as well as expression data from pooled, publicly available datasets, corroborated the hypothesis of an elevated and persistent risk among cases with loss of or low LRIG1. We concluded that loss/low expression of LRIG1 is an independent risk factor for breast cancer metastasis and death in stage I/II patients. Increased hazard in patients with loss/low LRIG1 persists years after diagnosis, suggesting that LRIG1 is acting as a critical suppressor of tumor metastasis and is an early clinical indicator of risk for late recurrences in otherwise low-risk patients.

Erratum to "LRIG1 Enhances Chemosensitivity by Modulating BCL-2 Expression and Receptor Tyrosine Kinase Signaling in Glioma Cells" by Guo Z, et al. (Yonsei Med J 2014;55:1196-205.)

[This corrects the article on p. 1196 in vol. 55, PMID: 25048475.].

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.