Regulation Of Growth Factor Signaling Research Articles

Abstract PR01: Oncogenic Kras-induced mitochondrial oxidative stress in pancreatic acini modulates the formation of precancerous lesions through autocrine EGFR signaling

Abstract The development of pancreatic cancer requires both obtain of oncogenic Kras mutations and up-regulation of growth factor signaling. However, how oncogenic Kras regulates growth factor signaling in pancreatic cancer development is still unclear. Using a transgenic mouse model harboring an oncogenic Kras mutation and a 3D organoid explant culture of primary pancreatic acini, we here show that expression of mutant Kras in pancreatic acinar cells alters their mitochondrial metabolism, resulting in increased generation of mitochondrial reactive oxygen species (mROS). We further demonstrate that mROS induced by oncogenic Kras is required for transdifferentiating acinar cells to a duct-like phenotype and eventually progression to pancreatic intraepithelial neoplasia (PanIN), the most common precursor lesions of pancreatic ductal adenocarcinoma (PDAC). This transdiffentiation process is mediated by increased levels of epidermal growth factor receptor (EGFR) as well as its ligands, EGF and TGFα, through activation of the ROS-receptive transcription factors, NF-κB1 and NF-κB2. In Kas transgenic mice, the interception of KrasG12D-mediated generation of mROS significantly reduced the formation of pre-neoplastic lesions. Hence, our data provide mechanistic insight of how oncogenic Kras mutant crosstalks with growth factor signaling to cause the formation of pancreatic cancer. Citation Format: Geou-Yarh Liou, Heike Doeppler, Kathleen E. DelGirono, Howard C. Crawford, Michael P. Murphy, Peter Storz. Oncogenic Kras-induced mitochondrial oxidative stress in pancreatic acini modulates the formation of precancerous lesions through autocrine EGFR signaling. [abstract]. In: Proceedings of the Fourth AACR International Conference on Frontiers in Basic Cancer Research; 2015 Oct 23-26; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2016;76(3 Suppl):Abstract nr PR01.

Beclin 1 regulates growth factor receptor signaling in breast cancer.

Beclin 1 is a haplo-insufficient tumor suppressor that is decreased in many human tumors. The function of Beclin 1 in cancer has been attributed primarily to its role in the degradative process of macroautophagy. However, Beclin 1 is a core component of the Vps34/Class III PI3K (PI3KC3) and Vps15/p150 complex that regulates multiple membrane trafficking events. In the current study, we describe an alternative mechanism of action for Beclin 1 in breast cancer involving its control of growth factor receptor signaling. We identify a specific stage of early endosome maturation that is regulated by Beclin 1, the transition of APPL1-containing phosphatidyIinositol 3-phosphate-negative (PI3P-) endosomes to PI3P+ endosomes. Beclin 1 regulates PI3P production in response to growth factor stimulation to control the residency time of growth factor receptors in the PI3P-/APPL+ signaling competent compartment. As a result, suppression of BECN1 sustains growth factor stimulated AKT and ERK activation resulting in increased breast carcinoma cell invasion. In human breast tumors, Beclin 1 expression is inversely correlated with AKT and ERK phosphorylation. Our data identify a novel role for Beclin 1 in regulating growth factor signaling and reveal a mechanism by which loss of Beclin 1 expression would enhance breast cancer progression.

Mechanism of the Anticancer Effect of Lycopene (Tetraterpenoids).

Increasing evidence suggests that lycopene, a major carotenoid detected in human plasma, may be preventive against the formation and the development of different types of human cancers including prostate, breast, and lung cancer. Experimental studies demonstrated that lycopene inhibits the growth of various cancer cells of different organs and prevent chemically induced carcinogenesis in animal models. Although the excellent antioxidant property of lycopene is most likely the basis for its preventive role toward cancer, the direct anticancer activities of lycopene through multiple mechanisms are disclosed, including regulation of growth factor signaling, cell cycle arrest and/or apoptosis induction, and changes in antioxidant and phase II detoxifying enzymes. The anti-inflammatory activity of lycopene is also considered as an important determinant that suppresses the promotion and progression of carcinogenesis. Moreover, lycopene inhibits cell invasion, angiogenesis, and metastasis. Importantly, those activities have been shown to be exhibited at the physiologically attainable concentration in humans. Although the preclinical data strongly suggest an antitumor activity of lycopene, a number of epidemiological and intervention studies indicate that there is still no clear clinical evidence that supports its use for the prevention of those cancers. More well controlled clinical intervention trials are needed to further clarify the exact role of lycopene in the cancer prevention. Nonetheless, because of its multiple tumor-inhibitory activities, lycopene still remains to be an attractive and promising carotenoid that will potentially contribute to the prevention and treatment of human cancers. This chapter reviews data on the cancer preventive activities of lycopene, possible mechanisms involved, and the relationship between lycopene consumption and human cancer risk.

Ion channel TRPV1-dependent activation of PTP1B suppresses EGFR-associated intestinal tumorigenesis.

The intestinal epithelium has a high rate of turnover, and dysregulation of pathways that regulate regeneration can lead to tumor development; however, the negative regulators of oncogenic events in the intestinal epithelium are not fully understood. Here we identified a feedback loop between the epidermal growth factor receptor (EGFR), a known mediator of proliferation, and the transient receptor potential cation channel, subfamily V, member 1 (TRPV1), in intestinal epithelial cells (IECs). We found that TRPV1 was expressed by IECs and was intrinsically activated upon EGFR stimulation. Subsequently, TRPV1 activation inhibited EGFR-induced epithelial cell proliferation via activation of Ca2+/calpain and resulting activation of protein tyrosine phosphatase 1B (PTP1B). In a murine model of multiple intestinal neoplasia (Apc(Min/+) mice), TRPV1 deficiency increased adenoma formation, and treatment of these animals with an EGFR kinase inhibitor reversed protumorigenic phenotypes, supporting a functional association between TRPV1 and EGFR signaling in IECs. Administration of a TRPV1 agonist suppressed intestinal tumorigenesis in Apc(Min/+) mice, similar to--as well as in conjunction with--a cyclooxygenase-2 (COX-2) inhibitor, which suggests that targeting both TRPV1 and COX-2 has potential as a therapeutic approach for tumor prevention. Our findings implicate TRPV1 as a regulator of growth factor signaling in the intestinal epithelium through activation of PTP1B and subsequent suppression of intestinal tumorigenesis.

PHLPP phosphatases are master regulators of cellular receptor tyrosine kinase levels (802.19)

Growth factor receptor levels are aberrantly high in diverse cancers, driving the proliferation and survival of tumor cells. Understanding the molecular basis for this aberrant elevation has profound clinical applications. Here we show that the PH domain leucine‐rich repeat protein phosphatase (PHLPP) suppresses the steady‐state levels of receptor tyrosine kinases (RTKs) by a novel mechanism unrelated to its previously described function as the hydrophobic motif phosphatase for AKT, protein kinase C and S6 kinase. Specifically, genetic depletion and pharmacological studies reveal that PHLPP1 and PHLPP2 promote histone deacetylase (HDAC)‐dependent repression of the transcription of diverse growth factor receptors, including the EGF receptor. These data uncover a novel, and much broader, role for PHLPP in regulation of growth factor signaling beyond its direct inactivation of AKT: by suppressing RTK levels, PHLPP dampens the downstream signaling output of two major oncogenic pathways, the PI3 kinase/AKT and the RAS/ERK pathways. Our data are consistent with a model in which PHLPP is a master regulator of the RTK signaling output of cells.

Identification and Expression Analysis of Zebrafish Glypicans during Embryonic Development

Heparan sulfate Proteoglycans (HSPG) are ubiquitous molecules with indispensable functions in various biological processes. Glypicans are a family of HSPG’s, characterized by a Gpi-anchor which directs them to the cell surface and/or extracellular matrix where they regulate growth factor signaling during development and disease. We report the identification and expression pattern of glypican genes from zebrafish. The zebrafish genome contains 10 glypican homologs, as opposed to six in mammals, which are highly conserved and are phylogenetically related to the mammalian genes. Some of the fish glypicans like Gpc1a, Gpc3, Gpc4, Gpc6a and Gpc6b show conserved synteny with their mammalian cognate genes. Many glypicans are expressed during the gastrulation stage, but their expression becomes more tissue specific and defined during somitogenesis stages, particularly in the developing central nervous system. Existence of multiple glypican orthologs in fish with diverse expression pattern suggests highly specialized and/or redundant function of these genes during embryonic development.

Abstract A01: Long noncoding RNA H19 regulates growth factor signaling in breast cancer cells

Abstract H19 is one of the earliest identified, and the most studied, long noncoding RNAs. H19 gene is submitted to genomic imprinting and expressed only from the maternal allele and has no protein associated to its transcription. It has been proposed that H19 RNA function as a riboregulator. H19 is essential for development regulation but is also associated with carcinogenesis in many organs. However, biological functions and regulatory mechanisms of this conserved non coding RNA remain largely undecipher. Previously, we have shown that H19 is overexpressed in 70% of human breast cancers. In addition, its over-expression promotes cells invasion and angiogenesis. H19, positively regulated by E2F1, promotes cell cycle progression and G1/S transition. Altogether, these data support oncogenic function in breast tumor genesis of H19. Recently, H19 has been showed to be a microRNA precursor of miR-675-5p and miR-675-3p. MicroRNAs are small non-coding RNA that regulate expression of up to 60% of genes. However, miR-675 targets have not yet been identified in breast cancer cells. H19 gene expression is positively regulated by several growth factors, in peculiar hepatocyte growth factor / scatter factor (HGF/SF). HGF/SF stimulates proliferation of epithelial cells and increases both their motility and morphogenesis. In the present study, in order to explain these phenotypes, we have searched for miR-675 targets in breast cancer cells. We demonstrate that H19, through its microRNA miR-675-5p, regulates negatively the expression of ubiquitin ligase E3 proteins: c-Cbl and Cbl-b. Both these proteins are involved in tyrosine kinase receptor degradation. In all breast cancer cells tested, c-Cbl and Cbl-b expression was significantly decreased after H19 or miR-675 over-expression. This downregulation promotes stability of growth factor receptors (EGFR, c-Met) that sustains and amplifies activation of downstream signaling pathways (Akt, MAP-kinase). Furthermore, we have shown that H19 overexpression increases breast cancer cells migration and invasion. Our data demonstrate that H19 gene overexpression increases HGF/SF receptor signaling as well as associated phenotypes. Our work propose a mechanism of action of H19 in breast cancer in increasing cell invasion and metastasis in this organ. H19 could also be involved in the mechanism of tumor resistance to treatment by increasing paracrine phenomena. Citation Format: Constance Vennin, Fatima Dhamani, Nathalie Spruyt, Eric Adriaenssens. Long noncoding RNA H19 regulates growth factor signaling in breast cancer cells. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr A01.

Thrombospondin-1 Induction in the Diabetic Myocardium Stabilizes the Cardiac Matrix in Addition to Promoting Vascular Rarefaction Through Angiopoietin-2 Upregulation

Diabetes mellitus is associated with cardiac fibrosis. Matricellular proteins are induced in fibrotic conditions and modulate fibrogenic and angiogenic responses by regulating growth factor signaling. Our aim was to test the hypothesis that the prototypical matricellular protein thrombospondin (TSP)-1, a potent angiostatic molecule and crucial activator of transforming growth factor-β, may play a key role in remodeling of the diabetic heart. Obese diabetic db/db mice exhibited marked myocardial TSP-1 upregulation in the interstitial and perivascular space. To study the role of TSP-1 in remodeling of the diabetic heart, we generated and characterized db/db TSP-1(-/-) (dbTSP) mice. TSP-1 disruption did not significantly affect weight gain and metabolic function in db/db animals. When compared with db/db animals, dbTSP mice had increased left ventricular dilation associated with mild nonprogressive systolic dysfunction. Chamber dilation in dbTSP mice was associated with decreased myocardial collagen content and accentuated matrix metalloproteinase-2 and -9 activity. TSP-1 disruption did not affect inflammatory gene expression and activation of transforming growth factor-β/small mothers against decapendaplegic signaling in the db/db myocardium. In cardiac fibroblasts populating collagen pads, TSP-1 incorporation into the matrix did not activate transforming growth factor-β responses, but inhibited leptin-induced matrix metalloproteinase-2 activation. TSP-1 disruption abrogated age-associated capillary rarefaction in db/db mice, attenuating myocardial upregulation of angiopoietin-2, a mediator that induces vascular regression. In vitro, TSP-1 stimulation increased macrophage, but not endothelial cell, angiopoietin-2 synthesis. TSP-1 upregulation in the diabetic heart prevents chamber dilation by exerting matrix-preserving actions on cardiac fibroblasts and mediates capillary rarefaction through effects that may involve angiopoietin-2 upregulation.

Renal Heparan Sulfate Proteoglycans Modulate Fibroblast Growth Factor 2 Signaling in Experimental Chronic Transplant Dysfunction

Depending on the glycan structure, proteoglycans can act as coreceptors for growth factors. We hypothesized that proteoglycans and their growth factor ligands orchestrate tissue remodeling in chronic transplant dysfunction. We have previously shown perlecan to be selectively up-regulated in the glomeruli and arteries in a rat renal transplantation model. Using the same model, here we present quantitative RT-PCR profiling data on proteoglycans and growth factors from laser-microdissected glomeruli, arterial tunicae mediae, and neointimae at 12 weeks after transplantation. In glomeruli and neointimae of allografts, selective induction of the matrix heparan sulfate proteoglycan perlecan was observed, along with massive accumulation of fibroblast growth factor 2 (FGF2). Profiling the heparan sulfate polysaccharide side chains revealed conversion from a non-FGF2-binding heparan sulfate phenotype in control and isografted kidneys toward a FGF2-binding phenotype in allografts. In vitro experiments with perlecan-positive rat mesangial cells showed that FGF2-induced proliferation is dependent on sulfation and can be inhibited by exogenously added heparan sulfate. These findings indicate that matrix proteoglycans such as perlecan serve as functional docking platforms for FGF2 in chronic transplant dysfunction. We speculate that heparin-like glycomimetics could be a promising intervention to retard development of glomerulosclerosis and neointima formation in chronic transplant dysfunction.

Lrig2-Deficient Mice Are Protected against PDGFB-Induced Glioma

BackgroundThe leucine-rich repeats and immunoglobulin-like domains (LRIG) proteins constitute an integral membrane protein family that has three members: LRIG1, LRIG2, and LRIG3. LRIG1 negatively regulates growth factor signaling, but little is known regarding the functions of LRIG2 and LRIG3. In oligodendroglial brain tumors, high expression of LRIG2 correlates with poor patient survival. Lrig1 and Lrig3 knockout mice are viable, but there have been no reports on Lrig2-deficient mice to date.Methodology/Principal Findings Lrig2-deficient mice were generated by the ablation of Lrig2 exon 12 (Lrig2E12). The Lrig2E12-/- mice showed a transiently reduced growth rate and an increased spontaneous mortality rate; 20-25% of these mice died before 130 days of age, with the majority of the deaths occurring before 50 days. Ntv-a transgenic mice with different Lrig2 genotypes were transduced by intracranial injection with platelet-derived growth factor (PDGF) B-encoding replication-competent avian retrovirus (RCAS)-producing DF-1 cells. All injected Lrig2E12+/+ mice developed Lrig2 expressing oligodendroglial brain tumors of lower grade (82%) or glioblastoma-like tumors of higher grade (18%). Lrig2E12-/- mice, in contrast, only developed lower grade tumors (77%) or had no detectable tumors (23%). Lrig2E12-/- mouse embryonic fibroblasts (MEF) showed altered induction-kinetics of immediate-early genes Fos and Egr2 in response to PDGF-BB stimulation. However, Lrig2E12-/- MEFs showed no changes in Pdgfrα or Pdgfrβ levels or in levels of PDGF-BB-induced phosphorylation of Pdgfrα, Pdgfrβ, Akt, or extracellular signal-regulated protein kinases 1 and 2 (ERK1/2). Overexpression of LRIG1, but not of LRIG2, downregulated PDGFRα levels in HEK-293T cells.ConclusionsThe phenotype of Lrig2E12-/- mice showed that Lrig2 was a promoter of PDGFB-induced glioma, and Lrig2 appeared to have important molecular and developmental functions that were distinct from those of Lrig1 and Lrig3.

Enhanced infarct stabilization and neovascularization mediated by VEGF-loaded PEGylated fibrinogen hydrogel in a rodent myocardial infarction model

Most tissue engineering therapies require biomaterials that are able to induce an angiogenic response to support tissue regeneration. In addition angiogenic growth factor signaling plays an essential role in controlling the process of angiogenesis and matrices have the potential of regulating the concentration of growth factors within the cellular microenvironment. Here we demonstrated myocardial protection and improved post-infarct vascularization of the infarcted hearts using a biosynthetic injectable hydrogel consisting of polyethylene glycol and fibrinogen (PEG-fibrinogen) loaded with vascular endothelial growth factor-A (VEGF-A). Our data revealed PEG-fibrinogen hydrogel was able to store and release VEGF-A in a sustained and controlled fashion. Upon injection after coronary artery ligation, the VEGF-loaded hydrogel significantly improved arteriogenesis and cardiac performance at 4 weeks post-infarction. The results support the future application of PEG-fibrinogen for regulating growth factor signaling in cellular microenvironment and may demonstrates a new strategy for cardiovascular repair with potential for future clinical applications.

Abstract 1309: ERβ1 induces apoptosis in lung cancer cells by regulating growth factor signaling.

Abstract Estrogens have recently been associated with the clinical outcome of patients with non-small cell lung cancer (NSCLC). The wild-type estrogen receptor β (ERβ1) one of the mediators of the estrogen signaling in cells is expressed in lung cancer. However, the role of ERβ1 in NSCLC cell growth has not been fully elucidated. Here we show that induction of ERβ1 expression inhibited cell growth in H1299 and A549 NSCLC cells. Treatment of these cells with the ERβ agonists 17β-estradiol or 3β-Adiol further decreased cell proliferation and induced apoptosis. ERβ1 was found to induce apoptosis through stimulation of the intrinsic apoptotic pathway that involves upregulation of the proapoptotic protein Bim. Inactivation of the extracellular-signal-regulated kinases ERK1/2 was found to be involved in the ERβ1-mediated induction of apoptosis since treatment with EGF that activates ERK1/2 abolished the ability of ERβ1 to sustain the apoptotic phenotype. These results suggest that, by regulating NSCLC cell growth, ERβ1 could be an important factor in biology of lung cancer and a potentially useful component in the clinical management of the disease. Citation Format: Christoforos Thomas, Fotis Nikolos, Gayani Rajapaksa, Igor Bado, Jan-Ake Gustafsson. ERβ1 induces apoptosis in lung cancer cells by regulating growth factor signaling. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1309. doi:10.1158/1538-7445.AM2013-1309

544P - Leucine-Rich and Immunoglobulin-Like Domains Germline Polymorphisms Predict Clinical outcome in Metastatic Colorectal Cancer

ABSTRACT Background Leucine-rich and immunoglobulin-like domains (LRIG) 1, 2, and 3 are integral membrane proteins recently discovered as regulators of the epidermal growth factor (EGF) signalling. LRIG1 negatively regulates growth factor signaling and increasing evidence indicates that LRIG1 is a tumor suppressor in certain cancer types. Lrig1 is expressed at low levels in several cancer types but is overexpressed in some colorectal tumors. We postulate that polymorphisms located in the LRIG1 gene could influence the EGFR signalling pathway and be related with the clinical outcome in metastatic colorectal cancer (mCRC). Methods We studied 126 mCRC treated with a first-line oxaliplatin/5-fluorouracil chemotherapeutic regimen. Common and putatively functional polymorphisms in the LRIG gene were selected using public literature resources and databases (NCBI, PubMed, db SNP, Ensembl and GeneCards Version 3). These germline polymorphisms were analyzed using a Fluidigm equipment in DNA samples extracted from peripheral blood. Overall survival (OS) was evaluated according to each genotype. Results Two non-synonymous (c3158A > C and c1843A > G) and two synonymous (c2221T > C and c1317C > T) common and putatively functional polymorphisms in the LRIG1 gene were selected. There were significant associations between LRIG1 c1317C > T and c3158A > C polymorphisms and clinical outcome. OS was lower for patients harboring a T/T genotype than for patients with the C/C or C/T genotypes (p= 0.01). In the case of the c3158A > C polymorphism, patients harboring a C/C genotype had a lower OS than patients with an A/A or A/C genotypes (p = 0.047). Conclusions In this study, we identified common germline variants in LRIG1 gene predicting clinical outcome in patients with mCRC receiving first-line oxaliplatin-based chemotherapy. Disclosure All authors have declared no conflicts of interest.

Margaret Kirby

Despite being told she would have “a stillborn PhD” if she got married, having a pitifully small starting salary as an assistant professor, and having a distinct aversion to the subject of heart development, Margaret Kirby went on to become Professor of Cell Biology at Duke University and one of the world's leading experts on heart development. She even wrote a well-known textbook on the subject.1 Kirby focused her research on cardiac neural crest cells. She had started her scientific life as a neuroanatomist and was drawn into cardiology only after discovering a population of neural crest cells in the heart. She went on to show that these cells control the division of the aorta and pulmonary artery,2 regulate growth factor signaling to the developing myocardium,3 and contribute to the development of the outflow tract.4 These studies caused significant steps forward in scientists' understanding of heart development and the defects that occur when it goes wrong. In the early 1970s, when Kirby was starting her career, women were often discouraged from pursuing science, and those who did tended to be unmarried and childless. Unbeknownst to Kirby, she was helping to forge a path for women scientists who wanted normal family lives. But, she explained to Circulation Research , she didn't blaze the trail by speaking out, she just quietly “worked her butt off.” Kirby retired from Duke University last December and now lives in Copper Harbor, Michigan, running a photography gallery. ### Where Did You Grow Up? In Fort Smith, Arkansas. My father was French; he was born in Paris and moved to America with his parents when he was about 11. They also lived in England, Cuba, and Mexico, so my father's family is pretty exotic. My mother was a 9th generation Arkansan, so just the opposite. They met in …

Use of leucine-rich and immunoglobulin-like domains germ-line polymorphisms to predict clinical outcome in metastatic colorectal cancer.

e14052 Background: Leucine-rich and immunoglobulin-like domains (LRIG) 1, 2, and 3 are integral membrane proteins recently discovered as regulators of the epidermal growth factor signalling. LRIG1 negatively regulates growth factor signaling and increasing evidence indicates that LRIG1 is a tumor suppressor in certain cancer types. Lrig1 is expressed at low levels in several cancer types but is overexpressed in some colorectal tumors.We postulate that polymorphisms located in the LRIG1 gene could influence the EGFR signalling pathway and be related with the clinical outcome in metastatic colorectal cancer (mCRC). Methods: This study included 318 patients with mCRC treated between 1992 and 2003 at the University of Southern California/Norris Comprehensive Cancer Center or Los Angeles County/University of Southern California Medical Center. Common and putatively functional polymorphisms in the LRIG genes were selected using public literature resources and databases (NCBI, PubMed, db SNP, Ensembl and GeneCards). Whole blood samples were analyzed for germline polymorphisms by direct DNA-sequencing. Overall survival (OS) was evaluated according to each genotype. Furthermore, polymorphisms with suggestive statistical significance were replicated in an independent validation cohort of 126 Spanish mCRC. Results: In a preliminary analysis, two non-synonymous (c3158A>C and c1843A>G) and two synonymous (c2221T>C and c1317C>T) polymorphisms in the LRIG1 gene were selected. There were significant interactions between LRIG1 c1317C>T polymorphisms and clinical outcome. OS was lower for patients harboring T/T genotype (median=11.9 months, 95% C.I (3.5-16 months) than for patients with the C/C or C/T genotypes (median=14.5 months; 95% C.I (12.2-18.3 months); p= 0.04, log-rank test) and the association was also significant in the validation cohort (p=0.01). Conclusions: In this study, we identified common germline variants in LRIG1 gene predicting clinical outcome in patients with mCRC. Although, no functionality has been documented for these SNPs to date, our clinical data suggest that these polymorphisms may affect the mRNA stability and/or translation efficiency of the gene.

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.

Multiparametric image analysis reveals role of Caveolin1 in endosomal progression rather than internalization of EGFR

Endosomes constitute a central layer in the regulation of growth factor signaling. We applied flow cytometry, confocal microscopy and automated image quantification to define the role of Caveolin1 (Cav1) in epidermal growth factor (EGF) receptor (i) internalization and (ii) endosomal trafficking. Antisense-downregulation of Cav1 did not affect internalization of EGF:EGFR-complexes from the plasma membrane. Instead, Cav1-knockdown had a profound effect on endosomal trafficking and caused a shift in EGF vesicle distribution towards Rab7-negative compartments at late timepoints. Moreover, image quantification with single-endosome resolution revealed that EGF:Cav1-complexes undergo a maturation pattern reminiscent of late endosomes. Our data suggest a model in which Caveolin1 acts upon EGF endosomes internalized via the Clathrin-pathway and functions at the transition from early to late endosomes.

Organ-specific Sulfation Patterns of Heparan Sulfate Generated by Extracellular Sulfatases Sulf1 and Sulf2 in Mice

Heparan sulfate endosulfatases Sulf1 and Sulf2 hydrolyze 6-O-sulfate in heparan sulfate, thereby regulating cellular signaling. Previous studies have revealed that Sulfs act predominantly on UA2S-GlcNS6S disaccharides and weakly on UA-GlcNS6S disaccharides. However, the specificity of Sulfs and their role in sulfation patterning of heparan sulfate in vivo remained unknown. Here, we performed disaccharide analysis of heparan sulfate in Sulf1 and Sulf2 knock-out mice. Significant increases in ΔUA2S-GlcNS6S were observed in the brain, small intestine, lung, spleen, testis, and skeletal muscle of adult Sulf1(-/-) mice and in the brain, liver, kidney, spleen, and testis of adult Sulf2(-/-) mice. In addition, increases in ΔUA-GlcNS6S were seen in the Sulf1(-/-) lung and small intestine. In contrast, the disaccharide compositions of chondroitin sulfate were not primarily altered, indicating specificity of Sulfs for heparan sulfate. For Sulf1, but not for Sulf2, mRNA expression levels in eight organs of wild-type mice were highly correlated with increases in ΔUA2S-GlcNS6S in the corresponding organs of knock-out mice. Moreover, overall changes in heparan sulfate compositions were greater in Sulf1(-/-) mice than in Sulf2(-/-) mice despite lower levels of Sulf1 mRNA expression, suggesting predominant roles of Sulf1 in heparan sulfate desulfation and distinct regulation of Sulf activities in vivo. Sulf1 and Sulf2 mRNAs were differentially expressed in restricted types of cells in organs, and consequently, the sulfation patterns of heparan sulfate were locally and distinctly altered in Sulf1 and Sulf2 knock-out mice. These findings indicate that Sulf1 and Sulf2 differentially contribute to the generation of organ-specific sulfation patterns of heparan sulfate.

Thrombospondin-1 acts as a ligand for CD148 tyrosine phosphatase

CD148 is a receptor-type protein tyrosine phosphatase that is expressed in several cell types, including vascular endothelial cells and duct epithelial cells. Growing evidence demonstrates a prominent role for CD148 in negative regulation of growth factor signals, suppressing cell proliferation and transformation. However, its extracellular ligand(s) remain unknown. To identify the ligand(s) of CD148, we introduced HA-tagged CD148 into cultured endothelial cells and then isolated its interacting extracellular protein(s) by biotin surface labeling and subsequent affinity purifications. The binding proteins were identified by mass spectrometry. Here we report that soluble thrombospondin-1 (TSP1) binds to the extracellular part of CD148 with high affinity and specificity, and its binding increases CD148 catalytic activity, leading to dephosphorylation of the substrate proteins. Consistent with these findings, introduction of CD148 conferred TSP1-mediated inhibition of cell growth to cells which lack CD148 and TSP1 inhibition of growth. Further, we demonstrate that TSP1-mediated inhibition of endothelial cell growth is antagonized by soluble CD148 ectodomain as well as by CD148 gene silencing. These findings provide evidence that CD148 functions as a receptor for TSP1 and mediates its inhibition of cell growth.

Regulation of Cellular Levels of Sprouty2 Protein by Prolyl Hydroxylase Domain and von Hippel-Lindau Proteins

Sprouty (Spry) proteins modulate the actions of receptor tyrosine kinases during development and tumorigenesis. Decreases in cellular levels of Spry, especially Sprouty2 (Spry2), have been implicated in the growth and progression of tumors of the breast, prostate, lung, and liver. During development and tumor growth, cells experience hypoxia. Therefore, we investigated how hypoxia modulates the levels of Spry proteins. Hypoxia elevated the levels of all four expressed Spry isoforms in HeLa cells. Amounts of endogenous Spry2 in LS147T and HEP3B cells were also elevated by hypoxia. Using Spry2 as a prototype, we demonstrate that silencing and expression of prolyl hydroxylase domain proteins (PHD1-3) increase and decrease, respectively, the cellular content of Spry2. Spry2 also preferentially interacted with PHD1-3 and von Hippel-Lindau protein (pVHL) during normoxia but not in hypoxia. Additionally, Spry2 is hydroxylated on Pro residues 18, 144, and 160, and substitution of these residues with Ala enhanced stability of Spry2 and abrogated its interactions with pVHL. Silencing of pVHL increased levels of Spry2 by decreasing its ubiquitylation and degradation and thereby augmented the ability of Spry2 to inhibit FGF-elicited activation of ERK1/2. Thus, prolyl hydroxylase mediated hydroxylation and subsequent pVHL-elicited ubiquitylation of Spry2 target it for degradation and, consequently, provide a novel mechanism of regulating growth factor signaling.