Targeting endothelial and tumor cells with semaphorins

Role of Semaphorins, neuropilins and plexins in cancer progression

Progress in understanding nervous system-cancer interconnections has emphasized the functional role of semaphorins (SEMAs) and their receptors, neuropilins (NRPs) and plexins (PLXNs), in cancer progression. SEMAs are a conserved and extensive family of broadly expressed soluble and membrane-associated proteins that were first described as regulators of axon guidance and neural and vascular development. However, recent advances have shown that they can have a dual role in cancer progression, acting either as tumor promoters or suppressors. SEMAs effects result from their interaction with specific co-receptors/receptors NRPs/PLXNs, that have also been described to play a role in cancer progression. They can influence both cancer cells and tumor microenvironment components modulating various aspects of tumorigenesis such as oncogenesis, tumor growth, invasion and metastatic spread or treatment resistance. In this review we focus on the role of these axon guidance signals and their receptors and co/receptors in various aspects of cancer. Furthermore, we also highlight their potential application as novel approaches for cancer treatment in the future.

Semaphorins in tumor microenvironment: Biological mechanisms and therapeutic progress

Hallmark features of the tumor microenvironment include immune cells, stromal cells, blood vessels, and extracellular matrix (ECM), providing a conducive environment for the growth and survival of tumors. Recent advances in the understanding of cancer biology have highlighted the functional role of semaphorins (SEMAs). SEMAs are a large and diverse family of widely expressed secreted and membrane-binding proteins, which were initially implicated in axon guidance and neural development. However, it is now clear that they are widely expressed beyond the nervous system and participate in regulating immune responses and cancer progression. In fact, accumulating evidence disclosed that different SEMAs can either stimulate or restrict tumor progression, some of which act as important regulators of tumor angiogenesis. Conversely, limited information is known about the functional relevance of SEMA signals in TME. In this setting, we systematically elaborate the role SEMAs and their major receptors played in characterized components of TME. Furthermore, we provide a convergent view of current SEMAs pharmacological progress in clinical treatment and also put forward their potential application value and clinical prospects in the future.

Neuropilin 2 Is a Novel Regulator of Distal Colon Contractility

Appropriate coordination of smooth muscle contraction and relaxation is essential for normal colonic motility. The impact of perturbed motility ranges from moderate, in conditions such as colitis, to potentially fatal in the case of pseudo-obstruction. The mechanisms underlying aberrant motility and the extent to which they can be targeted pharmacologically are incompletely understood. This study identified colonic smooth muscle as a major site of expression of neuropilin 2 (Nrp2) in mice and humans. Mice with inducible smooth muscle-specific knockout of Nrp2 had an increase in evoked contraction of colonic rings in response to carbachol at 1 and 4 weeks following initiation of deletion. KCl-induced contractions were also increased at 4 weeks. Colonic motility was similarly enhanced, as evidenced by faster bead expulsion in Nrp2-deleted mice versus Nrp2-intact controls. In length-tension analysis of the distal colon, passive tension was similar in Nrp2-deficient and Nrp2-intact mice, but at low strains, active stiffness was greater in Nrp2-deficient animals. Consistent with the findings in conditional Nrp2 mice, Nrp2-null mice showed increased contractility in response to carbachol and KCl. Evaluation of selected proteins implicated in smooth muscle contraction revealed no significant differences in the level of α-smooth muscle actin, myosin light chain, calponin, or RhoA. Together, these findings identify Nrp2 as a novel regulator of colonic contractility that may be targetable in conditions characterized by dysmotility.

Epigenetic Dysregulations in Arsenic-Induced Carcinogenesis

Arsenic is a crucial environmental metalloid whose high toxicity levels negatively impact human health. It poses significant health concerns to millions of people in developed and developing countries such as the USA, Canada, Bangladesh, India, China, and Mexico by enhancing sensitivity to various types of diseases, including cancers. However, how arsenic causes changes in gene expression that results in heinous conditions remains elusive. One of the proposed essential mechanisms that still has seen limited research with regard to causing disease upon arsenic exposure is the dysregulation of epigenetic components. In this review, we have extensively summarized current discoveries in arsenic-induced epigenetic modifications in carcinogenesis and angiogenesis. Importantly, we highlight the possible mechanisms underlying epigenetic reprogramming through arsenic exposure that cause changes in cell signaling and dysfunctions of different epigenetic elements.

Argonaute-2 protects the neurovascular unit from damage caused by systemic inflammation

BACKGROUND

The brain vasculature plays a pivotal role in the inflammatory process by modulating the interaction between blood cells and the neurovascular unit. Argonaute-2 (Ago2) has been suggested as essential for endothelial survival but its role in the brain vasculature or in the endothelial-glial crosstalk has not been addressed. Thus, our aim was to clarify the significance of Ago2 in the inflammatory responses elicited by these cell types.

METHODS

Mouse primary cultures of brain endothelial cells, astrocytes and microglia were used to evaluate cellular responses to the modulation of Ago2. Exposure of microglia to endothelial cell-conditioned media was used to assess the potential for in vivo studies. Adult mice were injected intraperitoneally with lipopolysaccharide (LPS) (2 mg/kg) followed by three daily intraperitoneal injections of Ago2 (0.4 nM) to assess markers of endothelial disruption, glial reactivity and neuronal function.

RESULTS

Herein, we demonstrated that LPS activation disturbed the integrity of adherens junctions and downregulated Ago2 in primary brain endothelial cells. Exogenous treatment recovered intracellular Ago2 above control levels and recuperated vascular endothelial-cadherin expression, while downregulating LPS-induced nitric oxide release. Primary astrocytes did not show a significant change in Ago2 levels or response to the modulation of the Ago2 system, although endogenous Ago2 was shown to be critical in the maintenance of tumor necrosis factor-α basal levels. LPS-activated primary microglia overexpressed Ago2, and Ago2 silencing contained the inflammatory response to some extent, preventing interleukin-6 and nitric oxide release. Moreover, the secretome of Ago2-modulated brain endothelial cells had a protective effect over microglia. The intraperitoneal injection of LPS impaired blood-brain barrier and neuronal function, while triggering inflammation, and the subsequent systemic administration of Ago2 reduced or normalized endothelial, glial and neuronal markers of LPS damage. This outcome likely resulted from the direct action of Ago2 over the brain endothelium, which reestablished glial and neuronal function.

CONCLUSIONS

Ago2 could be regarded as a putative therapeutic agent, or target, in the recuperation of the neurovascular unit in inflammatory conditions.

Vascular endothelial growth factor/semaphorin-3A ratio and SEMA3A expression in cutaneous malignant melanoma

Breslow thickness and Clark level are still important factors for cutaneous melanoma, but do not provide a precise prognosis in all cases. It is necessary to find new factors capable of a more accurate prediction of the tumor course. Angiogenesis is essential for tumor development and progression and is regulated by vascular endothelial growth factor A (VEGF-A) and semaphorins (SEMA), in particular, SEMA3A inhibits angiogenesis by affecting VEGF signaling. However, the prognostic role of angiogenetic factors remains unclear. To date, no information is available on SEMA3A in human melanoma. Microvessel density, immunohistochemical and mRNA VEGF and SEMA3A expression level in 60 thin (Breslow thickness ≤ 1.0 mm), 60 intermediate (1.1-4.0 mm) and 50 thick (>4.0 mm) primary human cutaneous melanomas were investigated and related to clinical/pathological parameters and disease-specific survival. No positive association between Breslow thickness, Clark level, metastasis presence and survival was identified; Clark level was poorly related to survival. VEGF and microvessel density were significantly higher in intermediate and thick melanomas and related to Breslow thickness and Clark level but not to metastasis status and survival. On the contrary, SEMA3A was significantly reduced in intermediate and thick melanomas and associated to metastasis and poor survival. VEGF/SEMA3A ratio was higher in the worst prognosis, resulting the most closely related factor with metastasis and survival. SEMA3A expression and VEGF/SEMA3A ratio turned out to be valuable prognostic biomarkers in patients affected by cutaneous melanoma, in particular with Breslow thickness >1 mm. SEMA3A might serve as a candidate tumor suppressor in cutaneous melanoma therapy.

Overexpression of Semaphorin 3A is a Marker Associated with Poor Prognosis in Patients with Nasopharyngeal Carcinoma

Semaphorins were discovered as guidance signals that mediate neural development. Recent studies suggest that semaphorin 3A (Sema3A), a member of the semaphorin family, is involved in the development of several cancers. This study aimed to analyze the association of Sema3A with the clinical features of nasopharyngeal carcinoma (NPC), an Epstein–Barr virus-associated carcinoma, and the Epstein–Barr virus primary oncogene latent membrane protein 1 (LMP1). The expression of Sema3A and LMP1 was immunohistochemically examined in the 35 NPC specimens. The mean expression scores for Sema3A and LMP1 were 20.8% ± 14.5% and 13.9% ± 14.8%, respectively. The expression of Sema3A significantly correlated with that of LMP1 (r = 0.41, p = 0.014). In addition, the Sema3A high cohort showed significantly poorer prognosis than the Sema3A low cohort. Sema3A expression was higher in the LMP1-positive KH-1 and KR-4 cell lines compared to the LMP1-negative HeLa cells. Overexpression of LMP1 in the LMP1-negative AdAH cell line upregulated Sema3A expression, both at the transcriptional and translational level. Finally, Sema3A expression was associated with poor prognosis in patients with NPC. Our data suggest that LMP1 induces the expression of Sema3A, which may promote tumor progression in NPC.

Changes in Expression Pattern of SEMA3F Depending on Endometrial Cancer Grade - Pilot Study

Background:

In the course of neoplastic diseases, a reduction in SEMA3F expression is observed, which translates into an increase in the proliferative and proangiogenic potential of cells forming the tumor and the surrounding microenvironment.

Objective:

The aim of this study was to determine the changes in SEMA3F level in endometrial cancer depending on its grade.

Methods:

The study material consisted of tissue samples: 15 without neoplastic changes (control group) and 45 with endometrial cancer (G1, 17; G2, 15; G3, 13; study group). SEMA3F expression was assessed using the immune-histochemical method.

Results:

The expression of SEMA3F was observed in the control group (Me = 159.38) and in the study group (G1, Me = 121.32; G2, Me = 0; G3, Me = 130.37). Differences between each grade and control and between individual grades were statistically significant. There were no significant correlations between SEMA3F expression and weight and Body Mass Index (BMI). The reduced SEMA3F expression in tumor tissue compared to healthy tissue indicates that this protein plays key roles in proliferation and angiogenesis.

Conclusion:

We found that depending on the severity of the disease, cancer adopts different survival strategies, where SEMA3F plays an important role. As a molecular marker, SEMA3F is not sensitive to weight and BMI.

Semaphorin 3F Modulates Corneal Lymphangiogenesis and Promotes Corneal Graft Survival

Purpose

Corneal vascularization significantly increases the risk for graft rejection after keratoplasty. Semaphorin 3F (Sema3F) is a known modulator of physiologic avascularity in the outer retina. The aim of this study was to investigate whether Sema3F is involved in maintaining corneal avascularity and can reduce the risk for corneal graft rejection.

Methods

Corneal Sema3F expression was investigated using immunohistochemistry and qPCR in human and murine tissue. Pathologic invasion of blood and lymph vessels into corneal tissue was analyzed in the murine corneal suture and high-risk keratoplasty model. The anti-lymphangiogenic effects of Sema3F were further investigated using an in vitro spheroidal sprouting model with supernatant from isolated primary human corneal epithelial cells (hCECs).

Results

Sema3F is constitutively expressed in human and murine corneal epithelium. In the corneal suture model, lymphangiogenesis was significantly suppressed by topical Sema3F treatment (P = 0.0003). In the murine high-risk keratoplasty model, pretreatment by topical Sema3F in the inflammation phase significantly promoted subsequent graft survival (P = 0.0006). In this model, both lymph- and blood angiogenesis were reduced (P < 0.05). In vitro, hCEC supernatant had a direct anti-lymphangiogenic effect on human lymphatic endothelial cells (P < 0.01). This effect was completely abolished by addition of anti-Sema3F antibodies.

Conclusions

Sema3F is a novel mediator of corneal avascularity with potent anti-lymphangiogenic properties. Topical treatment with Sema3F eye drops may help to limit corneal vascularization and improve outcomes in high-risk keratoplasty patients.

GIPC proteins negatively modulate Plexind1 signaling during vascular development

Semaphorins (SEMAs) and their Plexin (PLXN) receptors are central regulators of metazoan cellular communication. SEMA-PLXND1 signaling plays important roles in cardiovascular, nervous, and immune system development, and cancer biology. However, little is known about the molecular mechanisms that modulate SEMA-PLXND1 signaling. As PLXND1 associates with GIPC family endocytic adaptors, we evaluated the requirement for the molecular determinants of their association and PLXND1's vascular role. Zebrafish that endogenously express a Plxnd1 receptor with a predicted impairment in GIPC binding exhibit low penetrance angiogenesis deficits and antiangiogenic drug hypersensitivity. Moreover, gipc mutant fish show angiogenic impairments that are ameliorated by reducing Plxnd1 signaling. Finally, GIPC depletion potentiates SEMA-PLXND1 signaling in cultured endothelial cells. These findings expand the vascular roles of GIPCs beyond those of the Vascular Endothelial Growth Factor (VEGF)-dependent, proangiogenic GIPC1-Neuropilin 1 complex, recasting GIPCs as negative modulators of antiangiogenic PLXND1 signaling and suggest that PLXND1 trafficking shapes vascular development.

Expression of semaphorin class 3 is higher in the proliferative phase on the human endometrium

PURPOSE

The semaphorins are related to angiogenesis and cell proliferation depending on the tissue. The purpose of this study was to assess gene expression of class 3 semaphorin (SEMA3A-F) and protein expression of semaphorin 3A (SEMA3A) within human endometrium throughout the menstrual cycle.

METHODS

Gene expression of SEMA3A-F was analyzed by real-time PCR (qRT-PCR) and protein expression of SEMA3A was analyzed by ELISA in endometrial biopsies in the proliferative and secretory phase of the menstrual cycle.

RESULTS

Gene expression of SEMA3A, SEMA3C, SEMA3D, and SEMA3E was statistically significant decreased in secretory compared to proliferative phase endometrium (p < 0.05). Accordingly, SEMA3A protein expression in the secretory phase was lower than protein expression in proliferative phase endometrium (p ≤ 0.05).

CONCLUSION

SEMA3A, 3C, 3D, and 3E are possibly related to cell proliferation in the endometrium, being more expressed in the proliferative phase of the cycle. This finding may stimulate studies of class 3 semaphorins as a possible target for treatment of endometrial pathologies.

Neuropilin-2 promotes melanoma growth and progression in vivo

Tumor cell interactions with their microenvironment, and neighboring endothelial cells in particular, are critical for tumor cell survival and the metastatic process. Within the spectrum of tumors, melanomas are notorious for their ability to metastasize at a relatively early stage of development; however, little is known about the molecular pathways mediating this process. We recently performed a screen to assess critical mediators of melanoma metastasis by evaluating melanoma-endothelial cell communication. Neuropilin-2 (NRP2), a cell surface receptor involved in angiogenesis and axonal guidance, was found to be an important mediator of melanoma-endothelial cell cross-talk in these studies. Here we seek to further define the role of NRP2 in melanoma growth and progression. We use stable gene silencing of NRP2 in melanomas from varying stages of tumor progression to define the role of NRP2 in melanoma growth, migration, invasion, and metastasis. We found that NRP2 gene silencing in metastatic melanoma cell lines inhibited tumor cell growth in vitro; furthermore, knockdown of NRP2 expression in the metastatic melanoma cell line 1205Lu significantly inhibited in-vivo tumor growth and metastasis. We conclude that NRP2 plays an important role in mediating melanoma growth and metastasis and suggest that targeting this cell surface molecule may represent a significant therapeutic strategy for patients diagnosed with aggressive forms of melanoma.

Preparation, Purification, and Identification of a Monoclonal Antibody Against the C-Terminal Domain of Semaphorin3F

Class three semaphorins were originally identified as mediators of axon guidance, which repelled axons and collapsed growth cones. As a member of class three semaphorins, semaphorin3F (Sema3F) has been found to have similar effects on tumor cells and endothelial cells and also is implicated in the signaling of tumor metastasis by forming a complex with neuropilins and plexins. In this study, our laboratory produced a monoclonal antibody against the C-terminal domain of Sema3F (Sema3Fc mAb) using the hybridoma method, expecting to explore the potential role of the antibody and its application in the detection of Sema3F. The capture enzyme-linked immunosorbent assay (ELISA) method indicated that mAb belonged to the IgM subclass and purified Sema3Fc mAb had a titer of 5.12 × 10⁵ against Sema3Fc by indirect ELISA. In addition, results showed that the Sema3Fc mAb could be applied in such experiments as Western blotting, flow cytometry, immunofluorescence, and immunocytochemical staining. It indicates the Sema3Fc mAb is available in the detection of Sema3F with specificity and will help further study the role and mechanism of Sema3F among tumor cells.

The Neuropilins and Their Ligands in Hematogenous Metastasis of Salivary Adenoid Cystic Carcinoma-An Immunohistochemical Study

PURPOSE

We investigated the expression of neuropilin-1 (NRP1), neuropilin-2 (NRP2), vascular endothelial growth factor-A (VEGF-A), semaphorin-3A (Sema-3A), and semaphorin-3F (Sema-3F) in normal salivary gland (NSG) tissue, nonmetastatic salivary adenoid cystic carcinoma (SACC), and metastatic SACC to better understand their role in intratumoral angiogenesis and hematogenous metastasis of SACC.

PATIENTS AND METHODS

The study included 60 SACC patients, equally divided between nonmetastatic SACC and metastatic SACC. We used 30 NSG samples as the control. The expression of cytokines was studied by immunohistochemistry and compared using the integrated optical density. The relationship between NRP1, NRP2, VEGF-A, and Sema-3A expression and microvessel density (MVD) was analyzed in the 3 groups.

RESULTS

In metastatic SACC, the expression levels of NRP1 and VEGF-A were significantly greater than those in nonmetastatic SACC and NSG. The expression of Sema-3A and Sema-3F was significantly lower in metastatic SACC than that in nonmetastatic SACC and NSG (P < .0001). No significant differences were found in NRP2 expression among the 3 groups (P = .43). The MVD of metastatic SACC was significantly greater than that of nonmetastatic SACC and NSG (P < .0001). However, the lymphatic vessel density of the 3 groups was not significantly different statistically. The relationship between MVD and NRP1 or VEGF-A showed a significant positive correlation (P < .0001, for both). However, a significant negative correlation was found between the MVD and Sema-3A or Sema-3F expression (P < .0001, for both).

CONCLUSIONS

Hematogenous metastasis of SACC is correlated with high expression of NRP1 and VEGF-A and low expression of Sema-3A and Sema-3F. The increased numbers of microvessels induced by VEGF-A signaling, combined with NRP1, could be one of the key reasons leading to the enhanced hematogenous metastasis in SACC.

The design of peptide-amphiphiles as functional ligands for liposomal anticancer drug and gene delivery

Liposomal nanomedicine has led to clinically useful cancer therapeutics like Doxil and DaunoXome. In addition, peptide-functionalized liposomes represent an effective drug and gene delivery vehicle with increased cancer cell specificity, enhanced tumor-penetrating ability and high tumor growth inhibition. The goal of this article is to review the recently published literature of the peptide-amphiphiles that were used to functionalize liposomes, to highlight successful designs that improved drug and gene delivery to cancer cells in vitro, and cancer tumors in vivo, and to discuss the current challenges of designing these peptide-decorated liposomes for effective cancer treatment.

The intragraft microenvironment as a central determinant of chronic rejection or local immunoregulation/tolerance

PURPOSE OF REVIEW

Chronic rejection is associated with persistent mononuclear cell recruitment, endothelial activation and proliferation, local tissue hypoxia and related biology that enhance effector immune responses. In contrast, the tumor microenvironment elicits signals/factors that inhibit effector T cell responses and rather promote immunoregulation locally within the tissue itself. The identification of immunoregulatory check points and/or secreted factors that are deficient within allografts is of great importance in the understanding and prevention of chronic rejection.

RECENT FINDINGS

The relative deficiency of immunomodulatory molecules (cell surface and secreted) on microvascular endothelial cells within the intragraft microenvironment, is of functional importance in shaping the phenotype of rejection. These regulatory molecules include coinhibitory and/or intracellular regulatory signals/factors that enhance local activation of T regulatory cells. For example, semaphorins may interact with endothelial cells and CD4 T cells to promote local tolerance. Additionally, metabolites and electrolytes within the allograft microenvironment may regulate local effector and regulatory cell responses.

SUMMARY

Multiple factors within allografts shape the microenvironment either towards local immunoregulation or proinflammation. Promoting the expression of intragraft cell surface or secreted molecules that support immunoregulation will be critical for long-term graft survival and/or alloimmune tolerance.

Tumor cell-derived secretory factor downregulates Semaphorin-3a in osteoblasts by activating mammalian target of rapamycin pathway

We found that conditioned medium derived from Lewis Lung Carcinoma cells down-regulated Semaphorin3a (Sema3a) mRNA expression and increased the activity of mammalian target of rapamycin complex 1 (mTORC1) in osteoblast-like MC3T3-E1 cells. Furthermore, mTORC1 inhibition with rapamycin counteracted the effect of conditioned media on Sema3a mRNA expression. These results suggest that tumor cells decrease Sema3a mRNA expression in osteoblast in an mTORC1-dependent manner.

Neuropilin 1 Receptor Is Up-Regulated in Dysplastic Epithelium and Oral Squamous Cell Carcinoma

Neuropilins are receptors for disparate ligands, including proangiogenic factors such as vascular endothelial growth factor and inhibitory class 3 semaphorin (SEMA3) family members. Differentiated cells in skin epithelium and cutaneous squamous cell carcinoma highly express the neuropilin-1 (NRP1) receptor. We examined the expression of NRP1 in human and mouse oral mucosa. NRP1 was significantly up-regulated in oral epithelial dysplasia and oral squamous cell carcinoma (OSCC). NRP1 receptor localized to the outer suprabasal epithelial layers in normal tongue, an expression pattern similar to the normal skin epidermis. However, dysplastic tongue epithelium and OSCC up-regulated NRP1 in basal and proliferating epithelial layers, a profile unseen in cutaneous squamous cell carcinoma. NRP1 up-regulation is observed in a mouse carcinogen-induced OSCC model and in human tongue OSCC biopsies. Human OSCC cell lines express NRP1 protein in vitro and in mouse tongue xenografts. Sites of capillary infiltration into orthotopic OSCC tumors correlate with high NRP1 expression. HSC3 xenografts, which express the highest NRP1 levels of the cell lines examined, showed massive intratumoral lymphangiogenesis. SEMA3A inhibited OSCC cell migration, suggesting that the NRP1 receptor was bioactive in OSCC. In conclusion, NRP1 is regulated in the oral epithelium and is selectively up-regulated during epithelial dysplasia. NRP1 may function as a reservoir to sequester proangiogenic ligands within the neoplastic compartment, thereby recruiting neovessels toward tumor cells.

Opening Windows into Tumors

Delivery of nanoparticles to tumors is limited by vascular permeability and intratumoral diffusion. In this issue of ACS Nano, Jiang et al. show that the manipulation of tumor physiology using antiangiogenic therapy can improve the tumor penetration of quantum dots with 20 and 40 nm hydrodynamic diameters. This Perspective describes the problems, challenges, and perspectives of using antiangiogenic therapy in combination with nanometer-sized drugs and contrast agents in preclinical and clinical studies.

A7RC peptide modified paclitaxel liposomes dually target breast cancer

A7R peptide (ATWLPPR), a ligand of the NRP-1 receptor, regulates the intracellular signal transduction related to tumor vascularization and tumor growth. Here, we designed A7R-cysteine peptide (A7RC) surface modified paclitaxel liposomes (A7RC-LIPs) to achieve targeting delivery and inhibition of tumor growth and angiogenesis simultaneously. The cytotoxicity, inhibiting angiogenesis, and internalization of various liposomes by cells were assessed in vitro to confirm the influence of the peptide modification. The accumulations of A7RC-LIPs in various xenografts in mice were tracked to further identify the function of the peptide on the liposomes' surface. The results confirmed that A7RC peptides could enhance the uptake of vesicles by MDA-MB-231 cells, leading to stronger cytotoxicity in vitro and higher accumulation of vesicles in MDA-MB-231 xenografts in vivo. In addition, A7RC peptides enhanced the inhibitory effects of LIPs on the HUVEC tubular formation on Matrigel. The A7RC-LIPs may be promising drug carriers for anticancer therapy.

Tumor Suppressor Function of the SEMA3B Gene in Human Lung and Renal Cancers

The SEMA3B gene is located in the 3p21.3 LUCA region, which is frequently affected in different types of cancer. The objective of our study was to expand our knowledge of the SEMA3B gene as a tumor suppressor and the mechanisms of its inactivation. In this study, several experimental approaches were used: tumor growth analyses and apoptosis assays in vitro and in SCID mice, expression and methylation assays and other. With the use of the small cell lung cancer cell line U2020 we confirmed the function of SEMA3B as a tumor suppressor, and showed that the suppression can be realized through the induction of apoptosis and, possibly, associated with the inhibition of angiogenesis. In addition, for the first time, high methylation frequencies have been observed in both intronic (32-39%) and promoter (44-52%) CpG-islands in 38 non-small cell lung carcinomas, including 16 squamous cell carcinomas (SCC) and 22 adenocarcinomas (ADC), and in 83 clear cell renal cell carcinomas (ccRCC). Correlations between the methylation frequencies of the promoter and the intronic CpG-islands of SEMA3B with tumor stage and grade have been revealed for SCC, ADC and ccRCC. The association between the decrease of the SEMA3B mRNA level and hypermethylation of the promoter and the intronic CpG-islands has been estimated in renal primary tumors (P < 0.01). Using qPCR, we observed on the average 10- and 14-fold decrease of the SEMA3B mRNA level in SCC and ADC, respectively, and a 4-fold decrease in ccRCC. The frequency of this effect was high in both lung (92-95%) and renal (84%) tumor samples. Moreover, we showed a clear difference (P < 0.05) of the SEMA3B relative mRNA levels in ADC with and without lymph node metastases. We conclude that aberrant expression and methylation of SEMA3B could be suggested as markers of lung and renal cancer progression.

Regulation of soluble neuropilin 1, an endogenous angiogenesis inhibitor, in liver development and regeneration

Neuropilin-1 (NRP1) is a receptor for vascular endothelial growth factor (VEGF). A soluble isoform of Nrp1 (sNrp1) has not been described in the mouse. Our goal was to examine the expression of mouse sNrp1 during liver development and regeneration.sNrp1 was cloned from mouse liver. The expression of sNrp1 and VEGF was examined in mouse liver during post-natal development and regeneration using northern blot, western blot, in situ hybridisation, and immunohistochemical analyses. HGF/NRP1 binding was examined in vitro.A novel 588-amino acid sNrp1 isoform was found to contain the ligand binding regions of Nrp1. The adult liver expressed more sNrp1 than full-length Nrp1. In vivo, hepatocytes constitutively expressed VEGF and sNrp1 in the quiescent state. sNrp1 was highly up-regulated at P20, a time point coinciding with a plateau in liver and body weights. Following hepatectomy, endogenous levels of sNrp1 decreased during the rapid growth phase, and VEGF levels were highest just prior to and during the angiogenic phase. sNrp1 levels again rose 5-10 days post-hepatectomy, presumably to control regeneration. HGF protein bound NRP1 and binding was competed with sNRP1.We cloned a novel mouse sNrp1 isoform from liver and provide evidence that this endogenous angiogenesis inhibitor may regulate VEGF or HGF bioavailability during normal physiological growth and development as well as during liver regeneration.

Urinary semaphorin 3A correlates with diabetic proteinuria and mediates diabetic nephropathy and associated inflammation in mice

Semaphorin 3A (sema3A) was recently identified as an early diagnostic biomarker of acute kidney injury. However, its role as a biomarker and/or mediator of chronic kidney disease (CKD) related to diabetic nephropathy is unknown. We examined the expression of sema3A in diabetic animal models and in humans and tested whether sema3A plays a pathogenic role in the development of diabetic nephropathy. The expression of sema3A was localized to podocytes and epithelial cells in distal tubules and collecting ducts in control animals, and its expression was increased following the induction of diabetes. Quantification of sema3A urinary excretion in three different diabetic mouse models showed that excretion was increased as early as 2 weeks after the induction of diabetes and increased over time, in conjunction with the development of nephropathy. Consistent with the mouse data, increased sema3A urinary excretion was detected in diabetic patients with albuminuria, particularly in those with macroalbuminuria. Genetic ablation of sema3A or pharmacological inhibition with a novel sema3A inhibitory peptide was protected against diabetes-induced albuminuria, kidney fibrosis, inflammation, oxidative stress, and renal dysfunction. We conclude that sema3A is both a biomarker and a mediator of diabetic kidney disease and could be a promising therapeutic target in diabetic nephropathy. Key messages Diabetes induced sema3A excretion in urine. Increased semaphorin 3A was associated with severity of albuminuria. Seme3A-mediated diabetes induced glomerulosclerosis. Peptide-based inhibition of semaphorin3A suppressed diabetic nephropathy.

Lymphangiogenesis and metastasis--a closer look at the neuropilin/semaphorin3 axis

Metastasis is the leading cause of cancer-related deaths. Understanding how the lymphatic system responds to its environment and local stimuli may lead to therapies to combat metastasis and other lymphatic-associated diseases. This review compares lymphatic vessels and blood vessels, discusses markers of lymphatic vasculature, and elucidates some of the signaling motifs involved in lymphangiogenesis. Recent progress implicating the neuropilin and semaphorin axes in this process is discussed.

Neuropilin 1 expression correlates with differentiation status of epidermal cells and cutaneous squamous cell carcinomas

Neuropilins (NRPs) are cell surface receptors for vascular endothelial growth factor (VEGF) and SEMA3 (class 3 semaphorin) family members. The role of NRPs in neurons and endothelial cells has been investigated, but the expression and role of NRPs in epithelial cells is much less clear. Herein, the expression and localization of NRP1 was investigated in human and mouse skin and squamous cell carcinomas (SCCs). Results indicated that NRP1 mRNA and protein was expressed in the suprabasal epithelial layers of the skin sections. NRP1 staining did not overlap with that of keratin 14 (K14) or proliferating cell nuclear antigen, but did co-localize with staining for keratin 1, indicating that differentiated keratinocytes express NRP1. Similar to the expression of NRP1, VEGF-A was expressed in suprabasal epithelial cells, whereas Nrp2 and VEGFR2 were not detectable in the epidermis. The expression of NRP1 correlated with a high degree of differentiation in human SCC specimens, human SCC xenografts, and mouse K14-HPV16 transgenic SCC. UVB irradiation of mouse skin induced Nrp1 upregulation. In vitro, Nrp1 was upregulated in primary keratinocytes in response to differentiating media or epidermal growth factor-family growth factors. In conclusion, the expression of NRP1 is regulated in the skin and is selectively produced in differentiated epithelial cells. NRP1 may function as a reservoir to sequester VEGF ligand within the epithelial compartment, thereby modulating its bioactivity.

Semaphorin 3A inactivation suppresses ischemia-reperfusion-induced inflammation and acute kidney injury

Recent studies show that guidance molecules that are known to regulate cell migration during development may also play an important role in adult pathophysiologic states. One such molecule, semaphorin3A (sema3A), is highly expressed after acute kidney injury (AKI) in mice and humans, but its pathophysiological role is unknown. Genetic inactivation of sema3A protected mice from ischemia-reperfusion-induced AKI, improved tissue histology, reduced neutrophil infiltration, prevented epithelial cell apoptosis, and increased cytokine and chemokine excretion in urine. Pharmacological-based inhibition of sema3A receptor binding likewise protected against ischemia-reperfusion-induced AKI. In vitro, sema3A enhanced toll-like receptor 4-mediated inflammation in epithelial cells, macrophages, and dendritic cells. Moreover, administration of sema3A-treated, bone marrow-derived dendritic cells exacerbated kidney injury. Finally, sema3A augmented cisplatin-induced apoptosis in kidney epithelial cells in vitro via expression of DFFA-like effector a (cidea). Our data suggest that the guidance molecule sema3A exacerbates AKI via promoting inflammation and epithelial cell apoptosis.

The role of axon guidance factor semaphorin 6B in the invasion and metastasis of gastric cancer

OBJECTIVE

To investigate the role of semaphorin 6B in gastric cancer invasion and metastasis.

METHODS

Immunohistochemistry for semaphorin 6B was performed on gastric cancer tumour tissue samples in this retrospective study. Levels of semaphorin 6B protein and mRNA were determined in gastric cancer cell lines by Western blotting and quantitative reverse transcription-polymerase chain reaction, respectively. The human gastric cancer cell line SGC-7901 was transfected with small interfering RNA targeting semaphorin 6B; effects on cell adhesion, migration and invasion were determined by cell adhesion assay, transwell chamber migration assay and wound healing assay, respectively.

RESULTS

Tumour tissue samples from 220 patients were analysed. In vivo, semaphorin 6B immunopositivity correlated with tumour differentiation, lymph node metastasis and distant metastasis but not patient age, sex or tumour stage. Semaphorin 6B gene silencing significantly suppressed adhesion, migration and invasion of gastric cancer cells in vitro.

CONCLUSIONS

Semaphorin 6B is related to tumour differentiation and metastasis in vivo, and tumour cell migration, adhesion and invasion in vitro. Semaphorin 6B may represent a reliable biomarker for diagnosis, evaluation and gene-targeted therapy of gastric cancer.

Establishing an osteosarcoma associated protein-protein interaction network to explore the pathogenesis of osteosarcoma

Background

The aim of this study was to establish an osteosarcoma (OS) associated protein-protein interaction network and explore the pathogenesis of osteosarcoma.

Methods

The gene expression profile GSE9508 was downloaded from the Gene Expression Omnibus database, including five samples of non-malignant bone (the control), seven samples for non-metastatic patients (six of which were analyzed in duplicate), and 11 samples for metastatic patients (10 of which were analyzed in duplicate). Differentially expressed genes (DEGs) between osteosarcoma and control samples were identified by packages in R with the threshold of |logFC (fold change)| > 1 and false discovery rate < 0.05. Osprey software was used to construct the interaction network of DEGs, and genes at protein-protein interaction (PPI) nodes with high degrees were identified. The Database for Annotation, Visualization and Integrated Discovery and WebGestalt software were then used to perform functional annotation and pathway enrichment analyses for PPI networks, in which P < 0.05 was considered statistically significant.

Results

Compared to the control samples, the expressions of 42 and 341 genes were altered in non-metastatic OS and metastatic OS samples, respectively. A total of 15 significantly enriched functions were obtained with Gene Ontology analysis (P < 0.05). The DEGs were classified and significantly enriched in three pathways, including the tricarboxylic acid cycle, lysosome and axon guidance. Genes such as HRAS, IDH3A, ATP6ap1, ATP6V0D2, SEMA3F and SEMA3A were involved in the enriched pathways.

Conclusions

The hub genes from metastatic OS samples are not only bio-markers of OS, but also help to improve therapies for OS.

Repulsive guidance cue semaphorin 3A in urine predicts the progression of acute kidney injury in adult patients from a mixed intensive care unit

BACKGROUNDS

Predicting the development of acute kidney injury (AKI) in the critical care setting is challenging. Although several biomarkers showed somewhat satisfactory performance for detecting established AKI even in a heterogeneous disease-oriented population, identification of new biomarkers that predict the development of AKI accurately is urgently required.

METHODS

A single-center prospective observational cohort study was undertaken to evaluate for the first time the reliability of the newly identified biomarker semaphorin 3A for AKI diagnosis in heterogeneous intensive care unit populations. In addition to five urinary biomarkers of L-type fatty acid-binding protein (L-FABP), neutrophil gelatinase-associated lipocalin (NGAL), IL-18, albumin and N-acetyl-β-d-glucosaminidase (NAG), urinary semaphorin 3A was measured at intensive care unit (ICU) admission.

RESULTS AND CONCLUSION

Three hundred thirty-nine critically ill adult patients were recruited for this study. Among them, 131 patients (39%) were diagnosed with AKI by the RIFLE criteria and 66 patients were diagnosed as AKI at post-ICU admission (later-onset AKI). Eighty-four AKI patients showed worsening severity during 1 week observation (AKI progression). Although L-FABP, NGAL and IL-18 showed significantly higher area under the curve (AUC)-receiver operating characteristic (ROC) values than semaphorin 3A in detecting established AKI, semaphorin 3A was able to detect later-onset AKI and AKI progression with similar AUC-ROC values compared with the other five biomarkers [AUC-ROC (95% CI) for established AKI 0.64 (0.56-0.71), later-onset AKI 0.71 (0.64-0.78), AKI progression 0.71 (0.64-0.77)]. Urinary semaphorin 3A was not increased in non-progressive established AKI, while the other biomarkers were elevated regardless of further progression. Finally, sepsis did not have any impact on semaphorin 3A while the other urinary biomarkers were increased with sepsis. Semaphorin 3A is a new biomarker of AKI which may have a distinct predictive use for AKI progression when compared with other AKI biomarkers.

Expression of VEGF and semaphorin genes define subgroups of triple negative breast cancer

Triple negative breast cancers (TNBC) are difficult to treat due to a lack of targets and heterogeneity. Inhibition of angiogenesis is a promising therapeutic strategy, but has had limited effectiveness so far in breast cancer. To quantify heterogeneity in angiogenesis-related gene expression in breast cancer, we focused on two families – VEGFs and semaphorins – that compete for neuropilin co-receptors on endothelial cells. We compiled microarray data for over 2,600 patient tumor samples and analyzed the expression of VEGF- and semaphorin-related ligands and receptors. We used principal component analysis to identify patterns of gene expression, and clustering to group samples according to these patterns. We used available survival data to determine whether these clusters had prognostic as well as therapeutic relevance. TNBC was highly associated with dysregulation of VEGF- and semaphorin-related genes; in particular, it appeared that expression of both VEGF and semaphorin genes were altered in a pro-angiogenesis direction. A pattern of high VEGFA expression with low expression of secreted semaphorins was associated with 60% of triple-negative breast tumors. While all TNBC groups demonstrated poor prognosis, this signature also correlated with lower 5-year survival rates in non-TNBC samples. A second TNBC pattern, including high VEGFC expression, was also identified. These pro-angiogenesis signatures may identify cancers that are more susceptible to VEGF inhibition.

Semaphorin 3A is a new early diagnostic biomarker of experimental and pediatric acute kidney injury

BACKGROUND

Semaphorin 3A is a secreted protein that regulates cell motility and attachment in axon guidance, vascular growth, immune cell regulation and tumor progression. However, nothing is known about its role in kidney pathophysiology. Here, we determined whether semaphorin3A is induced after acute kidney injury (AKI) and whether urinary semaphorin 3A can predict AKI in humans undergoing cardiopulmonary bypass (CPB).

METHODS AND PRINCIPAL FINDINGS

In animals, semaphorin 3A is localized in distal tubules of the kidney and excretion increased within 3 hr after reperfusion of the kidney whereas serum creatinine was significantly raised at 24 hr. In humans, using serum creatinine, AKI was detected on average only 48 hours after CPB. In contrast, urine semaphorin increased at 2 hours after CPB, peaked at 6 hours (2596±591 pg/mg creatinine), and was no longer significantly elevated 12 hours after CPB. The predictive power of semaphorin 3A as demonstrated by area under the receiver-operating characteristic curve for diagnosis of AKI at 2, 6, and 12 hours after CPB was 0.88, 0.81, and 0.74, respectively. The 2-hour urine semaphorin measurement strongly correlated with duration and severity of AKI, as well as length of hospital stay. Adjusting for CPB time and gender, the 2-hour semaphorin remained an independent predictor of AKI, with an odds ratio of 2.19.

CONCLUSION

Our results suggest that semaphorin 3A is an early, predictive biomarker in experimental and pediatric AKI, and may allow for the reliable early diagnosis and prognosis of AKI after CPB, much before the rise in serum creatinine.

SOX4 transcriptionally regulates multiple SEMA3/plexin family members and promotes tumor growth in pancreatic cancer

Semaphorin signaling through Plexin frequently participates in tumorigenesis and malignant progression in various types of cancer. In particular, the role of semaphorin signaling in pancreatic ductal adenocarcinoma (PDAC) remains unexplored, despite a high likelihood of metastasis and mortality. Unlike other epithelial malignancies that often express a small number of specific genes in the Semaphorin/Plexin family, five or more are often expressed in human PDAC. Such concomitant expression of these SEMA3/Plexin family members is not a result of gene amplification, but (at least partially) from increased gene transcription activated by SOX4 de novo expressed in PDAC. Via chromatin-immunoprecipitation, luciferase promoter activity assay and electrophoresis mobility shift assay, SOX4 is demonstrated to bind to the consensus site at the promoter of each SEMA3 and Plexin gene to enhance transcription activity. Conversely, RNAi-knockdown of SOX4 in PDAC cell lines results in decreased expression of SEMA3/Plexin family members and is associated with restricted tumor growth both in vitro and in SCID mice. We further demonstrate that SOX4 levels parallel with the summed expression of SEMA3/Plexin family members (P = 0.033, NPar Kruskal-Wallis one-way analysis), which also correlates with poor survival in human PDAC (P = 0.0409, Kaplan-Meier analysis). Intriguingly, miR-129-2 and miR-335, both of which target SOX4 for degradation, are co-repressed in human PDAC cases associated with up-regulated SOX4 in a statistically significant way. In conclusion, we disclose a miR-129-2(miR-335)/SOX4/Semaphorin-Plexin regulatory axis in the tumorigenesis of pancreatic cancer.

Semaphorin-7a reverses the ERF-induced inhibition of EMT in Ras-dependent mouse mammary epithelial cells

Epithelial-to-mesenchymal transition (EMT) is a key process in cancer progression and metastasis, requiring cooperation of the epidermal growth factor/Ras with the transforming growth factor-β (TGF-β) signaling pathway in a multistep process. The molecular mechanisms by which Ras signaling contributes to EMT, however, remain elusive to a large extent. We therefore examined the transcriptional repressor Ets2-repressor factor (ERF)-a bona fide Ras-extracellular signal-regulated kinase/mitogen-activated protein kinase effector-for its ability to interfere with TGF-β-induced EMT in mammary epithelial cells (EpH4) expressing oncogenic Ras (EpRas). ERF-overexpressing EpRas cells failed to undergo TGF-β-induced EMT, formed three-dimensional tubular structures in collagen gels, and retained expression of epithelial markers. Transcriptome analysis indicated that TGF-β signaling through Smads was mostly unaffected, and ERF suppressed the TGF-β-induced EMT via Semaphorin-7a repression. Forced expression of Semaphorin-7a in ERF-overexpressing EpRas cells reestablished their ability to undergo EMT. In contrast, inhibition of Semaphorin-7a in the parental EpRas cells inhibited their ability to undergo TGF-β-induced EMT. Our data suggest that oncogenic Ras may play an additional role in EMT via the ERF, regulating Semaphorin-7a and providing a new interconnection between the Ras- and the TGF-β-signaling pathways.

Opportunities and challenges in tumor angiogenesis research: back and forth between bench and bed

Angiogenesis is essential for tumor growth and metastasis. Many signaling pathways are involved in regulating tumor angiogenesis, with the vascular endothelial growth factor pathway being of particular interest. The recognition of the heterogeneity in tumor vasculature has led to better predictions of prognosis through differential analyses of the vasculature. However, the clinical benefits from antiangiogenic therapy are limited, because many antiangiogenic agents cannot provide long-term survival benefits, suggesting the development of drug resistance. Activation of the hypoxia and c-Met pathways, as well as other proangiogenic factors, has been shown to be responsible for such resistance. Vessel co-option could be another important mechanism. For future development, research to improve the efficacy of antiangiogenic therapy includes (a) using tumor-derived endothelial cells for drug screening; (b) developing the drugs focusing on specific tumor types; (c) developing a better preclinical model for drug study; (d) developing more accurate biomarkers for patient selection; (e) targeting the c-Met pathway or other pathways; and (f) optimizing the dose and schedule of antiangiogenic therapy. In summary, the future of antiangiogenic therapy for cancer patients depends on our efforts to develop the right drugs, select the right patients, and optimize the treatment conditions.

Increased smooth muscle contractility in mice deficient for neuropilin 2

Neuropilins (NRPs) are transmembrane receptors that bind class 3 semaphorins and VEGF family members to regulate axon guidance and angiogenesis. Although expression of NRP1 by vascular smooth muscle cells (SMCs) has been reported, NRP function in smooth muscle (SM) in vivo is unexplored. Using Nrp2(+/LacZ) and Nrp2(+/gfp) transgenic mice, we observed robust and sustained expression of Nrp2 in the SM compartments of the bladder and gut, but no expression in vascular SM, skeletal muscle, or cardiac muscle. This expression pattern was recapitulated in vitro using primary human SM cell lines. Alterations in cell morphology after treatment of primary visceral SMCs with the NRP2 ligand semaphorin-3F (SEMA3F) were accompanied by inhibition of RhoA activity and myosin light chain phosphorylation, as well as decreased cytoskeletal stiffness. Ex vivo contractility testing of bladder muscle strips exposed to electrical stimulation or soluble agonists revealed enhanced tension generation of tissues from mice with constitutive or SM-specific knockout of Nrp2, compared with controls. Mice lacking Nrp2 also displayed increased bladder filling pressures, as assessed by cystometry in conscious mice. Together, these findings identify Nrp2 as a mediator of prorelaxant stimuli in SMCs and suggest a novel function for Nrp2 as a regulator of visceral SM contractility.

Merlin/NF2 regulates angiogenesis in schwannomas through a Rac1/semaphorin 3F-dependent mechanism

Neurofibromatosis type 2 (NF2) is an autosomal-dominant multiple neoplasia syndrome that results from mutations in the NF2 tumor suppressor gene. Patients with NF2 develop hallmark schwannomas that require surgery or radiation, both of which have significant adverse effects. Recent studies have indicated that the tumor microenvironment-in particular, tumor blood vessels-of schwannomas may be an important therapeutic target. Furthermore, although much has been done to understand how merlin, the NF2 gene product, functions as a tumor suppressor gene in schwannoma cells, the functional role of merlin in the tumor microenvironment and the mechanism(s) by which merlin regulates angiogenesis to support schwannoma growth is largely unexplored. Here we report that the expression of semaphorin 3F (SEMA3F) was specifically downregulated in schwannoma cells lacking merlin/NF2. When we reintroduced SEMA3F in schwannoma cells, we observed normalized tumor blood vessels, reduced tumor burden, and extended survival in nude mice bearing merlin-deficient brain tumors. Next, using chemical inhibitors and gene knockdown with RNA interference, we found that merlin regulated expression of SEMA3F through Rho GTPase family member Rac1. This study shows that, in addition to the tumor-suppressing activity of merlin, it also functions to maintain physiological angiogenesis in the nervous system by regulating antiangiogenic factors such as SEMA3F. Restoring the relative balance of proangiogenic and antiangiogenic factors, such as increases in SEMA3F, in schwannoma microenvironment may represent a novel strategy to alleviate the clinical symptoms of NF2-related schwannomas.

Semaphorin 3A suppresses tumor growth and metastasis in mice melanoma model

BACKGROUND

Recent understanding on cancer therapy indicated that targeting metastatic signature or angiogenic switch could be a promising and rational approach to combat cancer. Advancement in cancer research has demonstrated the potential role of various tumor suppressor proteins in inhibition of cancer progression. Current studies have shown that axonal sprouting inhibitor, semaphorin 3A (Sema 3A) acts as a potent suppressor of tumor angiogenesis in various cancer models. However, the function of Sema 3A in regulation of melanoma progression is not well studied, and yet to be the subject of intense investigation.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, using multiple in vitro and in vivo approaches we have demonstrated that Sema 3A acts as a potent tumor suppressor in vitro and in vivo mice (C57BL/6) models. Mouse melanoma (B16F10) cells overexpressed with Sema 3A resulted in significant inhibition of cell motility, invasiveness and proliferation as well as suppression of in vivo tumor growth, angiogenesis and metastasis in mice models. Moreover, we have observed that Sema 3A overexpressed melanoma clone showed increased sensitivity towards curcumin and Dacarbazine, anti-cancer agents.

CONCLUSIONS

Our results demonstrate, at least in part, the functional approach underlying Sema 3A mediated inhibition of tumorigenesis and angiogenesis and a clear understanding of such a process may facilitate the development of novel therapeutic strategy for the treatment of cancer.

A case study on Sema3E-Fc aggregation and assay-dependent differences in quantitation

Background: In evaluating the serum concentrations in mice of a Sema3E IgG1 Fc fusion protein, a possible antitumor agent, two ELISAs were developed: a generic assay detecting only the Fc portion of the therapeutic and a specific receptor-binding assay detecting intact protein. Results: An unexpected discrepancy was observed in the measured in vivo serum concentrations, with the generic ELISA yielding higher concentrations than the specific ELISA. Size-exclusion HPLC and SDS-PAGE analysis of in vitro serum stability samples revealed extensive aggregation of Sema3E-Fc. The generic assay recovered more Sema3E-Fc in the presence of aggregates than the specific assay. Conclusion: Biophysical characterization combined with immunochemical analysis was key to elucidating not only the nature of the protein instability, but also the cause for the assay discrepancy.

MicroRNA-181b and microRNA-9 mediate arsenic-induced angiogenesis via NRP1

Environmental exposure to inorganic arsenic compounds has been reported to have serious health effects on humans. Recent studies reported that arsenic targets endothelial cells lining blood vessels, and endothelial cell activation or dysfunction, may underlie the pathogenesis of arsenic-induced diseases and developmental toxicity. It has been reported that microRNAs (miRNAs) may act as an angiogenic switch by regulating related genes. The present study was designed to test the hypothesis that arsenite-regulated miRNAs play pivotal roles in arsenic-induced toxicity. Fertilized eggs were injected via the yolk sac with 100  nM sodium arsenite at Hamburger-Hamilton (HH) stages 6, 9, and 12, and harvested at HH stage 18. To identify the individual miRNAs and mRNAs that may regulate the genetic network, the expression profiles of chick embryos were analyzed by microarray analysis. Microarray analyses revealed that the expression of a set of miRNAs changed after arsenite administration, especially miRNA-9, 181b, 124, 10b, and 125b, which exhibited a massive decrease in expression. Integrative analyses of the microarray data revealed that several miRNAs, including miR-9 and miR-181b, might target several key genes involved in arsenic-induced developmental toxicity. A luciferase reporter assay confirmed neuropilin-1 (Nrp1) as a target of mir-9 and mir-181b. Data from the transwell migration assay and the tube-formation assay indicated that miR-9 and mir-181b inhibited the arsenic-induced EA.hy926 cell migration and tube formation by targeting NRP1. Our study demonstrates that the environmental toxin, sodium arsenite, induced angiogenesis by altering the expression of miRNAs and their cognate mRNA targets.

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.

Integration of genotypic and phenotypic screening reveals molecular mediators of melanoma-stromal interaction

Tumor-endothelium interactions are critical for tumor survival and metastasis. Melanomas can rapidly metastasize early in tumor progression, but the dependence of this aggressive behavior on tumor-stromal interaction is poorly understood. To probe the mechanisms involved, we developed a heterotypic coculture methodology, allowing simultaneous tracking of genomic and phenotypic changes in interacting tumor and endothelial cells in vitro. We found a dramatic rearrangement of endothelial cell networks into patterns reminiscent of vascular beds, even on plastic and glass. Multiple genes were upregulated in the process, many coding for cell surface and secreted proteins, including Neuropilin-2 (NRP2). A critical role of NRP2 in coordinated cell patterning and growth was confirmed using the coculture system. We conclude that NRP2 represents an important mediator of melanoma-endothelial interactions. Furthermore, the described methodology represents a powerful yet simple system to elucidate heterotypic intercellular interactions mediating diverse physiological and pathological processes.

Semaphorin 3E, an exception to the rule

Class 3 semaphorins (Sema3s) regulate axon guidance, angiogenesis, tumor growth, and tumor metastasis. Neuropilins (NRPs; NRP1 and NRP2) are the cell surface receptors for the Sema3s. However, to signal, interaction of Sema3s and NRPs with plexins is obligatory. In this issue of the JCI, Casazza and colleagues report data that challenge the conventional wisdom about the role of Sema3s in tumor metastasis. As a rule, Sema3B and Sema3F, for example, are inhibitors of tumor angiogenesis, progression, and metastasis. However, Casazza et al. found that Sema3E inhibited tumor growth but atypically promoted invasiveness and metastasis. This metastatic potential was dependent on Plexin D1 expression but was independent of NRP expression. Of clinical importance, Sema3E and Plexin D1 were found to be upregulated in human colon cancer, liver metastasis, and melanoma progression.

Id2 promotes tumor cell migration and invasion through transcriptional repression of semaphorin 3F

Id proteins (Id1 to Id4) are helix-loop-helix transcription factors that promote metastasis. It was found that Semaphorin 3F (SEMA3F), a potent inhibitor of metastasis, was repressed by Id2. High metastatic human tumor cell lines had relatively high amounts of Id2 and low SEMA3F levels compared with their low metastatic counterparts. No correlation between metastatic potential and expression of the other Id family members was observed. Furthermore, ectopic expression of Id2 in low metastatic tumor cells downregulated SEMA3F and, as a consequence, enhanced their ability to migrate and invade, two requisite steps of metastasis in vivo. Id2 overexpression was driven by the c-myc oncoprotein. SEMA3F was a direct target gene of the E47/Id2 pathway. Two E-box sites, which bind E protein transcription factors including E47, were identified in the promoter region of the SEMA3F gene. E47 directly activated SEMA3F promoter activity and expression and promoted SEMA3F biological activities, including filamentous actin depolymerization, inactivation of RhoA, and inhibition of cell migration. Silencing of SEMA3F inhibited the E47-induced SEMA3F expression and biological activities, confirming that these E47-induced effects were SEMA3F dependent. E47 did not induce expression of the other members of the SEMA3 family. Id2, a dominant-negative inhibitor of E proteins, abrogated the E47-induced SEMA3F expression and biological activities. Thus, high metastatic tumor cells overexpress c-myc, leading to upregulation of Id2 expression; the aberrantly elevated amount of Id2 represses SEMA3F expression and, as a consequence, enhances the ability of tumor cells to migrate and invade.

Expression of semaphorin 3A and its receptors in the human intervertebral disc: potential role in regulating neural ingrowth in the degenerate intervertebral disc

Introduction

Intervertebral disc (IVD) degeneration is considered a major underlying factor in the pathogenesis of chronic low back pain. Although the healthy IVD is both avascular and aneural, during degeneration there is ingrowth of nociceptive nerve fibres and blood vessels into proximal regions of the IVD, which may contribute to the pain. The mechanisms underlying neural ingrowth are, however, not fully understood. Semaphorin 3A (sema3A) is an axonal guidance molecule with the ability to repel nerves seeking their synaptic target. This study aimed to identify whether members of the Class 3 semaphorins were expressed by chondrocyte-like cells of the IVD addressing the hypothesis that they may play a role in repelling axons surrounding the healthy disc, thus maintaining its aneural condition.

Methods

Human IVD samples were investigated using reverse transcription polymerase chain reaction (RT-PCR) to identify gene expression of sema3A, 3F and their receptors: neuropilins (1 and 2) and plexins (A1-4). Sema3A protein was also localised within sections of normal and degenerate human IVD and immunopositivity quantified. Serial sections were stained using PGP9.5 and CD31 to correlate semaphorin 3A expression with nerve and blood vessel ingrowth, respectively.

Results

Sema3A protein was expressed highly in the healthy disc, primarily localised to the outer annulus fibrosus. In degenerate samples, sema3A expression decreased significantly in this region, although cell clusters within the degenerate nucleus pulposus exhibited strong immunopositivity. mRNA for sema3A receptors was also identified in healthy and degenerate tissues. CD31 and PGP9.5 were expressed most highly in degenerate tissues correlating with low expression of sema3A.

Conclusions

This study is the first to establish the expression of semaphorins and their receptors in the human IVD with a decrease seen in the degenerate painful IVD. Sema3A may therefore, amongst other roles, act as a barrier to neuronal ingrowth within the healthy disc.

Association of genetic variants in SEMA3F, CLEC16A, LAMA3, and PCSK2 with myocardial infarction in Japanese individuals

OBJECTIVE

The purpose of the present study was to identify genetic variants that confer susceptibility to myocardial infarction (MI) in Japanese individuals.

METHODS

The study population comprised 5014 Japanese individuals, including 1444 subjects with MI and 3570 controls. The 150 polymorphisms examined in the present study were selected by a genome-wide association study for ischemic stroke with the use of the GeneChip Human Mapping 500K Array Set (Affymetrix), and were determined by a method that combines the polymerase chain reaction and sequence-specific oligonucleotide probes with suspension array technology.

RESULTS

An initial screen by the chi-square test revealed that the A-->G polymorphism of SEMA3F (rs12632110), the C-->T polymorphism of CLEC16A (rs9925481), the A-->G polymorphism of LAMA3 (rs12373237), and the C-->G polymorphism of PCSK2 (rs6080699) were significantly (false discovery rate for allele frequencies of <0.05) associated with MI. Subsequent multivariable logistic regression analysis with adjustment for covariates and a stepwise forward selection procedure revealed that the A-->G polymorphism of SEMA3F (dominant model; P=0.0014; odds ratio, 0.76), the C-->T polymorphism of CLEC16A (dominant model; P=0.0009; odds ratio, 0.75), the A-->G polymorphism of LAMA3 (recessive model; P=0.0099; odds ratio, 0.80), and the C-->G polymorphism of PCSK2 (recessive model; P=0.0155; odds ratio, 1.19) were significantly (P<0.05) associated with the prevalence of MI.

CONCLUSION

Determination of these genotypes may prove informative for assessment of the genetic risk for MI in Japanese individuals.

Semaphorin 4D signaling requires the recruitment of phospholipase C gamma into the plexin-B1 receptor complex

The semaphorin 4D (Sema4D) receptor plexin-B1 constitutively interacts with particular Rho guanine nucleotide exchange factors (RhoGEFs) and thereby mediates Sema4D-induced RhoA activation, a process which involves the tyrosine phosphorylation of plexin-B1 by ErbB-2. It is, however, unknown how plexin-B1 phosphorylation regulates RhoGEF activity. We show here that activation of plexin-B1 by Sema4D and its subsequent tyrosine phosphorylation creates docking sites for the SH2 domains of phospholipase Cgamma (PLCgamma). PLCgamma is thereby recruited into the plexin-B1 receptor complex and via its SH3 domain activates the Rho guanine nucleotide exchange factor PDZ-RhoGEF. PLCgamma-dependent RhoGEF activation is independent of its lipase activity. The recruitment of PLCgamma has no effect on the R-Ras GTPase-activating protein activity of plexin-B1 but is required for Sema4D-induced axonal growth cone collapse as well as for the promigratory effects of Sema4D on cancer cells. These data demonstrate a novel nonenzymatic function of PLCgamma as an important mechanism of plexin-mediated signaling which links tyrosine phosphorylation of plexin-B1 to the regulation of a RhoGEF protein and downstream cellular processes.

Semaphorin 3A is an endogenous angiogenesis inhibitor that blocks tumor growth and normalizes tumor vasculature in transgenic mouse models

Tumor growth and progression rely upon angiogenesis, which is regulated by pro- and antiangiogenic factors, including members of the semaphorin family. By analyzing 3 different mouse models of multistep carcinogenesis, we show here that during angiogenesis, semaphorin 3A (Sema3A) is expressed in ECs, where it serves as an endogenous inhibitor of angiogenesis that is present in premalignant lesions and lost during tumor progression. Pharmacologic inhibition of endogenous Sema3A during the angiogenic switch, the point when pretumoral lesions initiate an angiogenic phase that persists throughout tumor growth, enhanced angiogenesis and accelerated tumor progression. By contrast, when, during the later stages of carcinogenesis following endogenous Sema3A downmodulation, Sema3A was ectopically reintroduced into islet cell tumors by somatic gene transfer, successive waves of apoptosis ensued, first in ECs and then in tumor cells, resulting in reduced vascular density and branching and inhibition of tumor growth and substantially extended survival. Further, long-term reexpression of Sema3A markedly improved pericyte coverage of tumor blood vessels, something that is thought to be a key property of tumor vessel normalization, and restored tissue normoxia. We conclude, therefore, that Sema3A is an endogenous and effective antiangiogenic agent that stably normalizes the tumor vasculature.