Get Back, a person-centred digital programme targeting physical activity for patients undergoing spinal stenosis surgery-a study protocol of a randomized feasibility study.

BACKGROUND: Spinal stenosis is the most common reason for elective spine surgery, and the cardinal symptom is leg pain and discomfort when walking. Patients with spinal stenosis have a decreased level of physical activity and thereby an increased risk of poor health. Get Back is a person-centred digital programme that strives to support patients being physically active after surgery. The aim is to explore if Get Back, in its present format (referred to as Get Backfeasibility), is feasible and contributes to detectable change in variables related to intervention content. METHODS: Thirty patients planned for decompression surgery due to central lumbar spinal stenosis who present with low physical activity, pain catastrophizing or fear of movement, will be included in a randomized feasibility study. All patients will be randomly allocated to either Get Backfeasibility or usual physical therapy. Get Backfeasibility aims to increase the patient's physical activity level by combining a person-centred and cognitive behavioural approach. It comprises 10 video and telephone sessions led by a physical therapist over 12 weeks (pre/postoperatively). Outcomes are treatment fidelity (treatment dose, adherence, and content), process feasibility (recruitment, intervention use, and acceptability of measurements and intervention), and variables related to the intervention content (steps per day, physical activity level, pain catastrophizing, fear of movement, and general self-efficacy). Treatment fidelity and feasibility data will be assessed during the full study period (12 weeks). Physical activity, physical capacity, and patient-reported outcomes will be assessed digitally at baseline (2 weeks preoperatively) and 11-12 weeks postoperatively. Variables related to the intervention content will be monitored weekly through a digital application. Feasibility data will be analysed descriptively and inferentially using a nonparametric approach, data from repeated measures will be displayed graphically and data from telephone interviews will be analysed using content analysis with a descriptive manifest approach. DISCUSSION: The results will provide information on whether Get Back in its present format is feasible and can be evaluated for effectiveness in a larger randomized controlled trial, for patients with a low physical activity level and a high fear of movement who are undergoing decompression surgery. TRIAL REGISTRATION: Registered at ClinicalTrails.gov 04/08/2023, registration no. NCT05806593.

Ligand-specific regulation of transforming growth factor beta superfamily factors by leucine-rich repeats and immunoglobulin-like domains proteins.

Leucine-rich repeats and immunoglobulin-like domains (LRIG) are transmembrane proteins shown to promote bone morphogenetic protein (BMP) signaling in Caenorhabditis elegans, Drosophila melanogaster, and mammals. BMPs comprise a subfamily of the transforming growth factor beta (TGFß) superfamily, or TGFß family, of ligands. In mammals, LRIG1 and LRIG3 promote BMP4 signaling. BMP6 signaling, but not BMP9 signaling, is also regulated by LRIG proteins, although the specific contributions of LRIG1, LRIG2, and LRIG3 have not been investigated, nor is it known whether other mammalian TGFß family members are regulated by LRIG proteins. To address these questions, we took advantage of Lrig-null mouse embryonic fibroblasts (MEFs) with doxycycline-inducible LRIG1, LRIG2, and LRIG3 alleles, which were stimulated with ligands representing all the major TGFß family subgroups. By analyzing the signal mediators pSmad1/5 and pSmad3, as well as the induction of Id1 expression, we showed that LRIG1 promoted BMP2, BMP4, and BMP6 signaling and suppressed GDF7 signaling; LRIG2 promoted BMP2 and BMP4 signaling; and LRIG3 promoted BMP2, BMP4, BMP6, and GDF7 signaling. BMP9 and BMP10 signaling was not regulated by individual LRIG proteins, however, it was enhanced in Lrig-null cells. LRIG proteins did not regulate TGFß1-induced pSmad1/5 signaling, or GDF11- or TGFß1-induced pSmad3 signaling. Taken together, our results show that some, but not all, TGFß family ligands are regulated by LRIG proteins and that the three LRIG proteins display differential regulatory effects. LRIG proteins thereby provide regulatory means for the cell to further diversify the signaling outcomes generated by a limited number of TGFß family ligands and receptors.

Low-grade glioma risk SNP rs11706832 is associated with type I interferon response pathway genes in cell lines.

Genome-wide association studies (GWAS) have contributed to our understanding of glioma susceptibility. To date, 25 risk loci for development of any of the glioma subtypes are known. However, GWAS studies reveal little about the molecular processes that lead to increased risk, especially for non-coding single nucleotide polymorphisms (SNP). A particular SNP in intron 2 of LRIG1, rs11706832, has been shown to increase the susceptibility for IDH1 mutated low-grade gliomas (LGG). Leucine-rich repeats and immunoglobulin-like domains protein 1 (LRIG1) is important in cancer development as it negatively regulates the epidermal growth factor receptor (EGFR); however, the mechanism responsible for this particular risk SNP and its potential effect on LRIG1 are not known. Using CRISPR-CAS9, we edited rs11706832 in HEK293T cells. Four HEK293T clones with the risk allele were compared to four clones with the non-risk allele for LRIG1 and SLC25A26 gene expression using RT-qPCR, for global gene expression using RNA-seq, and for metabolites using gas chromatography-mass spectrometry (GC-MS). The experiment did not reveal any significant effect of the SNP on the expression levels or splicing patterns of LRIG1 or SLC25A26. The global gene expression analysis revealed that the risk allele C was associated with upregulation of several mitochondrial genes. Gene enrichment analysis of 74 differentially expressed genes in the genome revealed a significant enrichment of type I interferon response genes, where many genes were downregulated for the risk allele C. Gene expression data of IDH1 mutated LGGs from the cancer genome atlas (TCGA) revealed a similar under expression of type I interferon genes associated with the risk allele. This study found the expression levels and splicing patterns of LRIG1 and SLC25A26 were not affected by the SNP in HEK293T cells. However, the risk allele was associated with a downregulation of genes involved in the innate immune response both in the HEK293T cells and in the LGG data from TCGA.

HYPOTHESIS: Do LRIG Proteins Regulate Stem Cell Quiescence by Promoting BMP Signaling?

Leucine-rich repeats and immunoglobulin-like domains (LRIG) proteins are evolutionarily conserved integral membrane proteins. Mammalian LRIG1 regulates stem cell quiescence in various tissue compartments, including compartments in the epidermis, oral mucosa, intestines, neural system, and incisors. The planarian LRIG1 homolog regulates the quiescence of multipotent neoblasts. The mechanism through which LRIG proteins regulate stem cell quiescence has not been well documented, although it is generally assumed that LRIG1 regulates the epidermal growth factor receptor (EGFR) or other receptor tyrosine kinases. However, Lrig-null (Lrig1-/-;Lrig2-/-; and Lrig3-/-) mouse embryonic fibroblasts (MEFs) have been recently found to exhibit apparently normal receptor tyrosine kinase functions. Moreover, bone morphogenetic protein (BMP) signaling has been shown to depend on LRIG1 and LRIG3 expression. BMPs are well-known regulators of stem cell quiescence. Here, we hypothesize that LRIG1 might regulate stem cell quiescence by promoting BMP signaling. HYPOTHESIS: Based on recent findings, it is hypothesized that LRIG1 regulates stem cell quiescence in mammalian tissues as well as in planarian neoblasts by promoting BMP signaling.

Single-molecule array assay reveals the prognostic impact of plasma LRIG1 in ovarian carcinoma.

BACKGROUND: Ovarian carcinoma is the eighth most common cause of cancer death in women worldwide. The disease is predominantly diagnosed at a late stage. This contributes to high recurrence rates, eventually leading to the development of treatment-resistant disease. Leucine-rich repeats and immunoglobulin-like domains protein 1 (LRIG1) is a transmembrane protein that functions as a tumor suppressor and regulator of growth factor signaling. LRIG1 levels have not been investigated in human plasma previously. MATERIALS AND METHODS: A quantitative LRIG1-specific single molecule array assay was developed and validated. LRIG1 levels were quantified in plasma samples from 486 patients with suspicious ovarian masses. RESULTS: Among women with ovarian carcinoma, LRIG1 levels were significantly elevated compared to women with benign or borderline type tumors. High LRIG1 plasma levels were associated with worse overall survival and shorter disease-free survival both in the group of all malignant cases and among the stage 3 cases only. LRIG1 was an independent prognostic factor in patients with stage 3 ovarian carcinoma. CONCLUSION: LRIG1 plasma levels were elevated in patients with ovarian carcinoma, and high levels were associated with poor prognosis, suggesting that LRIG1 might be an etiologic factor and a potentially useful biomarker in ovarian carcinoma.

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.

LRIG1 is a conserved EGFR regulator involved in melanoma development, survival and treatment resistance.

Leucine-rich repeats and immunoglobulin-like domains 1 (LRIG1) is a pan-negative regulator of receptor tyrosine kinase (RTK) signaling and a tumor suppressor in several cancers, but its involvement in melanoma is largely unexplored. Here, we aim to determine the role of LRIG1 in melanoma tumorigenesis, RTK signaling, and BRAF inhibitor resistance. We find that LRIG1 is downregulated during early tumorigenesis and that LRIG1 affects activation of the epidermal growth factor receptor (EGFR) in melanoma cells. LRIG1-dependent regulation of EGFR signaling is evolutionary conserved to the roundworm C. elegans, where negative regulation of the EGFR-Ras-Raf pathway by sma-10/LRIG completely depends on presence of the receptor let-23/EGFR. In a cohort of metastatic melanoma patients, we observe an association between LRIG1 and survival in the triple wild-type subtype and in tumors with high EGFR expression. During in vitro development of BRAF inhibitor resistance, LRIG1 expression decreases; and mimics LRIG1 knockout cells for increased EGFR expression. Treating resistant cells with recombinant LRIG1 suppresses AKT activation and proliferation. Together, our results show that sma-10/LRIG is a conserved regulator of RTK signaling, add to our understanding of LRIG1 in melanoma and identifies recombinant LRIG1 as a potential therapeutic against BRAF inhibitor-resistant melanoma.

Netrin-1 functions as a suppressor of bone morphogenetic protein (BMP) signaling.

Netrin-1 is a secreted protein that is well known for its involvement in axonal guidance during embryonic development and as an enhancer of cancer cell metastasis. Despite extensive efforts, the molecular mechanisms behind many of the physiological functions of netrin-1 have remained elusive. Here, we show that netrin-1 functions as a suppressor of bone morphogenetic protein (BMP) signaling in various cellular systems, including a mutually inhibitory interaction with the BMP-promoting function of leucine-rich repeats and immunoglobulin-like domains (LRIG) proteins. The BMP inhibitory function of netrin-1 in mouse embryonic fibroblasts was dependent on the netrin receptor neogenin, with the expression level regulated by both netrin-1 and LRIG proteins. Our results reveal a previously unrecognized function of netrin-1 that may help to explain several of the developmental, physiological, and cancer-promoting functions of netrins at the signal transduction level.

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

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

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

BACKGROUND: Leucine-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. METHODS: We 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. RESULTS: Four 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. CONCLUSIONS: Although 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.

LRIG1­2 and LMO7 immunoreactivity in vulvar squamous cell carcinoma: Association with prognosis in relation to HPV­DNA and p16INK4a status.

The present study was conducted to investigate the possible prognostic value of molecular markers LRIG1­2 and LIM domain 7 protein (LMO7) in vulvar squamous cell carcinoma (VSCC) and their possible correlation to human papilloma virus (HPV)­ and p16INK4a­status of the tumors. Patients diagnosed with VSCC at the University Hospital of Umeå, Sweden, during the years 1990­2013 were selected. Tumor blocks were retrieved from tissue archives and clinical data were collected from the records of patients. HPV­PCR analysis, HPV genotyping and immunohistochemistry were performed. In total, 112 patients were included. Forty percent of the tumors were HPV­positive, 27% were p16INK4a­positive and 23% were positive for both HPV and p16INK4a (considered HPV­driven). HPV­positivity and p16INK4a­positivity were associated with prolonged disease­free survival (DFS) in Kaplan­Meier survival analysis. Leucine­rich repeats and immunoglobulin­like domains 1 (LRIG1) immunoreactivity was not significantly associated with survival. High leucine­rich repeats and immunoglobulin­like domains 2 (LRIG2) immunoreactivity was associated with a prolonged overall survival (OS) (P=0.001). By analyzing HPV­negative 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, 0.24­0.71). High immunoreactivity with LMO7­1250 antibody was associated with survival benefits in the whole cohort (OS; P=0.011) although DFS was only prolonged in HPV­negative and not HPV­driven 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 HPV­driven 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.

Lrig2 and Hpse2, mutated in urofacial syndrome, pattern nerves in the urinary bladder.

Mutations in leucine-rich-repeats and immunoglobulin-like-domains 2 (LRIG2) or in heparanase 2 (HPSE2) cause urofacial syndrome, a devastating autosomal recessive disease of functional bladder outlet obstruction. It has been speculated that urofacial syndrome has a neural basis, but it is unknown whether defects in urinary bladder innervation are present. We hypothesized that urofacial syndrome features a peripheral neuropathy of the bladder. Mice with homozygous targeted Lrig2 mutations had urinary defects resembling those found in urofacial syndrome. There was no anatomical blockage of the outflow tract, consistent with a functional bladder outlet obstruction. Transcriptome analysis revealed differential expression of 12 known transcripts in addition to Lrig2, including 8 with established roles in neurobiology. Mice with homozygous mutations in either Lrig2 or Hpse2 had increased nerve density within the body of the urinary bladder and decreased nerve density around the urinary outflow tract. In a sample of 155 children with chronic kidney disease and urinary symptoms, we discovered novel homozygous missense LRIG2 variants that were predicted to be pathogenic in 2 individuals with non-syndromic bladder outlet obstruction. These observations provide evidence that a peripheral neuropathy is central to the pathobiology of functional bladder outlet obstruction in urofacial syndrome, and emphasize the importance of LRIG2 and heparanase 2 for nerve patterning in the urinary tract.

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.

LRIG1 negatively regulates RET mutants and is downregulated in thyroid cancer.

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

Lrig1 is a haploinsufficient tumor suppressor gene in malignant glioma.

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

A protein interaction network centered on leucine-rich repeats and immunoglobulin-like domains 1 (LRIG1) regulates growth factor receptors.

Leucine-rich repeats and immunoglobulin-like domains 1 (LRIG1) is a tumor suppressor and a negative regulator of several receptor tyrosine kinases. The molecular mechanisms by which LRIG1 mediates its tumor suppressor effects and regulates receptor tyrosine kinases remain incompletely understood. Here, we performed a yeast two-hybrid screen to identify novel LRIG1-interacting proteins and mined data from the BioPlex (biophysical interactions of ORFeome-based complexes) protein interaction data repository. The putative LRIG1 interactors identified in the screen were functionally evaluated using a triple co-transfection system in which HEK293 cells were co-transfected with platelet-derived growth factor receptor α, LRIG1, and shRNAs against the identified LRIG1 interactors. The effects of the shRNAs on the ability of LRIG1 to down-regulate platelet-derived growth factor receptor α expression were evaluated. On the basis of these results, we present an LRIG1 protein interaction network with many newly identified components. The network contains the apparently functionally important LRIG1-interacting proteins RAB4A, PON2, GAL3ST1, ZBTB16, LRIG2, CNPY3, HLA-DRA, GML, CNPY4, LRRC40, and LRIG3, together with GLRX3, PTPRK, and other proteins. In silico analyses of The Cancer Genome Atlas data sets revealed consistent correlations between the expression of the transcripts encoding LRIG1 and its interactors ZBTB16 and PTPRK and inverse correlations between the transcripts encoding LRIG1 and GLRX3. We further studied the LRIG1 function-promoting paraoxonase PON2 and found that it co-localized with LRIG1 in LRIG1-transfected cells. The proposed LRIG1 protein interaction network will provide leads for future studies aiming to understand the molecular functions of LRIG1 and the regulation of growth factor signaling.

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.

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

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

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.