NRP-1 interacts with GIPC1 and SYX to activate p38 MAPK signaling and cancer stem cell survival

NRP1 promotes osteo/odontogenic differentiation via shroom3 in dental pulp stem cells

Neuropilin-1 (NRP1) is a single transmembrane glycoprotein involved in a variety of physiological events. However, the exact mechanisms by which NRP1 regulates dental pulp stem cells (DPSCs) to differentiate toward an osteo/odontogenic phenotype are poorly understood. Here, we determined the significantly increased expression of full-length NRP1 and glycosaminoglycan (GAG)-modified NRP1 during osteo/odontogenesis in DPSCs. NRP1 was confirmed to promote alkaline phosphatase (ALP) activity, mineralized nodule deposition, protein and mRNA expression of Runx2, DSPP and DMP1 in DPSCs via the loss-of-function and gain-of-function approaches. Further, a non-GAG-modified NRP1 mutant (NRP1 S612A) was generated and the suppression of osteo/odontogenic differentiation was observed in the NRP1 S612A overexpression cells. Knockdown of the adaptor protein shroom3 resulted in the inhibition of osteo/odontogenesis. The protein-protein interaction network, the protein-protein docking and confocal analyses indicated the interactions between NRP1 and shroom3. Furthermore, immunoprecipitation followed by western analysis confirmed the binding of NRP1 to shroom3, but overexpression of NRP1 S612A greatly influenced the recruitment of shroom3 by NRP1. These results provide strong evidence that NRP1 is a critical regulator for osteo/odontogenesis through interacting with shroom3. Moreover, our results indicate that NRP1 S612A attenuates osteo/odontogenesis, suggesting that GAG modification is essential for NRP1 in DPSCs.

NRP1 knockdown inhibits the invasion and migration of rhabdoid tumor of the kidney cells

PURPOSE

The aim of this study was to detect candidate oncogenes of rhabdoid tumor of the kidney (RTK) and evaluate their roles in RTK in vitro.

METHODS

An integrated analysis of messenger RNA (mRNA) and microRNA (miRNA) sequencing was performed to determine the expression profile of exosome-derived miRNAs and mRNAs in human RTK-derived cell lines and a human embryonic renal cell line. A Gene Ontology enrichment analysis was performed to analyze the functional characteristics of differentially expressed mRNAs in RTK cells. Matrigel invasion and wound-healing assays were performed to evaluate the cell invasion and migration abilities.

RESULTS

Forty mRNAs were highly expressed in RTK cells targeted by exosomal miRNAs, the expression of which was lower in RTK cells than in the controls. These mRNAs were primarily related to cell adhesion. Of these mRNAs, we selected neuropilin 1 (NRP1) as a candidate oncogene because its upregulated expression is associated with a poor prognosis of several types of tumors. RTK cells in which NRP1 had been knocked down exhibited decreased invasive and migratory abilities.

CONCLUSION

Our study indicates that NRP1 acts as an oncogene by promoting the invasion and migration of RTK cells and that it could serve as a therapeutic target.

Preclinical evaluation of 68 Ga-labeled peptide CK2 for PET imaging of NRP-1 expression in vivo

PURPOSE

Neuropilin-1 (NRP-1) is a multifunctional protein involved in a variety of biological processes such as angiogenesis, tumorigenesis and immunomodulation. It was usually overexpressed in many cancer cell lines and correlated with poor prognosis of breast cancer. Positron emission tomography (PET) is an advanced imaging technique for detecting the function and metabolism of tumor-associated molecules in real time, dynamically, quantitatively and noninvasively. To improve the level of early diagnosis and evaluate the prognosis of breast cancer, an NRP-1 targeting peptide-based tracer [68 Ga]Ga-NOTA-PEG4-CK2 was designed to sensitively and specifically detect the NRP-1 expression in vivo via PET imaging.

METHODS

In silico modeling and microscale thermophoresis (MST) assay were carried out to design the NRP-1 targeting peptide NOTA-PEG4-CK2, and it was further radiolabeled with 68 Ga to prepare the tracer [68 Ga]Ga-NOTA-PEG4-CK2. The radiochemical yield (RCY), radiochemical purity (RCP), molar activity (Am), lipid-water partition coefficient (Log P) and stability of [68 Ga]Ga-NOTA-PEG4-CK2 were assessed. The targeting specificity of the tracer for NRP-1 was investigated by in vitro cellular uptake assay and in vivo PET imaging as well as blocking studies. The sensitivity of the tracer in monitoring the dynamic changes of NRP-1 expression induced by chemical drug was also investigated in vitro and in vivo. Ex vivo biodistribution, autoradiography, western blot, and immunofluorescence staining were also performed to study the specificity of [68 Ga]Ga-NOTA-PEG4-CK2 for NRP-1.

RESULTS

[68 Ga]Ga-NOTA-PEG4-CK2 was designed and synthesized with high RCY (> 98%), high stability (RCP > 95%) and high affinity to NRP-1 (KD = 25.39 ± 1.65 nM). In vitro cellular uptake assay showed that the tracer [68 Ga]Ga-NOTA-PEG4-CK2 can specifically bind to NRP-1 positive cancer cells MDA-MB-231 (1.04 ± 0.04% at 2 h) rather than NRP-1 negative cancer cells NCI-H1299 (0.43 ± 0.05%). In vivo PET imaging showed the maximum tumor uptake of [68 Ga]Ga-NOTA-PEG4-CK2 in MDA-MB-231 xenografts (4.16 ± 0.67%ID/mL) was significantly higher than that in NCI-H1299 xenografts (1.03 ± 0.19%ID/mL) at 10 min post injection, and the former exhibited higher tumor-to-muscle uptake ratio (5.22 ± 0.18) than the latter (1.07 ± 0.27) at 60 min post injection. MDA-MB-231 xenografts pretreated with nonradioactive precursor NOTA-PEG4-CK2 showed little tumor uptake of [68 Ga]Ga-NOTA-PEG4-CK2 (1.67 ± 0.38%ID/mL at 10 min post injection). Both cellular uptake assay and PET imaging revealed that NRP-1 expression in breast cancer MDA-MB-231 could be effectively suppressed by SB-203580 treatment and can be sensitively detected by [68 Ga]Ga-NOTA-PEG4-CK2. Ex vivo analysis also proved the high specificity and sensitivity of [68 Ga]Ga-NOTA-PEG4-CK2 for NRP-1 expression in MDA-MB-231 xenografts.

CONCLUSION

A promising NRP-1 targeting PET tracer [68 Ga]Ga-NOTA-PEG4-CK2 was successfully prepared. It showed remarkable specificity and sensitivity in monitoring the dynamic changes of NRP-1 expression. Hence, it could provide valuable information for early diagnosis of NRP-1 relevant cancers and evaluating the prognosis of cancer patients.

Revealing neuropilin expression patterns in pancreatic cancer: From single‑cell to therapeutic opportunities (Review)

Pancreatic cancer, one of the most fatal types of human cancers, includes several non-epithelial and stromal components, such as activated fibroblasts, vascular cells, neural cells and immune cells, that are involved in different cancers. Vascular endothelial cell growth factor 165 receptors 1 [neuropilin-1 (NRP-1)] and 2 (NRP-2) play a role in the biological behaviors of pancreatic cancer and may appear as potential therapeutic targets. The NRP family of proteins serve as co-receptors for vascular endothelial growth factor, transforming growth factor β, hepatocyte growth factor, fibroblast growth factor, semaphorin 3, epidermal growth factor, insulin-like growth factor and platelet-derived growth factor. Investigations of mechanisms that involve the NRP family of proteins may help develop novel approaches for overcoming therapy resistance in pancreatic cancer. The present review aimed to provide an in-depth exploration of the multifaceted roles of the NRP family of proteins in pancreatic cancer, including recent findings from single-cell analysis conducted within the context of pancreatic adenocarcinoma, which revealed the intricate involvement of NRP proteins at the cellular level. Through these efforts, the present study endeavored to further reveal their relationships with different biological processes and their potential as therapeutic targets in various treatment modalities, offering novel perspectives and directions for the treatment of pancreatic cancer.

Transglutaminase 2 Binds to the CD44v6 Cytoplasmic Domain to Stimulate CD44v6/ERK1/2 Signaling and Maintain an Aggressive Cancer Phenotype

Transglutaminase 2 (TG2) is a key cancer cell survival protein in many cancer types. As such, efforts are underway to characterize the mechanism of TG2 action. In this study, we report that TG2 stimulates CD44v6 activity to enhance cancer cell survival via a mechanism that involves formation of a TG2/CD44v6/ERK1/2 complex that activates ERK1/2 signaling to drive an aggressive cancer phenotype. TG2 and ERK1/2 bind to the CD44v6 C-terminal intracellular cytoplasmic domain to activate ERK1/2 and stimulate cell proliferation and invasion. This is the same region that binds to ERM proteins and ankyrin to activate CD44v6-dependent cell proliferation, invasion, and migration. We further show that treatment with hyaluronan (HA), the physiologic CD44v6 ligand, stimulates CD44v6 activity, as measured by ERK1/2 activation, but that this response is severely attenuated in TG2 or CD44v6 knockdown or knockout cells. Moreover, treatment with TG2 inhibitor reduces tumor growth and that is associated with reduced CD44v6 level and ERK1/2 activity, and reduced stemness and epithelial-mesenchymal transition (EMT). These changes are replicated in CD44v6 knockout cells. These findings suggest that a unique TG2/CD44v6/ERK1/2 complex leads to increased ERK1/2 activity to stimulate an aggressive cancer phenotype and stimulate tumor growth. These findings have important implications for cancer stem cell maintenance and suggest that cotargeting of TG2 and CD44v6 with specific inhibitors may be an effective anticancer treatment strategy.

IMPLICATIONS

TG2 and CD44v6 are important procancer proteins. TG2 and ERK1/2 bind to the CD44v6 C-terminal domain to form a TG2/CD44v6/ERK1/2 complex that activates ERK1/2 to stimulate the cancer phenotype.

The transglutaminase 2 cancer cell survival factor maintains mTOR activity to drive an aggressive cancer phenotype

Transglutaminase 2 (TG2) is an important cancer stem-like cell survival protein that is highly expressed in epidermal squamous cell carcinoma and drives an aggressive cancer phenotype. In the present study, we show that TG2 knockdown or inactivation results in a reduction in mammalian target of rapamycin (mTOR) level and activity in epidermal cancer stem-like cells which are associated with reduced spheroid formation, invasion, and migration, and reduced cancer stem cell and epithelial-mesenchymal transition (EMT) marker expression. Similar changes were observed in both cultured cells and tumors. mTOR knockdown or treatment with rapamycin phenocopies the reduction in spheroid formation, invasion, and migration, and cancer stem cell and EMT marker expression. Moreover, mTOR appears to be a necessary mediator of TG2 action, as a forced expression of constitutively active mTOR in TG2 knockdown cells partially restores the aggressive cancer phenotype and cancer stem cell and EMT marker expression. Tumor studies show that rapamycin reduces tumor growth and cancer stem cell marker expression and EMT. These studies suggest that TG2 stimulates mTOR activity to stimulate cancer cell stemness and EMT and drive aggressive tumor growth.

Neuropilin (NRPs) Related Pathological Conditions and Their Modulators

Neuropilin 1 (NRP1) represents one of the two homologous neuropilins (NRP, splice variants of neuropilin 2 are the other) found in all vertebrates. It forms a transmembrane glycoprotein distributed in many human body tissues as a (co)receptor for a variety of different ligands. In addition to its physiological role, it is also associated with various pathological conditions. Recently, NRP1 has been discovered as a coreceptor for the SARS-CoV-2 viral entry, along with ACE2, and has thus become one of the COVID-19 research foci. However, in addition to COVID-19, the current review also summarises its other pathological roles and its involvement in clinical diseases like cancer and neuropathic pain. We also discuss the diversity of native NRP ligands and perform a joint analysis. Last but not least, we review the therapeutic roles of NRP1 and introduce a series of NRP1 modulators, which are typical peptidomimetics or other small molecule antagonists, to provide the medicinal chemistry community with a state-of-the-art overview of neuropilin modulator design and NRP1 druggability assessment.

Transglutaminase 2 enhances hepatocyte growth factor signaling to drive the mesothelioma cancer cell phenotype

Transglutaminase 2 (TG2) is an important mesothelioma cancer cell survival protein. However, the mechanism whereby TG2 maintains mesothelioma cell survival is not well understood. We present studies showing that TG2 drives hepatocyte growth factor (HGF)-dependent MET receptor signaling to maintain the aggressive mesothelioma cancer phenotype. TG2 increases HGF and MET messenger RNA and protein levels to enhance MET signaling. TG2 inactivation reduces MET tyrosine kinase activity to reduce cancer cell spheroid formation, invasion and migration. We also confirm that HGF/MET signaling is a biologically important mediator of TG2 action. Reducing MET level using genetic methods or treatment with MET inhibitors reduces spheroid formation, invasion and migration and this is associated with reduced MEK1/2 and ERK1/2. In addition, MEK1/2 and ERK1/2 inhibitors suppress the cancer phenotype. Moreover, MET knockout mesothelioma cells form 10-fold smaller tumors compared to wild-type cells and these tumors display reduced MET, MEK1/2, and ERK1/2 activity. These findings suggest that TG2 maintains HGF and MET levels in cultured mesothelioma cells and tumors to drive HGF/MET, MEK1/2, and ERK1/2 signaling to maintain the aggressive mesothelioma cancer phenotype.

Transglutaminase 2 Maintains Hepatocyte Growth Factor Signaling to Enhance the Cancer Cell Phenotype

Transglutaminase 2 (TG2) is a key epidermal squamous cell carcinoma cancer cell survival protein. However, how TG2 maintains the aggressive cancer phenotype is not well understood. The present studies show that TG2, which is highly expressed in epidermal cancer stem-like cells (ECS cells), maintains hepatocyte growth factor (HGF) signaling to drive an aggressive ECS cell cancer phenotype. Inhibiting TG2 reduces MET tyrosine kinase receptor expression and activity and attenuates the cancer cell phenotype. Moreover, inhibition of TG2 or HGF/MET function reduces downstream MEK1/2 and ERK1/2 activity, and this is associated with reduced cancer cell spheroid formation, invasion, and migration, and reduced stem and EMT marker expression. Treatment of TG2 knockdown cells with HGF partially restores the aggressive cancer phenotype, confirming that MET signaling is downstream of TG2. MET knockout reduces ERK1/2 signaling, doubles the time to initial tumor appearance, and reduces overall tumor growth. These findings suggest that TG2 maintains HGF/MET and MAPK (MEK1/2 and ERK1/2) signaling to drive the aggressive ECS cell cancer phenotype and tumor formation, and that TG2-dependent MET signaling may be a useful anti-cancer target. IMPLICATIONS: TG2 is an important epidermal squamous cell carcinoma stem cell survival protein. We show that TG2 activates an HGF/MET, MEK1/2 ERK1/2 signaling cascade that maintains the aggressive cancer phenotype.

VGLL4 inhibits YAP1/TEAD signaling to suppress the epidermal squamous cell carcinoma cancer phenotype

Epidermal squamous cell carcinoma (SCC) develops in response to ultraviolet light exposure and is among the most common cancers. The transglutaminase 2 cancer cell survival protein stimulates the activity of the YAP1/TEAD transcription complex to drive the expression of genes that promote aggressive epidermal SCC cell invasion, migration, and tumor formation. Therefore, we are interested in mechanisms that may inhibit these events. Vestigial-like protein-4 (VGLL4) is a transcription cofactor/tumor suppressor that inhibits several pro-cancer pathways including YAP1 signaling. Our present studies show that VGLL4 inhibits YAP1/TEAD-dependent transcription to reduce the expression of YAP1 target genes (CCND1, CYR61, and CTGF) and pro-cancer collagen genes (COL1A2 and COL3A1). We further show that loss of these YAP1 regulated genes is required for VGLL4 suppression of the cancer cell phenotype, as forced CCND1 or COL1A2 expression partially restores the aggressive cancer phenotype in VGLL4 expressing cells. Consistent with these findings, VGLL4 expression reduces tumor formation, and this is associated with reduced CCND1, CYR61, CTGF, COL1A2, and COL1A3 mRNA and protein levels, and reduced EMT marker expression. These findings indicate that VGLL4 suppresses the malignant epidermal SCC cancer phenotype by inhibiting YAP1/TEAD-dependent pro-cancer signaling.

Role of NRP1 in Bladder Cancer Pathogenesis and Progression

Bladder urothelial carcinoma (BC) is a fatal invasive malignancy and the most common malignancy of the urinary system. In the current study, we investigated the function and mechanisms of Neuropilin-1 (NRP1), the co-receptor for vascular endothelial growth factor, in BC pathogenesis and progression. The expression of NRP1 was evaluated using data extracted from GEO and HPA databases and examined in BC cell lines. The effect on proliferation, apoptosis, angiogenesis, migration, and invasion of BC cells were validated after NRP1 knockdown. After identifying differentially expressed genes (DEGs) induced by NRP1 silencing, GO/KEGG and IPA^® bioinformatics analyses were performed and specific predicted pathways and targets were confirmed in vitro. Additionally, the co-expressed genes and ceRNA network were predicted using data downloaded from CCLE and TCGA databases, respectively. High expression of NRP1 was observed in BC tissues and cells. NRP1 knockdown promoted apoptosis and suppressed proliferation, angiogenesis, migration, and invasion of BC cells. Additionally, after NRP1 silencing the activity of MAPK signaling and molecular mechanisms of cancer pathways were predicted by KEGG and IPA^® pathway analysis and validated using western blot in BC cells. NRP1 knockdown also affected various biological functions, including antiviral response, immune response, cell cycle, proliferation and migration of cells, and neovascularisation. Furthermore, the main upstream molecule of the DEGs induced by NRP1 knockdown may be NUPR1, and NRP1 was also the downstream target of NUPR1 and essential for regulation of FOXP3 expression to activate neovascularisation. DCBLD2 was positively regulated by NRP1, and PPAR signaling was significantly associated with low NRP1 expression. We also found that NRP1 was a predicted target of miR-204, miR-143, miR-145, and miR-195 in BC development. Our data provide evidence for the biological function and molecular aetiology of NRP1 in BC and for the first time demonstrated an association between NRP1 and NUPR1, FOXP3, and DCBLD2. Specifically, downregulation of NRP1 contributes to BC progression, which is associated with activation of MAPK signaling and molecular mechanisms involved in cancer pathways. Therefore, NRP1 may serve as a target for new therapeutic strategies to treat BC and other cancers.

Harnessing the polyamine transport system to treat BRAF inhibitor-resistant melanoma

BRAF mutations are present in over half of all melanoma tumors. Although BRAF inhibitors significantly improve survival of patients with metastatic melanoma, recurrences occur within several months. We previously reported that BRAF mutant melanoma cells are more sensitive to a novel arylmethyl-polyamine (AP) compound that exploits their increased polyamine uptake compared to that of BRAF wildtype cells. Using an animal model of BRAF inhibitor-resistant melanoma, we show that co-treatment with the BRAF inhibitor, PLX4720, and AP significantly delays the recurrence of PLX4720-resistant melanoma tumors and decreases tumor-promoting macrophages. Development of BRAF inhibitor-resistance enriches for metastatic cancer stem cells (CSC) and increases tumor-promoting macrophages. In vitro studies demonstrated that CD304⁺, CXCR4⁺ spheroid cultures of BRAF mutant melanoma cells are resistant to PLX4720 but are more sensitive to AP compared to monolayer cultures of the same cells. AP significantly inhibited YUMM1.7 melanoma cell invasiveness across a Matrigel-coated filter using the CXCR4 ligand, SDF-1α, as the chemoattractant. AP also blocked the chemotactic effect of SDF-1α on CXCR4⁺ macrophages and inhibited M2 polarization of macrophages. In melanoma-macrophage co-cultures, AP prevented the PLX4720-induced release of pro-tumorigenic growth factors, such as VEGF, from macrophages and prevented the macrophage rescue of BRAF mutant melanoma cells treated with PLX4720. Our study offers a novel therapy (AP) to treat chemo-resistant melanoma. AP is unique because it targets the polyamine transport system in BRAF inhibitor-resistant CSCs and also blocks CXCR4 signaling in invasive melanoma cells and pro-tumorigenic macrophages.

Targeting neuropilin-1 interactions is a promising anti-tumor strategy

ABSTRACT

Neuropilins (NRP1 and NRP2) are multifunctional receptor proteins that are involved in nerve, blood vessel, and tumor development. NRP1 was first found to be expressed in neurons, but subsequent studies have demonstrated its surface expression in cells from the endothelium and lymph nodes. NRP1 has been demonstrated to be involved in the occurrence and development of a variety of cancers. NRP1 interacts with various cytokines, such as vascular endothelial growth factor family and its receptor and transforming growth factor β1 and its receptor, to affect tumor angiogenesis, tumor proliferation, and migration. In addition, NRP1+ regulatory T cells (Tregs) play an inhibitory role in tumor immunity. High numbers of NRP1+ Tregs were associated with cancer prognosis. Targeting NRP1 has shown promise, and antagonists against NRP1 have had therapeutic efficacy in preliminary clinical studies. NRP1 treatment modalities using nanomaterials, targeted drugs, oncolytic viruses, and radio-chemotherapy have gradually been developed. Hence, we reviewed the use of NRP1 in the context of tumorigenesis, progression, and treatment.

90 YEARS OF PROGESTERONE: Steroid receptors as MAPK signaling sensors in breast cancer: let the fates decide

Steroid hormone receptors (SRs) are classically defined as ligand-activated transcription factors that function as master regulators of gene programs important for a wide range of processes governing adult physiology, development, and cell or tissue homeostasis. A second function of SRs includes the ability to activate cytoplasmic signaling pathways. Estrogen (ER), androgen (AR), and progesterone (PR) receptors bind directly to membrane-associated signaling molecules including mitogenic protein kinases (i.e. c-SRC and AKT), G-proteins, and ion channels to mediate context-dependent actions via rapid activation of downstream signaling pathways. In addition to making direct contact with diverse signaling molecules, SRs are further fully integrated with signaling pathways by virtue of their N-terminal phosphorylation sites that act as regulatory hot-spots capable of sensing the signaling milieu. In particular, ER, AR, PR, and closely related glucocorticoid receptors (GR) share the property of accepting (i.e. sensing) ligand-independent phosphorylation events by proline-directed kinases in the MAPK and CDK families. These signaling inputs act as a 'second ligand' that dramatically impacts cell fate. In the face of drugs that reliably target SR ligand-binding domains to block uncontrolled cancer growth, ligand-independent post-translational modifications guide changes in cell fate that confer increased survival, EMT, migration/invasion, stemness properties, and therapy resistance of non-proliferating SR+ cancer cell subpopulations. The focus of this review is on MAPK pathways in the regulation of SR+ cancer cell fate. MAPK-dependent phosphorylation of PR (Ser294) and GR (Ser134) will primarily be discussed in light of the need to target changes in breast cancer cell fate as part of modernized combination therapies.

Transglutaminase 2 takes center stage as a cancer cell survival factor and therapy target

Transglutaminase 2 (TG2) has emerged as a key cancer cell survival factor that drives epithelial to mesenchymal transition, angiogenesis, metastasis, inflammation, drug resistance, cancer stem cell survival and stemness, and invasion and migration. TG2 can exist in a GTP-bound signaling-active conformation or in a transamidase-active conformation. The GTP bound conformation of TG2 contributes to cell survival and the transamidase conformation can contribute to cell survival or death. We present evidence suggesting that TG2 has a role in human cancer, summarize what is known about the TG2 mechanism of action in a range of cancer types, and discuss TG2 as a cancer therapy target.