Inhibition of lung cancer cell growth and induction of apoptosis after reexpression of 3p21.3 candidate tumor suppressor gene SEMA3B

SEMA3B inhibits TGFβ-induced extracellular matrix protein production and its reduced levels are associated with a decline in lung function in IPF

Idiopathic pulmonary fibrosis (IPF) is marked by the activation of fibroblasts, leading to excessive production and deposition of extracellular matrix (ECM) within the lung parenchyma. Despite the pivotal role of ECM overexpression in IPF, potential negative regulators of ECM production in fibroblasts have yet to be identified. Semaphorin class 3B (SEMA3B), a secreted protein highly expressed in lung tissues, has established roles in axonal guidance and tumor suppression. However, the role of SEMA3B in ECM production by fibroblasts in the pathogenesis of IPF remains unexplored. Here, we show the downregulation of SEMA3B and its cognate binding receptor, neuropilin 1 (NRP1), in IPF lungs compared with healthy controls. Notably, the reduced expression of SEMA3B and NRP1 is associated with a decline in lung function in IPF. The downregulation of SEMA3B and NRP1 transcripts was validated in the lung tissues of patients with IPF, and two alternative mouse models of pulmonary fibrosis. In addition, we show that transforming growth factor-β (TGFβ) functions as a negative regulator of SEMA3B and NRP1 expression in lung fibroblasts. Furthermore, we demonstrate the antifibrotic effects of SEMA3B against TGFβ-induced ECM production in IPF lung fibroblasts. Overall, our findings uncovered a novel role of SEMA3B in the pathogenesis of pulmonary fibrosis and provided novel insights into modulating the SEMA3B-NRP1 axis to attenuate pulmonary fibrosis.NEW & NOTEWORTHY The excessive production and secretion of collagens and other extracellular matrix proteins by fibroblasts lead to the scarring of the lung in severe fibrotic lung diseases. This study unveils an antifibrotic role for semaphorin class 3B (SEMA3B) in the pathogenesis of idiopathic pulmonary fibrosis. SEMA3B functions as an inhibitor of transforming growth factor-β-driven fibroblast activation and reduced levels of SEMA3B and its receptor, neuropilin 1, are associated with decreased lung function in idiopathic pulmonary fibrosis.

Serum Protein Fishing for Machine Learning-Boosted Diagnostic Classification of Small Nodules of Lung

Diagnosis of benign and malignant small nodules of the lung remains an unmet clinical problem which is leading to serious false positive diagnosis and overtreatment. Here, we developed a serum protein fishing-based spectral library (ProteoFish) for data independent acquisition analysis and a machine learning-boosted protein panel for diagnosis of early Non-Small Cell Lung Cancer (NSCLC) and classification of benign and malignant small nodules. We established an extensive NSCLC protein bank consisting of 297 clinical subjects. After testing 5 feature extraction algorithms and six machine learning models, the Lasso algorithm for a 15-key protein panel selection and Random Forest was chosen for diagnostic classification. Our random forest classifier achieved 91.38% accuracy in benign and malignant small nodule diagnosis, which is superior to the existing clinical assays. By integrating with machine learning, the 15-key protein panel may provide insights to multiplexed protein biomarker fishing from serum for facile cancer screening and tackling the current clinical challenge in prospective diagnostic classification of small nodules of the lung.

Global genetic diversity, introgression, and evolutionary adaptation of indicine cattle revealed by whole genome sequencing

Indicine cattle, also referred to as zebu (Bos taurus indicus), play a central role in pastoral communities across a wide range of agro-ecosystems, from extremely hot semiarid regions to hot humid tropical regions. However, their adaptive genetic changes following their dispersal into East Asia from the Indian subcontinent have remained poorly documented. Here, we characterize their global genetic diversity using high-quality whole-genome sequencing data from 354 indicine cattle of 57 breeds/populations, including major indicine phylogeographic groups worldwide. We reveal their probable migration into East Asia was along a coastal route rather than inland routes and we detected introgression from other bovine species. Genomic regions carrying morphology-, immune-, and heat-tolerance-related genes underwent divergent selection according to Asian agro-ecologies. We identify distinct sets of loci that contain promising candidate variants for adaptation to hot semi-arid and hot humid tropical ecosystems. Our results indicate that the rapid and successful adaptation of East Asian indicine cattle to hot humid environments was promoted by localized introgression from banteng and/or gaur. Our findings provide insights into the history and environmental adaptation of indicine cattle.

Semaphorins and Their Roles in Breast Cancer: Implications for Therapy Resistance

Breast cancer is the most common cancer worldwide and a leading cause of cancer-related deaths in women. The clinical management of breast cancer is further complicated by the heterogeneous nature of the disease, which results in varying prognoses and treatment responses in patients. The semaphorins are a family of proteins with varied roles in development and homoeostasis. They are also expressed in a wide range of human cancers and are implicated as regulators of tumour growth, angiogenesis, metastasis and immune evasion. More recently, semaphorins have been implicated in drug resistance across a range of malignancies. In breast cancer, semaphorins are associated with resistance to endocrine therapy as well as breast cancer chemotherapeutic agents such as taxanes and anthracyclines. This review will focus on the semaphorins involved in breast cancer progression and their association with drug resistance.

Plexins as Regulators of Cancer Cell Proliferation, Migration, and Invasivity

Plexins are a family of nine single-pass transmembrane receptors with a conserved GTPase activating protein (GAP) domain. The plexin family is divided into four subfamilies: Type-A, type-B, type-C, and type-D plexins. Plexins function as receptors for axon guidance factors of the semaphorin family. The semaphorin gene family contains 22 genes that are divided into eight subclasses of which subclasses three to seven represent vertebrate semaphorins. The plexins and their semaphorin ligands have important roles as regulators of angiogenesis, cancer proliferation, and metastasis. Class 3 semaphorins, with the exception of sema3E, are the only semaphorins that do not bind directly to plexins. In order to transduce their signals, they bind instead to complexes consisting of receptors of the neuropilin family and various plexins. Some plexins also form complexes with tyrosine-kinase receptors such as the epidermal growth factor receptor ErbB2, the mesenchymal epithelial transition factor receptor (MET), and the Vascular endothelial growth factor receptor 2 (VEGFR2) and, as a result, can modulate cell proliferation and tumor progression. This review focuses on the roles of the different plexins in the control of cancer cell proliferation and invasiveness. Plexins also affect tumor progression and tumor metastasis by indirect mechanisms, such as modulation of angiogenesis and immune responses. However, these topics are not covered in the present review.

Inhibition of VEGF binding to neuropilin-2 enhances chemosensitivity and inhibits metastasis in triple-negative breast cancer

Although blocking the binding of vascular endothelial growth factor (VEGF) to neuropilin-2 (NRP2) on tumor cells is a potential strategy to treat aggressive carcinomas, a lack of effective reagents that can be used clinically has hampered this potential therapy. Here, we describe the generation of a fully humanized, high-affinity monoclonal antibody (aNRP2-10) that specifically inhibits the binding of VEGF to NRP2, conferring antitumor activity without causing toxicity. Using triple-negative breast cancer as a model, we demonstrated that aNRP2-10 could be used to isolate cancer stem cells (CSCs) from heterogeneous tumor populations and inhibit CSC function and epithelial-to-mesenchymal transition. aNRP2-10 sensitized cell lines, organoids, and xenografts to chemotherapy and inhibited metastasis by promoting the differentiation of CSCs to a state that is more responsive to chemotherapy and less prone to metastasis. These data provide justification for the initiation of clinical trials designed to improve the response of patients with aggressive tumors to chemotherapy using this monoclonal antibody.

Identification of a novel immune-related gene signature for prognosis and the tumor microenvironment in patients with uveal melanoma combining single-cell and bulk sequencing data

Introduction

Uveal melanoma (UVM) is the most invasive intraocular malignancy in adults with a poor prognosis. Growing evidence revealed that immune-related gene is related to tumorigenesis and prognosis. This study aimed to construct an immune-related prognostic signature for UVM and clarify the molecular and immune classification.

Methods

Based on The Cancer Genome Atlas (TCGA) database, single-sample gene set enrichment (ssGSEA) and hierarchical clustering analysis were performed to identify the immune infiltration pattern of UVM and classify patients into two immunity clusters. Then, we proposed univariate and multivariate Cox regression analysis to identify immune-related genes that related to overall survival (OS) and validated in the Gene Expression Omnibus (GEO) external validation cohort. The molecular and immune classification in the immune-related gene prognostic signature defined subgroups were analyzed.

Results

The immune-related gene prognostic signature was constructed based on S100A13, MMP9, and SEMA3B genes. The prognostic value of this risk model was validated in three bulk RNA sequencing datasets and one single-cell sequencing dataset. Patients in the low-risk group had better OS than those in the high-risk group. The receiver-operating characteristic (ROC) analysis revealed its strong predictive ability for UVM patients. Lower expression of immune checkpoint genes was presented in the low-risk group. Functional studies showed that S100A13 knockdown via siRNA inhibited UVM cell proliferation, migration, and invasion in vitro, with the increased expression of reactive oxygen species (ROS) related markers in UVM cell lines.

Discussion

The immune-related gene prognostic signature is an independent predictive factor for the survival of patients with UVM and provides new information about cancer immunotherapy in UVM.

Advances in SEMA3F regulation of clinically high-incidence cancers

Cancer has become a leading cause of morbidity and mortality in recent years. Its high prevalence has had a severe impact on society. Researchers have achieved fruitful results in the causative factors, pathogenesis, treatment strategies, and cancer prevention. Semaphorin 3F (SEMA3F), a member of the signaling family, was initially reported in the literature to inhibit the growth, invasion, and metastasis of cancer cells in lung cancer. Later studies showed it has cancer-inhibiting effects in malignant tumors such as breast, colorectal, ovarian, oral squamous cell carcinoma, melanoma, and head and neck squamous carcinoma. In contrast, recent studies have reported that SEMA3F is expressed more in hepatocellular carcinoma than in normal tissue and promotes metastasis of hepatocellular carcinoma. We chose lung, breast, colorectal, and hepatocellular carcinomas with high clinical prevalence to review the roles and molecular mechanisms of SEMA3F in these four carcinomas. We concluded with an outlook on clinical interventions for patients targeting SEMA3F.

The Hippo pathway mediates Semaphorin signaling

Semaphorins were originally identified as axonal guidance molecules, but they also control processes such as vascular development and tumorigenesis. The downstream signaling cascades of Semaphorins in these biological processes remain unclear. Here, we show that the class 3 Semaphorins (SEMA3s) activate the Hippo pathway to attenuate tissue growth, angiogenesis, and tumorigenesis. SEMA3B restoration in lung cancer cells with SEMA3B loss of heterozygosity suppresses cancer cell growth via activating the core Hippo kinases LATS1/2 (large tumor suppressor kinase 1/2). Furthermore, SEMA3 also acts through LATS1/2 to inhibit angiogenesis. We identified p190RhoGAPs as essential partners of the SEMA3A receptor PlexinA in Hippo regulation. Upon SEMA3 treatment, PlexinA interacts with the pseudo-guanosine triphosphatase (GTPase) domain of p190RhoGAP and simultaneously recruits RND GTPases to activate p190RhoGAP, which then stimulates LATS1/2. Disease-associated etiological factors, such as genetic lesions and oscillatory shear, diminish Hippo pathway regulation by SEMA3. Our study thus discovers a critical role of Hippo signaling in mediating SEMA3 physiological function.

Extracellular domain of semaphorin 5A serves a tumor‑suppressing role by activating interferon signaling pathways in lung adenocarcinoma cells

Semaphorin 5A (SEMA5A), which was originally identified as an axon guidance molecule in the nervous system, has been subsequently identified as a prognostic biomarker for lung cancer in nonsmoking women. SEMA5A acts as a tumor suppressor by inhibiting the proliferation and migration of lung cancer cells. However, the regulatory mechanism of SEMA5A is not clear. Therefore, the purpose of the present study was to explore the roles of different domains of SEMA5A in its tumor‑suppressive effects in lung adenocarcinoma cell lines. First, it was revealed that overexpression of full length SEMA5A or its extracellular domain significantly inhibited the proliferation and migration of both A549 and H1299 cells using MTT, colony formation and gap closure assays. Next, microarray analyses were performed to identify genes regulated by different domains of SEMA5A. Among the differentially expressed genes, the most significant function of these genes that were enriched was the 'Interferon Signaling' pathway according to Ingenuity Pathway Analysis. The activation of the 'Interferon Signaling' pathway was validated by reverse transcription‑quantitative PCR and western blotting. In summary, the present study demonstrated that the extracellular domain of SEMA5A could upregulate genes in interferon signaling pathways, resulting in suppressive effects in lung adenocarcinoma cells.

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.

SH3BP4 promotes neuropilin-1 and α5-integrin endocytosis and is inhibited by Akt

Cells probe their surrounding matrix for attachment sites via integrins that are internalized by endocytosis. We find that SH3BP4 regulates integrin surface expression in a signaling-dependent manner via clathrin-coated pits (CCPs). Dephosphorylated SH3BP4 at S246 is efficiently recruited to CCPs, while upon Akt phosphorylation, SH3BP4 is sequestered by 14-3-3 adaptors and excluded from CCPs. In the absence of Akt activity, SH3BP4 binds GIPC1 and targets neuropilin-1 and α5/β1-integrin for endocytosis, leading to inhibition of cell spreading. Similarly, chemorepellent semaphorin-3a binds neuropilin-1 to activate PTEN, which antagonizes Akt and thus recruits SH3BP4 to CCPs to internalize both receptors and induce cell contraction. In PTEN mutant non-small cell lung cancer cells with high Akt activity, expression of non-phosphorylatable active SH3BP4-S246A restores semaphorin-3a induced cell contraction. Thus, SH3BP4 links Akt signaling to endocytosis of NRP1 and α5/β1-integrins to modulate cell-matrix interactions in response to intrinsic and extrinsic cues.

A comprehensive review of tumor proliferative and suppressive role of semaphorins and therapeutic approaches

Semaphorins have been traditionally known as axon guidance proteins that negatively regulate axonal growth. However, in the past couple of decades, their versatile role in so many other biological processes has come to prominence as well. One such example is their role in cancer. In this review article, the focus was on the tumor proliferative and tumor suppressive role of all 20 semaphorin family members under the 7 semaphorin classes found in vertebrates and invertebrates as well as the ongoing and emerging therapeutic approaches to combat semaphorin-mediated cancers. Except sema6C, 19 of the 20 non-viral semaphorin family members have been discovered to be associated with cancer in one way or another. Eleven semaphorin family members have been discovered to be tumor proliferative and 8 to be tumor suppressive. Six therapeutic avenues and their safety profiles have been discussed which are currently at use or at the various stages of development. Finally, perspectives on which approach is the best for treating cancers associated with semaphorins have been given.

Semaphorins in health and disease

Cell-cell communication is pivotal to guide embryo development, as well as to maintain adult tissues homeostasis and control immune response. Among extracellular factors responsible for this function, are the Semaphorins, a broad family of around 20 different molecular cues conserved in evolution and widely expressed in all tissues. The signaling cascades initiated by semaphorins depend on a family of conserved receptors, called Plexins, and on several additional molecules found in the receptor complexes. Moreover, multiple intracellular pathways have been described to act downstream of semaphorins, highlighting significant diversity in the signaling cascades controlled by this family. Notably, semaphorin expression is altered in many human diseases, such as immunopathologies, neurodegenerative diseases and cancer. This underscores the importance of semaphorins as regulatory factors in the tissue microenvironment and has prompted growing interest for assessing their potential relevance in medicine. This review article surveys the main contexts in which semaphorins have been found to regulate developing and healthy adult tissues, and the signaling cascades implicated in these functions. Vis a vis, we will highlight the main pathological processes in which semaphorins are thought to have a role thereof.

NRP2 as an Emerging Angiogenic Player; Promoting Endothelial Cell Adhesion and Migration by Regulating Recycling of α5 Integrin

Angiogenesis relies on the ability of endothelial cells (ECs) to migrate over the extracellular matrix via integrin receptors to respond to an angiogenic stimulus. Of the two neuropilin (NRP) orthologs to be identified, both have been reported to be expressed on normal blood and lymphatic ECs, and to play roles in the formation of blood and lymphatic vascular networks during angiogenesis. Whilst the role of NRP1 and its interactions with integrins during angiogenesis has been widely studied, the role of NRP2 in ECs is poorly understood. Here we demonstrate that NRP2 promotes Rac-1 mediated EC adhesion and migration over fibronectin (FN) matrices in a mechanistically distinct fashion to NRP1, showing no dependence on β3 integrin (ITGB3) expression, or VEGF stimulation. Furthermore, we highlight evidence of a regulatory crosstalk between NRP2 and α5 integrin (ITGA5) in ECs, with NRP2 depletion eliciting an upregulation of ITGA5 expression and disruptions in ITGA5 cellular organization. Finally, we propose a mechanism whereby NRP2 promotes ITGA5 recycling in ECs; NRP2 depleted ECs were found to exhibit reduced levels of total ITGA5 subunit recycling compared to wild-type (WT) ECs. Our findings expose NRP2 as a novel angiogenic player by promoting ITGA5-mediated EC adhesion and migration on FN.

T-cell specific upregulation of Sema4A as risk factor for autoimmunity in systemic lupus erythematosus and rheumatoid arthritis

The aim of the present study was to evaluate the impact of SEMA4A genetic variants on expression of sema4A protein and its relation to autoimmunity development in Systemic Lupus Erythematosus and Rheumatoid Arthritis patients. A total of 541 SLE patients, 390 RA patients and 607 healthy individuals were genotyped. We also assessed SEMA4A mRNA expression from whole blood cells and the in vitro protein production from resting and activated T lymphocytes as well as mature dendritic cells from healthy individuals stratified according to their genotypes for SLE/RA associated SEMA4A variants. Our results showed that T/T genotype for rs3738581 SNP is associated with both RA and SLE development (p = .000053, OR = 2.35; p = .0019, OR = 2.07, respectively; statistical power = 100%) and also to an increased in vitro sema4A production in active T lymphocytes. Our findings are indicative of a T cell-specific upregulation of sema4A in the presence of T/T genotype, being a risk factor for SLE and RA.

Semaphorin 5A suppresses the proliferation and migration of lung adenocarcinoma cells

Semaphorin 5A (SEMA5A), a member of the semaphorin family, plays an important role in axonal guidance. Previously, the authors identified another possible role of SEMA5A as a prognostic biomarker for non-smoking women with lung adenocarcinoma in Taiwan, and this phenomenon has been validated in other ethnic groups. However, the functional significance of SEMA5A in lung adenocarcinoma remains unclear. Therefore, we assessed the function of SEMA5A in three lung adenocarcinoma cell lines in this study. Kaplan-Meier Plotter for lung cancer was conducted for survival analyses. Reverse transcription-quantitative PCR (RT-qPCR) and western blot analysis were performed to investigate the expression and post-translational regulation of SEMA5A in lung adenocar-cinoma cell lines. A pre-designed PyroMark CpG assay and 5-aza-2′-deoxycytidine treatment were used to measure the methylation levels of SEMA5A. The biological functions of lung adenocarcinoma cells overexpressing SEMA5A were investigated by microarrays, and validated both in vitro (proliferation, colony formation and migration assays) and in vivo (tumor xenografts) experiments. The results revealed that the hypermethylation of SEMA5A and the cleavage of the extracellular domain of SEMA5A were responsible for the downregulation of the SEMA5A levels in lung adenocarcinoma cells (A549 and H1299) as compared to the normal controls. Functional analysis of SEMA5A-regulated genes revealed that they were involved in cellular growth and proliferation. The overexpression of SEMA5A in A549 and H1299 cells significantly decreased the proliferation (P<0.01), colony formation (P<0.001) and migratory ability (P<0.01) of the cells. The suppressive effects of SEMA5A on the proliferative and migratory ability of the cells were also observed in both in vitro and in vivo experiments using brain metastatic Bm7 lung adenocarcinoma cells. On the whole, the findings of this study suggest a suppressive role for SEMA5A in lung adenocarcinoma involving the inhibition of the proliferation and migration of lung transformed cells.

A rationally designed NRP1-independent superagonist SEMA3A mutant is an effective anticancer agent

Vascular normalizing strategies, aimed at ameliorating blood vessel perfusion and lessening tissue hypoxia, are treatments that may improve the outcome of cancer patients. Secreted class 3 semaphorins (SEMA3), which are thought to directly bind neuropilin (NRP) co-receptors that, in turn, associate with and elicit plexin (PLXN) receptor signaling, are effective normalizing agents of the cancer vasculature. Yet, SEMA3A was also reported to trigger adverse side effects via NRP1. We rationally designed and generated a safe, parenterally deliverable, and NRP1-independent SEMA3A point mutant isoform that, unlike its wild-type counterpart, binds PLXNA4 with nanomolar affinity and has much greater biochemical and biological activities in cultured endothelial cells. In vivo, when parenterally administered in mouse models of pancreatic cancer, the NRP1-independent SEMA3A point mutant successfully normalized the vasculature, inhibited tumor growth, curbed metastatic dissemination, and effectively improved the supply and anticancer activity of chemotherapy. Mutant SEMA3A also inhibited retinal neovascularization in a mouse model of age-related macular degeneration. In summary, mutant SEMA3A is a vascular normalizing agent that can be exploited to treat cancer and, potentially, other diseases characterized by pathological angiogenesis.

Semaphorin/neuropilin binding specificities are stable over 400 million years of evolution

Semaphorins are a large and important family of signaling molecules conserved in Bilateria. An important determinant of the biological function of their largest class, the secreted class 3 semaphorins, is the specificity of their binding to neuropilins, a key component of a larger holoreceptor complex. We compared these binding specificities in mice and zebrafish, species whose most recent common ancestor was more than 400 million years in the past. We also compared the binding specificities of zebrafish class 3 semaphorins that were duplicated very early within the teleost lineage. We found a surprising conservation of neuropilin binding specificities when comparing both paralogous zebrafish semaphorin pairs and orthologous zebrafish and mouse semaphorin pairs. This finding was further supported by a remarkable conservation of binding specificities in cross-species pairings of semaphorins and neuropilins. Our results suggest that the qualitative specificities with which particular semaphorins bind to particular neuropilins has remained nearly invariant over approximately 400 million years of evolution.

Expression of Semaphorin 3B (SEMA3B) in Various Grades of Endometrial Cancer

BACKGROUND SEMA3B is known as an inhibitor of angiogenesis and cell proliferation. During carcinogenesis, the loss of SEMA3B function is observed, which results in the progression of neoplastic changes. The aim of this study was to evaluate the expression profile of SEMA3B in endometrial cancer (G1-G3) in comparison to the control group and to assess whether the observed changes in expression could become a molecular marker in endometrial cancer. MATERIAL AND METHODS The study group consisted of 45 patients diagnosed with endometrial cancer (G1, 17; G2, 15; G3, 13). The control group included 15 patients. SEMA3B expression was assessed using the immunohistochemical method. Statistical analysis was carried out using the Statistica 12 PL program (StatSoft, USA). It included the Kruskal-Wallis test and post hoc Dunn's test (p<0.05). RESULTS Statistically significant differences in the level of SEMA3B expression were observed between all analyzed groups. The expression pattern of SEMA3B was as follows: cancer cells G1>G2>G3; endothelial cells: G3>G1>G2; stromal cells: G2>G1>G3. CONCLUSIONS Analysis of the SEMA3B expression profile shows the complexity of neoplastic transformation, which confirms the different expression of SEMA3B in endometrial cancer cells and endothelial cells. The present results and data in the literature data suggest that SEMA3B expression indicates the progression of carcinogenesis in the context of endometrial cancer.

Epidermal growth factor-containing fibulin-like extracellular matrix protein 1 (EFEMP1) suppressed the growth of hepatocellular carcinoma cells by promoting Semaphorin 3B(SEMA3B)

AIM

Epidermal growth factor-containing fibulin-like extracellular matrix protein 1(EFEMP1) has been found to be involved in the occurrence and development of many cancers. The relationship between EFEMP1 and the development of hepatocellular carcinoma (HCC) and the molecular mechanism are not fully understood.

METHODS

Real-time polymerase chain reaction (PCR) and tissue microarray were used to detect the expression of EFEMP1 in HCC cell lines and tissue. Methylation-specific PCR assay was used to measure the methylation level of EFEMP1 in HCC cell lines and tissue. To study the function of EFEMP1 on cell function, Huh7 and HepG2 were infected with lentiviral particles expressing EFEMP1. MTT assay and colony formation assay were used to examine the effect of EFEMP1 on cell proliferation. Annexin-VAPC/7-AAD double were used to detect the effect of EFEMP1 on cell apoptosis. To further detect the effect of EFEMP1 on the development of HCC in vivo, we performed the tumor formation experiment in nude mice. Gene chip was used to detect the expression profile of Huh7 and HepG2 overexpressing EFEMP1. To further screen out the differences, GO analysis and pathway analysis were performed. To study the effects of SEMA3B, specific siRNA was used to inhibit the expression of SEMA3B. Chi-squared test and rank sum test were used to analyze the relationship between EFEMP1 expression and HCC clinical characteristic.

RESULTS

The study found that the expression of EFEMP1 was significantly decreased in HCC cell lines and HCC tissues. The expression level of EFEMP1 was related to the TNM (the extent of the tumor, the extent of spread to the lymph nodes, the presence of metastasis) stage and the prognosis of patients with HCC. The decrease of protein expression suggested that the patient prognosis was worse, and the protein level of EFEMP1 may be an independent factor in the prognosis of HCC patients. Promoter methylation may be one of the reasons for EFEMP1 inhibition. EFEMP1 could inhibit the proliferation of HCC cells and promoted the apoptosis of HCC cells to regulate the development of HCC. And EFEMP1 promoted the apoptosis of HCC cells mainly through the mitochondrial apoptosis pathway. EFEMP1 may inhibit the proliferation of HCC cells through the SEMA3B gene in the Axon guidance pathway.

CONCLUSION

In summary, our research revealed the regulation of EFEMP1 on cell proliferation and apoptosis in HCC. EFEMP1 may suppress the growth of HCC cells by promoting SEMA3B.

Class-3 Semaphorins and Their Receptors: Potent Multifunctional Modulators of Tumor Progression

Semaphorins are the products of a large gene family containing 28 genes of which 21 are found in vertebrates. Class-3 semaphorins constitute a subfamily of seven vertebrate semaphorins which differ from the other vertebrate semaphorins in that they are the only secreted semaphorins and are distinguished from other semaphorins by the presence of a basic domain at their C termini. Class-3 semaphorins were initially characterized as axon guidance factors, but have subsequently been found to regulate immune responses, angiogenesis, lymphangiogenesis, and a variety of additional physiological and developmental functions. Most class-3 semaphorins transduce their signals by binding to receptors belonging to the neuropilin family which subsequently associate with receptors of the plexin family to form functional class-3 semaphorin receptors. Recent evidence suggests that class-3 semaphorins also fulfill important regulatory roles in multiple forms of cancer. Several class-3 semaphorins function as endogenous inhibitors of tumor angiogenesis. Others were found to inhibit tumor metastasis by inhibition of tumor lymphangiogenesis, by direct effects on the behavior of tumor cells, or by modulation of immune responses. Notably, some semaphorins such as sema3C and sema3E have also been found to potentiate tumor progression using various mechanisms. This review focuses on the roles of the different class-3 semaphorins in tumor progression.

The extracellular SEMA domain attenuates intracellular apoptotic signaling of semaphorin 6A in lung cancer cells

Semaphorin 6A (SEMA6A), a membrane-bound protein, is downregulated in lung cancer tissue compared to its adjacent normal tissue. However, the functions of SEMA6A in lung cancer cells are still unclear. In the present study, full length SEMA6A and various truncations were transfected into lung cancer cells to investigate the role of the different domains of SEMA6A in cell proliferation and survival, apoptosis, and in vivo tumor growth. SEMA6A-induced cell signaling was explored using gene silencing, co-immunoprecipitation, and co-culture assays. Our results showed that overexpression of SEMA6A reduced the growth of lung cancer cells in vitro and in vivo, and silencing SEMA6A increased the proliferation of normal lung fibroblasts. Truncated SEMA6A lacking the SEMA domain or the extracellular region induced more apoptosis than full length SEMA6A, and reintroducing the SEMA domain attenuated the apoptosis. Fas-associated protein with death domain (FADD) bound to the cytosolic region of truncated SEMA6A and was involved in SEMA6A-associated cytosol-induced apoptosis. This study suggests a novel function of SEMA6A in inducing apoptosis via FADD binding in lung cancer cells.

Semaphorins and their Signaling Mechanisms

Semaphorins are extracellular signaling proteins that are essential for the development and maintenance of many organs and tissues. The more than 20-member semaphorin protein family includes secreted, transmembrane and cell surface-attached proteins with diverse structures, each characterized by a single cysteine-rich extracellular sema domain, the defining feature of the family. Early studies revealed that semaphorins function as axon guidance molecules, but it is now understood that semaphorins are key regulators of morphology and motility in many different cell types including those that make up the nervous, cardiovascular, immune, endocrine, hepatic, renal, reproductive, respiratory and musculoskeletal systems, as well as in cancer cells. Semaphorin signaling occurs predominantly through Plexin receptors and results in changes to the cytoskeletal and adhesive machinery that regulate cellular morphology. While much remains to be learned about the mechanisms underlying the effects of semaphorins, exciting work has begun to reveal how semaphorin signaling is fine-tuned through different receptor complexes and other mechanisms to achieve specific outcomes in various cellular contexts and physiological systems. These and future studies will lead to a more complete understanding of semaphorin-mediated development and to a greater understanding of how these proteins function in human disease.

Genetic status of KRAS modulates the role of Neuropilin-1 in tumorigenesis

Neuropilin-1 (NRP1), a non-tyrosine kinase receptor, is overexpressed in many cancers including pancreatic and lung cancers. Inhibition of NRP1 expression, however, has differing pro-tumor vs. anti-tumor effects, depending on the cancer types. To understand the differential role of NRP1 in tumorigenesis process, we utilized cells from two different cancer types, pancreatic and lung, each containing either wild type KRAS (KRAS ^wt) or mutant KRAS (KRAS ^mt). Inhibition of NRP1 expression by shRNA in both pancreatic and lung cancer cells containing dominant active KRAS ^mt caused increased cell viability and tumor growth. On the contrary, inhibition of NRP1, in the tumor cells containing KRAS ^wt showed decreased tumor growth. Importantly, concurrent inhibition of KRAS ^mt and NRP1 in the tumor cells reverses the increased viability and leads to tumor inhibition. We found that NRP1 shRNA expressing KRAS ^mt tumor cells caused increased cell viability by decreasing SMAD2 phosphorylation. Our findings demonstrate that the effects of NRP1 knockdown in cancer cells are dependent on the genetic status of KRAS.

GATA3 targets semaphorin 3B in mammary epithelial cells to suppress breast cancer progression and metastasis

Semaphorin 3B (SEMA3B) is a secreted axonal guidance molecule that is expressed during development and throughout adulthood. Recently, SEMA3B has emerged as a tumor suppressor in non-neuronal cells. Here we show that SEMA3B is a direct target of GATA3 transcriptional activity. GATA3 is a key transcription factor that regulates genes involved in mammary luminal cell differentiation and tumor suppression. We show that GATA3 relies on SEMA3B for suppression of tumor growth. Loss of SEMA3B renders GATA3 inactive and promotes aggressive breast cancer development. Overexpression of SEMA3B in cells lacking GATA3 induces a GATA3-like phenotype and higher levels of SEMA3B are associated with better cancer patient prognosis. Moreover, SEMA3B interferes with activation of LIM kinases (LIMK1 and LIMK2) to abrogate breast cancer progression. Our data provide new insights into the role of SEMA3B in mammary gland and provides a new branch of GATA3 signaling that is pivotal for inhibition of breast cancer progression and metastasis.

131I-labeled monoclonal antibody targeting neuropilin receptor type-2 for tumor SPECT imaging

As a co-receptor for vascular endothelial growth factor‑3 (VEGF‑3), neuropilin receptor type‑2 (NRP‑2) plays a central role in lymphangiogenesis and angiogenesis. Recently, mounting data of evidence show that NRP‑2 is overexpressed in several human cancers, and its overexpression is often associated with poor prognosis. Therefore, it is necessary for us to develop an affinity reagent for noninvasive imaging of NRP‑2 expression because it may be possible to provide early cancer diagnosis, more accurate prognosis, and better treatment planning. Due to their high affinity, and specificity, monoclonal antibodies (mAbs) have been considered attractive candidates for targeted cancer therapy and diagnostics. We recently generated and validated a monoclonal antibody that specifically binds NRP‑2 b1b2 domain with no cross‑reactivity to NRP‑1 b1b2 domain, also known to be overexpressed in a variety of cancers. Here, we developed a single photon emission computed tomography (SPECT) probe for imaging NRP‑2- positive tumors. Anti‑NRP‑2 monoclonal antibodies were prepared by hybridomas and were labeled with iodine‑131 by chloramine‑T method. The in vitro physicochemical properties of 131I‑anti‑NRP‑2 mAb was determined. Binding affinity and specificity of 131I‑anti‑NRP‑2 mAb to NRP‑2 were assessed using human lung adenocarcinoma A549 cells. Biodistribution and SPECT studies were performed in mice bearing A549 tumor xenografts to evaluate the in vivo performance of 131I‑anti‑NRP‑2 mAb. The preparation of anti‑NRP‑2 mAb was completed successfully by hybridoma with high purity (>95%) and specific for NRP‑2 b1b2 domain, but not NRP‑1 b1b2 domain. The radiosynthesis of 131I‑anti‑NRP‑2 mAb was completed successfully within 60 min with high labelling efficiency (94.69±3.63%), and radiochemical purity (98.56±0.48%). The resulting probe, 131I‑anti‑NRP‑2 mAb displayed excellent stability in PBS solution during 24-72 h. 131I‑anti‑NRP‑2 mAb showed high binding affinity with A549 cells (96.6±1.44 nM). In vivo biodistribution and SPECT studies demonstrated targeting of A549 glioma xenografts was NRP‑2 specific. The tumor uptake was 5.86±0.27% ID/g at 6 h, and kept at high level of 4.64±0.82% ID/g at 72 h‑post‑injection. The tumor to contralateral muscle ratio (T/NT) was 2.08±0.33 at 6 h, and reached the highest level of 3.83±0.18 at 72 h after injection. SPECT imaging studies revealed that 131I‑anti‑NRP‑2 mAb could clearly identify A549 tumors with good contrast, especially at 48‑72 h after injection. In conclusion, this study demonstrates that 131I‑anti‑NRP‑2 mAb exhibited highly selective uptake in NRP‑2‑expressing tumors, and may provide a promising SPECT probe for imaging NRP‑2 positive tumors.

Proximal and distal regulation of the HYAL1 gene cluster by the estrogen receptor α in breast cancer cells

Chromosomal and genome abnormalities at the 3p21.3 locus are frequent events linked to epithelial cancers, including ovarian and breast cancers. Genes encoded in the 3p21.3 cluster include HYAL1, HYAL2 and HYAL3 members of hyaluronidases involved in the breakdown of hyaluronan, an abundant component of the vertebrate extracellular matrix. However, the transcriptional regulation of HYAL genes is poorly defined. Here, we identified the estrogen receptor ERα as a negative regulator of HYAL1 expression in breast cancer cells. Integrative data mining using METABRIC dataset revealed a significant inverse correlation between ERα and HYAL1 gene expression in human breast tumors. ChIP-Seq analysis identified several ERα binding sites within the 3p21.3 locus, supporting the role of estrogen as an upstream signal that diversely regulates the expression of 3p21.3 genes at both proximal and distal locations. Of these, HYAL1 was repressed by estrogen through ERα binding to a consensus estrogen response element (ERE) located in the proximal promoter of HYAL1 and flanked by an Sp1 binding site, required to achieve optimal estrogen repression. The repressive chromatin mark H3K27me3 was increased at the proximal HYAL1 ERE but not at other EREs contained in the cluster, providing a mechanism to selectively downregulate HYAL1. The HYAL1 repression was also specific to ERα and not to ERβ, whose expression did not correlate with HYAL1 in human breast tumors. This study identifies HYAL1 as an ERα target gene and provides a functional framework for the direct effect of estrogen on 3p21.3 genes in breast cancer cells.

The role of the semaphorins in cancer

The semaphorins were initially characterized as axon guidance factors, but have subsequently been implicated also in the regulation of immune responses, angiogenesis, organ formation, and a variety of additional physiological and developmental functions. The semaphorin family contains more then 20 genes divided into 7 subfamilies, all of which contain the signature sema domain. The semaphorins transduce signals by binding to receptors belonging to the neuropilin or plexin families. Additional receptors which form complexes with these primary semaphorin receptors are also frequently involved in semaphorin signaling. Recent evidence suggests that semaphorins also fulfill important roles in the etiology of multiple forms of cancer. Some semaphorins have been found to function as bona-fide tumor suppressors and to inhibit tumor progression by various mechanisms while other semaphorins function as inducers and promoters of tumor progression.

Expression of semaphorin 6D and its receptor plexin-A1 in gastric cancer and their association with tumor angiogenesis

The semaphorin and plexin family of ligands and receptor proteins provides important axon growth and guidance cues required for development. In recent years, studies have expanded their role in the regulation of cardiac morphogenesis and tumorigenesis. However, the mechanism responsible for their role in regulating cancer development and progression has not been clarified. In the present study, semaphorin 6D (Sema6D) and its receptor plexin-A1 were identified to be expressed at high levels in vascular epithelial cells within gastric cancer, and were positively correlated with vascular endothelial growth factor receptor 2 (VEGFR2). These findings verify our hypothesis that Sema6D and plexin-A1 may be closely associated with tumor angiogenesis. Combined with experimental observations in the MGC803 gastric cancer cell line, it was observed that knocking down plexin-A1 signaling led to a decreased expression of VEGFR2 at the messenger RNA and protein levels. Sema6D recognized and activated plexin-A1, which subsequently activated its downstream target, VEGFR2. The activation of VEGFR2 functioned as a positive regulator of tumor angiogenesis. Our data provided an understanding of the complex signaling cascades involved in the angiogenesis-related pathway in tumor cells. In light of our observations, pharmacological interventions targeting Sema6D/plexin-A1/VEGFR2 signaling may potentially be used as a target for the development of novel anti-angiogenic drugs in gastric cancer.

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.

Epigenetic regulation in gallbladder cancer: Promoter methylation profiling as emergent novel biomarkers

DNA methylation, once considered to rule the sex determination in Mary Lyon's hypothesis, has now reached the epicenter of human diseases, from monogenic (e.g. Prader Willi syndrome, Angelman syndromes and Beckwith-Wiedemann syndrome) to polygenic diseases, like cancer. Technological developments from gold standard to high throughput technologies have made tremendous advancement to define the epigenetic mechanism of cancer. Gallbladder cancer (GBC) is a fatal health issue affecting mostly the middle-aged women, whose survival rate is very low due to late symptomatic diagnosis. DNA methylation has become one of the key molecular mechanisms in the tumorigenesis of gallbladder. Various molecules have been reported to be epigenetically altered in GBC. In this review, we have discussed the classes of epigenetics, an overview of DNA methylation, technological approaches for its study, profile of methylated genes, their likely roles in GBC, future prospects of biomarker development and other discovery approaches, including therapeutics.

SEMA3B improves the survival of patients with esophageal squamous cell carcinoma by upregulating p53 and p21

As one of the most common malignancies, esophageal squamous cell carcinoma (ESCC) is ranked as the sixth leading cause of cancer-related death worldwide. In our previous study, by employing cDNA microarray analysis, semaphorin 3B (SEMA3B) was found to be significantly downregulated in ESCC. In the present study, SEMA3B downregulation at the mRNA level was found in 34 of 60 primary ESCCs (56.7%) and in 6 of 9 ESCC cell lines (66.7%) by transcription-polymerase chain reaction (RT-PCR). Moreover, immunohistochemical (IHC) staining of SEMA3B in a tissue microarray further indicated that downregulated expression of SEMA3B protein was found in 125 of 222 (56.3%) ESCC cases and downregulation of SEMA3B protein was significantly correlated with lymph node metastasis (P=0.000), advanced clinicopathological stage (P=0.001) and poor disease-specific survival (P=0.017) of ESCC patients. In addition, functional studies demonstrated that the SEMA3B gene could suppress the tumorigenic ability of ESCC cells and cell motility. Furthermore, it was found that by upregulating p53 and p21 expression and inhibiting Akt (Ser473) phosphorylation, SEMA3B could induce cell cycle arrest at G1/S phase. Taken together, our results suggest that SEMA3B may be an important tumor-suppressor gene in the malignant progression of ESCC, as well as a valuable prognostic marker for ESCC patients.

Mice deficient in poly(C)-binding protein 4 are susceptible to spontaneous tumors through increased expression of ZFP871 that targets p53 for degradation

Poly(C)-binding protein 4 (PCBP4), also called MCG10 and a target of p53, plays a role in the cell cycle and is implicated in lung tumor suppression. Here, we found that PCBP4-deficient mice are prone to lung adenocarcinoma, lymphoma, and kidney tumor and that PCBP4-deficient mouse embryo fibroblasts (MEFs) exhibit enhanced cell proliferation but decreased cellular senescence. We also found that p53 expression is markedly reduced in PCBP4-deficient MEFs and mouse tissues, suggesting that PCBP4 in turn regulates p53 expression. To determine how PCBP4 regulates p53 expression, PCBP4 targets were identified by RNA immunoprecipitation followed by RNA sequencing (RNA-seq). We found that the transcript encoding ZFP871 (zinc finger protein 871; also called ZNF709 in humans) interacts with and is regulated by PCBP4 via mRNA stability. Additionally, we found that ZFP871 physically interacts with p53 and MDM2 proteins. Consistently, ectopic expression of ZFP871 decreases-whereas knockdown of ZFP871 increases-p53 protein stability through a proteasome-dependent degradation pathway. Moreover, loss of ZFP871 reverses the reduction of p53 expression by lack of PCBP4, and thus increased expression of ZFP871 is responsible for decreased expression of p53 in the PCBP4-deficient MEFs and mouse tissues. Interestingly, we found that, like PCBP4, ZFP871 is also regulated by DNA damage and p53. Finally, we showed that knockdown of ZFP871 markedly enhances p53 expression, leading to growth suppression and apoptosis in a p53-dependent manner. Thus, the p53-PCBP4-ZFP871 axis represents a novel feedback loop in the p53 pathway. Together, we hypothesize that PCBP4 is a potential tissue-specific tumor suppressor and that ZFP871 is part of MDM2 and possibly other ubiquitin E3 ligases that target p53 for degradation.

Paired box 5 is a frequently methylated lung cancer tumour suppressor gene interfering β-catenin signalling and GADD45G expression

Recent studies suggest that paired box 5 (PAX5) is down‐regulated in multiple tumours through its promoter methylation. However, the role of PAX5 in non‐small cell lung cancer (NSCLC) pathogenesis remains unclear. The aim of this study is to examine PAX5 expression, its methylation status, biological functions and related molecular mechanism in NSCLC. We found that PAX5 was widely expressed in normal adult tissues but silenced or down‐regulated in 88% (7/8) of NSCLC cell lines. PAX5 expression level was significantly lower in NSCLC than that in adjacent non‐cancerous tissues (P = 0.0201). PAX5 down‐regulation was closely associated with its promoter hypermethylation status and PAX5 expression could be restored by demethylation treatment. Frequent PAX5 promoter methylation in primary tumours (70%) was correlated with lung tumour histological types (P = 0.006). Ectopic expression of PAX5 in silenced lung cancer cell lines (A549 and H1975) inhibited their colony formation and cell viability, arrested cell cycle at G2 phase and suppressed cell migration/invasion as well as tumorigenicity in nude mice. Restoration of PAX5 expression resulted in the down‐regulation of β‐catenin and up‐regulation of tissue inhibitors of metalloproteinase 2, GADD45G in lung tumour cells. In summary, PAX5 was found to be an epigenetically inactivated tumour suppressor that inhibits NSCLC cell proliferation and metastasis, through down‐regulating the β‐catenin pathway and up‐regulating GADD45G expression.

Identification of potential therapeutic targets for lung cancer by bioinformatics analysis

The aim of the present study was to identify potential therapeutic targets for lung cancer and explore underlying molecular mechanisms of its development and progression. The gene expression profile datasets no. GSE3268 and GSE19804, which included five and 60 pairs of tumor and normal lung tissue specimens, respectively, were downloaded from Gene Expression Omnibus. Differentially expressed genes (DEGs) between lung cancer and normal tissues were identified, and gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis of the DEGs was performed. Furthermore, protein‑protein interaction (PPI) networks and a transcription factor (TF) regulatory network were constructed and key target genes were screened. A total of 466 DEGs were identified, and the PPI network indicated that IL‑6 and MMP9 had key roles in lung cancer. A PPI module containing 34 nodes and 547 edges was obtained, including PTTG1. The TF regulatory network indicated that TFs of FOSB and LMO2 had a key role. Furthermore, MMP9 was indicated to be the target of FOSB, while PTTG1 was the target of LMO2. In conclusion, the bioinformatics analysis of the present study indicated that IL‑6, MMP9 and PTTG1 may have key roles in the progression and development of lung cancer and may potentially be used as biomarkers or specific therapeutic targets for lung cancer.

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.

Decreased semaphorin 3A expression is associated with a poor prognosis in patients with epithelial ovarian carcinoma

Semaphorin 3A (SEMA3A) was initially identified to play an important role in axonal guidance. Recently, SEMA3A has also been considered as a candidate tumor suppressor, since it is often downregulated in numerous types of cancer, including prostate cancer, breast cancer and glioma. However, the biological role of SEMA3A in ovarian cancer is not clear. In the present study, the expression of SEMA3A in ovarian cancer and normal ovarian epithelial tissues was detected by immunofluorescence, reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and western blotting, and the associations between the expression of SEMA3A with the development of ovarian cancer, clinicopathological characteristics and survival were also analyzed. Results from immunofluorescence, RT‑qPCR and western blotting showed that SEMA3A is significantly downregulated in epithelial ovarian carcinoma compared to normal ovarian epithelial specimens (P<0.05). The expression levels of SEMA3A were lower in the cancer tissues with III/IV stage [the International Federation of Gynecology and Obstetrics (FIGO) stage], poor histological grade, lymph node metastasis and distant metastasis compared to that in the cancer tissues with I/II stage (FIGO), well histological grade, or without lymph node metastasis and distant metastasis (P<0.05). A decreased expression of SEMA3A is associated with a poor prognosis (P<0.001). The present findings suggest that decreased SEMA3A expression may be associated with the development of epithelial ovarian carcinoma, and therefore, SEMA3A may be a valuable prognostic marker, as well as a potential molecular therapy target for ovarian cancer patients.

The emerging role of class-3 semaphorins and their neuropilin receptors in oncology

The semaphorins, discovered over 20 years ago, are a large family of secreted or transmembrane and glycophosphatidylinositol -anchored proteins initially identified as axon guidance molecules crucial for the development of the nervous system. It has now been established that they also play important roles in organ development and function, especially involving the immune, respiratory, and cardiovascular systems, and in pathological disorders, including cancer. During tumor progression, semaphorins can have both pro- and anti-tumor functions, and this has created complexities in our understanding of these systems. Semaphorins may affect tumor growth and metastases by directly targeting tumor cells, as well as indirectly by interacting with and influencing cells from the micro-environment and vasculature. Mechanistically, semaphorins, through binding to their receptors, neuropilins and plexins, affect pathways involved in cell adhesion, migration, invasion, proliferation, and survival. Importantly, neuropilins also act as co-receptors for several growth factors and enhance their signaling activities, while class 3 semaphorins may interfere with this. In this review, we focus on the secreted class 3 semaphorins and their neuropilin co-receptors in cancer, including aspects of their signaling that may be clinically relevant.

BRG1/SMARCA4 inactivation promotes non-small cell lung cancer aggressiveness by altering chromatin organization

SWI/SNF chromatin remodeling complexes regulate critical cellular processes, including cell-cycle control, programmed cell death, differentiation, genomic instability, and DNA repair. Inactivation of this class of chromatin remodeling complex has been associated with a variety of malignancies, including lung, ovarian, renal, liver, and pediatric cancers. In particular, approximately 10% of primary human lung non-small cell lung cancers (NSCLC) display attenuations in the BRG1 ATPase, a core factor in SWI/SNF complexes. To evaluate the role of BRG1 attenuation in NSCLC development, we examined the effect of BRG1 silencing in primary and established human NSCLC cells. BRG1 loss altered cellular morphology and increased tumorigenic potential. Gene expression analyses showed reduced expression of genes known to be associated with progression of human NSCLC. We demonstrated that BRG1 losses in NSCLC cells were associated with variations in chromatin structure, including differences in nucleosome positioning and occupancy surrounding transcriptional start sites of disease-relevant genes. Our results offer direct evidence that BRG1 attenuation contributes to NSCLC aggressiveness by altering nucleosome positioning at a wide range of genes, including key cancer-associated genes.

NRP-1 expression in bladder cancer and its implications for tumor progression

Neuropilin-1 (NRP-1) overexpression has been reported in a variety of human cancers. However, the role of NRP-1 in bladder cancer (BC) remains unclear. The aim of present study was to analyze NRP-1 protein expression in BC tissues and to assess its prognostic significance for BC. NRP-1 messenger ribonucleic acid (mRNA) and protein expression were determined by real-time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) and immunohistochemistry in specimens of primary cancer and their adjacent noncancerous tissues in BC patients. Additionally, NRP-1 protein expression in 139 archived paraffin-embedded BC samples was analyzed by immunohistochemistry and correlated with clinicopathological characteristics and survival. Student's t test, Spearman's rank correlation, Kaplan-Meier plots, and Cox's proportional hazards regression model were used to analyze the data. By qRT-PCR and immunohistochemistry, the levels of NRP-1 mRNA and protein were significantly higher in BC, compared to that in adjacent noncancerous tissues (P<0.001). High expression of NRP-1 was significantly associated with histologic grade (P=0.016) and tumor stage (P=0.001). Multivariate analysis showed that high expression of NRP-1 was an independent prognostic factor for overall survival. Our study suggests that overexpression of NRP-1 may play an important role in the progression of BC, and NRP-1 expression may serve as a biomarker for poor prognosis for BC.

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.

The role of the plexin-A2 receptor in semaphorin-3A and semaphorin-3B signal transduction

Class-3 semaphorins are anti-angiogenic and anti-tumorigenic guidance factors that bind to neuropilins which in turn associate with class-A plexins to transduce semaphorin signals. To study the role of the plexin-A2 receptor in semaphorin signaling, we silenced its expression in endothelial cells and in glioblastoma cells. The silencing did not affect sema3A signaling which depended on neuropilin-1, plexin-A1 and plexin-A4, but abolished completely sema3B signaling which required in addition plexin-A4 and one of the two neuropilins. Interestingly, over-expression of plexin-A2 in plexin-A1 or plexin-A4 silenced cells restored responses to both semaphorins although it nullified their ability to differentiate between them, suggesting that when over-expressed plexin-A2 is functionally interchangeable with other class-A plexins. In-contrast, although plexin-A4 over-expression restored sema3A signaling in plexin-A1 silenced cells, it failed to restore sema3B signaling in plexin-A2 silenced cells. It follows that the identity of plexins in functional semaphorin receptors can be flexible depending on their expression level. Our results suggest that changes in the expression of plexins induced by microenvironmental cues can trigger differential responses of different populations of migrating cells to encountered gradients of semaphorins.

Elimination of aberrant DRG circuitries in Sema3A mutant mice leads to extensive neuronal deficits

Axon guidance molecules determine the pattern of neuronal circuits. Accuracy of the process is ensured by unknown mechanisms that correct early guidance errors. Since the time frame of error correction in Sema3A null mice partly overlaps with the period of naturally occurring cell death in dorsal root ganglia (DRG) development, we tested the hypothesis that apoptosis of misguided neurons enables error correction. We crossed BAX null mice, in which DRG apoptosis is blocked, with Sema3A null mice to induce errors. Analyses of these double-null mouse embryos showed that the elimination of abnormal projections is not blocked in the absence of BAX. Surprisingly however, there are fewer surviving neurons in Sema3A null or Sema3A/BAX double-null newborn mice than in wild-type mice. These results suggest that guidance errors are corrected by a BAX-independent cell death mechanism. Thus, aberrant axonal guidance may lead to reductions in neuronal numbers to suboptimal levels, perhaps increasing the likelihood of neuropathological consequences later in life.

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.