Semaphorin 3E suppresses tumor cell death triggered by the plexin D1 dependence receptor in metastatic breast cancers

Plexin D1 accumulation in the spinal motor neurons of patients with amyotrophic lateral sclerosis

BACKGROUND

Plexin D1 in endothelial cells (ECs) in the spinal cord (SC) has emerged as a key protein in spinal motor neuron (MN) maturation. Here, we pathologically investigated plexin D1 expression in the SCs of patients with sporadic amyotrophic lateral sclerosis (sALS) to clarify the association between plexin D1 expression in ECs and MN degeneration.

METHODS

We measured plexin D1 expression in the ECs of lumbar SC tissue samples from 11 patients with sALS and 8 age- and sex-matched patients with other non-inflammatory neurological diseases (OND) by immunohistochemistry. Additionally, the number and percentage of plexin D1-positive MNs in lumbar MNs were assessed in each case. We also evaluated the immunoreactivity of TAR DNA binding protein (TARDBP) in plexin D1-positive MNs.

RESULTS

Immunohistochemistry showed that there was no obvious difference in plexin D1 expression in ECs between sALS and OND cases. Unexpectedly, plexin D1 accumulation was greater in MNs of patients with sALS compared with those with OND. The number and percentage of plexin D1-positive MNs in patients with sALS were significantly greater than in patients with OND (median [interquartile range], 6 [1-11] vs. 1 [0-3.3], p = 0.0349; and 12.9 % [5.5-15.5] vs. 1.1 % [0-3.5], p = 0.0032, respectively). Plexin D1-positive MNs showed TARDBP cytoplasmic mislocalization and aggregation.

CONCLUSIONS

Plexin D1 was similarly expressed in ECs between sALS and OND cases, but accumulated in the degenerated MNs of patients with sALS. Plexin D1 accumulation in MNs may provide new insights into the mechanism of MN degeneration in ALS.

Semaphorin 3E-Plexin D1 Axis Drives Lung Fibrosis through ErbB2-Mediated Fibroblast Activation

Idiopathic pulmonary fibrosis (IPF) is characterized by excessive fibroblast recruitment and persistent extracellular matrix deposition at sites of tissue injury, leading to severe morbidity and mortality. However, the precise mechanisms by which fibroblasts contribute to IPF pathogenesis remain poorly understood. The study reveals that Sema3E and its receptor Plexin D1 are significantly overexpressed in the lungs of IPF patients and bleomycin (BLM)-induced lung fibrotic mice. Elevated plasma levels of Sema3E in IPF patients are negatively correlated with lung function. Importantly, Sema3E in IPF lungs predominantly exists as the P61-Sema3E. The knockdown of Sema3E or Plexin D1 effectively inhibits fibroblast activation, proliferation, and migration. Mechanistically, Furin-mediated cleavage of P87-Sema3E into P61-Sema3E drives these pro-fibrotic activities, with P61-Sema3E-PlexinD1 axis promoting fibroblast activation, proliferation, and migration by affecting the phosphorylation of ErbB2, which subsequently activates the ErbB2 pathways. Additionally, Furin inhibition reduces fibroblast activity by decreasing P61-Sema3E production. In vivo, both whole-lung Sema3E knockdown and fibroblast-specific Sema3E knockout confer protection against BLM-induced lung fibrosis. These findings underscore the crucial role of the P61-Sema3E-Plexin D1 axis in IPF pathogenesis and suggest that targeting this pathway may hold promise for the development of novel therapeutic strategies for IPF treatment.

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.

Expression of Semaphorin3E/PlexinD1 in human airway smooth muscle cells of patients with COPD

Semaphorin3E (Sema3E) is a member of axon guidance proteins that have emerged recently as essential regulators of cell migration and proliferation. It binds to PlexinD1 with high affinity and is expressed in different cell types, including immune, cancer, and epithelial cells. Recent work in our lab has revealed a critical immunoregulatory role of Sema3E in experimental allergic asthma; however, its role in chronic obstructive pulmonary disease (COPD) remains unclear. This study aimed to investigate the expression of Sema3E and its receptor, PlexinD1, in the airways of patients with COPD and whether Sema3E regulates airway smooth muscle (ASM) cell proliferation, a key feature of airway remodeling in COPD. We first demonstrate that human ASM cells obtained from COPD express Sema3E and PlexinD1 at both mRNA and protein levels. Also, bronchial sections from patients with COPD displayed immunoreactivity of Sema3E and its receptor PlexinD1, suggestive of functional contribution of Sema3E in airway remodeling. In contrast to ASM cells from healthy donors, Sema3E did not inhibit the platelet-derived growth factor (PDGF) induced cell proliferation in ASM cells of patients with COPD that were consistent with the binding of endogenous Sema3E to its receptors on the cell surface and the expression and release of p61KDa-Sema3E isoform. Our results support the Sema3E-PlexinD1 axis involvement in COPD airway smooth muscle remodeling.NEW & NOTEWORTHY Semaphorin3E (Sema3E), a protein guiding cell movement, is found in various cell types like neural, immune, cancer, and epithelial cells. This study examines Sema3E in chronic obstructive pulmonary disease (COPD) airways. In patients with COPD, airway smooth muscle cells express Sema3E and its receptor PlxD1. Unlike healthy cells, Sema3E does not hinder cell proliferation in COPD, indicating involvement in airway remodeling. These findings highlight the Sema3E-PlxD1 axis in COPD airway changes.

Semaphorin 3D promotes pancreatic ductal adenocarcinoma progression and metastasis through macrophage reprogramming

Axon guidance molecules are frequently altered in pancreatic ductal adenocarcinoma (PDA) and influence PDA progression. However, the molecular mechanism remained unclear. Using genetically engineered mouse models to examine semaphorin 3D (SEMA3D), we identified a dual role for tumor- and nerve-derived SEMA3D in the malignant transformation of pancreatic epithelial cells and invasive PDA development. Pancreatic-specific knockout of the SEMA3D gene from the KRASG12D and TP53R172H mutation knock-in, PDX1-Cre(KPC) mouse model demonstrated delayed tumor initiation, prolonged survival, absence of metastasis, and reduced M2 macrophage expression. Mechanistically, tumor- and nerve-derived SEMA3D indirectly reprograms macrophages through KRASMUT-dependent ARF6 signaling in PDA cells, resulting in increased lactate production, which is sensed by GPCR132 on macrophages to stimulate protumorigenic M2 polarization. Multiplex immunohistochemistry demonstrated increased M2-polarized macrophages proximal to nerves in SEMA3D-expressing human PDA tissue. This study suggests that altered SEMA3D expression leads to an acquisition of cancer-promoting functions, and nerve-derived SEMA3D is "hijacked" by PDA cells to support growth and metastasis in a KRASMUT-dependent manner.

Sema-3E/PlexinD1 axis modulates dendritic cell phenotypes and functions: Current status and future implications

This comprehensive research review explores the complex interplay between the Sema-3E/PlexinD1 axis and dendritic cells (DCs), highlighting its critical role in immune modulation with implications for clinical application Critical regulators of immune responses Dendritic cells are central to adaptive immunity, and the Sema-3E /PlexinD1 axis emerges as a key modulator affecting their phenotypes and functions Review delineates the impact of this signaling axis on DC maturation, migration, antigen presentation, and cytokine production, unravels its multifaceted role in shaping the immune response. Recognizing the limitations and gaps in current knowledge, the study highlights the need for further studies to condition downstream signaling events and related information experienced by the Sema-3E/PlexinD1 axis emphasizes the clarity of the immune system. The review concludes by identifying opportunities for translation, focusing on therapeutic and diagnostic potential. It highlights the importance of collaborative, interdisciplinary efforts to address the challenges and harness the therapeutic and pathological potential of targeting the Sema-3E/PlexinD1 axis, thus opening the way for transformative advances in immunology and clinical medicine.

Plexin D1 emerges as a novel target in the development of neural lineage plasticity in treatment-resistant prostate cancer

Treatment-induced neuroendocrine prostate cancer (t-NEPC) often arises from adenocarcinoma via lineage plasticity in response to androgen receptor signaling inhibitors, such as enzalutamide. However, the specific regulators and targets involved in the transition to NEPC are not well understood. Plexin D1 (PLXND1) is a cellular receptor of the semaphorin (SEMA) family that plays important roles in modulating the cytoskeleton and cell adhesion. Here, we found that PLXND1 was highly expressed and positively correlated with neuroendocrine markers in patients with NEPC. High PLXND1 expression was associated with poorer prognosis in prostate cancer patients. Additionally, PLXND1 was upregulated and negatively regulated by androgen receptor signaling in enzalutamide-resistant cells. Knockdown or knockout of PLXND1 inhibited neural lineage pathways, thereby suppressing NEPC cell proliferation, patient derived xenograft (PDX) tumor organoid viability, and xenograft tumor growth. Mechanistically, the heat shock protein 70 (HSP70) regulated PLXND1 protein stability through degradation, and inhibition of HSP70 decreased PLXND1 expression and NEPC organoid growth. In summary, our findings indicate that PLXND1 could serve as a promising therapeutic target and molecular marker for NEPC.

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.

FOXP1 regulates the development of excitatory synaptic inputs onto striatal neurons and induces phenotypic reversal with reinstatement

Long-range glutamatergic inputs originating from the cortex and thalamus are indispensable for striatal development, providing the foundation for motor and cognitive functions. Despite their significance, transcriptional regulation governing these inputs remains largely unknown. We investigated the role of a transcription factor encoded by a high-risk autism-associated gene, FOXP1, in sculpting glutamatergic inputs onto spiny projection neurons (SPNs) within the striatum. We find a neuron subtype-specific role of FOXP1 in strengthening and maturing glutamatergic inputs onto dopamine receptor 2-expressing SPNs (D2 SPNs). We also find that FOXP1 promotes synaptically driven excitability in these neurons. Using single-nuclei RNA sequencing, we identify candidate genes that mediate these cell-autonomous processes through postnatal FOXP1 function at the post-synapse. Last, we demonstrate that postnatal FOXP1 reinstatement rescues electrophysiological deficits, cell type-specific gene expression changes, and behavioral phenotypes. Together, this study enhances our understanding of striatal circuit development and provides proof of concept for a therapeutic approach for FOXP1 syndrome and other neurodevelopmental disorders.

Plexin D1 emerges as a novel target in the development of neural lineage plasticity in treatment-resistant prostate cancer

Treatment-induced neuroendocrine prostate cancer (t-NEPC) often arises from adenocarcinoma via lineage plasticity in response to androgen receptor signaling inhibitors, such as enzalutamide. However, the specific regulators and targets involved in the transition to NEPC are not well understood. Plexin D1 (PLXND1) is a cellular receptor of the semaphorin (SEMA) family that plays important roles in modulating the cytoskeleton and cell adhesion. Here, we found that PLXND1 is highly expressed and positively correlated with neuroendocrine markers in patients with NEPC. High PLXND1 expression is associated with poorer prognosis in prostate cancer patients. Additionally, PLXND1 was upregulated and negatively regulated by androgen receptor signaling in enzalutamide-resistant cells. Knockdown or knockout of PLXND1 inhibit neural lineage pathways, suppressing NEPC cell proliferation, PDX tumor organoid viability, and xenograft tumor growth. Mechanistically, the chaperone protein HSP70 regulates PLXND1 protein stability through degradation, and inhibition of HSP70 decreases PLXND1 expression and NEPC organoid growth. In summary, our findings suggest that PLXND1 could be a new therapeutic target and molecular indicator for NEPC.

Plexina4 and cell survival in the developing zebrafish hindbrain

BACKGROUND

Growth factors are important in the developing and mature nervous system to support the survival of neurons. Developmental signaling molecules are known for their roles in controlling neurogenesis and neural circuit formation. Whether or not these molecules also have roles in cell survival in the developing nervous system is poorly understood. Plexins are a family of transmembrane receptors that bind Semaphorin ligands and are known to function in the guidance of developing axons and blood vessels.

RESULTS

In embryonic zebrafish, plexina4 is expressed widely in the brain, becoming largely restricted to the hindbrain as neurogenesis and differentiation proceed. Apoptosis is increased in the embryonic hindbrain of a plexina4ca307/ca307 CRISPR mutant. Based on the literature, we tested the secreted heat shock protein, Clusterin, as a candidate ligand to mediate cell survival through Plexina4. clusterin is expressed by the floor plate of the embryonic zebrafish hindbrain, in proximity to plexina4-expressing hindbrain cells. Morpholino-mediated knockdown of Clusterin increases cell apoptosis in the hindbrain, with additional cell death observed in epistasis experiments where Clusterin is knocked down in a plexina4 mutant background.

CONCLUSIONS

Our data suggest that Plexina4 promotes cell survival in the developing zebrafish hindbrain, likely through a pathway independent of Clusterin.

Tumor- and Nerve-Derived Axon Guidance Molecule Promotes Pancreatic Ductal Adenocarcinoma Progression and Metastasis through Macrophage Reprogramming

Axon guidance molecules were found to be the gene family most frequently altered in pancreatic ductal adenocarcinoma (PDA) through mutations and copy number changes. However, the exact molecular mechanism regarding PDA development remained unclear. Using genetically engineered mouse models to examine one of the axon guidance molecules, semaphorin 3D (SEMA3D), we found a dual role for tumor-derived SEMA3D in malignant transformation of pancreatic epithelial cells and a role for nerve-derived SEMA3D in PDA development. This was demonstrated by the pancreatic-specific knockout of the SEMA3D gene from the KRAS G12D and TP53 R 172 H mutation knock-in, PDX1-Cre (KPC) mouse model which demonstrated a delayed tumor initiation and growth comparing to the original KPC mouse model. Our results showed that SEMA3D knockout skews the macrophages in the pancreas away from M2 polarization, providing a potential mechanistic role of tumor-derived SEMA3D in PDA development. The KPC mice with the SEMA3D knockout remained metastasis-free, however, died from primary tumor growth. We then tested the hypothesis that a potential compensation mechanism could result from SEMA3D which is naturally expressed by the intratumoral nerves. Our study further revealed that nerve-derived SEMA3D does not reprogram macrophages directly, but reprograms macrophages indirectly through ARF6 signaling and lactate production in PDA tumor cells. SEMA3D increases tumor-secreted lactate which is sensed by GPCR132 on macrophages and subsequently stimulates pro-tumorigenic M2 polarization in vivo. Tumor intrinsic- and extrinsic-SEMA3D induced ARF6 signaling through its receptor Plexin D1 in a mutant KRAS-dependent manner. Consistently, RNA sequencing database analysis revealed an association of higher KRAS MUT expression with an increase in SEMA3D and ARF6 expression in human PDAs. Moreover, multiplex immunohistochemistry analysis showed an increased number of M2-polarized macrophages proximal to nerves in human PDA tissue expressing SEMA3D. Thus, this study suggests altered expression of SEMA3D in tumor cells lead to acquisition of cancer-promoting functions and the axon guidance signaling originating from nerves is "hijacked" by tumor cells to support their growth. Other axon guidance and neuronal development molecules may play a similar dual role which is worth further investigation.

One sentence summary

Tumor- and nerve-derived SEMA3D promotes tumor progression and metastasis through macrophage reprogramming in the tumor microenvironment.

STATEMENT OF SIGNIFICANCE

This study established the dual role of axon guidance molecule, SEMA3D, in the malignant transformation of pancreatic epithelial cells and of nerve-derived SEMA3D in PDA progression and metastasis. It revealed macrophage reprogramming as the mechanism underlying bothroles. Together, this research elucidated how inflammatory responses promote invasive PDA progression and metastasis through an oncogenic process.

Mind the (guidance) signals! Translational relevance of semaphorins, plexins, and neuropilins in pancreatic cancer

Pancreatic cancer is a major cause of demise worldwide. Although key associated genetic changes have been discovered, disease progression is sustained by pathogenic mechanisms that are poorly understood at the molecular level. In particular, the tissue microenvironment of pancreatic adenocarcinoma (PDAC) is usually characterized by high stromal content, scarce recruitment of immune cells, and the presence of neuronal fibers. Semaphorins and their receptors, plexins and neuropilins, comprise a wide family of regulatory signals that control neurons, endothelial and immune cells, embryo development, and normal tissue homeostasis, as well as the microenvironment of human tumors. We focus on the role of these molecular signals in pancreatic cancer progression, as revealed by experimental research and clinical studies, including novel approaches for cancer treatment.

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.

HOXA5 is a key regulator of class 3 semaphorins expression in the synovium of rheumatoid arthritis patients

OBJECTIVE

Class 3 semaphorins are reduced in the synovial tissue of RA patients and these proteins are involved in the pathogenesis of the disease. The aim of this study was to identify the transcription factors involved in the expression of class 3 semaphorins in the synovium of RA patients.

METHODS

Protein and mRNA expression in synovial tissue from RA and individuals at risk (IAR) patients, human umbilical vein endothelial cells (HUVEC) and RA fibroblast-like synoviocytes (FLS) was determined by ELISA, immunoblotting and quantitative PCR. TCF-3, EBF-1 and HOXA5 expression was knocked down using siRNA. Cell viability, migration and invasion were determined using MTT, calcein, wound closure and invasion assays, respectively.

RESULTS

mRNA expression of all class 3 semaphorins was significantly lower in the synovium of RA compared with IAR patients. In silico analysis suggested TCF-3, EBF-1 and HOXA5 as transcription factors involved in the expression of these semaphorins. TCF-3, EBF-1 and HOXA5 silencing significantly reduced the expression of several class 3 semaphorin members in FLS and HUVEC. Importantly, HOXA5 expression was significantly reduced in the synovium of RA compared with IAR patients and was negatively correlated with clinical disease parameters. Additionally, TNF-α down-regulated the HOXA5 expression in FLS and HUVEC. Finally, HOXA5 silencing enhanced the migratory and invasive capacities of FLS and the viability of HUVEC.

CONCLUSION

HOXA5 expression is reduced during the progression of RA and could be a novel therapeutic strategy for modulating the hyperplasia of the synovium, through the regulation of class 3 semaphorins expression.

Adult expression of Semaphorins and Plexins is essential for motor neuron survival

Axon guidance cues direct the growth and steering of neuronal growth cones, thus guiding the axons to their targets during development. Nonetheless, after axons have reached their targets and established functional circuits, many mature neurons continue to express these developmental cues. The role of axon guidance cues in the adult nervous system has not been fully elucidated. Using the expression pattern data available on FlyBase, we found that more than 96% of the guidance genes that are expressed in the Drosophila melanogaster embryo continue to be expressed in adults. We utilized the GeneSwitch and TARGET systems to spatiotemporally knockdown the expression of these guidance genes selectively in the adult neurons, once the development was completed. We performed an RNA interference (RNAi) screen against 44 guidance genes in the adult Drosophila nervous system and identified 14 genes that are required for adult survival and normal motility. Additionally, we show that adult expression of Semaphorins and Plexins in motor neurons is necessary for neuronal survival, indicating that guidance genes have critical functions in the mature nervous system.

Emerging roles and mechanisms of semaphorins activity in cancer

Semaphorins are regulatory molecules that are linked to the modulation of several cancer processes, such as angiogenesis, cancer cell invasiveness and metastasis, tumor growth, as well as cancer cell survival. Semaphorin (SEMA) activity depends on the cancer histotypes and their particularities. In broad terms, the effects of SEMAs result from their interaction with specific receptors/co-receptors - Plexins, Neuropilins and Integrins - and the subsequent effects upon the downstream effectors (e.g. PI3K/AKT, MAPK/ERK). The present article serves as an integrative review work, discussing the broad implications of semaphorins in cancer, focusing on cell proliferation/survival, angiogenesis, invasion, metastasis, stemness, and chemo-resistance/response whilst highlighting their heterogeneity as a family. Herein, we emphasized that semaphorins are largely implicated in cancer progression, interacting with the tumor microenvironment components. Whilst some SEMAs (e.g. SEMA3A, SEMA3B) function widely as tumor suppressors, others (e.g. SEMA3C) act as pro-tumor semaphorins. The differences observed in terms of the biological structure of SEMAs and the particularities of each cancer histotypes require that each semaphorin be viewed as a unique entity, and its roles must be researched accordingly. A more in-depth and comprehensive view of the molecular mechanisms that promote and sustain the malignant behavior of cancer cells is of utmost importance.

Breast tumors interfere with endothelial TRAIL at the premetastatic niche to promote cancer cell seeding

Endothelial cells (ECs) grant access of disseminated cancer cells to distant organs. However, the molecular players regulating the activation of quiescent ECs at the premetastatic niche (PMN) remain elusive. Here, we find that ECs at the PMN coexpress tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and its cognate death receptor 5 (DR5). Unexpectedly, endothelial TRAIL interacts intracellularly with DR5 to prevent its signaling and preserve a quiescent vascular phenotype. In absence of endothelial TRAIL, DR5 activation induces EC death and nuclear factor κB/p38-dependent EC stickiness, compromising vascular integrity and promoting myeloid cell infiltration, breast cancer cell adhesion, and metastasis. Consistently, both down-regulation of endothelial TRAIL at the PMN by proangiogenic tumor-secreted factors and the presence of the endogenous TRAIL inhibitors decoy receptor 1 (DcR1) and DcR2 favor metastasis. This study discloses an intracrine mechanism whereby TRAIL blocks DR5 signaling in quiescent endothelia, acting as gatekeeper of the vascular barrier that is corrupted by the tumor during cancer cell dissemination.

Important Cells and Factors from Tumor Microenvironment Participated in Perineural Invasion

Perineural invasion (PNI) as the fourth way for solid tumors metastasis and invasion has attracted a lot of attention, recent research reported a new point that PNI starts to include axon growth and possible nerve "invasion" to tumors as the component. More and more tumor-nerve crosstalk has been explored to explain the internal mechanism for tumor microenvironment (TME) of some types of tumors tends to observe nerve infiltration. As is well known, the interaction of tumor cells, peripheral blood vessels, extracellular matrix, other non-malignant cells, and signal molecules in TME plays a key role in the occurrence, development, and metastasis of cancer, as to the occurrence and development of PNI. We aim to summarize the current theories on the molecular mediators and pathogenesis of PNI, add the latest scientific research progress, and explore the use of single-cell spatial transcriptomics in this invasion way. A better understanding of PNI may help to understand tumor metastasis and recurrence and will be beneficial for improving staging strategies, new treatment methods, and even paradigm shifts in our treatment of patients.

Coadaptation fostered by the SLIT2-ROBO1 axis facilitates liver metastasis of pancreatic ductal adenocarcinoma

To explore the mechanism of coadaptation and the potential drivers of pancreatic ductal adenocarcinoma (PDAC) metastasis to the liver, we study key molecules involved in this process and their translational value. Premetastatic niche (PMN) and macrometastatic niche (MMN) formation in a mouse model is observed via CT combined with 3D organ reconstruction bioluminescence imaging, and then we screen slit guidance ligand 2 (SLIT2) and its receptor roundabout guidance receptor 1 (ROBO1) as important factors. After we confirm the expression and distribution of SLIT2 and ROBO1 in samples from PDAC patients and several mouse models, we discover that SLIT2-ROBO1-mediated coadaptation facilitated the implantation and outgrowth of PDAC disseminated tumour cells (DTCs) in the liver. We also demonstrate the dependence receptor (DR) characteristics of ROBO1 in a follow-up mechanistic study. A neutralizing antibody targeting ROBO1 significantly attenuate liver metastasis of PDAC by preventing the coadaptation effect. Thus, we demonstrate that coadaptation is supported by the DR characteristics in the PMN and MMN.

The pan-cancer landscape of abnormal DNA methylation and intratumor microorganisms

Microorganisms play very important roles in carcinogenesis, tumor progression, and resistance upon treatment. Due to the challenge of accurately acquiring samples and quantifying low-biomass tissue microorganisms, most studies have focused on the effect of gut microorganisms on cancer treatments, especially the efficacy of immunotherapy. Although recent publications reveal the potential interactions between intratumor microorganisms and the immune microenvironment, whether and to what extent the intratumor microorganism could affect progression and treatment outcome remain controversial. This study is aiming to evaluate the associations among intratumor microorganisms, DNA methylation cancer driver genes, immune response, and clinical outcomes from a pan-cancer perspective, using 6,876 TCGA samples across 21 cancer types. We revealed that tumor microorganism dysbiosis is closely associated with the abnormal tumor methylome and/or tumor microenvironment, which might serve to enhance the proliferation ability and fitness for the therapy of tumors. These findings shed the light on a better understanding of the interactions between tumor cells and carcinogens during and after tumor formation, as well as microorganism-associated methylation alterations that could further serve as biomarkers for clinical outcome assessment.

SEMA5A-PLXNB3 Axis Promotes PDAC Liver Metastasis Outgrowth through Enhancing the Warburg Effect

Patients bearing liver metastasis of pancreatic adeno carcinoma (PDAC) suffer from poor prognosis due to its short duration and high mortality. Complex tumor microenvironment (TME) exists in liver metastatic niches, and tumor-associated macrophages (TAMs) have play vital roles in metastasis generation and outgrowth. We have discovered that M2 type TAM-derived SEMA5A could bind to its tumor cell-expressed receptor PLXNB3 to promote tumor cell proliferation and outgrowth. We utilized liver metastasis samples of PDAC patients, intrasplenic injection mouse models, and Kras G12D/Trp53 R172H/Pdx1-Cre (KPC) mouse models for in vivo study. In mechanism investigation, we have discovered that SEMA5A-PLXNB3 axis could achieve tumor cell proliferation and survival via enhancing aerobic glycolysis termed as the Warburg effects. Targeting this axis may be a potential therapeutic approach for PDAC patients with unresectable liver metastasis.

Genomic Profiling of Metastatic Basal cell Carcinoma Reveals Candidate Drivers of Disease and Therapeutic Targets

Basal cell carcinomas (BCCs) are human beings' most common malignant tumors. Most are easily managed by surgery or topical therapies, and metastasis is rare. Although BCCs can become locally advanced, metastatic BCCs are very uncommon and may be biologically distinct. We assessed the clinicopathologic characteristics of 17 patients with metastatic BCC and pursued whole-exome sequencing of tumor and germline DNA from 8 patients. Genomic profiling revealed aberrant activation of Hedgehog signaling and alterations in GLI transcriptional regulators and Notch and Hippo signaling. Matched local recurrences of primary BCCs and metastases from 3 patients provided evidence of a clonal origin in all cases. Mutations associated with YAP inhibition were found exclusively in 2 hematogenously-spread lung metastases, and metastatic BCCs were enriched for mutations in the YAP/TAZ-binding domain of TEAD genes. Accordingly, YAP/TAZ nuclear localization was associated with metastatic types and Hippo mutations, suggesting an enhanced oncogenic role in hematogenously-spread metastases. Mutations in RET, HGF, and phosphatidylinositol 3‑kinase (PI3K)/protein kinase B (AKT) signaling were enriched compared with a cohort of low clinical-risk BCCs. Our results implicate Hippo and PI3K/AKT dysregulation in metastatic progression of BCCs, making these potential therapeutic targets in metastatic disease. The common clonal origin of matched recurrent and metastatic BCCs suggests that molecular profiling can assist in determining the nature/origin of poorly differentiated metastatic tumors of uncertain type. Genes and pathways enriched for mutations in this cohort are candidate drivers of metastasis and can be used to identify patients at high risk of metastasis who may benefit from aggressive local treatment and careful clinical follow-up.

Silence of a dependence receptor CSF1R in colorectal cancer cells activates tumor-associated macrophages

BACKGROUND

Colony-stimulating factor 1 receptor (CSF1R), a classic tyrosine kinase receptor, has been identified as a proto-oncogene in multiple cancers. The CSF1/CSF1R axis is essential for the survival and differentiation of M2-phenotype tumor-associated macrophages (M2 TAMs). However, we found here that the CSF1R expression was abnormally down-regulated in colorectal cancer (CRC), and its biological functions and underlying mechanisms have become elusive in CRC progression.

METHODS

The expression of class III receptor tyrosine kinases in CRC and normal intestinal mucosa was accessed using The Cancer Genome Atlas and Gene Expression Omnibus datasets and was further validated by our tested cohort. CSF1R was reconstructed in CRC cells to identify its biological functions in vitro and in vivo. We compared CSF1R expression and methylation differences between CRC cells and macrophages. Furthermore, a co-culture system was used to mimic a competitive mechanism between CSF1R-overexpressed CRC cells and M2-like macrophages. We utilized a CSF1R inhibitor PLX3397 to ablate M2 TAMs and evaluated its efficacy on CRC treatment in animal models.

RESULTS

We found here that the CSF1R is silenced in CRC, and the reintroduced expression of the receptor in CRC cells can be cleaved by caspases and constrain tumor growth in vitro and in vivo, functioning as a tumor suppressor gene. We further identified CSF1R as a novel dependence receptor, which has the potential to act as either a tumor suppressor gene or an oncogene, depending on its activated state. In CRC tumors, CSF1R expression is enriched in TAMs, and its expression is associated with poor prognosis in patients ith CRC. In a co-culture system, CRC cells expressing CSF1R compete with M2-like macrophages for CSF1R ligands, resulting in a decrease in CSF1R activation and cell proliferation in macrophages. Blocking CSF1R by PLX3397 could deplete M2 TAMs and augments CD8⁺ T cell infiltration, effectively inhibiting tumor growth and metastasis and improving responses to chemotherapy and immunotherapy.

CONCLUSION

Our findings revealed that CSF1R is a novel identified dependence receptor silenced in CRC. The silence abalienates its ligands to stimulate CSF1R expressed on M2 TAMs, which is an appealing therapeutic target for M2 TAM depletion and CRC treatment.

Crosstalk between the peripheral nervous system and breast cancer influences tumor progression

Recent studies have shown that peripheral nerves play an important role in the progression of breast cancer. Breast cancer cells (BCCs) promote local peripheral nerve growth and branching by secreting neuroactive molecules, including neurotrophins and axon guidance molecules (AGMs). Sympathetic nerves promote breast cancer progression, while parasympathetic and sensory nerves mainly have anti-tumor effects in the progression of breast cancer. Specifically, peripheral nerves can influence the progression of breast cancer by secreting neurotransmitters not only directly binding to the corresponding receptors of BCCs, but also indirectly acting on immune cells to modulate anti-tumor immunity. In this review, we summarize the crosstalk between breast cancer and peripheral nerves and the roles of important neuroactive molecules in the progression of breast cancer. In addition, we summarize indicators, including nerve fiber density and perineural invasion (PNI), that may help determine the prognosis of breast cancer based on current research results, as well as potential therapeutic approaches, such as β-blockers and retroviral-mediated genetic neuroengineering techniques, that may enhance the prognosis of breast cancer. In addition, we propose suggestions for future research priorities based on a current lack of knowledge in this area.

PLXND1/SEMA3E Promotes Epithelial-Mesenchymal Transition Partly via the PI3K/AKT-Signaling Pathway and Induces Heterogenity in Colorectal Cancer

Colorectal cancer (CRC) is a major cause of cancer-related deaths. Metastasis is enhanced through epithelial-mesenchymal transition (EMT), a process primarily induced by the transforming growth factor beta (TGF-β)-mediated canonical Smad pathway. This study focused on plexin D1 (PLXND1), a chemoreceptor for the ligand SEMA3E to mechanosensory, showing that PLXND1 induces EMT via activation of the PI3K/AKT pathway in CRC cells. The findings showed that PLXND1-knockdown decreases cell migration and invasion significantly, and that the binding of p61-SEMA3E to the PLXND1 enhances the invasiveness and migration through EMT. Furin inhibitor suppresses EMT, decreasing cell migration and invasion. Furin cleaves full-length SEMA3E and converts it to p61-SEMA3E, suggesting that furin inhibitors block PLXND1 and p61-SEMA3E binding. Furin is a potential therapeutic target for the purpose of suppressing EMT by inhibiting the binding of p61-SEMA3E to PLXND1. In vivo experiments have shown that PLXND1-knockdown suppresses EMT. Mesenchymal cells labeled with ZEB1 showed heterogeneity depending on PLXND1 expression status. The high-expression group of PLXND1 in 182 CRC samples was significantly associated with poor overall survival compared with the low-expression group (P = 0.0352, median follow-up period of 60.7 months) using quantitative real-time polymerase chain reaction analysis. Further research is needed to determine whether cell fractions with a different expression of PLXND1 have different functions.

Exogenous Semaphorin 3E treatment protects against chlamydial lung infection in mice

Recent studies reported that semaphorins play a significant role in various settings of the immune response. In particular, Semaphorin 3E (Sema3E), a secreted semaphorin protein, is involved in cell proliferation, migration, inflammatory responses, and host defence against infections. However, the therapeutic function of Sema3E in bacterial infection has not been investigated. Our data showed that exogenous Sema3E treatment protects mice from chlamydial infection with lower bacterial burden, reduced body weight loss, and pathological lung changes. Cytokine analysis in the lung and spleen revealed that Sema3E-Fc treated mice, compared to saline-Fc treated mice, showed enhanced production of IFN-γ and IL-17 but reduced IL-4 and IL-10 production. Cellular analysis showed that Sema3E treatment leads to enhanced Th1/Th17 response but reduced Treg response in lungs following chlamydial infection. Moreover, Sema3E treatment also enhanced the recruitment of pulmonary dendritic cells, which express higher co-stimulatory but lower inhibitory surface molecules. The data demonstrate that Sema3E plays a vital role in protective immunity against chlamydial lung infection, mainly through coordinating functions of T cells and DCs.

Endothelial Mechanosensors for Atheroprone and Atheroprotective Shear Stress Signals

Vascular endothelial cells (ECs), derived from the mesoderm, form a single layer of squamous cells that covers the inner surface of blood vessels. In addition to being regulated by chemical signals from the extracellular matrix (ECM) and blood, ECs are directly confronted to complex hemodynamic environment. These physical inputs are translated into biochemical signals, dictating multiple aspects of cell behaviour and destination, including growth, differentiation, migration, adhesion, death and survival. Mechanosensors are initial responders to changes in mechanical environments, and the overwhelming majority of them are located on the plasma membrane. Physical forces affect plasma membrane fluidity and change of protein complexes on plasma membrane, accompanied by altering intercellular connections, cell-ECM adhesion, deformation of the cytoskeleton, and consequently, transcriptional responses in shaping specific phenotypes. Among the diverse forces exerted on ECs, shear stress (SS), defined as tangential friction force exerted by blood flow, has been extensively studied, from mechanosensing to mechanotransduction, as well as corresponding phenotypes. However, the precise mechanosensors and signalling pathways that determine atheroprone and atheroprotective phenotypes of arteries remain unclear. Moreover, it is worth to mention that some established mechanosensors of atheroprotective SS, endothelial glycocalyx, for example, might be dismantled by atheroprone SS. Therefore, we provide an overview of the current knowledge on mechanosensors in ECs for SS signals. We emphasize how these ECs coordinate or differentially participate in phenotype regulation induced by atheroprone and atheroprotective SS.

Dependence receptors: new targets for cancer therapy

Dependence receptors are known to promote survival and positive signaling such as proliferation, migration, and differentiation when activated, but to actively trigger apoptosis when unbound to their ligand. Their abnormal regulation was shown to be an important feature of tumorigenesis, allowing cancer cells to escape apoptosis triggered by these receptors while promoting in parallel major aspects of tumorigenesis such as proliferation, angiogenesis, invasiveness, and chemoresistance. This involvement in multiple cancer hallmarks has raised interest in dependence receptors as targets for cancer therapy. Although additional studies remain necessary to fully understand the complexity of signaling pathways activated by these receptors and to target them efficiently, it is now clear that dependence receptors represent very exciting targets for future cancer treatment. This manuscript reviews current knowledge on the contribution of dependence receptors to cancer and highlights the potential for therapies that activate pro-apoptotic functions of these proteins.

Role of PLEXIND1/TGFβ Signaling Axis in Pancreatic Ductal Adenocarcinoma Progression Correlates with the Mutational Status of KRAS

Simple Summary

Pancreatic cancer is among the most lethal cancers. The expression of PLEXIND1, a receptor, is upregulated in many cancers (including pancreatic cancer). Traditionally, PLEXIND1 is known to be involved in neuron development and mediate semaphorin signaling. However, its role and signaling in cancer is not fully understood. In our study, we present a new mechanism through which PLEXIND1 mediates its roles in cancer. For the first time, we demonstrate that it can function as a transforming growth factor beta coreceptor and modulate SMAD3 signaling. Around 90% of pancreatic cancer patients have mutant KRAS. Our work suggests that PLEXIND1 functions differently in pancreatic cancer cell lines, and the difference correlates with KRAS mutational status. Additionally, we demonstrate a novel peptide based therapeutic approach to target PLEXIND1 in cancer cells. Our work is valuable to both neuroscience and cancer fields, as it demonstrates an association between two previously unrelated signaling pathways.

Abstract

PLEXIND1 is upregulated in several cancers, including pancreatic ductal adenocarcinoma (PDAC). It is an established mediator of semaphorin signaling, and neuropilins are its known coreceptors. Herein, we report data to support the proposal that PLEXIND1 acts as a transforming growth factor beta (TGFβ) coreceptor, modulating cell growth through SMAD3 signaling. Our findings demonstrate that PLEXIND1 plays a pro-tumorigenic role in PDAC cells with oncogenic KRAS (KRAS^mut). We show in KRAS^mut PDAC cell lines (PANC-1, AsPC-1,4535) PLEXIND1 downregulation results in decreased cell viability (in vitro) and reduced tumor growth (in vivo). Conversely, PLEXIND1 acts as a tumor suppressor in the PDAC cell line (BxPC-3) with wild-type KRAS (KRAS^wt), as its reduced expression results in higher cell viability (in-vitro) and tumor growth (in vivo). Additionally, we demonstrate that PLEXIND1-mediated interactions can be selectively disrupted using a peptide based on its C-terminal sequence (a PDZ domain-binding motif), an outcome that may possess significant therapeutic implications. To our knowledge, this is the first report showing that (1) PLEXIND1 acts as a TGFβ coreceptor and mediates SMAD3 signaling, and (2) differential roles of PLEXIND1 in PDAC cell lines correlate with KRAS^mut and KRAS^wt status.

The emerging roles of semaphorin4D/CD100 in immunological diseases

In vertebrates, the semaphorin family of proteins is composed of 21 members that are divided into five subfamilies, i.e. classes 3 to 7. Semaphorins play crucial roles in regulating multiple biological processes, such as neural remodeling, tissue regeneration, cancer progression, and, especially, in immunological regulation. Semaphorin 4D (SEMA4D), also known as CD100, is an important member of the semaphorin family and was first characterized as a lymphocyte-specific marker. SEMA4D has diverse effects on immunologic processes, including immune cell proliferation, differentiation, activation, and migration, through binding to its specific membrane receptors CD72, PLXNB1, and PLXNB2. Furthermore, SEMA4D and its underlying signaling have been increasingly linked with several immunological diseases. This review focuses on the significant immunoregulatory role of SEMA4D and the associated underlying mechanisms, as well as the potential application of SEMA4D as a diagnostic marker and therapeutic target for the treatment of immunological diseases.

Profilin2 regulates actin rod assembly in neuronal cells

Nuclear and cytoplasmic actin-cofilin rods are formed transiently under stress conditions to reduce actin filament turnover and ATP hydrolysis. The persistence of these structures has been implicated in disease pathology of several neurological disorders. Recently, the presence of actin rods has been discovered in Spinal Muscular Atrophy (SMA), a neurodegenerative disease affecting predominantly motoneurons leading to muscle weakness and atrophy. This finding underlined the importance of dysregulated actin dynamics in motoneuron loss in SMA. In this study, we characterized actin rods formed in a SMA cell culture model analyzing their composition by LC–MS-based proteomics. Besides actin and cofilin, we identified proteins involved in processes such as ubiquitination, translation or protein folding to be bound to actin rods. This suggests their sequestration to actin rods, thus impairing important cellular functions. Moreover, we showed the involvement of the cytoskeletal protein profilin2 and its upstream effectors RhoA/ROCK in actin rod assembly in SMA. These findings implicate that the formation of actin rods exerts detrimental effects on motoneuron homeostasis by affecting actin dynamics and disturbing essential cellular pathways.

Insights into the regulatory role of Plexin D1 signalling in cardiovascular development and diseases

Plexin D1 (PLXND1), which was previously thought to mediate semaphorin signalling, belongs to the Plexin family of transmembrane proteins. PLXND1 cooperates mostly with the coreceptor neuropilin and participates in many aspects of axonal guidance. PLXND1 can also act as both a tumour promoter and a tumour suppressor. Emerging evidence suggests that mutations in PLXND1 or Semaphorin 3E, the canonical ligand of PLXND1, can lead to serious cardiovascular diseases, such as congenital heart defects, CHARGE syndrome and systemic sclerosis. Upon ligand binding, PLXND1 can act as a GTPase‐activating protein (GAP) and modulate integrin‐mediated cell adhesion, cytoskeletal dynamics and cell migration. These effects may play regulatory roles in the development of the cardiovascular system and disease. The cardiovascular effects of PLXND1 signalling have gradually been elucidated. PLXND1 was recently shown to detect physical forces and translate them into intracellular biochemical signals in the context of atherosclerosis. Therefore, the role of PLXND1 in cardiovascular development and diseases is gaining research interest because of its potential as a biomarker and therapeutic target. In this review, we describe the cardiac effects, vascular effects and possible molecular mechanisms of PLXND1 signalling.

Assessment of Phenylboronic Acid Nitrogen Mustards as Potent and Selective Drug Candidates for Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) has limited treatment options and the worst prognosis among all types of breast cancer. We describe two prodrugs, namely, CWB-20145 (1) and its methyl analogue FAN-NM-CH3 (2) that reduced the size of TNBC-derived tumors. The DNA cross-linking of nitrogen mustard prodrugs 1 and 2 was superior to that of chlorambucil and melphalan once activated in the presence of H2O2. The cellular toxicity of 1 and 2 was demonstrated in seven human cancer cell lines. The TNBC cell line MDA-MB-468 was particularly sensitive toward 1 and 2. Compound 2 was 10 times more cytotoxic than chlorambucil and 16 times more active than melphalan. An evaluation of the gene expression demonstrated an upregulation of the tumor suppressor genes p53 and p21 supporting a transcriptional mechanism of a reduced tumor growth. Pharmacokinetic studies with 1 showed a rapid conversion of the prodrug. The introduction of a methyl group generated 2 with an increased half-life. An in vivo toxicity study in mice demonstrated that both prodrugs were less toxic than chlorambucil. Compounds 1 and 2 reduced tumor growth with an inhibition rate of more than 90% in athymic nude mice xenografted with MDA-MB-468 cells. Together, the in vivo investigations demonstrated that treatment with 1 and 2 suppressed tumor growth without affecting normal tissues in mice. These phenylboronic acid nitrogen mustard prodrugs represent promising drug candidates for the treatment of TNBC. However, the mechanisms underlying their superior in vivo activity and selectivity as well as the correlation between H2O2 level and in vivo efficacy are not yet fully understood.

The involvement of semaphorin 7A in tumorigenic and immunoinflammatory regulation

Semaphorins, a large group of highly conserved proteins, consist of eight subfamilies that are widely expressed in vertebrates, invertebrates, and viruses and exist in membrane-bound or secreted forms. First described as axon guidance cues during neurogenesis, semaphorins also perform physiological functions in other organ systems, such as bone homeostasis, immune response, and tumor progression. Semaphorin 7A (SEMA7A), also known as CDw108, is an immune semaphorin that modulates diverse immunoinflammatory processes, including immune cell interactions, inflammatory infiltration, and cytokine production. In addition, SEMA7A regulates the proliferation, migration, invasion, lymph formation, and angiogenesis of multiple types of tumor cells, and these effects are mediated by the interaction of SEMA7A with two specific receptors, PLXNC1 and integrins. Thus, SEMA7A is intimately related to the pathogenesis of multiple autoimmune and inflammation-related diseases and tumors. This review focuses on the role of SEMA7A in the pathogenesis of autoimmune disorders, inflammatory diseases, and tumors, as well as the underlying mechanisms. Furthermore, strategies targeting SEMA7A as a potential predictive, diagnostic, and therapeutic agent for these diseases are also addressed.

The Paradoxical Roles of Orphan Nuclear Receptor 4A (NR4A) in Cancer

The three-orphan nuclear receptor 4A genes are induced by diverse stressors and stimuli, and there is increasing evidence that NR4A1 (Nur77), NR4A2 (Nurr1), and NR4A3 (Nor1) play an important role in maintaining cellular homeostasis and in pathophysiology. In blood-derived tumors (leukemias and lymphomas), NR4A expression is low and NR4A1-/-/NR4A3-/- double knockout mice rapidly develop acute myelocytic leukemia, suggesting that these receptors exhibit tumor suppressor activity. Treatment of leukemia and most lymphoma cells with drugs that induce expression of NR4A1and NR4A3 enhances apoptosis, and this represents a potential clinical application for treating this disease. In contrast, most solid tumor-derived cell lines express high levels of NR4A1 and NR4A2, and both receptors exhibit pro-oncogenic activities in solid tumors, whereas NR4A3 exhibits tumor-specific activities. Initial studies with retinoids and apoptosis-inducing agents demonstrated that their cytotoxic activity is NR4A1 dependent and involved drug-induced nuclear export of NR4A1 and formation of a mitochondrial proapoptotic NR4A1-bcl-2 complex. Drug-induced nuclear export of NR4A1 has been reported for many agents/biologics and involves interactions with multiple mitochondrial and extramitochondrial factors to induce apoptosis. Synthetic ligands for NR4A1, NR4A2, and NR4A3 have been identified, and among these compounds, bis-indole derived (CDIM) NR4A1 ligands primarily act on nuclear NR4A1 to inhibit NR4A1-regulated pro-oncogenic pathways/genes and similar results have been observed for CDIMs that bind NR4A2. Based on results of laboratory animal studies development of NR4A inducers (blood-derived cancers) and NR4A1/NR4A2 antagonists (solid tumors) may be promising for cancer therapy and also for enhancing immune surveillance.

Semaphorin 3E Protects against Chlamydial Infection by Modulating Dendritic Cell Functions

Recent studies have identified semaphorin 3E (Sema3E) as a novel mediator of immune responses. However, its function in immunity to infection has yet to be investigated. Using a mouse model of chlamydial lung infection, we show that Sema3E plays a significant role in the host immune response to the infection. We found that Sema3E is induced in the lung after chlamydial infection, and Sema3E deficiency has a detrimental impact on disease course, dendritic cell (DC) function, and T cell responses. Specifically, we found that Sema3E knockout (KO) mice exhibited higher bacterial burden, severe body weight loss, and pathological changes after Chlamydia muridarum lung infection compared with wild-type (WT) mice. The severity of disease in Sema3E KO mice was correlated with reduced Th1/Th17 cytokine responses, increased Th2 response, altered Ab response, and a higher number of regulatory CD4 T cells. Moreover, DCs isolated from Sema3E KO mice showed lower surface expression of costimulatory molecules and production of IL-12, but higher expression of PD-L1, PD-L2, and IL-10 production. Functional DC-T cell coculture studies revealed that DCs from infected Sema3E KO mice failed to induce Th1 and Th17 cell responses compared with DCs from infected WT mice. Upon adoptive transfer, mice receiving DCs from Sema3E KO mice, unlike those receiving DCs from WT mice, were not protected against challenge infection. In conclusion, our data evidenced that Sema3E acts as a critical factor for protective immunity against intracellular bacterial infection by modulating DC functions and T cell subsets.

Semaphorins as emerging clinical biomarkers and therapeutic targets in cancer

Semaphorins are a large family of developmental regulatory signals, characterized by aberrant expression in human cancers. These molecules crucially control cell-cell communication, cell migration, invasion and metastasis, tumor angiogenesis, inflammatory and anti-cancer immune responses. Semaphorins comprise secreted and cell surface-exposed molecules and their receptors are mainly found in the Plexin and Neuropilin families, which are further implicated in a signaling network controlling the tumor microenvironment. Accumulating evidence indicates that semaphorins may be considered as novel clinical biomarkers for cancer, especially for the prediction of patient survival and responsiveness to therapy. Moreover, preclinical experimental studies have demonstrated that targeting semaphorin signaling can interfere with tumor growth and/or metastatic dissemination, suggesting their relevance as novel therapeutic targets in cancer; this has also prompted the development of semaphorin-interfering molecules for application in the clinic. Here we will survey, in diverse human cancers, the current knowledge about the relevance of semaphorin family members, and conceptualize potential lines of future research development in this field.

Prognostic Value of PLXND1 and TGF-β1 Coexpression and Its Correlation With Immune Infiltrates in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy with no curative treatments. Plexin D1 (PLXND1) is a cellular receptor whose functions have been explored in several human cancers; however, the critical roles of PLXND1 in HCC have rarely been probed. Therefore, the present study attempted to elucidate the expression pattern, prognostic significance, and potential roles of PLXND1 in HCC. We found that PLXND1 expression in HCC tissues was significantly higher compared with normal liver tissue from Gene Expression Profiling Interactive Analysis (GEPIA) and Integrative Molecular Database of Hepatocellular Carcinoma (HCCDB) databases. This result was further validated by immunohistochemistry staining (IHC) using tissue microarrays, which contained 216 HCC cases collected from our hospital. Additionally, PLXND1 expression showed a significant correlation with several clinical characteristics, including tumor grade and tumor hemorrhage (TH). Moreover, TISIDB and GEPIA databases were used to investigate the roles of PLXND1 in tumor-immune system interactions in HCC. As an immunoinhibitor, transforming growth factor-beta (TGF-β1) displayed the greatest correlations with PLXND1 in HCC. Finally, Kaplan-Meier curves and Cox analysis were conducted to further examine the potential clinical value of PLXND1 in HCC. We described a subclassification of HCC based on PLXND1 and TGF-β1 expression, which could be used to predict clinical outcomes and patient prognosis. Taken together, the results of this study indicate that PLXND1 might be a promising prognostic biomarker and potential therapeutic target in HCC.

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.

Characterization of Class-3 Semaphorin Receptors, Neuropilins and Plexins, as Therapeutic Targets in a Pan-Cancer Study

Class-3 semaphorins (SEMA3s), initially characterized as axon guidance cues, have been recognized as key regulators for immune responses, angiogenesis, tumorigenesis and drug responses. The functions of SEMA3s are attributed to the activation of downstream signaling cascades mainly mediated by cell surface receptors neuropilins (NRPs) and plexins (PLXNs), yet their roles in human cancers are not completely understood. Here, we provided a detailed pan-cancer analysis of NRPs and PLXNs in their expression, and association with key signal transducers, patient survival, tumor microenvironment (TME), and drug responses. The expression of NRPs and PLXNs were dysregulated in many cancer types, and the majority of them were further dysregulated in metastatic tumors, indicating a role in metastatic progression. Importantly, the expression of these genes was frequently associated with key transducers, patient survival, TME, and drug responses; however, the direction of the association varied for the particular gene queried and the specific cancer type/subtype tested. Specifically, NRP1, NRP2, PLXNA1, PLXNA3, PLXNB3, PLXNC1, and PLXND1 were primarily associated with aggressive phenotypes, whereas the rest were more associated with favorable prognosis. These data highlighted the need to study each as a separate entity in a cancer type- and subtype-dependent manner.

Painful trigeminal neuropathy associated with anti-Plexin D1 antibody

OBJECTIVE

To determine whether anti-Plexin D1 antibody (Plexin D1-immunoglobulin G [IgG]), which is associated with limb and trunk neuropathic pain (NP) and binds to pain-conducting small unmyelinated dorsal root ganglion (DRG) neurons, exists in patients with idiopathic painful trigeminal neuropathy (IPTN) and whether Plexin D1-IgG binds to trigeminal ganglion (TG) neurons.

METHODS

We enrolled 21 consecutive patients with IPTN and 35 age- and sex-matched controls without NP (25 healthy persons and 10 with neurodegenerative diseases). We measured serum Plexin D1-IgG using a mouse DRG tissue-based indirect immunofluorescence assay (IFA) and by Western blotting (WB) using a recombinant human Plexin D1 (rhPlexin D1) accompanied by immunoadsorption tests with rhPlexin D1. The reactivity of Plexin D1-IgG toward mouse TG, brain, heart, and kidney was assessed by tissue-based IFAs.

RESULTS

Serum Plexin D1-IgG was detected more frequently in IPTN than in controls by both IFA and WB (14.3% vs 0%, p = 0.048). Three Plexin D1-IgG-positive patients also had limb or trunk NP and commonly showed tongue pain. In tissue-based IFAs, IgG from 2 Plexin D1-IgG-positive patients immunostained small TG neurons, which was prevented by preincubation with rhPlexin D1. Moreover, Plexin D1-IgG immunostaining mostly colocalized with isolectin B4-positive pain-conducting unmyelinated TG neurons. IFAs of other tissues with the same IgG revealed weak immunoreactivity only in endothelial cells, which was prevented by preincubation with rhPlexin D1.

CONCLUSIONS

Plexin D1-IgG, which binds to pain-conducting small TG neurons in addition to DRG neurons, can be present in IPTN as well as limb and trunk NP.

A pan-cancer study of class-3 semaphorins as therapeutic targets in cancer

BACKGROUND

Initially characterized as axon guidance factors, semaphorins also have been implicated to have critical roles in multiple physiological and developmental functions, including the regulation of immune responses, angiogenesis, organ formation, and the etiology of multiple forms of cancer. Moreover, their contribution in immunity and the regulation of tumour microenvironment is becoming increasingly recognized. Here, we provide a comprehensive analysis of class-3 semaphorins, the only secreted family of genes among veterbrate semaphorins, in terms of their expression profiles and their association with patient survival. We also relate their role with immune subtypes, tumour microenvironment, and drug sensitivity using a pan-cancer study.

RESULTS

Expression profiles of class-3 semaphorins (SEMA3s) and their association with patient survival and tumour microenvironment were studied in 31 cancer types using the TCGA pan-cancer data. The expression of SEMA3 family varies in different cancer types with striking inter- and intra- cancer heterogeneity. In general, our results show that SEMA3A, SEMA3C, and SEMA3F are primarily upregulated in cancer cells, while the rest of SEMA3s are mainly down-regulated in the tested tumours. The expression of SEMA3 family members was frequently associated with patient overall survival. However, the direction of the association varied with regards to the particular SEMA3 isoform queried and the specific cancer type tested. More specifically, SEMA3A and SEMA3E primarily associate with a poor prognosis of survival, while SEMA3G typically associates with survival advantage. The rest of SEMA3s show either survival advantage or disadvantage dependent on cancer type. In addition, all SEMA3 genes show significant association with immune infiltrate subtypes, and they also correlate with level of stromal cell infiltration and tumour cell stemness with various degrees. Finally, our study revealed that SEMA3 genes, especially SEMA3C and SEMA3F may contribute to drug induced cancer cell resistance.

CONCLUSIONS

Our systematic analysis of class-3 semaphorin gene expression and their association with immune infiltrates, tumour microenvironment and cancer patient outcomes highlights the need to study each SEMA3 member as a separate entity within each specific cancer type. Also our study validated the identification of class-3 semaphorin signals as promising therapeutic targets in cancer although further laboratory validation still needed.

Blocking SHH/Patched Interaction Triggers Tumor Growth Inhibition through Patched-Induced Apoptosis

The Sonic Hedgehog (SHH) pathway plays a key role in cancer. Alterations of SHH canonical signaling, causally linked to tumor progression, have become rational targets for cancer therapy. However, Smoothened (SMO) inhibitors have failed to show clinical benefit in patients with cancers displaying SHH autocrine/paracrine expression. We reported earlier that the SHH receptor Patched (PTCH) is a dependence receptor that triggers apoptosis in the absence of SHH through a pathway that differs from the canonical one, thus generating a state of dependence on SHH for survival. Here, we propose a dual function for SHH: its binding to PTCH not only activates the SHH canonical pathway but also blocks PTCH-induced apoptosis. Eighty percent, 64%, and 8% of human colon, pancreatic, and lung cancer cells, respectively, overexpressed SHH at transcriptional and protein levels. In addition, SHH-overexpressing cells expressed all the effectors of the PTCH-induced apoptotic pathway. Although the canonical pathway remained unchanged, autocrine SHH interference in colon, pancreatic, and lung cell lines triggered cell death through PTCH proapoptotic signaling. In vivo, SHH interference in colon cancer cell lines decreased primary tumor growth and metastasis. Therefore, the antitumor effect associated to SHH deprivation, usually thought to be a consequence of the inactivation of the canonical SHH pathway, is, at least in part, because of the engagement of PTCH proapoptotic activity. Together, these data strongly suggest that therapeutic strategies based on the disruption of SHH/PTCH interaction in SHH-overexpressing cancers should be explored. SIGNIFICANCE: Sonic Hedgehog-overexpressing tumors express PTCH-induced cell death effectors, suggesting that this death signaling could be activated as an antitumor strategy.

Mutant IDH Sensitizes Gliomas to Endoplasmic Reticulum Stress and Triggers Apoptosis via miR-183-Mediated Inhibition of Semaphorin 3E

Human astrocytomas and oligodendrogliomas are defined by mutations of the metabolic enzymes isocitrate dehydrogenase (IDH) 1 or 2, resulting in the production of the abnormal metabolite D-2 hydroxyglutarate. Here, we studied the effect of mutant IDH on cell proliferation and apoptosis in a glioma mouse model. Tumors were generated by inactivating Pten and p53 in forebrain progenitors and compared with tumors additionally expressing the Idh1 R132H mutation. Idh-mutant cells proliferated less in vitro and mice with Idh-mutant tumors survived significantly longer compared with Idh-wildtype mice. Comparison of miRNA and RNA expression profiles of Idh-wildtype and Idh-mutant cells and tumors revealed miR-183 was significantly upregulated in IDH-mutant cells. Idh-mutant cells were more sensitive to endoplasmic reticulum (ER) stress, resulting in increased apoptosis and thus reduced cell proliferation and survival. This was mediated by the interaction of miR-183 with the 5' untranslated region of semaphorin 3E, downregulating its function as an apoptosis suppressor. In conclusion, we show that mutant Idh1 delays tumorigenesis and sensitizes tumor cells to ER stress and apoptosis. This may open opportunities for drug treatments targeting the miR-183-semaphorin axis. SIGNIFICANCE: The pathologic metabolite 2-hydroxyglutarate, generated by IDH-mutant astrocytomas, sensitizes tumor cells to ER stress and delays tumorigenesis. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/79/19/4994/F1.large.jpg.

Refueling the Ischemic CNS: Guidance Molecules for Vascular Repair

Stroke patients have only limited therapeutic options and often remain with considerable disabilities. To promote neurological recovery, angiogenesis in the ischemic peri-infarct region has been recognized as an encouraging therapeutic target. Despite advances in mechanistic understanding of vascular growth and repair, effective and safe angiogenic treatments are currently missing. Besides the most intensively studied angiogenic growth factors, recent research has indicated that the process of vascular sprouting and migration also requires the participation of guidance molecules, many of which were initially identified as regulators of axonal growth. Here, we review the inhibitory and growth-promoting effects of guidance molecules on the vascular system and discuss their potential as novel angiogenic targets for neurovascular diseases.

Semaphorin 3E regulates apoptosis in the intestinal epithelium during the development of colitis

Semaphorin 3E (SEMA3E) has emerged as an axon-guiding molecule that regulates various biological processes including the immune responses and apoptosis. However, its role in the pathophysiology of colitis remains elusive. We investigated the role of SEMA3E in intestinal epithelial cells (IECs) activation, using biopsies from patients with active ulcerative colitis (UC), a mouse model of UC, and an in-vitro model of intestinal mucosal healing. In this study, we confirmed that the mRNA level of SEMA3E is reduced significantly in patients with UC and demonstrated a negative linear association between SEMA3E mRNA and p53-associated genes. In mice, genetic deletion of Sema3e resulted in an increase onset and severity of colitis, p53-associated genes, apoptosis, and IL-1beta production. Recombinant SEMA3E treatment protected against colitis and decreased these effects. Furthermore, in stimulated epithelial cells, recombinant SEMA3E treatment enhanced wound healing, resistance to oxidative stress and decreased apoptosis and p53-associated genes. Together, these findings identify SEMA3E as a novel regulator in intestinal inflammation that regulates IECs apoptosis and suggest a potential novel approach to treat UC.

Divergent roles of Plexin D1 in cancer

Plexin D1 belongs to a family of transmembrane proteins called plexins. It was characterized as a receptor for semaphorins and is known to be essential for axonal guidance and vascular patterning. Mutations in Plexin D1 have been implicated in pathologic conditions such as truncus arteriosus and Möbius syndrome. Emerging data show that expression of Plexin D1 is deregulated in several cancers; it can support tumor development by aiding in tumor metastasis and EMT; and conversely, it can act as a dependence receptor and stimulate cell death in the absence of its canonical ligand, semaphorin 3E. The role of Plexin D1 in tumor development and progression is thereby garnering research interest for its potential as a biomarker and as a therapeutic target. In this review, we describe its discovery, structure, mutations, role(s) in cancer, and therapeutic potential.