Neuropilin-2 is a novel marker expressed in pancreatic islet cells and endocrine pancreatic tumours

Development and Characterization of a Novel Neuropilin-2 Antibody for Immunohistochemical Staining of Cancer and Sarcoidosis Tissue Samples

Neuropilin-2 (NRP2) is a cell surface receptor that plays key roles in lymphangiogenesis, but also in pathophysiological conditions such as cancer and inflammation. NRP2 targeting by efzofitimod, a novel immunomodulatory molecule, is currently being tested for the treatment of pulmonary sarcoidosis. To date, no anti-NRP2 antibodies are available for companion diagnostics. Here we describe the development and characterization of a novel NRP2 antibody. Using a variety of research techniques, that is, enzyme-linked immunoassay, Western blot, biolayer interferometry, and immunohistochemistry, we demonstrate that our antibody detects all major NRP2 isoforms and does not cross-react with NRP1. Using this antibody, we show high NRP2 expression in granulomas from sarcoidosis patient skin and lung biopsies. Our novel anti-NRP2 antibody could prove to be a useful clinical tool for sarcoidosis and other indications where NRP2 has been implicated. Clinical Trial Registration: clinicaltrials.gov NCT05415137.

Angiogenesis in NENs, with a focus on gastroenteropancreatic NENs: from biology to current and future therapeutic implications

Neuroendocrine neoplasms (NENs) are highly vascularized malignancies arising from cells of the diffuse neuroendocrine system. An intricated cross-talk exists between NEN cells and the tumor microenvironment, and three main molecular circuits (VEGF/VEGFR pathway, FGF-dependent signaling and PDGF/PDGFR axis) have been shown to regulate angiogenesis in these neoplasms. Multiple randomized trials have investigated antiangiogenic agents over the past two decades, and sunitinib is currently approved for the treatment of advanced, progressive, G1/G2 pancreatic NENs. In recent years, two phase III clinical trials have demonstrated the efficacy and safety of surufatinib, a multi-tyrosine kinase angioimmune inhibitor, in patients with well-differentiated pancreatic and extrapancreatic NENs, and two studies of this agent are currently underway in Europe and US. The HIF-2α inhibitor belzutifan has recently received regulatory approval for the treatment of tumors arising in the context of Von-Hippel Lindau syndrome including pancreatic NENs, and a study of this drug in patients with sporadic tumors is presently ongoing. Combinations of antiangiogenic agents with chemotherapeutics and targeted drugs have been tested, with accumulating toxicities being a matter of concern. The potential of antiangiogenic agents in fine-tuning the immune microenvironment of NENs to enhance the activity of immune checkpoint inhibitors has been only partially elucidated, and further research should be carried out at this regard. Here, we review the current understanding of the biology of angiogenesis in NENs and provide a summary of the latest clinical investigations on antiangiogenic drugs in this malignancy.

MUC16 Promotes Liver Metastasis of Pancreatic Ductal Adenocarcinoma by Upregulating NRP2-Associated Cell Adhesion

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal types of cancer, as it commonly metastasizes to the liver resulting in an overall poor prognosis. However, the molecular mechanism involved in liver metastasis remains poorly understood. Here, we aimed to identify the MUC16-mediated molecular mechanism of PDAC-liver metastasis. Previous studies demonstrated that MUC16 and its C-terminal (Cter) domain are involved in the aggressiveness of PDAC. In this study, we observed MUC16 and its Cter expression significantly high in human PDAC tissues, PDAC organoids, and metastatic liver tissues, while no expression was observed in normal pancreatic tissues using IHC and immunofluorescence (IFC) analyses. MUC16 knockdown in SW1990 and CD18/HPAF PDAC cells significantly decreased the colony formation, migration, and endothelial/p-selectin binding. In contrast, MUC16-Cter ectopic overexpression showed significantly increased colony formation and motility in MiaPaCa2 pancreatic cancer cells. Interestingly, MUC16 promoted cell survival and colonization in the liver, mimicking an ex vivo environment. Furthermore, MUC16 enhanced liver metastasis in the in vivo mouse model. Our integrated analyses of RNA-sequencing suggested that MUC16 alters Neuropilin-2 (NRP2) and cell adhesion molecules in pancreatic cancer cells. Furthermore, we identified that MUC16 regulated NRP2 via JAK2/STAT1 signaling in PDAC. NRP2 knockdown in MUC16-overexpressed PDAC cells showed significantly decreased cell adhesion and migration. Overall, the findings indicate that MUC16 regulates NRP2 and induces metastasis in PDAC.

IMPLICATIONS

This study shows that MUC16 plays a critical role in PDAC liver metastasis by mediating NRP2 regulation by JAK2/STAT1 axis, thereby paving the way for future therapy efforts for metastatic PDAC.

Role of Neuropilin-2-mediated signaling axis in cancer progression and therapy resistance

Neuropilins (NRPs) are transmembrane proteins involved in vascular and nervous system development by regulating angiogenesis and axon guidance cues. Several published reports have established their role in tumorigenesis. NRPs are detectable in tumor cells of several cancer types and participate in cancer progression. NRP2 is also expressed in endothelial and immune cells in the tumor microenvironment and promotes functions such as lymphangiogenesis and immune suppression important for cancer progression. In this review, we have taken a comprehensive approach to discussing various aspects of NRP2-signaling in cancer, including its regulation, functional significance in cancer progression, and how we could utilize our current knowledge to advance the studies and target NRP2 to develop effective cancer therapies.

The Role of Neuropilin-2 in the Epithelial to Mesenchymal Transition of Colorectal Cancer: A Systematic Review

Neuropilin-2 (NRP-2) expression has been found in various investigations on the expression and function of NRP-2 in colorectal cancer. The link between NRP-2 and colorectal cancer, as well as the mechanism that regulates it, is still mostly unclear. This systematic review was carried out according to the Cochrane guidelines for systematic reviews. We searched PubMed, Embase^®, MEDLINE, Allied & Complementary Medicine^TM, Medical Toxicology & Environmental Health, DH-DATA: Health Administration for articles published before 1 October 2021. The following search terms were used: “neuropilin-2” “neuropilin 2”, “NRP2” and “NRP-2”, “colorectal cancer”, “colon cancer”. Ten articles researching either tumor tissue samples, cell lines, or mice models were included in this review. The majority of human primary and metastatic colon cancer cell lines expressed NRP-2 compared to the normal colonic mucosa. NRPs have been discovered in human cancers as well as neovasculature. The presence of NRP-2 appears to be connected to the epithelial–mesenchymal transition’s function in cancer dissemination and metastatic evolution. The studies were heterogeneous, but the data assessed indicates NRP-2 might have an impact on the metastatic potential of colorectal cancer cells. Nevertheless, further research is needed.

Re-Expression of Poly/Oligo-Sialylated Adhesion Molecules on the Surface of Tumor Cells Disrupts Their Interaction with Immune-Effector Cells and Contributes to Pathophysiological Immune Escape

Glycans linked to surface proteins are the most complex biological macromolecules that play an active role in various cellular mechanisms. This diversity is the basis of cell-cell interaction and communication, cell growth, cell migration, as well as co-stimulatory or inhibitory signaling. Our review describes the importance of neuraminic acid and its derivatives as recognition elements, which are located at the outermost positions of carbohydrate chains linked to specific glycoproteins or glycolipids. Tumor cells, especially from solid tumors, mask themselves by re-expression of hypersialylated neural cell adhesion molecule (NCAM), neuropilin-2 (NRP-2), or synaptic cell adhesion molecule 1 (SynCAM 1) in order to protect themselves against the cytotoxic attack of the also highly sialylated immune effector cells. More particularly, we focus on α-2,8-linked polysialic acid chains, which characterize carrier glycoproteins such as NCAM, NRP-2, or SynCam-1. This characteristic property correlates with an aggressive clinical phenotype and endows them with multiple roles in biological processes that underlie all steps of cancer progression, including regulation of cell-cell and/or cell-extracellular matrix interactions, as well as increased proliferation, migration, reduced apoptosis rate of tumor cells, angiogenesis, and metastasis. Specifically, re-expression of poly/oligo-sialylated adhesion molecules on the surface of tumor cells disrupts their interaction with immune-effector cells and contributes to pathophysiological immune escape. Further, sialylated glycoproteins induce immunoregulatory cytokines and growth factors through interactions with sialic acid-binding immunoglobulin-like lectins. We describe the processes, which modulate the interaction between sialylated carrier glycoproteins and their ligands, and illustrate that sialic acids could be targets of novel therapeutic strategies for treatment of cancer and immune diseases.

Vascular NRP2 triggers PNET angiogenesis by activating the SSH1-cofilin axis

Background

Angiogenesis is a critical step in the growth of pancreatic neuroendocrine tumors (PNETs) and may be a selective target for PNET therapy. However, PNETs are robustly resistant to current anti-angiogenic therapies that primarily target the VEGFR pathway. Thus, the mechanism of PNET angiogenesis urgently needs to be clarified.

Methods

Dataset analysis was used to identify angiogenesis-related genes in PNETs. Immunohistochemistry was performed to determine the relationship among Neuropilin 2 (NRP2), VEGFR2 and CD31. Cell proliferation, wound-healing and tube formation assays were performed to clarify the function of NRP2 in angiogenesis. The mechanism involved in NRP2-induced angiogenesis was detected by constructing plasmids with mutant variants and performing Western blot, and immunofluorescence assays. A mouse model was used to evaluate the effect of the NRP2 antibody in vivo, and clinical data were collected from patient records to verify the association between NRP2 and patient prognosis.

Results

NRP2, a VEGFR2 co-receptor, was positively correlated with vascularity but not with VEGFR2 in PNET tissues. NRP2 promoted the migration of human umbilical vein endothelial cells (HUVECs) cultured in the presence of conditioned medium PNET cells via a VEGF/VEGFR2-independent pathway. Moreover, NRP2 induced F-actin polymerization by activating the actin-binding protein cofilin. Cofilin phosphatase slingshot-1 (SSH1) was highly expressed in NRP2-activating cofilin, and silencing SSH1 ameliorated NRP2-activated HUVEC migration and F-actin polymerization. Furthermore, blocking NRP2 in vivo suppressed PNET angiogenesis and tumor growth. Finally, elevated NRP2 expression was associated with poor prognosis in PNET patients.

Conclusion

Vascular NRP2 promotes PNET angiogenesis by activating the SSH1/cofilin/actin axis. Our findings demonstrate that NRP2 is an important regulator of angiogenesis and a potential therapeutic target of anti-angiogenesis therapy for PNET.

miR-331-3p Suppresses Cell Proliferation in TNBC Cells by Downregulating NRP2

PURPOSE

Triple-negative breast cancer is characterized by fast progression with high possible for metastasis and poor survival. Dysfunction of microRNAs plays an important role in the initiation and progression of cancer. Our previous microRNA-seq data indicated the downregulation of miR-331-3p in triple-negative breast cancer tissues compared with that of the noncancer tissues. However, the function of miR-331-3p in triple-negative breast cancer remains largely unknown. Herein, the involvement of miR-331-3p in triple-negative breast cancer was investigated and the therapeutic potential of miR-331-3p was also explored.

METHODS

Real-time quantitative polymerase chain reaction was performed to detect the expression of miR-331-3p in triple-negative breast cancer tissues and cell lines. The cell proliferation was determined by the cell counting kit-8 assay. Apoptosis of triple-negative breast cancer cells was examined by annexin V/propidium iodide staining. miRDB database was used to predict the potential targets of miR-331-3p. Western blot was performed to examine the expression of the target protein.

RESULTS

miR-331-3p was significantly downregulated in triple-negative breast cancer tissues and cell line. Lower miR-331-3p expression was significantly correlated with the tumor size, TNM stage, and lymph node metastasis of patients with triple-negative breast cancer. Functional experiments showed that the overexpression of miR-331-3p inhibited the proliferation and increased apoptosis of triple-negative breast cancer cells. Neuropilin-2 was identified as a target of miR-331-3p, which harbored binding site of miR-331-3p in its 3'-untranslated region. Overexpression of miR-331-3p decreased the messenger RNA and protein levels of neuropilin-2 in triple-negative breast cancer cells. Restoration of neuropilin-2 partially reversed the inhibitory effects of miR-331-3p on the proliferation of triple-negative breast cancer cells.

CONCLUSIONS

Our results demonstrated the novel function of miR-331-3p/neuropilin-2 signaling in regulating the malignant behaviors of triple-negative breast cancer cells, which suggested miR-331-3p as a potential target for the treatment of triple-negative breast cancer.

The Tumor Microenvironment in Neuroendocrine Tumors: Biology and Therapeutic Implications

Neuroendocrine tumors (NETs) include a heterogeneous group of malignancies arising in the diffuse neuroendocrine system and characterized by indolent growth. Complex interactions take place among the cellular components of the microenvironment of these tumors, and the recognition of the molecular mediators of their interplay and cross talk is crucial to discover novel therapeutic targets. NET cells overexpress a plethora of proangiogenic molecules including vascular endothelial growth factor, platelet-derived growth factor, fibroblast growth factor, semaphorins, and angiopoietins that promote both recruitment and proliferation of endothelial cell precursors, thus resulting among the most vascularized cancers with a microvessel density 10-fold higher than epithelial tumors. Also, NETs operate multifaceted interactions with stromal cells, both at local and distant sites, and whether their paracrine secretion of serotonin, connective tissue growth factor, and transforming growth factor β primarily drives the fibroblast activation to enhance the tumor proliferation, on the other side NET-derived profibrotic factors accelerate the extracellular matrix remodeling and contribute to heart valves and/or mesenteric fibrosis development, namely, major complications of functioning NETs. However, at present, little is known on the immune landscape of NETs, but accumulating evidence shows that tumor-infiltrating neutrophils, mast cells, and/or macrophages concur to promote the neoangiogenic switch of these tumors by either direct or indirect mechanisms. On the other hand, immune checkpoint molecules are heterogeneously expressed in NETs' surrounding cells, and it is unclear whether or not tumor-infiltrating lymphocytes are antitumor armed within the microenvironment, given their low mutational load. Here, we review the current knowledge on both gastroenteropancreatic and pulmonary NETs' microenvironment as well as both established and innovative treatments aimed at targeting the tumor-host interplay.

A radial axis defined by semaphorin-to-neuropilin signaling controls pancreatic islet morphogenesis

The islets of Langerhans are endocrine organs characteristically dispersed throughout the pancreas. During development, endocrine progenitors delaminate, migrate radially and cluster to form islets. Despite the distinctive distribution of islets, spatially localized signals that control islet morphogenesis have not been discovered. Here, we identify a radial signaling axis that instructs developing islet cells to disperse throughout the pancreas. A screen of pancreatic extracellular signals identified factors that stimulated islet cell development. These included semaphorin 3a, a guidance cue in neural development without known functions in the pancreas. In the fetal pancreas, peripheral mesenchymal cells expressed Sema3a, while central nascent islet cells produced the semaphorin receptor neuropilin 2 (Nrp2). Nrp2 mutant islet cells developed in proper numbers, but had defects in migration and were unresponsive to purified Sema3a. Mutant Nrp2 islets aggregated centrally and failed to disperse radially. Thus, Sema3a-Nrp2 signaling along an unrecognized pancreatic developmental axis constitutes a chemoattractant system essential for generating the hallmark morphogenetic properties of pancreatic islets. Unexpectedly, Sema3a- and Nrp2-mediated control of islet morphogenesis is strikingly homologous to mechanisms that regulate radial neuronal migration and cortical lamination in the developing mammalian brain.

Genome-Wide Association Study Identifies Risk Variants for Lichen Planus in Patients With Hepatitis C Virus Infection

BACKGROUND & AIMS

There is a close relationship between hepatitis C virus (HCV) infection and lichen planus, a chronic inflammatory mucocutaneous disease. We performed a genome-wide association study (GWAS) to identify genetic variants associated with HCV-related lichen planus.

METHODS

We conducted a GWAS of 261 patients with HCV infection treated at a tertiary medical center in Japan from October 2007 through January 2013; a total of 71 had lichen planus and 190 had normal oral mucosa. We validated our findings in a GWAS of 38 patients with HCV-associated lichen planus and 7 HCV-infected patients with normal oral mucosa treated at a medical center in Italy.

RESULTS

Single-nucleotide polymorphisms in NRP2 (rs884000) and IGFBP4 (rs538399) were associated with risk of HCV-associated lichen planus (P < 1 × 10^-4). We also found an association between a single-nucleotide polymorphism in the HLA-DR/DQ genes (rs9461799) and susceptibility to HCV-associated lichen planus. The odds ratios for the minor alleles of rs884000, rs538399, and rs9461799 were 3.25 (95% confidence interval, 1.95-5.41), 0.40 (95% confidence interval, 0.25-0.63), and 2.15 (95% confidence interval, 1.41-3.28), respectively.

CONCLUSIONS

In a GWAS of Japanese patients with HCV infection, we replicated associations between previously reported polymorphisms in HLA class II genes and risk for lichen planus. We also identified single-nucleotide polymorphisms in NRP2 and IGFBP4 loci that increase and reduce risk of lichen planus, respectively. These genetic variants might be used to identify patients with HCV infection who are at risk for lichen planus.

The axon guidance molecule semaphorin 3F is a negative regulator of tumor progression and proliferation in ileal neuroendocrine tumors

Gastro-intestinal neuroendocrine tumors (GI-NETs) are rare neoplasms, frequently metastatic, raising difficult clinical and therapeutic challenges due to a poor knowledge of their biology. As neuroendocrine cells express both epithelial and neural cell markers, we studied the possible involvement in GI-NETs of axon guidance molecules, which have been shown to decrease tumor cell proliferation and metastatic dissemination in several tumor types. We focused on the role of Semaphorin 3F (SEMA3F) in ileal NETs, one of the most frequent subtypes of GI-NETs.

SEMA3F expression was detected in normal neuroendocrine cells but was lost in most of human primary tumors and all their metastases. SEMA3F loss of expression was associated with promoter gene methylation. After increasing endogenous SEMA3F levels through stable transfection, enteroendocrine cell lines STC-1 and GluTag showed a reduced proliferation rate in vitro. In two different xenograft mouse models, SEMA3F-overexpressing cells exhibited a reduced ability to form tumors and a hampered liver dissemination potential in vivo. This resulted, at least in part, from the inhibition of mTOR and MAPK signaling pathways.

This study demonstrates an anti-tumoral role of SEMA3F in ileal NETs. We thus suggest that SEMA3F and/or its cellular signaling pathway could represent a target for ileal NET therapy.

Promotion of metastasis of thyroid cancer cells via NRP-2-mediated induction

Tumor-node-metastasis is one of the leading causes of morbidity and mortality in thyroid cancer patients. Upregulation of vascular endothelial growth factor-C (VEGF-C) increases the migratory ability of thyroid cancer cells to lymph nodes. Expression of neuropilin-2 (NRP-2), the co-receptor of VEGF-C, has been reported to be correlated with lymph node metastasis in human thyroid cancer. The present study investigated the role of VEGF-C/NRP-2 signaling in the regulation of metastasis of two different types of human thyroid cancer cells. The results indicated that the VEGF-C/NRP-2 axis significantly promoted the metastatic activities of papillary thyroid carcinoma cells through the activation of the mitogen-activated protein kinase (MAPK) kinase (MEK)/extracellular signal-regulated kinase and p38 MAPK signaling cascades. However, neither MEK or p38 MAPK inhibitors produced significant inhibition of the migratory activity and invasiveness regulated by the VEGF-C/NRP-2 axis in follicular thyroid carcinoma cells. Finally, VEGF-C/NRP-2-mediated invasion and migration of thyroid cancer cells required the expression of NRP-2. The present results demonstrate that the promotion of metastasis by VEGF-C is mainly due to the upregulation of NRP-2 in thyroid cancer cells, and this metastatic activity regulated by the VEGF-C/NRP-2 axis provides further insight into the process of tumor metastasis.

Preparation, Purification, and Identification of a Monoclonal Antibody Against NRP2 b1b2 Domain

First identified as a high-affinity kinase-deficient receptor for class-3 semaphorins and vascular endothelial growth factor (VEGF) families, Neuropilin2 (NRP2) is a transmembrane non-tyrosine-kinase glycoprotein that has a vital function in neuronal patterning. Furthermore, NRP2 expression is often upregulated in cancer tissues and correlated with poor prognosis. In the present study, we report the establishment of a monoclonal antibody specific for NRP2b1b2 domain (NRP2 MAb) through hybridoma method. NRP2 MAb is measured to have a titer of 5.12 × 10(5) against NRP2b1b2 in indirect ELISA. Western blotting, flow cytometry, and immunofluorescence analysis indicate that NRP2 MAb can combine full-length NRP2 in LoVo and SW480 cells. Besides helping further understand NRP2-related pathological mechanisms and cell-signaling pathways, NRP2 MAb may act as a therapeutic agent for cancer in the future.

Neuropilin-2 promotes extravasation and metastasis by interacting with endothelial α5 integrin

Metastasis, the leading cause of cancer death, requires tumor cell intravasation, migration through the bloodstream, arrest within capillaries, and extravasation to invade distant tissues. Few mechanistic details have been reported thus far regarding the extravasation process or re-entry of circulating tumor cells at metastatic sites. Here, we show that neuropilin-2 (NRP-2), a multifunctional nonkinase receptor for semaphorins, vascular endothelial growth factor (VEGF), and other growth factors, expressed on cancer cells interacts with α5 integrin on endothelial cells to mediate vascular extravasation and metastasis in zebrafish and murine xenograft models of clear cell renal cell carcinoma (RCC) and pancreatic adenocarcinoma. In tissue from patients with RCC, NRP-2 expression is positively correlated with tumor grade and is highest in metastatic tumors. In a prospectively acquired cohort of patients with pancreatic cancer, high NRP-2 expression cosegregated with poor prognosis. Through biochemical approaches as well as Atomic Force Microscopy (AFM), we describe a unique mechanism through which NRP-2 expressed on cancer cells interacts with α5 integrin on endothelial cells to mediate vascular adhesion and extravasation. Taken together, our studies reveal a clinically significant role of NRP-2 in cancer cell extravasation and promotion of metastasis.

Semaphorins in cancer: biological mechanisms and therapeutic approaches

The hallmarks of cancer include multiple alterations in the physiological processes occurring in normal tissues, such as cell proliferation, apoptosis, and restricted cell migration. These aberrant behaviors are due to genetic and epigenetic changes that affect signaling pathways controlling cancer cells, as well as the surrounding "normal" cells in the tumor microenvironment. Semaphorins and their receptors (mainly plexins and neuropilins) are aberrantly expressed in human tumors, and multiple family members are emerging as pivotal signals deregulated in cancer. Notably, different semaphorins can promote or inhibit tumor progression, depending on the implicated receptor complexes and responsive cell type. The important role of semaphorin signals in the regulation of tumor angiogenesis, invasion and metastasis has initiated multiple experimental approaches aimed at targeting these pathways to inhibit cancer.

Role of the VEGF/VEGFR axis in cancer biology and therapy

New vessel formation (angiogenesis) is an essential physiological process for embryologic development, normal growth, and tissue repair. Angiogenesis is tightly regulated at the molecular level; however, this process is dysregulated in several pathological conditions such as cancer. The imbalance between pro- and antiangiogenic signaling molecules within tumors creates an abnormal vascular network that is characterized by dilated, tortuous, and leaky vessels. The pathophysiological consequences of these vascular abnormalities include temporal and spatial heterogeneity in tumor blood flow, oxygenation, and increased tumor interstitial fluid pressure. The resultant microenvironment deeply impacts on tumor progression, and also leads to a reduction in therapy efficacy. The discovery of vascular endothelial growth factor (VEGF) as a major driver of tumor angiogenesis has led to efforts to develop novel therapeutics aimed at inhibiting its activity. Anti-VEGF therapy has become an important option for the management of several human malignancies; however, a significant number of patients do not respond to anti-VEGF therapy when used either as single agent or in combination with chemotherapy. In addition, the benefit of antiangiogenic therapy is relatively short lived and the majority of patients relapse and progress. An increasing amount of reports suggest several potential mechanisms of resistance to antiangiogenic therapy including, but not limited to, tumor hypoxia. This chapter discusses the role of the VEGF axis in tumor biology and highlights the clinical application of anti-VEGF therapies elaborating on pitfalls and strategies to improve clinical outcome.

Neuropilin signalling in angiogenesis

VEGFs (vascular endothelial growth factors) are master regulators of vascular development and of blood and lymphatic vessel function during health and disease in adults. This family of five mammalian ligands acts through three RTKs (receptor tyrosine kinases). In addition, co-receptors such as NRPs (neuropilins) associate with the ligand-receptor signalling complex and modulate the output. Therapeutics to block several of the VEGF signalling components as well as NRP function have been developed with the aim of halting blood vessel formation, angiogenesis, in diseases that involve tissue growth and inflammation, such as cancer. The present review outlines the current understanding of NRPs in relation to blood and lymphatic vessel biology.

Neuropilins: expression and roles in the epithelium

Initially found expressed in neuronal and then later in endothelial cells, it is well established that the transmembrane glycoproteins neuropilin-1 (NRP1) and neuropilin-2 (NRP2) play essential roles in axonal growth and guidance and in physiological and pathological angiogenesis. Neuropilin expression and function in epithelial cells has received little attention when compared with neuronal and endothelial cells. Overexpression of NRPs is shown to enhance growth, correlate with invasion and is associated with poor prognosis in various tumour types, especially those of epithelial origin. The contribution of NRP and its ligands to tumour growth and metastasis has spurred a strong interest in NRPs as novel chemotherapy drug targets. Given NRP's role as a multifunctional co-receptor with an ability to bind with disparate ligand families, this has sparked new areas of research implicating NRPs in diverse biological functions. Here, we review the growing body of research demonstrating NRP expression and role in the normal and neoplastic epithelium.

Neuropilin-2 expression in cancer

AIMS

Neuropilin-2 is a coreceptor for vascular endothelial growth factor family members. Blockade of neuropilin-2 is able to suppress lymphogenous metastasis in preclinical models. The aim of this study was to validate a protocol for the evaluation of neuropilin-2 protein expression in situ, by comparison with in-situ hybridization, western blotting, and mRNA expression levels.

METHODS AND RESULTS

Immunohistochemistry was performed on normal human tissues, and whole sections for 79 primary non-small-cell lung carcinomas, 65 primary breast carcinomas, 79 primary colorectal cancers, and 52 metastases. Neuropilin-2 expression was observed in lymphatic and blood vessels from all normal and malignant tissues examined. In addition, 32% of primary non-small-cell lung carcinomas, 15% of primary breast carcinomas and 22% of primary colorectal cancers showed tumour cell expression. Fifty-five primary and nine secondary malignant melanomas were also examined for neuropilin-2 expression by in-situ hybridization. All showed vascular expression, and 85% of primary malignant melanomas showed tumour cell expression.

CONCLUSIONS

In the majority of lung, breast and colorectal cancers, the effects of anti-neuropilin-2 are likely to be restricted to the vasculature. These results will assist in pharmacokinetic evaluations, tolerability assessments and the choice of setting to evaluate the activity of anti-neuropilin-2 therapies.

Neuropilin-2 mediated β-catenin signaling and survival in human gastro-intestinal cancer cell lines

NRP-2 is a high-affinity kinase-deficient receptor for ligands belonging to the class 3 semaphorin and vascular endothelial growth factor families. NRP-2 has been detected on the surface of several types of human cancer cells, but its expression and function in gastrointestinal (GI) cancer cells remains to be determined. We sought to determine the function of NRP-2 in mediating downstream signals regulating the growth and survival of human gastrointestinal cancer cells. In human gastric cancer specimens, NRP-2 expression was detected in tumor tissues but not in adjacent normal mucosa. In CNDT 2.5 cells, shRNA mediated knockdown NRP-2 expression led to decreased migration and invasion in vitro (p<0.01). Focused gene-array analysis demonstrated that loss of NRP-2 reduced the expression of a critical metastasis mediator gene, S100A4. Steady-state levels and function of β-catenin, a known regulator of S100A4, were also decreased in the shNRP-2 clones. Furthermore, knockdown of NRP-2 sensitized CNDT 2.5 cells in vitro to 5FU toxicity. This effect was associated with activation of caspases 3 and 7, cleavage of PARP, and downregulation of Bcl-2. In vivo growth of CNDT 2.5 cells in the livers of nude mice was significantly decreased in the shNRP-2 group (p<0.05). Intraperitoneal administration of NRP-2 siRNA-DOPC decreased the tumor burden in mice (p = 0.01). Collectively, our results demonstrate that tumor cell–derived NRP-2 mediates critical survival signaling in gastrointestinal cancer cells.

Neuropilin-2: a novel biomarker for malignant melanoma?

Neuropilin-2, a cell surface receptor involved in angiogenesis and axonal guidance, has recently been shown to be a critical mediator of tumor-associated lymphangiogenesis. Given that lymphangiogenesis is a major conduit of metastasis in melanomas and that blocking neuropilin-2 function in vivo is effective in inhibiting tumor cell metastasis, we sought to determine the clinical relevance of neuropilin-2 expression in cutaneous melanoma. Immunohistochemical analysis of neuropilin-2 expression was evaluated in nevomelanocytic proliferations that included a tissue microarray and histologic sections from samples of primary melanomas (n = 42; 40 for tissue microarray, 2 for histologic sections), metastatic melanomas (n = 30; 22 for tissue microarray, 8 for histologic sections), and nevi (n = 30; 5 for tissue microarray, 25 for histologic sections), as well as a panel of normal human tissues and select nonmelanocytic tumors. Staining for grading and intensity of neuropilin-2 expression was estimated semiquantitatively as follows for the former: less than 20%, 20% to 60%, and more than 60% of tissue present, and for the latter from 0 to 3, with 3 being the highest and 0 the lowest intensity. In nevomelanocytic proliferations, more than 20% staining for neuropilin-2 was noted in 36 (86%) of 42 cases of primary melanoma, in 27 (90%) of 30 cases of metastatic melanoma, and in 9 (30%) of 30 cases of nevi with differences achieving statistical significance between melanoma (primary and metastatic) and nevi (P < .0001). For staining intensity, an intensity of 2 or more was noted in 36 (86%) of 42 cases of primary melanoma, in 17 (57%) of 30 cases of metastatic melanoma and in 7 (30%) of 23 cases of nevi, with differences achieving statistical significance between melanoma (primary and metastatic) and nevi (P < .0001). In normal human tissue, consistently strong neuropilin-2 staining was noted in kidney (glomerular endothelial cells, collecting tubules, and collecting ducts), skin (epidermal keratinocytes), and testes (epithelium of the seminiferous tubules), whereas in tumoral tissue, consistently strong staining was noted only in renal cell carcinoma but not in any of the other tumors studied. More recently, using a heterotypic coculture methodology with melanoma and endothelial cells, we have demonstrated successful up-regulation of neuropilin-2 and confirmed the critical role of neuropilin-2 in melanoma-endothelial interactions. Because these coculture methods were developed to model melanoma metastasis, the significantly increased and enhanced expression of neuropilin-2 staining in primary and metastatic melanoma versus nevi in the current study suggests that it is also relevant in vivo.

Neuropilin-2 expression promotes TGF-β1-mediated epithelial to mesenchymal transition in colorectal cancer cells

Neuropilins, initially characterized as neuronal receptors, act as co-receptors for cancer related growth factors and were recently involved in several signaling pathways leading to cytoskeletal organization, angiogenesis and cancer progression. Then, we sought to investigate the ability of neuropilin-2 to orchestrate epithelial-mesenchymal transition in colorectal cancer cells. Using specific siRNA to target neuropilin-2 expression, or gene transfer, we first observed that neuropilin-2 expression endows HT29 and Colo320 for xenograft formation. Moreover, neuropilin-2 conferred a fibroblastic-like shape to cancer cells, suggesting an involvement of neuropilin-2 in epithelial-mesenchymal transition. Indeed, the presence of neuropilin-2 in colorectal carcinoma cell lines was correlated with loss of epithelial markers such as cytokeratin-20 and E-cadherin and with acquisition of mesenchymal molecules such as vimentin. Furthermore, we showed by surface plasmon resonance experiments that neuropilin-2 is a receptor for transforming-growth factor-β1. The expression of neuropilin-2 on colon cancer cell lines was indeed shown to promote transforming-growth factor-β1 signaling, leading to a constitutive phosphorylation of the Smad2/3 complex. Treatment with specific TGFβ-type1 receptor kinase inhibitors restored E-cadherin levels and inhibited in part neuropilin-2-induced vimentin expression, suggesting that neuropilin-2 cooperates with TGFβ-type1 receptor to promote epithelial-mesenchymal transition in colorectal cancer cells. Our results suggest a direct role of NRP2 in epithelial-mesenchymal transition and highlight a cross-talk between neuropilin-2 and TGF-β1 signaling to promote cancer progression. These results suggest that neuropilin-2 fulfills all the criteria of a therapeutic target to disrupt multiple oncogenic functions in solid tumors.

Neuropilins: a new target for cancer therapy

Recent investigations highlighted strong similarities between neural crest migration during embryogenesis and metastatic processes. Indeed, some families of axon guidance molecules were also reported to participate in cancer invasion: plexins/semaphorins/neuropilins, ephrins/Eph receptors, netrin/DCC/UNC5. Neuropilins (NRPs) are transmembrane non tyrosine-kinase glycoproteins first identified as receptors for class-3 semaphorins. They are particularly involved in neural crest migration and axonal growth during development of the nervous system. Since many types of tumor and endothelial cells express NRP receptors, various soluble molecules were also found to interact with these receptors to modulate cancer progression. Among them, angiogenic factors belonging to the Vascular Endothelial Growth Factor (VEGF) family seem to be responsible for NRP-related angiogenesis. Because NRPs expression is often upregulated in cancer tissues and correlated with poor prognosis, NRPs expression might be considered as a prognostic factor. While NRP1 was intensively studied for many years and identified as an attractive angiogenesis target for cancer therapy, the NRP2 signaling pathway has just recently been studied. Although NRP genes share 44% homology, differences in their expression patterns, ligands specificities and signaling pathways were observed. Indeed, NRP2 may regulate tumor progression by several concurrent mechanisms, not only angiogenesis but lymphangiogenesis, epithelial-mesenchymal transition and metastasis. In view of their multiples functions in cancer promotion, NRPs fulfill all the criteria of a therapeutic target for innovative anti-tumor therapies. This review focuses on NRP-specific roles in tumor progression.

Vascular endothelial growth factors and receptors: anti-angiogenic therapy in the treatment of cancer

Vascular endothelial growth factors (VEGFs) are critical regulators of vascular and lymphatic function during development, in health and in disease. There are five mammalian VEGF ligands and three VEGF receptor tyrosine kinases. In addition, several VEGF co-receptors that lack intrinsic catalytic activity, but that indirectly modulate the responsiveness to VEGF contribute to the final biological effect. This review describes the molecular features of VEGFs, VEGFRs and co-receptors with focus on their role in the treatment of cancer.

A fuller understanding of pancreatic neuroendocrine tumours combined with aggressive management improves outcome

BACKGROUND

Neuroendocrine tumours of the pancreas (PNETs) represent 1-2% of all pancreatic tumours. The terms 'islet cell tumours' and 'carcinoids' of the pancreas should be avoided. The aim of this review is to offer an overview of the history and diagnosis of PNETs followed by a discussion of the available treatment options.

METHODS

A search on PubMed using the keywords 'neuroendocrine', 'pancreas' and 'carcinoid' was performed to identify relevant literature over the last 30 years.

RESULTS

The introduction of a revised classification of neuroendocrine tumours by the World Health Organisation (WHO) in 2000 significantly changed our understanding of and approach to the management of these tumours. Advances in laboratory and radiological techniques have also led to an increased detection of PNETs. Surgery remains the only treatment that offers a chance of cure with increasing number of non-surgical options serving as beneficial adjuncts. The better understanding of the behaviours of PNETs together with improvements in tumour localisation has resulted in a more aggressive management strategy with a concomitant improvement in symptom palliation and a prolongation of survival.

CONCLUSION

Due to their complex nature and the wide range of therapeutic options, the involvement of specialists from all necessary disciplines in a multidisciplinary team setting is vital to provide optimal treatment of this disease.

Neuropilins: structure, function and role in disease

NRPs (neuropilins) are co-receptors for class 3 semaphorins, polypeptides with key roles in axonal guidance, and for members of the VEGF (vascular endothelial growth factor) family of angiogenic cytokines. They lack a defined signalling role, but are thought to mediate functional responses as a result of complex formation with other receptors, such as plexins in the case of semaphorins and VEGF receptors (e.g. VEGFR2). Mutant mouse studies show that NRP1 is essential for neuronal and cardiovascular development, whereas NRP2 has a more restricted role in neuronal patterning and lymphangiogenesis, but recent findings indicate that NRPs may have additional biological roles in other physiological and disease-related settings. In particular, NRPs are highly expressed in diverse tumour cell lines and human neoplasms and have been implicated in tumour growth and vascularization in vivo. However, despite the wealth of information regarding the probable biological roles of these molecules, many aspects of the regulation of cellular function via NRPs remain uncertain, and little is known concerning the molecular mechanisms through which NRPs mediate the functions of their various ligands in different cell types.

Targeting angiogenesis in pancreatic cancer: rationale and pitfalls

INTRODUCTION

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive cancer responsible for over 20% of deaths due to gastrointestinal malignancies. PDAC is usually diagnosed at an advanced stage which, in part, helps to explain its high resistance to chemotherapy and radiotherapy. In addition, the cancer cells in PDAC have a high propensity to metastasize and to aberrantly express several key regulators of angiogenesis and invasion. Chemotherapy has only provided a modest impact on mean survival and often induces side effects. Targeting angiogenesis alone or in combination with other modalities should be investigated to determine if it may provide for increased survival.

MATERIALS AND METHODS

This review summarizes the alterations in PDAC that play a critical role in angiogenesis and provides an overview of current and therapeutic strategies that may be useful for targeting angiogenesis in this malignancy.

Functional significance of vascular endothelial growth factor receptors on gastrointestinal cancer cells

Vascular endothelial growth factor (VEGF) has been shown to be the major mediator of physiologic and pathologic angiogenesis. VEGF was initially thought to be an endothelial cell specific ligand, but recently, VEGF has been shown to mediate tumor cell function via activation of receptors on tumor cells themselves. Here, we review the expression patterns and binding profiles of the VEGF receptors and their ligands on gastrointestinal tumor cells. Furthermore, we describe the current knowledge in regards to the function of these receptors on tumor cells. Elucidating the function of VEGF receptors on tumor cells should help us to better understand the potential mechanisms of action of anti-VEGF therapies.

The direct effects of anti-vascular endothelial growth factor therapy on tumor cells

The vascular endothelial growth factor (VEGF) family members are essential mediators of tumor angiogenesis. The multiple functions of the VEGFs are mediated through complex interactions between their ligands, the high-affinity tyrosine kinase receptors, and co-receptors (neuropilins). Emerging evidence has shown that these receptors, formerly described as being exclusively expressed on endothelial cells, are also expressed on a number of nonendothelial cells, including tumor cells. Moreover, it has been shown that their receptors (VEGFRs) are functional in a number of nonendothelial systems, where they can serve as targets for anti-VEGF therapy. As the expression of VEGFRs on tumor cells contributes to the understanding of the complex roles of VEGF within the tumor microenvironment and elucidation of VEGF activity might further refine antineoplastic regimens, this article will review the main effects and selective interactions of the VEGFRs, the evidence for their expression and function on tumor cells, and the direct efforts of anti-VEGF therapy on tumor cells.

Polysialylated Neuropilin-2 Is Expressed on the Surface of Human Dendritic Cells and Modulates Dendritic Cell-T Lymphocyte Interactions

Polysialic acid (PSA) is a unique linear homopolymer of alpha2,8-linked sialic acid that has been identified as a posttranslational modification on only five mammalian proteins. Studied predominantly on neural cell adhesion molecule (NCAM) during development of the vertebrate nervous system, PSA modulates cell interactions mediated by NCAM and other adhesion molecules. An isoform of NCAM (CD56) on natural killer (NK) cells is the only protein known to be polysialylated in cells of the immune system, yet the function of PSA in NK cells remains unclear. We show here that neuropilin-2 (NRP-2), a receptor for the semaphorin and vascular endothelial growth factor families in neurons and endothelial cells, respectively, is expressed on the surface of human dendritic cells and is polysialylated. Expression of NRP-2 is up-regulated during dendritic cell maturation, coincident with increased expression of ST8Sia IV, one of the key enzymes of PSA biosynthesis, and with the appearance of PSA on the cell surface. PSA on NRP-2 is resistant to digestion with peptide N-glycosidase F but is sensitive to release under alkaline conditions, suggesting that PSA chains are added to O-linked glycans of NRP-2. Removal of polysialic acid from the surface of dendritic cells or binding of NRP-2 with specific IgG promoted dendritic cell-induced activation and proliferation of T lymphocytes. Thus, this newly recognized polysialylated protein on the surface of dendritic cells influences dendritic cell-T lymphocyte interactions through one or more of its distinct extracellular domains.

Targeting endothelial and tumor cells with semaphorins

Neuropilins (NRP) are receptors for the class 3 semaphorin (SEMA3) family of axon guidance molecules and the vascular endothelial growth factor (VEGF) family of angiogenesis factors. Although the seminal studies on SEMA3s and NRPs first showed them to be mediators of axon guidance, it has become very apparent that these proteins play an important role in vascular and tumor biology as well. Neuronal guidance and angiogenesis are regulated similarly at the molecular level. For example, SEMA3s not only repel neurons and collapse axon growth cones, but have similar effects on endothelial cells and tumor cells. Preclinical studies indicate that SEMA3F is a potent inhibitor of tumor angiogenesis and metastasis. In addition, neutralizing antibodies to NRP1 enhance the effects of anti-VEGF antibodies in suppressing tumor growth in xenograft models. This article reviews NRP and SEMA3 structural interactions and their role in developmental angiogenesis, tumor angiogenesis and metastasis based on cell culture, zebrafish and murine studies.

Islet Cell Carcinoma: Neuroendocrine Tumors of the Pancreas and Periampullary Region

Most patients who have islet cell tumors, except those who have insulinomas, present with locally advanced or metastatic disease. In contrast with patients who have adenocarcinoma of the pancreas, those who have islet cell carcinomas can achieve long-term survival even if their disease is advanced. Liver-directed therapies, somatostatin analogs, and interferon are not curative but can be used to relieve tumor-associated symptoms. Similarly, palliative chemotherapy has been used with limited success. Advances in our understanding of the molecular mechanisms underlying tumor progression have translated into intense interest in biologically based strategies to treat this disease.

Neuropilins in physiological and pathological angiogenesis

Neuropilin-1 (Np1) and neuropilin-2 (Np2) are transmembrane glycoproteins with large extracellular domains that interact with both class 3 semaphorins and vascular endothelial growth factor (VEGF), and are involved in the regulation of many physiological pathways, including angiogenesis. The neuropilins also interact directly with the classical receptors for VEGF, VEGF-R1 and -R2, mediating signal transduction. The heart, glomeruli and osteoblasts express both Np1 and Np2, but there is differential expression in the adult vasculature, with Np1 expressed mainly by arterial endothelium, whereas Np2 is only expressed by venous and lymphatic endothelium. Both neuropilins are commonly over-expressed in regions of physiological (wound-healing) and pathological (tumour) angiogenesis, but the signal transduction pathways, neuropilin-mediated gene expression and the definitive role of neuropilins in angiogenic processes are not fully characterized. This review details the current evidence for the role of neuropilins in angiogenesis, and suggests future research directions that may enhance our understanding of the mechanisms of action of this unique family of proteins.

Neuropilins in neoplasms: expression, regulation, and function

Neuropilins (NRP) are membranous receptors capable of binding two disparate ligands, class 3 semaphorins (SEMA) and vascular endothelial growth factors (VEGF), and regulating two diverse systems, neuronal guidance and angiogenesis. The neuropilin genes, NRP1 and NRP2, share similar protein structure, but differ in their expression patterns, regulation, and ligand-binding specificities. NRPs vary in their expression patterns; for example, endothelial cells express both NRP1 and NRP2, lymphatic endothelial cells predominantly express NRP2, and epidermal cells predominantly express NRP1. NRP expression can be differentially regulated by transcription factors, e.g. prox-1 induces NRP2 while suppressing NRP1, or by growth factors, e.g. epidermal growth factor (EGF) induces NRP1 but not NRP2. Nearly all tumor cells express NRP1, NRP2, or both. Carcinomas express NRP1, whereas neuronal tumors and melanomas predominantly express NRP2. SEMAs play a role in neoplasms as angiogenesis inhibitors. For example, SEMA3F, which binds specifically to NRP2, inhibits tumor angiogenesis and metastasis. Metastatic tumor cells lose SEMA3F expression during progression. Therefore, SEMA3F may have therapeutic potential. This article focuses on the role of NRPs and SEMAs in tumor progression and angiogenesis.

Genes involved in neuroendocrine tumor biology

The fascinating, but often unpredictable, biology of neuroendocrine tumors (NETs) make the management of these malignancies a real challenge. The more recent development of high-throughput genomic and proteomic techniques, have opened a window to an increased knowledge of the biology of NETs. This review will discuss genes thought to play a role in the context of NE tumor biology, with particularly attention to those that may be potential new diagnostic and prognostic markers, as well as therapeutic targets. NETs constitute a heterogeneous group of neoplasm that may arise in virtually every topographic localization in the body, as a consequence of malignant transformation of various types of NE cells. Since NETs arising in the gastroenteropancreatic (GEP) or bronchopulmonary system are by far the most common, this review focuses on these entities, but lines are drawn to other NETs as well. Although large-scale gene expression analysis undoubtly have raised interesting new hypothesis concerning genes thought to play a role in tumor biology, discrepancies observed between studies and various platforms used, emphasizes the need to not only standardize the way microarray data are reported, but also to introduce standards in sample taking, processing and study design. In addition, the recognition of the complexity of the human proteome, with regard to generation of multiple isoforms from one gene, has created additional challenges. However,some goals have been reached already, as new knowledge has been translated into development of novel promising therapeutics.

Roles of neuropilins in neuronal development, angiogenesis, and cancers

Neuropilin-1 (NRP1) and neuropilin-2 (NRP2) are transmembrane glycoproteins that have been characterized as receptors for both semaphorins for neuronal guidance and vascular endothelial growth factor (VEGF) for angiogenesis. Biologic properties of NRPs have been linked to their unique domain structures. However, molecular interaction among NRPs, VEGF, and VEGF receptors is still not clear. Although several types of cancer cells can express NRPs, the role of NRPs in tumor pathogenesis is largely unknown. Thus, future investigations should include determining the effects and mechanisms of NRPs on proliferation, apoptosis, and migration of neuronal , endothelial, and cancer cells. Study of protein-protein interaction, signal transduction pathways, and NRP-mediated gene expression is particularly important to understand NRPs functions, which may have significant clinical applications in the treatment of neurological disorders, cardiovascular diseases, and certain cancers.

Association between endocrine pancreas and ductal system. More than an epiphenomenon of endocrine differentiation and development?

Traditional histological descriptions of the pancreas distinguish between the exocrine and the endocrine pancreas, as if they were two functionally distinct glands. This view has been proven incorrect and can be considered obsolete. Interactions between acinar and islet tissues have been well established through numerous studies that reveal the existence of anatomical and functional relationships between these compartments of the gland. Less attention, however, has traditionally been paid to the relationships occurring between the endocrine pancreas and the ductal system. Associations between islet tissue and ducts are considered by most researchers as only a transient epiphenomenon of endocrine development. This article reviews the evidence that has emerged in the last 10 years demonstrating the existence of stable, close, and systematic relationships between these two pancreatic compartments. Functional and pathophysiological implications are considered, and the existence of an "acinar-duct-islet" axis is put forward. The pancreas appears at present to be an integrated organ composed of three functionally related components of well-orchestrated endocrine and exocrine physiological responses.

Peanut-like 1 (septin 5) gene expression in normal and neoplastic human endocrine pancreas

Peanut-like 1 (PNUTL1) is a septin gene which is expressed at high levels in human brain. There it plays a role in the process of membrane fusion during exocytosis by interacting with syntaxin and synaptophysin. As the secretory apparatus of pancreatic islet cells closely resembles that of neurons, we decided to study the expression of PNUTL1 in the human endocrine pancreas, both in normal islets and in pancreatic endocrine tumors (PETs). Normal pancreatic tissue, purified islets, 11 PETs and two cell lines were used to evaluate the presence of PNUTL1 by RT-PCR and Western blot. The expression of the PNUTL1 protein was also evaluated by immunohistochemistry on normal pancreas, additional 26 PETs, eight pancreatic adenocarcinomas, one mixed endocrine-exocrine pancreatic neoplasm, a specimen of solid papillary pseudomucinous tumor, an adult islet cell hyperplasia and a case of neonatal nesidioblastosis. In addition, a tissue array (LandMark High Density Cancer Tissue MicroArray) comprising 280 various tumor and matched normal specimens was utilized. In PETs, the expression of pancreatic hormones, chromogranin-A, synaptophysin and Ki-67 were also evaluated. In the normal pancreas PNUTL1 expression is almost exclusively confined to the islet cells, weak expression was occasionally seen in some acinar cells, while immunoreactivity was completely absent in the ductal epithelia. PNUTL1 expression is maintained at similar high levels in hyperplastic and neoplastic islet cells, but this did not correlate with any of the clinicopathological data nor with proliferation status in PETs. Weak immunoreactivity was also noted in a proportion of exocrine neoplasms. Our findings describe for the first time the high expression levels of PNUTL1 in human pancreatic endocrine cells that suggests a similar role of this protein in islet cells to that demonstrated in neuronal tissues, and warrants further functional studies of this protein.

Neuroendocrine cell markers for pancreatic islets and tumors

The authors review the application of a variety of neuroendocrine cell markers to identify pancreatic islet cells and tumors. In the past, several empiric histochemical techniques had been used to demonstrate neuroendocrine cells, particularly the Grimelius argyrophilic stain. The development of immunohistochemistry made it possible to demonstrate specific cell products such as regulatory peptides, thus allowing the classification of pancreatic neuroendocrine tumors with a view to clinical symptoms. However, it is not always possible to visualize regulatory peptides in these tumors. It is therefore important to use broad-spectrum neuroendocrine cell markers to identify the neuroendocrine nature. These markers are proteins localized in the secretory granules (core- or membrane-related), in the cytosol, or in the cellular membrane. The markers most commonly used in routine histopathology are the secretory granule proteins chromogranin A and synaptophysin and the cytosolic enzyme neuronspecific enolase. Other new markers (e.g., synaptic vesicle protein 2) are of general diagnostic value. Region-specific antibodies to chromogranin A can be valuable in differentiating between benign and malignant neuroendocrine tumors. Some markers may be related to the functioning characteristics of pancreatic neuroendocrine tumors, such as prohormone convertases. In addition, markers giving further complementary information have been identified, such as five somatostatin receptor subtypes, the expression of which varies markedly in pancreatic neuroendocrine tumors. Antibodies against all somatostatin receptor subtypes are now commercially available, and immunohistochemical investigation of its expression should be routinely applied when considering treatment with somatostatin analogs.

Aberrant expression of neuropilin-1 and -2 in human pancreatic cancer cells

PURPOSE

Neuropilin (Np)-1 and -2 are coreceptors for vascular endothelial growth factor (VEGF). This study was designed to assess their role in pancreatic ductal adenocarcinoma (PDAC).

EXPERIMENTAL DESIGN

We assessed Np-1 and Np-2 expression by real-time quantitative PCR in relation to the expression of VEGF ligands and receptors in pancreatic cancer cell lines and tissues.

RESULTS

ASPC-1, CAPAN-1, and PANC-1 pancreatic cancer cells and tumor-derived, laser-captured pancreatic cancer cells exhibited higher Np-1 and Np-2 mRNA levels than VEGF receptor-1, -2, or -3 mRNA levels. Transfection of Np-1 and Np-2 cDNAs in COS-7 cells, and treatment with tunicamycin revealed that both proteins were glycosylated. Both proteins were expressed in pancreatic cancer cell lines, in the PDAC samples, and in acinar cells adjacent to the cancer cells. The normal pancreas was devoid of Np-1 immunoreactivity, whereas Np-2 immunoreactivity was present in the endocrine islets and in some acinar cells, but not in ductal cells.

CONCLUSIONS

The aberrant localization of Np-1 and Np-2 in the cancer cells in PDAC suggests that in addition to exerting proangiogenic effects, these coreceptors may contribute to novel autocrine-paracrine interactions in this malignancy.

Pancreatic carcinoma cells express neuropilins and vascular endothelial growth factor, but not vascular endothelial growth factor receptors

BACKGROUND

Neuropilins (NRPs) are characterized as coreceptors of vascular endothelial growth factor (VEGF). In the current study, the authors assessed the expression of NRPs, VEGF, and vascular endothelial growth factor receptors (VEGFRs), as well as VEGF-induced cell proliferation, in pancreatic carcinoma cell lines and tissue specimens.

METHODS

Human pancreatic carcinoma cell lines (Panc-1 and MIA PaCa-2), normal human pancreatic ductal epithelial cells (HPDE), and human umbilical vein endothelial cells (HUVECs) were cultured. Human pancreatic adenocarcinoma tissue specimens were also studied. Expression levels of NRPs, VEGFRs, and VEGF were determined by real-time polymerase chain reaction analysis and immunostaining. Cell proliferation was examined using a [3H]thymidine incorporation assay.

RESULTS

Both NRP-1 and NRP-2 were expressed in Panc-1 cells, HPDE cells, and HUVECs but were expressed minimally in MIA PaCa-2 cells. Panc-1 expressed 30 times more NRP-1 mRNA than NRP-2 mRNA. NRP-1 levels in Panc-1 cells were 5.3 times higher than in HPDE cells but were similar to NRP-1 levels in HUVECs. NRP-2 levels in Panc-1 cells were similar to NRP-2 levels in HPDE cells but lower than NRP-2 levels in HUVECs. Expression of all three VEGFRs was observed only in HUVECs. However, VEGF mRNA was detected in all cell types except for HUVECs. NRP-1 immunoreactivity levels were much higher than NRP-2 immunoreactivity levels in Panc-1 and human pancreatic adenocarcinoma tissue specimens, whereas VEGFRs were not detected in either of these two settings. In response to VEGF165, [3H]thymidine incorporation in Panc-1 cells increased significantly (by 61%; P < 0.01). A monoclonal antibody against human NRP-1 significantly blocked VEGF-induced cell proliferation in Panc-1 cells.

CONCLUSIONS

The pancreatic carcinoma cell line Panc-1 and adenocarcinoma tissue specimens expressed high levels of NRP-1 and VEGF, but not VEGFRs, and exogenous VEGF significantly increased NRP-1-mediated, but not VEGFR-mediated, Panc-1 cell proliferation. These data suggested that NRP-1 may be involved in the pathogenesis of pancreatic carcinoma.