Tumor-neuroglia interaction promotes pancreatic cancer metastasis

E3 ubiquitin ligase RBCK1 confers ferroptosis resistance in pancreatic cancer by facilitating MFN2 degradation

Ferroptosis, a novel form of iron-dependent non-apoptotic cell death, plays an active role in the pathogenesis of diverse diseases, including cancer. However, the mechanism through which ferroptosis is regulated in pancreatic ductal adenocarcinoma (PDAC) remains unclear. Here, our study, via combining bioinformatic analysis with experimental validation, showed that ferroptosis is inhibited in PDAC. Genome-wide sequencing further revealed that the ferroptosis activator imidazole ketone erastin (IKE) induced upregulation of the E3 ubiquitin ligase RBCK1 in PDAC cells at the transcriptional or translational level. RBCK1 depletion or knockdown rendered PDAC cells more vulnerable to IKE-induced ferroptotic death in vitro. In a mouse xenograft model, genetic depletion of RBCK1 increased the killing effects of ferroptosis inducer on PDAC cells. Mechanistically, RBCK1 interacts with and polyubiquitylates mitofusin 2 (MFN2), a key regulator of mitochondrial dynamics, to facilitate its proteasomal degradation under ferroptotic stress, leading to decreased mitochondrial reactive oxygen species (ROS) production and lipid peroxidation. These findings not only provide new insights into the defense mechanisms of PDAC cells against ferroptotic death but also indicate that targeting the RBCK1-MFN2 axis may be a promising option for treating patients with PDAC.

FBXO32 Stimulates Protein Synthesis to Drive Pancreatic Cancer Progression and Metastasis

Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of cancer-related death worldwide, primarily due to its rapid progression. The current treatment options for PDAC are limited, and a better understanding of the underlying mechanisms responsible for PDAC progression is required to identify improved therapeutic strategies. In this study, we identified FBXO32 as an oncogenic driver in PDAC. FBXO32 was aberrantly upregulated in PDAC, and high FBXO32 expression was significantly associated with an unfavorable prognosis in patients with PDAC. FRG1 deficiency promoted FBXO32 upregulation in PDAC. FBXO32 promoted cell migration and invasion in vitro and tumor growth and metastasis in vivo. Mechanistically, FBXO32 directly interacted with eEF1A1 and promoted its polyubiquitination at the K273 site, leading to enhanced activity of eEF1A1 and increased protein synthesis in PDAC cells. Moreover, FBXO32-catalyzed eEF1A1 ubiquitination boosted the translation of ITGB5 mRNA and activated focal adhesion kinase (FAK) signaling, thereby facilitating focal adhesion assembly and driving PDAC progression. Importantly, interfering with the FBXO32-eEF1A1 axis or pharmaceutical inhibition of FAK by defactinib, an FDA-approved FAK inhibitor, substantially inhibited PDAC growth and metastasis driven by aberrantly activated FBXO32-eEF1A1 signaling. Overall, this study uncovers a mechanism by which PDAC cells rely on FBXO32-mediated eEF1A1 activation to drive progression and metastasis. FBXO32 may serve as a promising biomarker for selecting eligible patients with PDAC for treatment with defactinib. Significance: FBXO32 upregulation in pancreatic cancer induced by FRG1 deficiency increases eEF1A1 activity to promote ITGB5 translation and stimulate FAK signaling, driving cancer progression and sensitizing tumors to the FAK inhibitor defactinib.

Nerve-tumor crosstalk in tumor microenvironment: From tumor initiation and progression to clinical implications

The autonomic nerve system (ANS) innervates organs and tissues throughout the body and maintains functional balance among various systems. Further investigations have shown that excessive activation of ANS not only causes disruption of homeostasis, but also may promote tumor formation. In addition, the dynamic interaction between nerve and tumor cells in the tumor microenvironment also regulate tumor progression. On the one hand, nerves are passively invaded by tumor cells, that is, perineural invasion (PNI). On the other hand, compared with normal tissues, tumor tissues are subject to more abundant innervation, and nerves can influence tumor progression through regulating tumor proliferation, metastasis and drug resistance. A large number of studies have shown that nerve-tumor crosstalk, including PNI and innervation, is closely related to the prognosis of patients, and contributes to the formation of cancer pain, which significantly deteriorates the quality of life for patients. These findings suggest that nerve-tumor crosstalk represents a potential target for anti-tumor therapies and the management of cancer pain in the future. In this review, we systematically describe the mechanism by which nerve-tumor crosstalk regulates tumorigenesis and progression.

Promotion of perineural invasion of cholangiocarcinoma by Schwann cells via nerve growth factor

Background

Cholangiocarcinoma (CCA), a highly lethal tumor of the hepatobiliary system originating from bile duct epithelium, can be divided into the intrahepatic, hilar, and extrahepatic types. Due to its insidious onset and atypical early clinical symptoms, the overall prognosis is poor. One of the important factors contributing to the poor prognosis of CCA is the occurrence of perineural invasion (PNI), but the specific mechanisms regarding how it contributes to the occurrence of PNI are still unclear. The main purpose of this study is to explore the molecular mechanism leading to the occurrence of PNI and provide new ideas for clinical treatment.

Methods

CCA cell lines and Schwann cells (SCs) were stimulated to observe the changes in cell behavior. SCs cocultured with tumor supernatant and SCs cultured in normal medium were subjected to transcriptome sequencing to screen the significantly upregulated genes. Following this, the two types of tumor cells were cultured with SC supernatant, and the changes in behavior of the tumor cells were observed. Nonobese diabetic-severe combined immunodeficiency disease (NOD-SCID) mice were injected with cell suspension supplemented with nerve growth factor (NGF) via the sciatic nerve. Four weeks later, the mice were euthanized and the tumor sections were removed and stained.

Results

Nerve invasion by tumor cells was common in CCA tissues. SCs were observed in tumor tissues, and the number of SCs in tumor tissues and the degree of PNI were much higher than were those in normal tissues or tissues without PNI. The overall survival time was shorter in patients with CCA with PNI than in patients without PNI. SCs were enriched in CCA tissues, indicating the presence of PNI and associated with poor prognosis in CCA patients. CCA was found to promote NGF secretion from SCs in vitro. After the addition of exogenous NGF in CCA cell culture medium, the proliferation activity and migration ability of CCA cells were significantly increased, suggesting that SCs can promote the proliferation and migration of CCA through the secretion of NGF. NGF, in turn, was observed to promote epithelial-mesenchymal transition in CCA through tropomyosin receptor kinase A (TrkA), thus promoting its progression. Tumor growth in mice shows that NGF can promote PNI in CCA.

Conclusions

In CCA, tumor cells can promote the secretion of NGF by SCs, which promotes the progression of CCA and PNI by binding to its high-affinity receptor TrkA, leading to poor prognosis.

Function and mechanism of exosomes derived from different cells as communication mediators in colorectal cancer metastasis

Colorectal cancer (CRC) ranks as the second leading cause of cancer-related mortality, with metastasis being the primary determinant of poor prognosis in patients. Investigating the molecular mechanisms underlying CRC metastasis is currently a prominent and challenging area of research. Exosomes, as crucial intercellular communication mediators, facilitate the transfer of metabolic and genetic information from cells of origin to recipient cells. Their roles in mediating information exchange between CRC cells and immune cells, fibroblasts, and other cell types are pivotal in reshaping the tumor microenvironment, regulating key biological processes such as invasion, migration, and formation of pre-metastatic niche. This article comprehensively examines the communication function and mechanism of exosomes derived from different cells in cancer metastasis, while also presenting an outlook on current research advancements and future application prospects. The aim is to offer a distinctive perspective that contributes to accurate diagnosis and rational treatment strategies for CRC.

Schwann cells in pancreatic cancer: Unraveling their multifaceted roles in tumorigenesis and neural interactions

Pancreatic ductal adenocarcinoma (PDAC), characterized by heightened neural density, presents a challenging prognosis primarily due to perineural invasion. Recognized for their crucial roles in neural support and myelination, Schwann cells (SCs) significantly influence the process of tumorigenesis. This review succinctly outlines the interplay between PDAC and neural systems, positioning SCs as a nexus in the tumor-neural interface. Subsequently, it delves into the cellular origin and influencers of SCs within the pancreatic tumor microenvironment, emphasizing their multifaceted roles in tumor initiation, progression, and modulation of the neural and immune microenvironment. The discussion encompasses potential therapeutic interventions targeting SCs. Lastly, the review underscores pressing issues, advocating for sustained exploration into the diverse contributions of SCs within the intricate landscape of PDAC, with the aim of enhancing our understanding of their involvement in this complex malignancy.

Chloroxine inhibits pancreatic cancer progression through targeted antagonization of the PI3K/AKT/mTOR signaling pathway

BACKGROUND

Patients with pancreatic cancer have a dismal prognosis due to tumor cell infiltration and metastasis. Many reports have documented that EMT and PI3K-AKT-mTOR axis control pancreatic cancer cell infiltration and metastasis. Chloroxine is an artificially synthesized antibacterial compound that demonstrated anti-pancreatic cancer effects in our previous drug-screening trial. We have explored the impact of chloroxine on pancreatic cancer growth, infiltration, migration, and apoptosis.

METHODS

The proliferation of pancreatic cancer cell lines (PCCs) treated with chloroxine was assessed through real-time cell analysis (RTCA), colony formation assay, CCK-8 assay, as well as immunofluorescence. Chloroxine effects on the infiltrative and migratory capacities of PCCs were assessed via Transwell invasion and scratch experiments. To assess the contents of EMT- and apoptosis-associated proteins in tumor cells, we adopted Western immunoblotting as well as immunofluorescence assays, and flow cytometry to determine chloroxine effects on PCCs apoptosis. The in vivo chloroxine antineoplastic effects were explored in nude mice xenografts.

RESULTS

Chloroxine repressed pancreatic cancer cell growth, migration, and infiltration in vitro, as well as in vivo, and stimulated apoptosis of the PCCs. Chloroxine appeared to inhibit PCC growth by Ki67 downregulation; this targeted and inhibited aberrant stimulation of the PI3K-AKT-mTOR signaling cascade, triggered apoptosis in PCC via mitochondria-dependent apoptosis, and modulated the EMT to inhibit PCC infiltration and migration.

CONCLUSIONS

Chloroxine targeted and inhibited the PI3K-AKT-mTOR cascade to repress PCCs growth, migration, as well as invasion, and triggered cellular apoptosis. Therefore, chloroxine may constitute a potential antineoplastic drug for the treatment of pancreatic cancer.

Cholangiocarcinoma Malignant Traits Are Promoted by Schwann Cells through TGFβ Signaling in a Model of Perineural Invasion

The term cholangiocarcinoma (CCA) defines a class of epithelial malignancies originating from bile ducts. Although it has been demonstrated that CCA patients with perineural invasion (PNI) have a worse prognosis, the biological features of this phenomenon are yet unclear. Our data show that in human intrahepatic CCA specimens with documented PNI, nerve-infiltrating CCA cells display positivity of the epithelial marker cytokeratin 7, lower with respect to the rest of the tumor mass. In an in vitro 3D model, CCA cells move towards a peripheral nerve explant allowing contact with Schwann cells (SCs) emerging from the nerve. Here, we show that SCs produce soluble factors that favor the migration, invasion, survival and proliferation of CCA cells in vitro. This effect is accompanied by a cadherin switch, suggestive of an epithelial-mesenchymal transition. The influence of SCs in promoting the ability of CCA cells to migrate and invade the extracellular matrix is hampered by a specific TGFβ receptor 1 (TGFBR1) antagonist. Differential proteomic data indicate that the exposure of CCA cells to SC secreted factors induces the upregulation of key oncogenes and the concomitant downregulation of some tumor suppressors. Taken together, these data concur in identifying SCs as possible promoters of a more aggressive CCA phenotype, ascribing a central role to TGFβ signaling in regulating this process.

Clinical Evaluation of the Pancreatic Cancer Microenvironment: Opportunities and Challenges

Advances in our understanding of pancreatic ductal adenocarcinoma (PDAC) and its tumor microenvironment (TME) have the potential to transform treatment for the hundreds of thousands of patients who are diagnosed each year. Whereas the clinical assessment of cancer cell genetics has grown increasingly sophisticated and personalized, current protocols to evaluate the TME have lagged, despite evidence that the TME can be heterogeneous within and between patients. Here, we outline current protocols for PDAC diagnosis and management, review novel biomarkers, and highlight potential opportunities and challenges when evaluating the PDAC TME as we prepare to translate emerging TME-directed therapies to the clinic.

Dedifferentiated Schwann cells promote perineural invasion mediated by the PACAP paracrine signalling in cervical cancer

Perineural invasion (PNI) has emerged as a key pathological feature and be considered as a poor prognostic factor in cervical cancer. However, the underlying molecular mechanisms are largely unknown. Here, PNI status of 269 cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC) samples were quantified by using whole-slide diagnostic images obtained from The Cancer Genome Atlas. Integrated analyses revealed that PNI was an indicative marker of poorer disease-free survival for CESC patients. Among the differentially expressed genes, ADCYAP1 were identified. Clinical specimens supported that high expression of PACAP (encoded by ADCYAP1) contributed to PNI in CESC. Mechanistically, PACAP, secreted from cervical cancer cells, reversed myelin differentiation of Schwann cells (SCs). Then, dedifferentiated SCs promoted PNI by producing chemokine FGF17 and by degrading extracellular matrix through secretion of Cathepsin S and MMP-12. In conclusion, this study identified PACAP was associated with PNI in cervical cancer and suggested that tumour-derived PACAP reversed myelin differentiation of SCs to aid PNI.

Glial cell-derived soluble factors increase the metastatic potential of pancreatic adenocarcinoma cells and induce epithelial-to-mesenchymal transition

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive types of cancer, characterized by the spreading of highly metastatic cancer cells, including invasion into surrounding nerves and perineural spaces. Nerves, in turn, can invade the tumor tissue and, through the secretion of neurotrophic factors, chemokines, and cytokines, contribute to PDAC progression. However, the contribution of the nerve-associated glial cells to PDAC progression is not well characterized.

METHODS

Two murine PDAC cell lines were cultured with the conditioned media (CM) of primary enteric glial cells or IMS32 Schwann cells (SCs). Different properties of PDAC cells, such as invasiveness, migratory capacity, and resistance to gemcitabine, were measured by RT-qPCR, microscopy, and MTT assays. Using a neuronal cell line, the observed effects were confirmed to be specific to the glial lineage.

RESULTS

Compared to the control medium, PDAC cells in the glial cell-conditioned medium showed increased invasiveness and migratory capacity. These cells showed reduced E-cadherin and increased N-cadherin and Vimentin levels, all markers of epithelial-mesenchymal transition (EMT). Primary enteric glial cell CM inhibited the proliferation of PDAC cells but preserved their viability, upregulated transcription factor Snail, and increased their resistance to gemcitabine. The conditioned medium generated from the IMS32 SCs produced comparable results.

CONCLUSION

Our data suggest that glial cells can increase the metastatic potential of PDAC cells by increasing their migratory capacity and inducing epithelial-to-mesenchymal transition, a re-programming that many solid tumors use to undergo metastasis. Glial cell-conditioned medium also increased the chemoresistance of PDAC cells. These findings may have implications for future therapeutic strategies, such as targeting glial cell-derived factor signaling in PDAC.

Reduced expression of phosphorylated ataxia-telangiectasia mutated gene is related to poor prognosis and gemcitabine chemoresistance in pancreatic cancer

BACKGROUND

Loss of expression of the gene ataxia-telangiectasia mutated (ATM), occurring in patients with multiple primary malignancies, including pancreatic cancer, is associated with poor prognosis. In this study, we investigated the detailed molecular mechanism through which ATM expression affects the prognosis of patients with pancreatic cancer.

METHODS

The levels of expression of ATM and phosphorylated ATM in patients with pancreatic cancer who had undergone surgical resection were analyzed using immunohistochemistry staining. RNA sequencing was performed on ATM-knockdown pancreatic-cancer cells to elucidate the mechanism underlying the invlovement of ATM in pancreatic cancer.

RESULTS

Immunohistochemical analysis showed that 15.3% and 27.8% of clinical samples had low levels of ATM and phosphorylated ATM, respectively. Low expression of phosphorylated ATM substantially reduced overall and disease-free survival in patients with pancreatic cancer. In the pancreatic cancer cell lines with ATM low expression, resistance to gemcitabine was demonstrated. The RNA sequence demonstrated that ATM knockdown induced the expression of MET and NTN1. In ATM knockdown cells, it was also revealed that the protein expression levels of HIF-1α and antiapoptotic BCL-2/BAD were upregulated.

CONCLUSIONS

These findings demonstrate that loss of ATM expression increases tumor development, suppresses apoptosis, and reduces gemcitabine sensitivity. Additionally, loss of phosphorylated ATM is associated with a poor prognosis in patients with pancreatic cancer. Thus, phosphorylated ATM could be a possible target for pancreatic cancer treatment as well as a molecular marker to track patient prognosis.

Perineural invasion: A potential driver of cancer-induced pain

Perineural invasion (PNI) is the process through which tumors invade and interact with nerves. The dynamic changes in the nerves caused by PNI may induce disturbing symptoms. PNI-related cancer pain in neuro-rich tumors has attracted much attention because the occurrence of tumor-induced pain is closely related to the invasion of nerves in the tumor microenvironment. PNI-related pain might indicate the occurrence of PNI, guide the improvement of treatment strategies, and predict the unresectability of tumors and the necessity of palliative care. Although many studies have investigated PNI, its relationship with tumor-induced pain and its common mechanisms have not been summarized thoroughly. Therefore, in this review, we evaluated the relationship between PNI and cancer-associated pain. We showed that PNI is a major cause of cancer-related pain and that this pain can predict the occurrence of PNI. We also elucidated the cellular and molecular mechanisms of PNI-induced pain. Finally, we analyzed the possible targets for alleviating PNI-related pain or combined antitumor and pain management. Our findings might provide new perspectives for improving the treatment of patients with malignant tumors.

Schwann cells regulate tumor cells and cancer-associated fibroblasts in the pancreatic ductal adenocarcinoma microenvironment

Neuropathy is a feature more frequently observed in pancreatic ductal adenocarcinoma (PDAC) than other tumors. Schwann cells, the most prevalent cell type in peripheral nerves, migrate toward tumor cells and associate with poor prognosis in PDAC. To unveil the effects of Schwann cells on the neuro-stroma niche, here we perform single-cell RNA-sequencing and microarray-based spatial transcriptome analysis of PDAC tissues. Results suggest that Schwann cells may drive tumor cells and cancer-associated fibroblasts (CAFs) to more malignant subtypes: basal-like and inflammatory CAFs (iCAFs), respectively. Moreover, in vitro and in vivo assays demonstrate that Schwann cells enhance the proliferation and migration of PDAC cells via Midkine signaling and promote the switch of CAFs to iCAFs via interleukin-1α. Culture of tumor cells and CAFs with Schwann cells conditioned medium accelerates PDAC progression. Thus, we reveal that Schwann cells induce malignant subtypes of tumor cells and CAFs in the PDAC milieu.

Identifying a baicalein-related prognostic signature contributes to prognosis prediction and tumor microenvironment of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the most malignant and lethal human cancers in the world due to its high metastatic potential, and patients with PDAC have a poor prognosis, yet quite little is understood regarding the underlying biological mechanisms of its high metastatic capacity. Baicalein has a dramatic anti-tumor function in the treatment of different types of cancer. However, the therapeutic effects of baicalein on human PDAC and its mechanisms of action have not been extensively understood. In order to explore the biological characteristic, molecular mechanisms, and potential clinical value of baicalein in inhibiting the metastatic capacity of PDAC. We performed several in vitro, in vivo, and in silico studies. We first examined the potential regulation of baicalein in the metastatic capacity of PDAC cells. We showed that baicalein could dramatically suppress liver metastasis of PDAC cells with highly metastatic potential in mice model. The high-throughput sequencing analysis was employed to explore the biological roles of baicalein in PDAC cells. We found that baicalein might be involved in the infiltration of Cancer-Associated Fibroblasts (CAF) in PDAC. Moreover, a baicalein-related risk model and a lncRNA-related model were built by Cox analysis according to the data set of PDAC from TCGA database which suggested a clinical value of baicalein. Finally, we revealed a potential downstream target of baicalein in PDAC, we proposed that baicalein might contribute to the infiltration of CAF via FGFBP1. Thus, we uncovered a novel role for baicalein in regulation of PDAC liver metastasis that may contribute to its anti-cancer effect. We proposed that baicalein might suppress PDAC liver metastasis via regulation of FGFBP1-mediated CAF infiltration. Our results provide a new perspective on clinical utility of baicalein and open new avenues for the inhibition of liver-metastasis of PDAC.

Pancreatic Tumor-Derived Extracellular Vesicles Stimulate Schwann Cell Phenotype Indicative of Perineural Invasion via IL-8 Signaling

Pancreatic cancer remains a pre-eminent cause of cancer-related deaths with late-stage diagnoses leading to an 11% five-year survival rate. Moreover, perineural invasion (PNI), in which cancer cells migrate into adjacent nerves, occurs in an overwhelming majority of patients, further enhancing tumor metastasis. PNI has only recently been recognized as a key contributor to cancer progression; thus, there are insufficient treatment options for the disease. Attention has been focused on glial Schwann cells (SC) for their mediation of pancreatic PNI. Under stress, SCs dedifferentiate from their mature state to facilitate the repair of peripheral nerves; however, this signaling can also re-direct cancer cells to accelerate PNI. Limited research has explored the mechanism that causes this shift in SC phenotype in cancer. Tumor-derived extracellular vesicles (TEV) have been implicated in other avenues of cancer development, such as pre-metastatic niche formation in secondary locations, yet how TEVs contribute to PNI has not been fully explored. In this study, we highlight TEVs as initiators of SC activation into a PNI-associated phenotype. Proteomic and pathway assessments of TEVs revealed an elevation in interleukin-8 (IL-8) signaling and nuclear factor kappa B (NFκB) over healthy cell-derived EVs. TEV-treated SCs exhibited higher levels of activation markers, which were successfully neutralized with IL-8 inhibition. Additionally, TEVs increased NFκB subunit p65 nuclear translocation, which may lead to increased secretion of cytokines and proteases indicative of SC activation and PNI. These findings present a novel mechanism that may be targeted for the treatment of pancreatic cancer PNI.

Statement of Significance

Identifying pancreatic tumor extracellular vesicles as key players in Schwann cell activation and perineural invasion by way of IL-8 will educate for more specialized and effective targets for an under-valued disease.

Melanoma-associated repair-like Schwann cells suppress anti-tumor T-cells via 12/15-LOX/COX2-associated eicosanoid production

Peripheral glia, specifically the Schwann cells (SCs), have been implicated in the formation of the tumor microenvironment (TME) and in cancer progression. However, in vivo and ex vivo analyses of how cancers reprogram SC functions in different organs of tumor-bearing mice are lacking. We generated Plp1-CreERT/tdTomato mice which harbor fluorescently labeled myelinated and non-myelin forming SCs. We show that this model enables the isolation of the SCs with high purity from the skin and multiple other organs. We used this model to study phenotypic and functional reprogramming of the SCs in the skin adjacent to melanoma tumors. Transcriptomic analyses of the peritumoral skin SCs versus skin SCs from tumor-free mice revealed that the former existed in a repair-like state typically activated during nerve and tissue injury. Peritumoral skin SCs also downregulated pro-inflammatory genes and pathways related to protective anti-tumor responses. In vivo and ex vivo functional assays confirmed immunosuppressive activities of the peritumoral skin SCs. Specifically, melanoma-reprogrammed SCs upregulated 12/15-lipoxygenase (12/15-LOX) and cyclooxygenase (COX)-2, and increased production of anti-inflammatory polyunsaturated fatty acid (PUFA) metabolites prostaglandin E2 (PGE2) and lipoxins A4/B4. Inhibition of 12/15-LOX or COX2 in SCs, or EP4 receptor on lymphocytes reversed SC-dependent suppression of anti-tumor T-cell activation. Therefore, SCs within the skin adjacent to melanoma tumors demonstrate functional switching to repair-like immunosuppressive cells with dysregulated lipid oxidation. Our study suggests the involvement of the melanoma-associated repair-like peritumoral SCs in the modulation of locoregional and systemic anti-tumor immune responses.

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.

A reciprocal feedback between colon cancer cells and Schwann cells promotes the proliferation and metastasis of colon cancer

BACKGROUND

Research has indicated that the emergence of Schwann cells around premalignant lesions of colon cancer might be an early indicator promoting the onset of tumorigenesis. The present study explored the communication between colon cancer cells and Schwann cells.

METHODS

Immunofluorescence analyses were conducted to examine the differential distribution of Schwann cells within colon cancer tissues and normal colon tissues. CCK8 assay, colony formation assay, wound healing assay, and transwell assay were performed to investigate the interaction between colon cancer cells and Schwann cells. Exosomes derived from colon cancer cells were isolated to further explore the effect of colon cancer cells on Schwann cells. Gain- and loss-of function experiments, luciferase reporter assays, chromatin immunoprecipitation assays, and immunohistochemistry assays were performed to reveal the cross-talk between colon cancer cells and Schwann cells. Furthermore, colon cancer cells co-cultured with Schwann cells were transplanted into nude mice for evaluating their effect on tumor proliferation and metastasis in vivo.

RESULTS

The clinicopathological characteristics indicated that Schwann cells were enriched in colon cancer tissues and were associated with tumor metastasis and poor prognosis. The co-culture of Schwann cells with colon cancer cells promoted the proliferation and migration of colon cancer cells and Schwann cells, which was mediated by nerve growth factor (NGF) secreted from Schwann cells. Exosomal miR-21-5p released by colon cancer cells inhibited VHL expression in Schwann cells, which in turn stabilized the HIF-1α protein and increased the transcription of NGF. Meanwhile, the Schwann cells-derived NGF activated TrkA/ERK/ELK1/ZEB1 signaling pathway in colon cancer cells, which further enhanced the expression of exosomal miR-21-5p. Inhibition of either NGF or miR-21-5p significantly inhibited the proliferation and metastasis of transplanted colon cancer cells in nude mice. Coincidently, miR-21-5p was positively associated with the expression of NGF, p-ERK, p-ELK1, and ZEB1 in human colon cancer tissues.

CONCLUSIONS

Our results implicated a reciprocal communication between colon cancer cells and Schwan cells that promoted the proliferation and metastasis of colon cancer, and identified NGF and exosomal miR-21-5p as potential therapeutic targets for the treatment of colon cancer.

A Novel Therapeutic Target for Small-Cell Lung Cancer: Tumor-Associated Repair-like Schwann Cells

Small-cell lung cancer (SCLC), representing 15-20% of all lung cancers, is an aggressive malignancy with a distinct natural history, poor prognosis, and limited treatment options. We have previously identified Schwann cells (SCs), the main glial cells of the peripheral nervous system, in tumor tissues and demonstrated that they may support tumor spreading and metastasis formation in the in vitro and in vivo models. However, the role of SCs in the progression of SCLC has not been investigated. To clarify this issue, the cell proliferation assay, the annexin V apoptosis assay, and the transwell migration and invasion assay were conducted to elucidate the roles in SCLC of tumor-associated SCs (TA-SCs) in the proliferation, apoptosis, migration, and invasion of SCLC cells in vitro, compared to control group. In addition, the animal models to assess SC action's effects on SCLC in vivo were also developed. The result confirmed that TA-SCs have a well-established and significant role in facilitating SCLC cell cancer migration and invasion of SCLC in vitro, and we also observed that SC promotes tumor growth of SCLC in vivo and that TA-SCs exhibited an advantage and show a repair-like phenotype, which allowed defining them as tumor-associated repair SCs (TAR-SCs). Potential molecular mechanisms of pro-tumorigenic activity of TAR-SCs were investigated by the screening of differentially expressed genes and constructing networks of messenger-, micro-, and long- non-coding RNA (mRNA-miRNA-lncRNA) using DMS114 cells, a human SCLC, stimulated with media from DMS114-activated SCs, non-stimulated SCs, and appropriate controls. This study improves our understanding of how SCs, especially tumor-activated SCs, may promote SCLC progression. Our results highlight a new functional phenotype of SCs in cancer and bring new insights into the characterization of the nervous system-tumor crosstalk.

Schwann cells promote the migration and invasion of colorectal cancer cells via the activated NF-κB/IL-8 axis in the tumor microenvironment

BACKGROUND

Evidence has shown neurons and glial cells were closely related to tumor progression. As the predominant glial cells in the external innervated nerves of the gastrointestinal, the role of Schwann cells (SCs) in colorectal cancer (CRC) has not been well explored.

METHODS

HCT-116 and HT-29 CRC cells were treated with conditioned medium (CM) from SCs, and the cells' proliferative and migrating capacities were examined. Cytokine array analysis was used to identify the tumor-promoting-cytokines from SCs-CM. Molecular changes from SCs after being co-cultured with tumor cells were detected by ELISA and reverse transcription-quantitative PCR. The activation of the nuclear factor kappa B (NF-κB) signaling pathway in SCs was demonstrated by immunofluorescence staining. Neutralizing antibody was used to verify the tumor-promoting effects of key cytokine.

RESULTS

Migration and invasion of CRC cells were markedly aided by CM from SCs in vitro. Interleukin-8 (IL-8) was identified as an effective factor. SCs co-cultured with CRC cells upregulated IL-8 expression, which may be related to its activated NF-κB signaling pathway. Neutralization of IL-8 attenuated the tumor-promoting effect of SCs.

CONCLUSION

The present study identified a new mechanism of tumor-neuroglia interaction, enriching the concept of the tumor-neural axis in the tumor microenvironment of CRC, which also inspired potential targets for anti-cancer therapies.

Perineural invasion-associated biomarkers for tumor development

Perineural invasion (PNI) is the process of neoplastic invasion of peripheral nerves and is considered to be the fifth mode of cancer metastasis. PNI has been detected in head and neck tumors and pancreatic, prostate, bile duct, gastric, and colorectal cancers. It leads to poor prognostic outcomes and high local recurrence rates. Despite the increasing number of studies on PNI, targeted therapeutic modalities have not been proposed. The identification of PNI-related biomarkers would facilitate the non-invasive and early diagnosis of cancers, the establishment of prognostic panels, and the development of targeted therapeutic approaches. In this review, we compile information on the molecular mediators involved in PNI-associated cancers. The expression and prognostic significance of molecular mediators and their receptors in PNI-associated cancers are analyzed, and the possible mechanisms of action of these mediators in PNI are explored, as well as the association of cells in the microenvironment where PNI occurs.

The Role of Schwann Cells in Cancer

Schwann cells (SCs) are the most abundant cell type in the nerves in the peripheral nervous system and compose a family of subtypes that are endowed with a variety of different functions. SCs facilitate the transmission of neural impulses, provide nutrients and protection for neurons, guide axons in nerve repair, and regulate immune functions. In the context of cancer, recent studies have revealed an active role of SCs in promoting cancer cell invasion, modulating immune responses, and transmitting pain sensation.

Drug repurposing in cancer neuroscience: From the viewpoint of the autophagy-mediated innervated niche

Based on the bidirectional interactions between neurology and cancer science, the burgeoning field “cancer neuroscience” has been proposed. An important node in the communications between nerves and cancer is the innervated niche, which has physical contact with the cancer parenchyma or nerve located in the proximity of the tumor. In the innervated niche, autophagy has recently been reported to be a double-edged sword that plays a significant role in maintaining homeostasis. Therefore, regulating the innervated niche by targeting the autophagy pathway may represent a novel therapeutic strategy for cancer treatment. Drug repurposing has received considerable attention for its advantages in cost-effectiveness and safety. The utilization of existing drugs that potentially regulate the innervated niche via the autophagy pathway is therefore a promising pharmacological approach for clinical practice and treatment selection in cancer neuroscience. Herein, we present the cancer neuroscience landscape with an emphasis on the crosstalk between the innervated niche and autophagy, while also summarizing the underlying mechanisms of candidate drugs in modulating the autophagy pathway. This review provides a strong rationale for drug repurposing in cancer treatment from the viewpoint of the autophagy-mediated innervated niche.

Yiqi Jianpi Huayu Jiedu Decoction Inhibits Metastasis of Colon Adenocarcinoma by Reversing Hsa-miR-374a-3p/Wnt3/β-Catenin-Mediated Epithelial–Mesenchymal Transition and Cellular Plasticity

Colon adenocarcinoma (COAD) accounts for 95% of colon cancer cases, with the 5-year survival rate significantly affected by local or distant metastases. Yiqi Jianpi Huayu Jiedu decoction (YJHJD), based on the theory of “nourish qi, invigorate the spleen, remove blood stasis, and detoxify”, has long been applied and shown to be remarkable in the prevention and treatment of gastrointestinal tumors. However, the underlying therapeutic mechanisms of YJHJD have not been fully elucidated. Herein, we first confirmed hsa-miR-374a-3p as a tumor suppressor based on its lower expression in the plasma of patients with COAD with liver metastasis and association with more advanced local progression. We also verified WNT3 as a potential target of hsa-miR-374a-3p and observed its increased expression in COAD tissues. Furthermore, we showed that the hsa-miR-374a-3p/Wnt3/β-catenin axis was responsible for epithelial–mesenchymal transition (EMT) and cellular plasticity in COAD, as well as poorer patient prognosis. Our results showed that YJHJD inhibited motility and colony potential in vitro, as well as liver metastasis of COAD in vivo. Moreover, YJHJD induced a reversal of EMT and cellular plasticity-related molecular expression, increased hsa-miR-374a-3p, and decreased Wnt3 and β-catenin levels. In addition, silencing of hsa-miR-374a-3p weakened YJHJD inhibition, whereas the β-catenin inhibitor XAV939 partially repaired it. Taken together, these results demonstrated that YJHJD suppressed the EMT and cellular plasticity of COAD by regulating hsa-miR-374a-3p/Wnt3/β-catenin signaling.

Paracrine Interaction of Cholangiocellular Carcinoma with Cancer-Associated Fibroblasts and Schwann Cells Impact Cell Migration

Although the Mitogen-activated protein kinase (MAPK) pathway is enriched in cholangiocarcinoma (CCA), treatment with the multityrosine kinase-inhibitor Sorafenib is disappointing. While cancer-associated fibroblasts (CAF) are known to contribute to treatment resistance in CCA, knowledge is lacking for Schwann cells (SC). We investigated the impact of stromal cells on CCA cells and whether this is affected by Sorafenib. Immunohistochemistry revealed elevated expression of CAF and SC markers significantly correlating with reduced tumor-free survival. In co-culture with CAF, CCA cells mostly migrated, which could be diminished by Sorafenib, while in SC co-cultures, SC predominantly migrated towards CCA cells, unaffected by Sorafenib. Moreover, increased secretion of pro-inflammatory cytokines MCP-1, CXCL-1, IL-6 and IL-8 was determined in CAF mono- and co-cultures, which could be reduced by Sorafenib. Corresponding to migration results, an increased expression of phospho-AKT was measured in CAF co-cultured HuCCT-1 cells, although was unaffected by Sorafenib. Intriguingly, CAF co-cultured TFK-1 cells showed increased activation of STAT3, JNK, ERK and AKT pathways, which was partly reduced by Sorafenib. This study indicates that CAF and SC differentially impact CCA cells and Sorafenib partially reverts these stroma-mediated effects. These findings contribute to a better understanding of the paracrine interplay of CAF and SC with CCA cells.

Exploring the Role of Metabolites in Cancer and the Associated Nerve Crosstalk

Since Otto Warburg's first report on the increased uptake of glucose and lactate release by cancer cells, dysregulated metabolism has been acknowledged as a hallmark of cancer that promotes proliferation and metastasis. Over the last century, studies have shown that cancer metabolism is complex, and by-products of glucose and glutamine catabolism induce a cascade of both pro- and antitumorigenic processes. Some vitamins, which have traditionally been praised for preventing and inhibiting the proliferation of cancer cells, have also been proven to cause cancer progression in a dose-dependent manner. Importantly, recent findings have shown that the nervous system is a key player in tumor growth and metastasis via perineural invasion and tumor innervation. However, the link between cancer-nerve crosstalk and tumor metabolism remains unclear. Here, we discuss the roles of relatively underappreciated metabolites in cancer-nerve crosstalk, including lactate, vitamins, and amino acids, and propose the investigation of nutrients in cancer-nerve crosstalk based on their tumorigenicity and neuroregulatory capabilities. Continued research into the metabolic regulation of cancer-nerve crosstalk will provide a more comprehensive understanding of tumor mechanisms and may lead to the identification of potential targets for future cancer therapies.

Cancer-associated fibroblast-induced lncRNA UPK1A-AS1 confers platinum resistance in pancreatic cancer via efficient double-strand break repair

The tumor stroma of pancreatic ductal adenocarcinoma (PDAC) is characterized by an abundant and heterogeneous population of cancer-associated fibroblasts (CAFs), which are critically involved in chemoresistance. However, the underlying mechanism of CAFs in chemoresistance is unclear. Here, we show that CAFR, a CAF subset derived from platinum-resistant PDAC patients, assumes an iCAF phenotype and produces more IL8 than CAFS isolated from platinum-sensitive PDAC patients. CAFR-derived IL8 promotes oxaliplatin chemoresistance in PDAC. Based on long noncoding RNA (lncRNA) profiling in tumor cells incubated with CAF-CM, we found that UPK1A-AS1, whose expression is directly induced by IL8/NF-kappa B signaling, functions as a chemoresistance-promoting lncRNA and is critical for active IL8-induced oxaliplatin resistance. Impressively, blocking the activation of UPK1A-AS1 expression increases the oxaliplatin sensitivity of tumor cells in vivo. Mechanistically, UPK1A-AS1 strengthens the interaction between Ku70 and Ku80 to facilitate nonhomologous end joining (NHEJ), thereby enhancing DNA double-strand break (DSB) repair. Clinically, UPK1A-AS1 expression is positively correlated with IL8 expression, a poor chemotherapeutic response and a shorter progression-free survival (PFS) time in advanced PDAC patients. Collectively, our study reveals a lncRNA-mediated mechanism of CAF-derived paracrine IL8-dependent oxaliplatin resistance and highlights UPK1A-AS1 as a potential therapeutic target.

Schwann Cells in Digestive System Disorders

Proper functioning of the digestive system is ensured by coordinated action of the central and peripheral nervous systems (PNS). Peripheral innervation of the digestive system can be viewed as intrinsic and extrinsic. The intrinsic portion is mainly composed of the neurons and glia of the enteric nervous system (ENS), while the extrinsic part is formed by sympathetic, parasympathetic, and sensory branches of the PNS. Glial cells are a crucial component of digestive tract innervation, and a great deal of research evidence highlights the important status of ENS glia in health and disease. In this review, we shift the focus a bit and discuss the functions of Schwann cells (SCs), the glial cells of the extrinsic innervation of the digestive system. For more context, we also provide information on the basic findings regarding the function of innervation in disorders of the digestive organs. We find diverse SC roles described particularly in the mouth, the pancreas, and the intestine. We note that most of the scientific evidence concerns the involvement of SCs in cancer progression and pain, but some research identifies stem cell functions and potential for regenerative medicine.

Schwann Cells in the Tumor Microenvironment: Need More Attention

The tumor microenvironment (TME), which is composed of various cell components and signaling molecules, plays an important role in the occurrence and progression of tumors and has become the central issue of current cancer research. In recent years, as a part of the TME, the peripheral nervous system (PNS) has attracted increasing attention. Moreover, emerging evidence shows that Schwann cells (SCs), which are the most important glial cells in the PNS, are not simply spectators in the TME. In this review article, we focused on the up-to-date research progress on SCs in the TME and introduced our point of view. In detail, we described that under two main tumor-nerve interaction patterns, perineural invasion (PNI) and tumor innervation, SCs were reprogrammed and acted as important participants. We also investigated the newest mechanisms between the interactions of SCs and tumor cells. In addition, SCs can have profound impacts on other cellular components in the TME, such as immune cells and cancer-associated fibroblasts (CAFs), involving immune regulation, tumor-related pain, and nerve remodeling. Overall, these innovative statements can expand the scope of the TME, help fully understand the significant role of SCs in the tumor-nerve-immune axis, and propose enlightenments to innovate antitumor therapeutic methods and future research.

Autophagic Schwann cells promote perineural invasion mediated by the NGF/ATG7 paracrine pathway in pancreatic cancer

Background

Perineural invasion (PNI) and autophagy are two common features in the tumor microenvironment of pancreatic cancer (PanCa) and have a negative effect on prognosis. Potential mediator cells and the molecular mechanism underlying their relationships need to be fully elucidated.

Methods

To investigate the autophagy of Schwann cells (SCs) in PNI, we reproduced the microenvironment of PNI by collecting clinical PNI tissue, performing sciatic nerve injection of nude mice with cancer cells and establishing a Dorsal root ganglion (DRG) coculture system with cancer cell lines. Autophagy was detected by IHC, IF, transmission electron microscopy (TEM) and western blotting assays. Apoptosis was detected by IF, TEM and western blotting. NGF targeting molecular RO 08–2750(RO) and the autophagy inhibitor Chloroquine (CQ) were utilized to evaluate the effect on autophagy and apoptosis in SCs and PanCa cells in PNI samples.

Results

SC autophagy is activated in PNI by paracrine NGF from PanCa cells. Autophagy-activated Schwann cells promote PNI through a) enhanced migration and axon guidance toward PanCa cells and b) increased chemoattraction to PanCa cells. The NGF-targeting reagent RO and autophagy inhibitor CQ inhibited Schwann cell autophagic flux and induced Schwann cell apoptosis. Moreover, RO and CQ could induce PanCa cell apoptosis and showed good therapeutic effects in the PNI model.

Conclusions

PanCa cells can induce autophagy in SCs through paracrine pathways such as the NGF/ATG7 pathway. Autophagic SCs exert a “nerve-repair like effect”, induce a high level of autophagy of cancer cells, provide a “beacon” for the invasion of cancer cells to nerve fibers, and induce directional growth of cancer cells. Targeting NGF and autophagy for PNI treatment can block nerve infiltration and is expected to provide new directions and an experimental basis for the research and treatment of nerve infiltration in pancreatic cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02198-w.

Fisetin inhibits the proliferation, migration and invasion of pancreatic cancer by targeting PI3K/AKT/mTOR signaling

Pancreatic cancer is an extremely malignant digestive tract tumor. With the increase of chemotherapeutic resistance of pancreatic cancer, clinical treatment is in a dilemma. Hence, it is pivotal to design an effective drug for treating individuals with pancreatic cancer. Fisetin extracted from vegetables, as well as fruits was explored to possess antioxidant, anti-cancer, anti-inflammatory along with anti-microbial properties. Nonetheless, there is limited research focusing on the utility of fisetin as an inhibitor of pancreatic cancer. Similarly, the mechanism through which Fisetin dampens pancreatic cancer remains unknown. This research work systematically evaluated the possible anti-cancer influences of fisetin in pancreatic cancer, as well as explored its responsible molecular mechanism. Our data revealed that fisetin obviously dampens pancreatic cancer progress in vitro along with in vivo dose-dependently. Furthermore, we established that fisetin repressed pancreatic cancer via explicitly targeting PI3K/AKT/mTOR signaling cascade and not the JAK2 cascade. Our data clarified that fisetin is a prospective anti-cancer drug for pancreatic cancer, as well as indicated the distinct molecular target of fisetin.

Perineural Invasion and Associated Pain Transmission in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the cancers with the highest incidence of perineural invasion (PNI), which often indicates a poor prognosis. Aggressive tumor cells invade nerves, causing neurogenic inflammation; the tumor microenvironment also induces nerves to undergo a series of structural and functional reprogramming. In turn, neurons and the surrounding glial cells promote the development of pancreatic cancer through autocrine and/or paracrine signaling. In addition, hyperalgesia in PDAC patients implies alterations of pain transmission in the peripheral and central nervous systems. Currently, the studies on this topic are relatively limited. This review will elaborate on the mechanisms of tumor-neural interactions and its possible relationship with pain from several aspects that have been focused on in recent years.

Immune-related genes LAMA2 and IL1R1 correlate with tumor sites and predict poor survival in pancreatic adenocarcinoma

Aims: The aim of this study was to identify the immune- and locus-associated genes in pancreatic ductal adenocarcinoma and evaluate their value in prognosis. Methods: The pancreatic ductal adenocarcinoma stromal and immune scores were calculated with the estimation of stromal and immune cells in malignant tumor tissues using expression data algorithm. The authors screened the differentially expressed genes to generate immune- and stromal-related differentially expressed genes. Next, the authors conducted weighted correlation network analysis to find the gene sets related to tumor sites. Results: IL1R1 and LAMA2 were identified as the site- and immune-related genes in pancreatic ductal adenocarcinoma, and their high expression in pancreatic head cancer exhibited high immune scores and predicted unfavorable prognosis. Conclusion: The authors identified IL1R1 and LAMA2 as immune- and locus-associated genes, and their high expression predicted a poor prognosis.

Prussian blue nanozyme-mediated nanoscavenger ameliorates acute pancreatitis via inhibiting TLRs/NF-κB signaling pathway

Rationale: Acute pancreatitis (AP) is a serious acute condition affecting the abdomen and shows high morbidity and mortality rates. Its global incidence has increased in recent years. Inflammation and oxidative stress are potential therapeutic targets for AP. This study was conducted to investigate the intrinsic anti-oxidative and anti-inflammatory effects of Prussian blue nanozyme (PBzyme) on AP, along with its underlying mechanism. Methods: Prussian blue nanozymes were prepared by polyvinylpyrrolidone modification method. The effect of PBzyme on inhibiting inflammation and scavenging reactive oxygen species was verified at the cellular level. The efficacy and mechanism of PBzyme for prophylactically treating AP were evaluated using the following methods: serum testing in vivo, histological scoring following hematoxylin and eosin staining, terminal deoxynucleotidyl transferase dUTP nick end labeling fluorescence staining, polymerase chain reaction array, Kyoto Encyclopedia of Genes and Genomes analysis and Western blotting analysis. Results: The synthetic PBzyme showed potent anti-oxidative and anti-inflammatory effects in reducing oxidative stress and alleviating inflammation both in vitro and in vivo in the prophylactic treatment of AP. The prophylactic therapeutic efficacy of PBzyme on AP may involve inhibition of the toll-like receptor/nuclear factor-κB signaling pathway and reactive oxygen species scavenging. Conclusion: The single-component, gram-level mass production, stable intrinsic biological activity, biosafety, and good therapeutic efficacy suggest the potential of PBzyme in the preventive treatment of AP. This study provides a foundation for the clinical application of PBzyme.

Hepatocyte nuclear factor 1 alpha influences pancreatic cancer growth and metastasis

Hepatocyte nuclear factor 1 homeobox alpha (HNF1α) is a transcription factor involved in endodermal organogenesis and pancreatic precursor cell differentiation and development. Earlier studies have reported a role for HNF1α in pancreatic ductal adenocarcinoma (PDAC) but it is controversial. The mechanism by which it impacts PDAC is yet to be explored in depth. In this study, using the online databases we observed that HNF1α is upregulated in PDAC, which was also confirmed by our immunohistochemical analysis of PDAC tissue microarray. Silencing HNF1α reduced the proliferative, migratory, invasive and colony forming capabilities of pancreatic cancer cells. Key markers involved in these processes (pPI3K, pAKT, pERK, Bcl2, Zeb, Snail, Slug) were significantly changed in response to alterations in HNF1α expression. On the other hand, overexpression of HNF1α did not induce any significant change in the aggressiveness of pancreatic cancer cells. Our results demonstrate that reduced expression of HNF1α leads to inhibition of pancreatic cancer growth and progression, which indicates that it could be a potential oncogene and target for PDAC.

Schwann Cell Stimulation of Pancreatic Cancer Cells: A Proteomic Analysis

Schwann cells (SCs), the glial component of peripheral nerves, have been identified as promoters of pancreatic cancer (PC) progression, but the molecular mechanisms are unclear. In the present study, we aimed to identify proteins released by SCs that could stimulate PC growth and invasion. Proteomic analysis of human primary SC secretome was performed using liquid chromatography–tandem mass spectrometry, and a total of 13,796 unique peptides corresponding to 1,470 individual proteins were identified. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment were conducted using the Database for Annotation, Visualization, and Integrated Discovery. Metabolic and cell–cell adhesion pathways showed the highest levels of enrichment, a finding in line with the supportive role of SCs in peripheral nerves. We identified seven SC-secreted proteins that were validated by western blot. The involvement of these SC-secreted proteins was further demonstrated by using blocking antibodies. PC cell proliferation and invasion induced by SC-conditioned media were decreased using blocking antibodies against the matrix metalloproteinase-2, cathepsin D, plasminogen activator inhibitor-1, and galectin-1. Blocking antibodies against the proteoglycan biglycan, galectin-3 binding protein, and tissue inhibitor of metalloproteinases-2 decreased only the proliferation but not the invasion of PC cells. Together, this study delineates the secretome of human SCs and identifies proteins that can stimulate PC cell growth and invasion and therefore constitute potential therapeutic targets.

Nerve input to tumours: Pathophysiological consequences of a dynamic relationship

It is well known that tumours arising in different organs are innervated and that 'perineural invasion' (cancer cells escaping from the tumour by following the nerve trunk) is a negative prognostic factor. More surprisingly, increasing evidence suggests that the nerves can provide active inputs to tumours and there is two-way communication between nerves and cancer cells within the tumour microenvironment. Cells of the immune system also interact with the nerves and cancer cells. Thus, the nerve connections can exert significant control over cancer progression and modulating these (physically or chemically) can affect significantly the cancer process. Nerve inputs to tumours are derived mainly from the sympathetic (adrenergic) and the parasympathetic (cholinergic) systems, which are interactive. An important component of the latter is the vagus nerve, the largest of the cranial nerves. Here, we present a two-part review of the nerve inputs to tumours and their effects on tumorigenesis. First, we review briefly some relevant general issues including ultrastructural aspects, stemness, interactions between neurones and primary tumours, and communication between neurones and metastasizing tumour cells. Ultrastructural characteristics include synaptic vesicles, tumour microtubes and gap junctions enabling formation of cellular networks. Second, we evaluate the pathophysiology of the nerve input to five major carcinomas: cancers of prostate, stomach, colon, lung and pancreas. For each cancer, we present (i) the nerve inputs normally present in the cancer organ and (ii) how these interact and influence the cancer process. The best clinical evidence for the role of nerves in promoting tumorigenesis comes from prostate cancer patients where metastatic progression has been shown to be suppressed significantly in cases of spinal cord injury. The balance of the sympathetic and parasympathetic contributions to early versus late tumorigenesis varies amongst the different cancers. Different branches of the vagus provide functional inputs to several of the carcinomas and, in two-way interaction with the sympathetic nervous system, affect different stages of the cancer process. Overall, the impact of the vagus nerve can be 'direct' or 'indirect'. Directly, the effect of the vagus is primarily to promote tumorigenesis and this is mediated through cholinergic receptor mechanisms. Indirectly, pro- and anti-tumour effects can occur by stimulation or inhibition of the sympathetic nervous system, respectively. Less well understood are the 'indirect' anti-tumour effect of the vagus nerve via immunomodulation/inflammation, and the role of sensory innervation. A frequent occurrence in the nerve-tumour interactions is the presence of positive feedback driven by agents like nerve growth factor. We conclude that the nerve inputs to tumours can actively and dynamically impact upon cancer progression and are open to clinical exploitation.

Mechanical stimulation of Schwann cells promote peripheral nerve regeneration via extracellular vesicle-mediated transfer of microRNA 23b-3p

Rationale: Peripheral nerves are unique in their remarkable elasticity. Schwann cells (SCs), important components of the peripheral nervous system (PNS), are constantly subjected to physiological and mechanical stresses from dynamic stretching and compression forces during movement. So far, it is not clear if SCs sense and respond to mechanical signals. It is also unknown whether mechanical stimuli can interfere with the intercellular communications between neurons and SCs, and what role extracellular vesicles (EVs) play in this process. The present study aimed to examine the effect of mechanical stimuli on the EV-mediated intercellular communication between neurons and SCs, explore their effect on axonal regeneration, and investigate the underlying mechanism. Methods: Purified SCs were stimulated using a magnetic force-based mechanical stimulation (MS) system and EVs were purified from mechanically stimulated SCs (MS-SCs-EVs) and non-stimulated SCs (SCs-EVs). The effect of MS-SCs-EVs on axonal elongation was examined in vitro and in vivo. High throughput miRNA sequencing was performed to compare the differential miRNA profiles between MS-SCs-EVs and SCs-EVs. The functional role of differentially expressed miRNAs on neurite extension in MS-SCs-EVs was examined. Also, the putative target genes of differentially expressed miRNAs in MS-SCs-EVs were predicted by bioinformatics tools, and the regulatory effect of those miRNAs on putative target genes was validated both in vitro and in vivo. Results: The MS-SCs-EVs showed an average size of 137.52±1.77 nm, and could be internalized by dorsal root ganglion (DRG) neurons. Compared to SCs-EVs, MS-SCs-EVs showed a stronger ability to enhance neurite outgrowth in vitro and nerve regeneration in vivo. High throughput miRNA sequencing identified a number of differentially expressed miRNAs in MS-SCs-EVs. Further analysis of those EV-miRNAs demonstrated that miR-23b-3p played a predominant role in MS-SCs-EVs since its deprivation abolished their enhanced axonal elongation. Furthermore, we identified neuropilin 1 (Nrp1) in neurons as the target gene of miR-23b-3p in MS-SCs-EVs. This observation was supported by the evidence that miR-23b-3p could decrease Nrp1-3'-UTR-WT luciferase activity in vitro and down-regulate Nrp1 expression in neurons. Conclusion: Our findings suggested that mechanical stimuli are capable of modulating the intercellular communication between neurons and SCs by altering miRNA composition in MS-SCs-EVs. Transfer of miR-23b-3p by MS-SCs-EVs from mechanically stimulated SCs to neurons decreased neuronal Nrp1 expression, which was responsible, at least in part, for the beneficial effect of MS-SCs-EVs on axonal regeneration. Our results highlighted the potential therapeutic value of MS-SCs-EVs and miR-23b-3p-enriched EVs in peripheral nerve injury repair.

Increased intracellular Cl- concentration improves airway epithelial migration by activating the RhoA/ROCK Pathway

In the airway, Cl- is the most abundant anion and is critically involved in transepithelial transport. The correlation of the abnormal expression and activation of chloride channels (CLCs), such as cystic fibrosis transmembrane conductance regulators (CFTRs), anoctamin-1, and CLC-2, with cell migration capability suggests a relationship between defective Cl- transport and epithelial wound repair. However, whether a correlation exists between intracellular Cl- and airway wound repair capability has not been explored thus far, and the underlying mechanisms involved in this relationship are not fully defined. Methods: In this work, the alteration of intracellular chloride concentration ([Cl-]i) was measured by using a chloride-sensitive fluorescent probe (N-[ethoxycarbonylmethyl]-6-methoxyquinolium bromide). Results: We found that clamping with high [Cl-]i and 1 h of treatment with the CLC inhibitor CFTR blocker CFTRinh-172 and chloride intracellular channel inhibitor IAA94 increased intracellular Cl- concentration ([Cl-]i) in airway epithelial cells. This effect improved epithelial cell migration. In addition, increased [Cl-]i in cells promoted F-actin reorganization, decreased cell stiffness, and improved RhoA activation and LIMK1/2 phosphorylation. Treatment with the ROCK inhibitor of Y-27632 and ROCK1 siRNA significantly attenuated the effects of increased [Cl-]i on LIMK1/2 activation and cell migration. In addition, intracellular Ca2+ concentration was unaffected by [Cl-]i clamping buffers and CFTRinh-172 and IAA94. Conclusion: Taken together, these results suggested that Cl- accumulation in airway epithelial cells could activate the RhoA/ROCK/LIMK cascade to induce F-actin reorganization, down-regulate cell stiffness, and improve epithelial migration.