The chemokine (CCL2-CCR2) signaling axis mediates perineural invasion

Molecular pathway of pancreatic cancer-associated neuropathic pain

The pancreas is a heterocrine gland that has both exocrine and endocrine parts. Most pancreatic cancer begins in the cells that line the ducts of the pancreas and is called pancreatic ductal adenocarcinoma (PDAC). PDAC is the most encountered pancreatic cancer type. One of the most important characteristic features of PDAC is neuropathy which is primarily due to perineural invasion (PNI). PNI develops tumor microenvironment which includes overexpression of fibroblasts cells, macrophages, as well as angiogenesis which can be responsible for neuropathy pain. In tumor microenvironment inactive fibroblasts are converted into an active form that is cancer-associated fibroblasts (CAFs). Neurotrophins they also increase the level of Substance P, calcitonin gene-related peptide which is also involved in pain. Matrix metalloproteases are the zinc-associated proteases enzymes which activates proinflammatory interleukin-1β into its activated form and are responsible for release and activation of Substance P which is responsible for neuropathic pain by transmitting pain signal via dorsal root ganglion. All the molecules and their role in being responsible for neuropathic pain are described below.

NK cells and the profile of inflammatory cytokines in the peripheral blood of patients with advanced carcinomas

BACKGROUND

Natural killer (NK) cells are one of the most crucial immune cells that mediate the antitumoral response due to their ability to immediately recognize and eliminate transformed cells. Because of their great cytotoxic activity, the function of NK cells must be robustly regulated to avoid tissue damage. Such regulation is mediated by a coordinated engagement of activating (NKp46) and inhibitory (CD158b) receptors, which tumor cells may use to escape from immunosurveillance. Also, NK cells are generally divided based on surface molecules, such as CD16 and CD56, and can be classified as CD56brightCD16- (regulatory) and CD56dimCD16+ (cytotoxic) NK cells. Here, we aimed to evaluate the frequency and phenotype of circulating NK cells in patients with advanced carcinomas, as well as their systemic cytokine/chemokine and growth factors production.

METHODS

Peripheral blood was collected from 24 patients with advanced solid cancer during or after treatment and from 10 healthy donors. The frequency and the expression of activating (NKp46) and inhibitory (CD158b) molecules of CD56brightCD16- and CD56dimCD16+ NK cells were assessed by flow cytometry and the multiplex Luminex platform was used to quantify the secreted factors in peripheral blood serum.

RESULTS

Cancer patients had a lower frequency of the cytotoxic CD56dim CD16+ NK cells subset in comparison with healthy controls. Also, the regulatory CD56bright CD16- NKs isolated from cancer patients exhibited a significantly lower expression of NKp46. Among 29 immunological and growth factors analyzed in the peripheral blood of oncologic patients, MCP-1, IP-10, and eotaxin, and VEGF they have presented a higher proportion. The Pearson correlation test showed that IL-12p40 positively correlates with CD56brightCD16- NK cells. We also observed a positive correlation between MCP-1 and the activating marker NKp46, as well as a negative correlation between IP-10 and TNF-α and NKp46. CD158b expression in CD56dimCD16+ was positively correlated with EGF and negatively correlated with MIP-1β.

CONCLUSIONS

Taken together, these results suggest that cancer patients present a shift towards a poorly cytotoxic and less activated NK profile which may contribute to tumor development and progression. The understanding of NK cell biology and soluble factors during tumor development could aid in the design of possible targeting therapeutic approaches.

Phenotype screens of murine pancreatic cancer identify a Tgf-α-Ccl2-paxillin axis driving human-like neural invasion

Solid cancers like pancreatic ductal adenocarcinoma (PDAC), a type of pancreatic cancer, frequently exploit nerves for rapid dissemination. This neural invasion (NI) is an independent prognostic factor in PDAC, but insufficiently modeled in genetically engineered mouse models (GEMM) of PDAC. Here, we systematically screened for human-like NI in Europe's largest repository of GEMM of PDAC, comprising 295 different genotypes. This phenotype screen uncovered 2 GEMMs of PDAC with human-like NI, which are both characterized by pancreas-specific overexpression of transforming growth factor α (TGF-α) and conditional depletion of p53. Mechanistically, cancer-cell-derived TGF-α upregulated CCL2 secretion from sensory neurons, which induced hyperphosphorylation of the cytoskeletal protein paxillin via CCR4 on cancer cells. This activated the cancer migration machinery and filopodia formation toward neurons. Disrupting CCR4 or paxillin activity limited NI and dampened tumor size and tumor innervation. In human PDAC, phospho-paxillin and TGF-α-expression constituted strong prognostic factors. Therefore, we believe that the TGF-α-CCL2-CCR4-p-paxillin axis is a clinically actionable target for constraining NI and tumor progression in PDAC.

Development of an in vivo murine model of perineural invasion and spread of cutaneous squamous cell carcinoma of the head and neck

Introduction

Cutaneous squamous cell carcinoma of the head and neck (cSCCHN) can metastasize by invading nerves and spread toward the central nervous system. This metastatic process is called perineural invasion (PNI) and spread (PNS). An in vivo sciatic nerve mouse model is used for cSCCHN PNI/PNS. Here we describe a complementary whisker pad model which allows for molecular studies investigating drivers of PNI/PNS in the head and neck environment.

Methods

A431 cells were injected into the whisker pads of BALB/c Foxn1nu and NSG-A2 mice. Tumor progression was monitored by bioluminescence imaging and primary tumor resection was performed. PNI was detected by H&E and IHC. Tumor growth and PNI were assessed with inducible ablation of LOXL2.

Results

The rate of PNI development in mice was 10%-28.6%. Tumors exhibited PNI/PNS reminiscent of the morphology seen in the human disease. Our model's utility was demonstrated with inducible ablation of LOXL2 reducing primary tumor growth and PNI.

Discussion

This model consists in a feasible way to test molecular characteristics and potential therapies, offers to close a gap in the described in vivo methods for PNI/PNS of cSCCHN and has uses in concert with the established sciatic nerve model.

Calcium signalling pathways in prostate cancer initiation and progression

Cancer cells proliferate, differentiate and migrate by repurposing physiological signalling mechanisms. In particular, altered calcium signalling is emerging as one of the most widespread adaptations in cancer cells. Remodelling of calcium signalling promotes the development of several malignancies, including prostate cancer. Gene expression data from in vitro, in vivo and bioinformatics studies using patient samples and xenografts have shown considerable changes in the expression of various components of the calcium signalling toolkit during the development of prostate cancer. Moreover, preclinical and clinical evidence suggests that altered calcium signalling is a crucial component of the molecular re-programming that drives prostate cancer progression. Evidence points to calcium signalling re-modelling, commonly involving crosstalk between calcium and other cellular signalling pathways, underpinning the onset and temporal progression of this disease. Discrete alterations in calcium signalling have been implicated in hormone-sensitive, castration-resistant and aggressive variant forms of prostate cancer. Hence, modulation of calcium signals and downstream effector molecules is a plausible therapeutic strategy for both early and late stages of prostate cancer. Based on this premise, clinical trials have been undertaken to establish the feasibility of targeting calcium signalling specifically for prostate cancer.

Bioinformatic-based genetic characterizations of neural regulation in skin cutaneous melanoma

Background

Recent discoveries uncovered the complex cancer-nerve interactions in several cancer types including skin cutaneous melanoma (SKCM). However, the genetic characterization of neural regulation in SKCM is unclear.

Methods

Transcriptomic expression data were collected from the TCGA and GTEx portal, and the differences in cancer-nerve crosstalk-associated gene expressions between normal skin and SKCM tissues were analyzed. The cBioPortal dataset was utilized to implement the gene mutation analysis. PPI analysis was performed using the STRING database. Functional enrichment analysis was analyzed by the R package clusterProfiler. K-M plotter, univariate, multivariate, and LASSO regression were used for prognostic analysis and verification. The GEPIA dataset was performed to analyze the association of gene expression with SKCM clinical stage. ssGSEA and GSCA datasets were used for immune cell infiltration analysis. GSEA was used to elucidate the significant function and pathway differences.

Results

A total of 66 cancer-nerve crosstalk-associated genes were identified, 60 of which were up- or downregulated in SKCM and KEGG analysis suggested that they are mainly enriched in the calcium signaling pathway, Ras signaling pathway, PI3K-Akt signaling pathway, and so on. A gene prognostic model including eight genes (GRIN3A, CCR2, CHRNA4, CSF1, NTN1, ADRB1, CHRNB4, and CHRNG) was built and verified by independent cohorts GSE59455 and GSE19234. A nomogram was constructed containing clinical characteristics and the above eight genes, and the AUCs of the 1-, 3-, and 5-year ROC were 0.850, 0.811, and 0.792, respectively. Expression of CCR2, GRIN3A, and CSF1 was associated with SKCM clinical stages. There existed broad and strong correlations of the prognostic gene set with immune infiltration and immune checkpoint genes. CHRNA4 and CHRNG were independent poor prognostic genes, and multiple metabolic pathways were enriched in high CHRNA4 expression cells.

Conclusion

Comprehensive bioinformatics analysis of cancer-nerve crosstalk-associated genes in SKCM was performed, and an effective prognostic model was constructed based on clinical characteristics and eight genes (GRIN3A, CCR2, CHRNA4, CSF1, NTN1, ADRB1, CHRNB4, and CHRNG), which were widely related to clinical stages and immunological features. Our work may be helpful for further investigation in the molecular mechanisms correlated with neural regulation in SKCM, and in searching new therapeutic targets.

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.

Single-cell RNA sequencing reveals intratumoral heterogeneity and potential mechanisms of malignant progression in prostate cancer with perineural invasion

Background: Prostate cancer (PCa) is the second most common cancer among men worldwide. Perineural invasion (PNI) was a prominent characteristic of PCa, which was recognized as a key factor in promoting PCa progression. As a complex and heterogeneous disease, its true condition is difficult to explain thoroughly with conventional bulk RNA sequencing. Thus, an improved understanding of PNI-PCa progression at the single-cell level is needed. Methods: In this study, we performed scRNAseq on tumor tissues of three PNI-PCa patients. Principal component analysis (PCA) and Uniform manifold approximation and projection (UMAP) were used to reduce dimensionality and visualize the cellular composition of tumor tissues. The differently expressed genes among each cluster were identified by EdgeR. GO enrichment analysis was used to understand the roles of genes within the clusters. Pseudotime cell trajectory was used to reveal the molecular pathways underlying cell fate decisions and identify genes whose expression changed as the cells underwent transition. We applied CellPhoneDB to identify cell-cell interactions among the epithelial and neural cells in PNI-PCa. Results: Analysis of the ∼17,000 single-cell transcriptomes in three PNI prostate cancer tissues, we identified 12 major cell clusters, including neural cells and two epithelial subtypes with different expression profiles. We found that basal/intermediate epithelial cell subtypes highly expressed PCa progression-related genes, including PIGR, MMP7, and AGR2. Pseudotime trajectory analysis showed that luminal epithelial cells could be the initiating cells and transition to based/intermediate cells. Gene ontology (GO) enrichment analysis showed that pathways related to cancer progressions, such as lipid catabolic and fatty acid metabolic processes, were significantly enriched in basal/intermediate cells. Our analysis also suggested that basal/intermediate cells communicate closely with neural cells played a potential role in PNI-PCa progression. Conclusion: These results provide our understanding of PNI-PCa cellular heterogeneity and characterize the potential role of basal/intermediate cells in the PNI-PCa progression.

Predicting Tumor Perineural Invasion Status in High-Grade Prostate Cancer Based on a Clinical-Radiomics Model Incorporating T2-Weighted and Diffusion-Weighted Magnetic Resonance Images

PURPOSE

To explore the role of bi-parametric MRI radiomics features in identifying PNI in high-grade PCa and to further develop a combined nomogram with clinical information.

METHODS

183 high-grade PCa patients were included in this retrospective study. Tumor regions of interest (ROIs) were manually delineated on T2WI and DWI images. Radiomics features were extracted from lesion area segmented images obtained. Univariate logistic regression analysis and the least absolute shrinkage and selection operator (LASSO) method were used for feature selection. A clinical model, a radiomics model, and a combined model were developed to predict PNI positive. Predictive performance was estimated using receiver operating characteristic (ROC) curves, calibration curves, and decision curves.

RESULTS

The differential diagnostic efficiency of the clinical model had no statistical difference compared with the radiomics model (area under the curve (AUC) values were 0.766 and 0.823 in the train and test group, respectively). The radiomics model showed better discrimination in both the train cohort and test cohort (train AUC: 0.879 and test AUC: 0.908) than each subcategory image (T2WI train AUC: 0.813 and test AUC: 0.827; DWI train AUC: 0.749 and test AUC: 0.734). The discrimination efficiency improved when combining the radiomics and clinical models (train AUC: 0.906 and test AUC: 0.947).

CONCLUSION

The model including radiomics signatures and clinical factors can accurately predict PNI positive in high-grade PCa patients.

Cell Dissemination in Pancreatic Cancer

Pancreatic cancer is a disease notorious for its high frequency of recurrence and low survival rate. Surgery is the most effective treatment for localized pancreatic cancer, but most cancer recurs after surgery, and patients die within ten years of diagnosis. The question persists: what makes pancreatic cancer recur and metastasize with such a high frequency? Herein, we review evidence that subclinical dormant pancreatic cancer cells disseminate before developing metastatic or recurring cancer. We then discuss several routes by which pancreatic cancer migrates and the mechanisms by which pancreatic cancer cells adapt. Lastly, we discuss unanswered questions in pancreatic cancer cell migration and our perspectives.

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.

The Role of Neural Signaling in the Pancreatic Cancer Microenvironment

Simple Summary

Pancreatic cancer is a highly lethal malignant disease with a dense stroma, called the tumor microenvironment. Accumulating evidence indicates the important role of sympathetic, parasympathetic, and sensory nerves in the tumor microenvironment of various cancers, including pancreatic cancer. Cancer cells and neural cells interact with each other to form a complex network and cooperatively promote cancer growth and invasion. In this review article, we describe the current understanding of the role of nerves in the tumor microenvironment.

Abstract

Pancreatic cancer is one of the most lethal malignant diseases. Various cells in the tumor microenvironment interact with tumor cells and orchestrate to support tumor progression. Several kinds of nerves are found in the tumor microenvironment, and each plays an essential role in tumor biology. Recent studies have shown that sympathetic, parasympathetic, and sensory neurons are found in the pancreatic cancer microenvironment. Neural signaling not only targets neural cells, but tumor cells and immune cells via neural receptors expressed on these cells, through which tumor growth, inflammation, and anti-tumor immunity are affected. Thus, these broad-range effects of neural signaling in the pancreatic cancer microenvironment may represent novel therapeutic targets. The modulation of neural signaling may be a therapeutic strategy targeting the whole tumor microenvironment. In this review, we describe the current understanding of the role of nerves in the tumor microenvironment of various cancers, with an emphasis on pancreatic cancer. We also discuss the underlying mechanisms and the possibility of therapeutic applications.

The Role of Perineural Invasion in Prostate Cancer and Its Prognostic Significance

Simple Summary

Prostate cancer is one of the most frequently diagnosed cancers in men worldwide. Perineural invasion (PNI), the movement of cancer cells along nerves, is a commonly observed approach to tumor spread and is important in both research and clinical practice of prostate cancer. However, despite many studies reporting on molecules and pathways involved in PNI, understanding its clinical relevance remains insufficient. In this review, we aim to summarize the current knowledge of mechanisms and prognostic significance of PNI in prostate cancer, which may provide new perspectives for future studies and improved treatment.

Abstract

Perineural invasion (PNI) is a common indication of tumor metastasis that can be detected in multiple malignancies, including prostate cancer. In the development of PNI, tumor cells closely interact with the nerve components in the tumor microenvironment and create the perineural niche, which provides a supportive surrounding for their survival and invasion and benefits the nerve cells. Various transcription factors, cytokines, chemokines, and their related signaling pathways have been reported to be important in the progress of PNI. Nevertheless, the current understanding of the molecular mechanism of PNI is still very limited. Clinically, PNI is commonly associated with adverse clinicopathological parameters and poor outcomes for prostate cancer patients. However, whether PNI could act as an independent prognostic predictor remains controversial among studies due to inconsistent research aim and endpoint, sample type, statistical methods, and, most importantly, the definition and inclusion criteria. In this review, we provide a summary and comparison of the prognostic significance of PNI in prostate cancer based on existing literature and propose that a more standardized description of PNI would be helpful for a better understanding of its clinical relevance.

Perineural Invasion is a Powerful Prognostic Factor for Upper Tract Urothelial Carcinoma Following Radical Nephroureterectomy

BACKGROUND

Taiwan has the highest incidence of upper tract urothelial carcinoma (UTUC) worldwide. Although many pathological factors can predict the prognosis of UTUC, previous studies have rarely discussed perineural invasion (PNI). Therefore, we aimed to investigate the effect of PNI on a well-established cohort of patients with UTUC.

METHODS

This retrospective study included 803 patients with non-metastatic UTUC who underwent radical nephroureterectomy between June 2000 and August 2019. Demographic and clinicopathological parameters, including PNI, were collected for analysis. Using the Kaplan-Meier method and Cox proportional hazards model, we evaluated the significance of PNI with respect to progression-free survival (PFS), cancer-specific survival (CSS), and overall survival (OS).

RESULTS

The median follow-up was 30.9 months, and there were 83 cases of PNI (10.3%). PNI-positive patients had unfavorable pathological features, including high pT stage, positive lymph node involvement, high tumor grade, and more lymphovascular invasion (all p < 0.001). Kaplan-Meier analysis showed that PNI was significantly associated with PFS, CSS, and OS (all p < 0.00001), and when combined with lymphovascular invasion, patients could be divided into groups with distinct survival rates (all p < 0.00001). In multivariate analysis, PNI was an independent factor leading to worse PFS (hazard ratio [HR] 1.72, 95% confidence interval [CI] 1.19-2.50; p = 0.004), CSS (HR 2.54, 95% CI 1.58-4.10; p = 0.0001), and OS (HR 1.78, 95% CI 1.19-2.65; p = 0.005).

CONCLUSIONS

We demonstrated an association between PNI and the prognosis of UTUC. Routine assessment of PNI in UTUC with standardized protocols may help achieve better risk stratification and subject selection for perioperative treatment.

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.

The Role of Extracellular Vesicles in Cancer-Nerve Crosstalk of the Peripheral Nervous System

Although the pathogenic operations of cancer–nerve crosstalk (e.g., neuritogenesis, neoneurogensis, and perineural invasion—PNI) in the peripheral nervous system (PNS) during tumorigenesis, as well as the progression of all cancer types is continuing to emerge as an area of unique scientific interest and study, extensive, wide-ranging, and multidisciplinary investigations still remain fragmented and unsystematic. This is especially so in regard to the roles played by extracellular vesicles (EVs), which are lipid bilayer-enclosed nano- to microsized particles that carry multiple-function molecular cargos, facilitate intercellular communication in diverse processes. Accordingly, the biological significance of EVs has been greatly elevated in recent years, as there is strong evidence that they could contribute to important and possibly groundbreaking diagnostic and therapeutic innovations. This can be achieved and the pace of discoveries accelerated through cross-pollination from existing knowledge and studies regarding nervous system physiology and pathology, as well as thoroughgoing collaborations between oncologists, neurobiologists, pathologists, clinicians, and researchers. This article offers an overview of current and recent past investigations on the roles of EVs in cancer–nerve crosstalk, as well as in neural development, physiology, inflammation, injury, and regeneration in the PNS. By highlighting the mechanisms involved in physiological and noncancerous pathological cellular crosstalk, we provide hints that may inspire additional translational studies on cancer–nerve interplay.

Emerging experimental models for assessing perineural invasion in human cancers

Cancer neuroscience has emerged as a burgeoning field for the investigation of cancer-nervous system interactions. Perineural invasion (PNI) is defined as the presence of cancer cells that surround and/or invade the nerves infiltrating the tumor microenvironment. PNI is closely associated with increased tumor recurrence and diminished survival in many cancer types. Based on diverse in vitro, ex vivo, and in vivo models, mounting evidence suggests that the reciprocal crosstalk between nerves and cancer cells drives PNI, which is mediated by several factors including secreted neurotrophins, chemokines, exosomes, and inflammatory cells. Typical in vitro models using dorsal root ganglia (DRG) cells cocultured with cancer cells or other cell types allow the study of isolated factors. Ex vivo PNI models created by cocultivating cancer cells with explanted vagus and sciatic nerves enable the study of neuroaffinity in a time-saving and cost-efficient manner. In vivo models such as genetically engineered mouse models (GEMMs) and the chicken embryo chorioallantoic membrane (CAM)-DRG model, provide the nerve microenvironment needed to recapitulate the complex pathophysiological processes of PNI. Here, we summarize the current methods commonly used for modeling PNI and discuss the inherent pros and cons of these approaches for understanding PNI biology.

Roles of the nervous system in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC), with its extremely poor prognosis, presents a substantial health problem worldwide. Outcomes have improved thanks to progress in surgical technique, chemotherapy, pre-/postoperative management, and centralization of patient care to high-volume centers. However, our goals are yet to be met. Recently, exome sequencing using PDAC surgical specimens has demonstrated that the most frequently altered genes were the axon guidance genes, indicating involvement of the nervous system in PDAC carcinogenesis. Moreover, perineural invasion has been widely identified as one poor prognostic factor. The combination of innovative technologies and extensive clinician experience with the nervous system come together here to create a new treatment option. However, evidence has emerged that suggests that the relationship between cancer and nerves in PDAC, the underlying mechanism, is not fully understood. In an attempt to tackle this lethal cancer, this review summarizes the anatomy and physiology of the pancreas and discusses the role of the nervous system in the pathophysiology of PDAC.

CXCR5 induces perineural invasion of salivary adenoid cystic carcinoma by inhibiting microRNA-187

CXCR5 played critical roles in tumorigenesis and metastasis. Nevertheless, little was known about the involvement of CXCR5 in perineural invasion (PNI) of salivary adenoid cystic carcinoma (SACC). Here, we confirmed upregulation of CXCR5 in SACC specimens and cells and identified that CXCR5 exhibited a significant positive correlation with PNI. Functionally, knockdown of CXCR5 suppressed SACC cells migration, invasion and PNI ability, whereas CXCR5 overexpression displayed the opposite effects. Moreover, CXCR5 downregulated microRNA (miR)-187, which could competitively sponge S100A4. The PNI-inhibitory effect of CXCR5 knockdown or miR-187 overexpression could be reversed by elevated expression of S100A4. Conjointly, our data revealed that CXCR5 facilitated PNI through downregulating miR-187 to disinhibit S100A4 expression in SACC.

Unveiling the pathogenesis of perineural invasion from the perspective of neuroactive molecules

Perineural invasion (PNI) is characterized by an encounter between the cancer cells and neuronal fibers and holds an extremely poor prognosis for malignant tumors. The exact molecular mechanism behind PNI yet remains to be explored. However, it is worth-noting that an involvement of the neuroactive molecules plays a major part in this process. A complex signaling network comprising the interplay between immunological cascades and neurogenic molecules such as tumor-derived neurotrophins, neuromodulators, and growth factors constitutes an active microenvironment for PNI associated with malignancy. The present review aims at discussing the following points in relation to PNI: a) Communication between PNI and neuroplasticity mechanisms can explain the pathophysiology of poor, short and long-term outcomes in cancer patients; b) Neuroactive molecules can significantly alter the neurons and cancer cells so as to sustain PNI progression; c) Finally, careful manipulation of neurogenic pathways and/or their crosstalk with the immunological molecules implicated in PNI could provide a potential breakthrough in cancer therapeutics.

C-C motif chemokine ligand 2/C-C receptor 2 is associated with glioma recurrence and poor survival

Several studies have explored the mechanisms of C-C motif chemokine ligand (CCL)2/CC receptor (R)2 function in tumorigenesis and inflammation. However, little is known about the role of CCL2/CCR2 in tumor recurrence, especially after radiotherapy. The present study aimed to determine the association between CCL2/CCR2 and glioma relapse. Moreover, the difference in the expression of CCL2/CCR2 between post-radiation and non-radiation recurrent glioma tissues was compared. A retrospective analysis of 80 patients with glioma who underwent tumor resection twice was performed. Primary group refers to glioma patients who received glioma resection surgery for the first time. Recurrent group refers to glioma patients who received glioma resection surgery after first relapse. In total, 10 patients with brain trauma who underwent partial resection of the normal brain as decompression treatment were used as controls. Protein expression levels of CCL2 and CCR2 were evaluated using immunohistochemistry. Prognostic analyses of patient survival using Kaplan-Meier curves and Cox regression models were performed. The expression levels of CCL2 and CCR2 were higher in recurrent glioma compared with the primary group. There was a positive correlation between tumor grade and protein expression of CCL2/CCR2. Furthermore, irradiation had a significant effect on CCR2 protein expression (P=0.014), but not on CCL2 protein expression (P=0.626). However, the expression of CCL2 and CCR2 showed no significant difference between primary and secondary glioblastoma. After adjusting for sex, radiotherapy and location of tumors in these gliomas, CCL2 was a prognostic factor for disease-free and overall survival (OS) times, as well as age and tumor grade. In the multivariate Cox modeling for glioma, CCR2 was significantly associated with OS rather than DFI. The significant correlations between CCL2/CCR2 expression and glioma tumor grade suggested that CCL2/CCR2 has a role in glioma progression. Combined with previous in vitro experiments, it was proposed that irradiation (radiotherapy)-induced expression of CCL2 is transient, while irradiation-induced expression of CCR2 is lasting. Therefore, CCL2/CCR2 is a potential therapeutic target for patients with glioma.

Mini-review: Trophic interactions between cancer cells and primary afferent neurons

Cancer neurobiology is an emerging discipline that inevitably unfurls new perspectives in oncology. The role that nerves play in cancer progression resonates with the long-reported dependency of tumors on neuro-molecular mechanisms that remain insufficiently elucidated. Whereas interactions between neurotrophic growth factors and receptors have been heavily studied in the nervous system, their expression in cancers and their impact on tumor cell growth and metastasis through their corresponding signaling pathways has been undervalued. Accumulating evidence suggests that trophic factors released by nerves strongly influence tumor development and that this neural contribution appears to not only play a stimulatory role but also function as an essential part of the tumor's microenvironment. This bidirectional communication between proliferating cells and tumor-infiltrating nerves drives axonogenesis and tumor growth and migration. Acquiring a better understanding of the trophic interactions between primary afferent neurons and invading tumors will guide clinically actionable strategies to prevent tumor-associated axonogenesis, disrupting the chemical crosstalk between neurons and tumors and ultimately decreasing tumor growth and spread.

Nerves in the Tumor Microenvironment: Origin and Effects

Studies have reported the vital role of nerves in tumorigenesis and cancer progression. Nerves infiltrate the tumor microenvironment thereby enhancing cancer growth and metastasis. Perineural invasion, a process by which cancer cells invade the surrounding nerves, provides an alternative route for metastasis and generation of tumor-related pain. Moreover, central and sympathetic nervous system dysfunctions and psychological stress-induced hormone network disorders may influence the malignant progression of cancer through multiple mechanisms. This reciprocal interaction between nerves and cancer cells provides novel insights into the cellular and molecular bases of tumorigenesis. In addition, they point to the potential utility of anti-neurogenic therapies. This review describes the evolving cross-talk between nerves and cancer cells, thus uncovers potential therapeutic targets for cancer.

Interrupting Neuron-Tumor Interactions to Overcome Treatment Resistance

Neurons in the tumor microenvironment release neurotransmitters, neuroligins, chemokines, soluble growth factors, and membrane-bound growth factors that solid tumors leverage to drive their own survival and spread. Tumors express nerve-specific growth factors and microRNAs that support local neurons and guide neuronal growth into tumors. The development of feed-forward relationships between tumors and neurons allows tumors to use the perineural space as a sanctuary from therapy. Tumor denervation slows tumor growth in animal models, demonstrating the innervation dependence of growing tumors. Further in vitro and in vivo experiments have identified many of the secreted signaling molecules (e.g., acetylcholine, nerve growth factor) that are passed between neurons and cancer cells, as well as the major signaling pathways (e.g., MAPK/EGFR) involved in these trophic interactions. The molecules involved in these signaling pathways serve as potential biomarkers of disease. Additionally, new treatment strategies focus on using small molecules, receptor agonists, nerve-specific toxins, and surgical interventions to target tumors, neurons, and immune cells of the tumor microenvironment, thereby severing the interactions between tumors and surrounding neurons. This article discusses the mechanisms underlying the trophic relationships formed between neurons and tumors and explores the emerging therapies stemming from this work.

CC Chemokines in a Tumor: A Review of Pro-Cancer and Anti-Cancer Properties of the Ligands of Receptors CCR1, CCR2, CCR3, and CCR4

CC chemokines, a subfamily of 27 chemotactic cytokines, are a component of intercellular communication, which is crucial for the functioning of the tumor microenvironment. Although many individual chemokines have been well researched, there has been no comprehensive review presenting the role of all known human CC chemokines in the hallmarks of cancer, and this paper aims at filling this gap. The first part of this review discusses the importance of CCL1, CCL3, CCL4, CCL5, CCL18, CCL19, CCL20, CCL21, CCL25, CCL27, and CCL28 in cancer. Here, we discuss the significance of CCL2 (MCP-1), CCL7, CCL8, CCL11, CCL13, CCL14, CCL15, CCL16, CCL17, CCL22, CCL23, CCL24, and CCL26. The presentation of each chemokine includes its physiological function and then the role in tumor, including proliferation, drug resistance, migration, invasion, and organ-specific metastasis of tumor cells, as well as the effects on angiogenesis and lymphangiogenesis. We also discuss the effects of each CC chemokine on the recruitment of cancer-associated cells to the tumor niche (eosinophils, myeloid-derived suppressor cells (MDSC), tumor-associated macrophages (TAM), tumor-associated neutrophils (TAN), regulatory T cells (T_reg)). On the other hand, we also present the anti-cancer properties of CC chemokines, consisting in the recruitment of tumor-infiltrating lymphocytes (TIL).

Perineural Invasion in Adenoid Cystic Carcinoma of the Salivary Glands: Where We Are and Where We Need to Go

Adenoid cystic carcinoma of the salivary gland (SACC) is a rare malignant tumors of the head and neck region, but it is one of the most common malignant tumors that are prone to perineural invasion (PNI) of the head and neck. The prognosis of patients with SACC is strongly associated with the presence of perineural spread (PNS). Although many contributing factors have been reported, the mechanisms underlying the preferential destruction of the blood-nerve barrier (BNB) by tumors and the infiltration of the tumor microenvironment by nerve fibers in SACC, have received little research attention. This review summarizes the current knowledge concerning the characteristics of SACC in relation to the PNI, and then highlights the interplay between components of the tumor microenvironment and perineural niche, as well as their contributions to the PNI. Finally, we provide new insights into the possible mechanisms underlying the pathogenesis of PNI, with particular emphasis on the role of extracellular vesicles that may serve as an attractive entry point in future studies.

The biology and engineered modeling strategies of cancer-nerve crosstalk

A recent finding critical to cancer aggravation is the interaction between cancer cells and nerves. There exist two main modes of cancer-nerve interaction: perineural invasion (PNI) and tumor innervation. PNI occurs when cancer cells infiltrate the adjacent nerves, and its relative opposite, tumor innervation, occurs when axons extend into tumor bodies. Like most cancer studies, these crosstalk interactions have mostly been observed in patient samples and animal models at this point, making it difficult to understand the mechanisms in a controlled manner. As such, in recent years in vitro studies have emerged that have helped identify various microenvironmental factors responsible for cancer-nerve crosstalk, including but not limited to neurotrophic factors, neurotransmitters, chemokines, cancer-derived exosomes, and Schwann cells. The versatility of in vitro systems warrants continuous development to increase physiological relevance to study PNI and tumor innervation, for example by utilizing biomimetic three-dimensional (3D) culture systems. Despite the wealth of 3D in vitro cancer models, comparatively there exists a lack of 3D in vitro models of nerve, PNI, and tumor innervation. Native-like 3D in vitro models of cancer-nerve interactions may further help develop therapeutic strategies to curb nerve-mediated cancer aggravation. As such, we provide an overview of the key players of cancer-nerve crosstalk and current in vitro models of the crosstalk, as well as cancer and nerve models. We also discuss a few future directions in cancer-nerve crosstalk research.

CXCL10 and CCL21 Promote Migration of Pancreatic Cancer Cells Toward Sensory Neurons and Neural Remodeling in Tumors in Mice, Associated With Pain in Patients

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma (PDAC) is frequently accompanied by excruciating pain, which has been associated with attraction of cancer cells and their invasion of intrapancreatic sensory nerves. Neutralization of the chemokine CCL2 reduced cancer-associated pain in a clinical trial, but there have been no systematic analyses of the highly diverse chemokine families and their receptors in PDAC.

METHODS

We performed an open, unbiased RNA-interference screen of mammalian chemokines in co-cultures of mouse PDAC cells (K8484) and mouse peripheral sensory neurons, and confirmed findings in studies of DT8082 PDAC cells. We studied the effects of chemokines on migration of PDAC cell lines. Orthotopic tumors were grown from K8484 cells in mice, and mice were given injections of neutralizing antibodies against chemokines, antagonists, or control antibodies. We analyzed abdominal mechanical hypersensitivity and collected tumors and analyzed them by histology and immunohistochemistry to assess neural remodeling. We collected PDAC samples and information on pain levels from 74 patients undergoing resection and measured levels of CXCR3 and CCR7 by immunohistochemistry and immunoblotting.

RESULTS

Knockdown of 9 chemokines in DRG neurons significantly reduced migration of PDAC cells towards sensory neurons. Sensory neuron-derived CCL21 and CXCL10 promoted migration of PDAC cells via their receptors CCR7 and CXCR3, respectively, which were expressed by cells in orthotopic tumors and PDAC specimens from patients. Neutralization of CCL21 or CXCL10, or their receptors, in mice with orthotopic tumors significantly reduced nociceptive hypersensitivity and nerve fiber hypertrophy and improved behavioral parameters without affecting tumor infiltration by T cells or neutrophils. Increased levels of CXCR3 and CCR7 in human PDAC specimens were associated with increased frequency of cancer-associated pain, determined from patient questionnaires.

CONCLUSIONS

In an unbiased screen of chemokines, we identified CCL21 and CXCL10 as proteins that promote migration of pancreatic cancer cells toward sensory neurons. Inhibition of these chemokines or their receptors reduce hypersensitivity in mice with orthotopic tumors, and patients with PDACs with high levels of the chemokine receptors of CXCR3 and CCR7 had increased frequency of cancer-associated pain.

Tumor-induced neurogenesis and immune evasion as targets of innovative anti-cancer therapies

Normal cells are hijacked by cancer cells forming together heterogeneous tumor masses immersed in aberrant communication circuits that facilitate tumor growth and dissemination. Besides the well characterized angiogenic effect of some tumor-derived factors; others, such as BDNF, recruit peripheral nerves and leukocytes. The neurogenic switch, activated by tumor-derived neurotrophins and extracellular vesicles, attracts adjacent peripheral fibers (autonomic/sensorial) and neural progenitor cells. Strikingly, tumor-associated nerve fibers can guide cancer cell dissemination. Moreover, IL-1β, CCL2, PGE₂, among other chemotactic factors, attract natural immunosuppressive cells, including T regulatory (Tregs), myeloid-derived suppressor cells (MDSCs), and M2 macrophages, to the tumor microenvironment. These leukocytes further exacerbate the aberrant communication circuit releasing factors with neurogenic effect. Furthermore, cancer cells directly evade immune surveillance and the antitumoral actions of natural killer cells by activating immunosuppressive mechanisms elicited by heterophilic complexes, joining cancer and immune cells, formed by PD-L1/PD1 and CD80/CTLA-4 plasma membrane proteins. Altogether, nervous and immune cells, together with fibroblasts, endothelial, and bone-marrow-derived cells, promote tumor growth and enhance the metastatic properties of cancer cells. Inspired by the demonstrated, but restricted, power of anti-angiogenic and immune cell-based therapies, preclinical studies are focusing on strategies aimed to inhibit tumor-induced neurogenesis. Here we discuss the potential of anti-neurogenesis and, considering the interplay between nervous and immune systems, we also focus on anti-immunosuppression-based therapies. Small molecules, antibodies and immune cells are being considered as therapeutic agents, aimed to prevent cancer cell communication with neurons and leukocytes, targeting chemotactic and neurotransmitter signaling pathways linked to perineural invasion and metastasis.

Cdc42 Mediates Cancer Cell Chemotaxis in Perineural Invasion

Perineural invasion (PNI) is an ominous form of cancer progression along nerves associated with poor clinical outcome. Glial derived neurotrophic factor (GDNF) interacts with cancer cell RET receptors to enable PNI, but downstream events remain undefined. We demonstrate that GDNF leads to early activation of the GTPase Cdc42 in pancreatic cancer cells, but only delayed activation of RhoA and does not affect Rac1. Depletion of Cdc42 impairs pancreatic cancer cell chemotaxis toward GDNF and nerves. An siRNA library of guanine nucleotide exchange factors was screened to identify activators of Cdc42. ARHGEF7 (β-Pix) was required for Cdc42 activation and chemotaxis toward nerves, and also colocalizes with RET under GDNF stimulation. Cdc42 enables PNI in an in vitro dorsal root ganglia coculture model, and controls the directionality of migration but does not affect cell speed or cell viability. In contrast, Rac1 was necessary for cell speed but not directionality, while the RhoA was not necessary for either cell speed or directionality. Cdc42 was required for PNI in an in vivo murine sciatic nerve model. Depletion of Cdc42 significantly diminished the length of PNI, volume of PNI, and motor nerve paralysis resulting from PNI. Activated Cdc42 is expressed in human salivary ductal cancer cells invading nerves. These findings establish the GDNF-RET-β-Pix-Cdc42 pathway as a directional regulator of pancreatic cancer cell migration toward nerves, highlight the importance of directional migration in PNI, and offer novel targets for therapy. IMPLICATIONS: Cdc42 regulates cancer cell directional migration toward and along nerves in PNI.

Schwann Cell-Derived CCL2 Promotes the Perineural Invasion of Cervical Cancer

Perineural invasion (PNI) has guiding significances for nerve preservation in cervical cancer, but there is no definite marker indicating PNI. Two cervical cancer cell lines (HeLa and ME-180) showed significant abilities to migrate along neurites in vitro and in vivo. Morphological observation revealed that Schwann cells (SC) arrived at the sites of cervical cancer cells before the onset of cancer metastasis. We used high-throughput antibody array to screen the signals mediating the interaction of nerve cells and cancer cells and found the high expression of CCL2 in dorsal root ganglion (DRG). Meanwhile, serum CCL2 showed a notable raise especially in cervical adenocarcinoma. SC-derived CCL2 bound to its receptor CCR2 and promoted the proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) of cervical cancer cells. In turn, cancer cell-derived signals triggered the expression of metalloproteinases (MMPs) including MMP2, MMP9, and MMP12 in SCs, promoting SCs to dissolve matrix. These data demonstrated that the cancer-nerve crosstalk formed a tumor microenvironment (TME) that facilitated to PNI. We identified the CCL2/CCR2 axis as a potential marker to predict the PNI and affect the nerve preservation for cervical cancer.

Tumour innervation and neurosignalling in prostate cancer

Prostate cancer progression has been shown to be dependent on the development of autonomic nerves into the tumour microenvironment. Sympathetic nerves activate adrenergic neurosignalling that is necessary in early stages of tumour progression and for initiating an angiogenic switch, whereas parasympathetic nerves activate cholinergic neurosignalling resulting in tumour dissemination and metastasis. The innervation of prostate cancer seems to be initiated by neurotrophic growth factors, such as the precursor to nerve growth factor secreted by tumour cells, and the contribution of brain-derived neural progenitor cells has also been reported. Current experimental, epidemiological and clinical evidence shows the stimulatory effect of tumour innervation and neurosignalling in prostate cancer. Using nerves and neurosignalling could have value in the management of prostate cancer by predicting aggressive disease, treating localized disease through denervation and relieving cancer-associated pain in bone metastases.

Nerve-tumour interaction enhances the aggressiveness of oral squamous cell carcinoma

OBJECTIVES

Perineural invasion (PNI) is a poor prognostic pathologic feature of oral squamous cell carcinoma (OSCC). The mechanisms of PNI remain poorly understood, and nerve-tumour interactions have been implicated for its pathogenesis.

DESIGN AND SETTING

Systematic investigation of nerve-tumour interactions was performed using fresh human peripheral nerve. In vitro and in vivo models were used to determine the ability of human peripheral nerves to enhance OSCC migration/invasion. Retrospective cohort study was also carried out in one medical centre from 2001 to 2009.

PARTICIPANTS

314 T1-2 OSCC patients.

MAIN OUTCOME MEASURES

In the transwell migration/invasion assay, the cells in five representative fields were counted. In the nerve implantation model, tumour size was estimated. PNI quantification by PNI focus number was carried out in the OSCC patients to correlate with cervical lymph node metastasis and oncologic outcomes.

RESULTS

The transwell migration/invasion assay demonstrated that human peripheral nerves, compared with subcutaneous soft tissue, significantly enhanced the migration/invasion abilities of OSCC. Moreover, the enhanced migration was dose-dependent with increased length or number of peripheral nerve segments. The nerve implantation model showed that human peripheral nerve also enhanced OSCC growth in vivo. Finally, increased PNI focus number was found dose-dependently associated with increased cervical lymph node metastasis and decreased 5-year disease-specific survival rates.

CONCLUSIONS

These results clearly indicated the presence of nerve-tumour interaction that involved paracrine influences leading to aggressiveness of OSCC. Further investigations are required to explore key cell types and molecules involved in nerve-tumour interactions for future therapeutic targeting of PNI in OSCC.

CCL2 secreted from cancer-associated mesothelial cells promotes peritoneal metastasis of ovarian cancer cells through the P38-MAPK pathway

Epithelial ovarian cancer (EOC) is considered to secrete various factors in order to promote peritoneal dissemination through cell-to-cell interaction between cancer and mesothelial cells. We previously revealed that TGF-β secreted from EOC induces normal human peritoneal mesothelial cells (HPMCs) to differentiate into cancer-associated mesothelial cells (CAMCs). However, the relationship between tumor cells and CAMCs in EOC is still unclear. We hypothesized that CAMCs also secrete chemokines that attract cancer cells and induce peritoneal dissemination of EOC. We examined chemokines secreted from HPMCs and CAMCs by human chemokine array, and revealed that conditioned medium of CAMCs (CAMCs-CM) included many types of chemokines. The signals of CCL2 were the highest compared with other chemokines. The secretion and relative expression of CCL2 were significantly higher in CAMCs. Recombinant CCL2 promoted trans-mesothelial migration of HPMCs and the migration and invasion by EOC cells. In addition, CCL2 secreted from CAMCs promoted invasion of EOC cells. Furthermore, the neutralizing antibody of CCL2 reduced invasion by EOC. Clinical outcomes of patients whose tissue expressed higher CCR2 were significantly poorer than in patients whose tissue expression was lower. CCL2 activated the phosphorylation of p38 mitogen-activated protein kinase (MAPK). In addition, CAMCs-CM activated the p38 MAPK pathway. Phosphorylation of p38 MAPK reduced with the presence of neutralizing antibody of CCL2. In conclusion, these data indicate CCL2 in CAMCs-CM promoted the malignant potential of EOC. CCL2 plays a crucial role in the tumor microenvironment of EOC.

Tumor-derived exosomes educate fibroblasts to promote salivary adenoid cystic carcinoma metastasis via NGF-NTRK1 pathway

Salivary adenoid cystic carcinoma (SACC) is a rare head and neck malignancy characterized by unpredictable expansion, considerable perineural invasion and high risk of metastasis; however, the underlying mechanism of SACC progression remains unclear. Cancer-associated fibroblasts localized within the tumor microenvironment may promote cancer malignant transformation by enhancing tumor growth, blood vessel formation, inflammation development and metastasis occurrence. Small extracellular vesicles, including exosomes, are mediators of intercellular communication and can influence major tumor-associated pathways. The present study aimed to explore the exosome-mediated communication between SACC cells and fibroblasts. The results from confocal microscopy demonstrated that exosomes derived from the human cell line SACC-83 were internalized by the human periodontal ligament fibroblast (HPLF) cells. Following exosome internalization, HPLF cells appeared to enhance SACC-83 cell metastasis and were educated toward a protumorigenesis phenotype according to transcriptome RNA sequencing and reverse transcription-quantitative polymerase chain reaction analysis. This phenomenon included exosome-mediated stimulation of proinflammatory cytokines and nerve growth factor (NGF) secretion. Furthermore, NGF blockage reduced the enhanced SACC-83 cell invasion stimulated by the supernatant isolated from exosome-educated HPLF cells. In addition, the results reported that neurotrophic receptor tyrosine kinase 1 (NTRK1), which is the high-affinity NGF receptor, was significantly upregulated in human SACC-83 cells. These results demonstrated that SACC-83 cell-derived exosomes educated HPLF cells toward the protumorigenic phenotype via the NGF-NTRK1 pathway, which suggested that this type of exosomes may be used as a potential therapeutic target for SACC.

Functional and mechanistic studies reveal MAGEA3 as a pro-survival factor in pancreatic cancer cells

Background

In the era of personalized therapy, functional annotation of less frequent genetic aberrations will be instrumental in adapting effective therapeutic in clinic. Overexpression of Melanoma associated antigen A3 (MAGEA3) is reported in certain pancreatic cancer (PCA) patients. The major objective of the current study was to investigate the functional role of MAGEA3 in pancreatic cancer cells (PCCs) growth and survival.

Methods

Using overexpression (tet-on regulated system and constitutive expression system) and knockdown (by siRNA and shRNA) approach, we dissected the mechanistic role of MAGEA3 in pancreatic cancer pathogenesis. We generated MAGEA3 expressing stable PCA cell lines and mouse primary pancreatic epithelial cells. MAGEA3 was also depleted in certain MAGEA3 positive PCCs by siRNA or shRNA. The stable cells were subjected to in vitro assays like proliferation and survival assays under growth factor deprivation or in the presence of cytotoxic drugs. The MAGEA3 overexpressing or depleted stable PCCs were evaluated in vivo using xenograft model to check the role of MAGEA3 in tumor progression. We also dissected the mechanism behind the MAGEA3 role in tumor progression using western blot analysis and CCL2 neutralization.

Results

MAGEA3 overexpression in PCA cells did not alter the cell proliferation but protected the cells during growth factor deprivation and also in the presence of cytotoxic drugs. However, depletion of MAGEA3 in MAGEA3 positive cells resulted in reduced cell proliferation and increased apoptosis upon growth factor deprivation and also in response to cytotoxic drugs. The in vivo xenograft study revealed that overexpression of MAGEA3 promoted tumor growth however depleting the same hindered the tumor progression. Mechanistically, our in vitro and in vivo study revealed that MAGEA3 has tumor-promoting role by reducing macro-autophagy and overexpressing pro-survival molecules like CCL2 and survivin.

Conclusion

Our data proves tumor-promoting role of MAGEA3 and provides the rationale to target MAGEA3 and/or its functional mediators like CCL2 for PCA, which may have a better impact in PCA therapy.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1272-2) contains supplementary material, which is available to authorized users.

Netrin-1 promotes cell neural invasion in gastric cancer via its receptor neogenin

Neural invasion (NI) is one of the important routes for local spread of gastric cancer (GC) correlated with poor prognosis. However, the exact cellular characteristics and molecular mechanisms of NI in GC are still unclear. Netrin-1(NTN1) as an axon guidance molecule was firstly found during neural system development. Importantly, NTN1 has an essential role in the progression of malignant tumor and specifically mediates the induction of invasion. In this study, we found NTN1 expression was significantly increased in 97 tumor tissues from GC patients and positively correlated with NI (p<0.05). In addition, we detected NTN1 knockdown significantly suppressed GC cells migration and invasion. Moreover, our results showed that reciprocity was observed between GC cells and neurites colonies in dorsal root ganglia (DRG)-GC cells co-culture vitro model. GC cells with NTN1 silencing could suppress their abilities to navigate along surrounding neuritis and this effect was depended on its receptor neogenin. In vivo, NTN1 inhibition also decreased GC cells sciatic nerve invasion. Taken together, our findings argue that NTN1 and its receptor neogenin might act synergistically in promoting GC cells neural invasion. Inhibiting the activity of NTN1 could be a potential strategy targeting NI in GC therapy.

Perineural invasion of cancer: a complex crosstalk between cells and molecules in the perineural niche

Perineural invasion (PNI) can be found in a variety of malignant tumors. It is a sign of tumor metastasis and invasion and portends the poor prognosis of patients. The pathological description and clinical significance of PNI are clearly understood, but exploration of the underlying molecular mechanism is ongoing. It was previously thought that the low-resistance channel in the anatomic region led to the occurrence of PNI. However, with rapid development of precision medicine and molecular biology, we have gradually realized that the occurrence of PNI is not the result of a single factor. The latest study suggests that PNI of cancer is a continuous and multistep process. A specific peripheral microenvironment, also called the perineural niche, is formed by neural cells, supporting cells, recruited inflammatory cells, altered extracellular matrix, blood vessels, and immune components in the background of carcinoma. Various soluble signaling molecules and their receptors comprise a complex signal network, which achieves the interaction between nerve and tumor. Nerve cells and tumor cells can interact directly or through the opening and closing of the signal transduction pathways and/or the recognition and response of the ligands and receptors. The information is transferred to the targets accurately and effectively, leading to the specific interactions between the nerve cells and the malignant tumor cells. PNI occurs through changes in nerve cells and supporting cells in the background of cancer; change and migration of the perineural matrix; enhancement of the viability, mobility, and invasiveness of the tumor cells; injury and regeneration of nerve cells; interaction, chemotactic movement, contact, and adherence of the nerve cells and the tumor cells; escape from autophagy, apoptosis, and immunological surveillance of tumor cells; and so on. Certainly, exploring the mechanism of PNI clearly has great significance for blocking tumor progression and improving patient survival. The current review aims to elucidate the cellular and molecular mechanisms of PNI, which may help us find a strategy for improving the prognosis of malignant tumors.

Eotaxin‑1 and MCP‑1 serve as circulating indicators in response to power frequency electromagnetic field exposure in mice

The increasing public concern regarding the potential health risks of exposure to electromagnetic fields (EMFs) has led to intensive research in this area. However, it remains unclear whether potential pro-oncogenic effects may be caused by power frequency EMF (PFEMF) exposure. To address the associated risk factors, the present study exposed 4-week old Balb/c mice to 0, 0.1, 0.5 and 2.5 mT of constant 50 Hz Helmholtz coil-type PFEMF for 90 days to explore the circulating chemokine indicators that may be associated with inflammation or cancer. No measurable weight difference existed between the control and PFEMF-exposure groups; however, the Luminex assay clearly demonstrated differentially responsive profiles of circulating chemokines upon PFEMF treatment. Monocyte chemoattractant protein (MCP)-3, macrophage inflammatory protein (MIP)-1α, MIP-1β and MIP-2 levels in serum were not significantly altered by PFEMF during the 3-month exposure period; however, the circulating levels of other chemokines including IP-10, GROα, RANTES, EOTAXIN-1 and MCP-1 exhibited significant changes upon treatment. Among the responsive chemokines, EOTAXIN-1 and MCP-1 were significantly increased by 0.5 mT of PFEMF treatment, which may support their use as indicators of PFEMF exposure. This novel finding highlights the potential pro-inflammatory nature of power frequency, which may shed light on the mechanisms underlying PFEMF-induced diseases, including cancer.

An In Vivo Murine Sciatic Nerve Model of Perineural Invasion

Cancer cells invade nerves through a process termed perineural invasion (PNI), in which cancer cells proliferate and migrate in the nerve microenvironment. This type of invasion is exhibited by a variety of cancer types, and very frequently is found in pancreatic cancer. The microscopic size of nerve fibers within mouse pancreas renders the study of PNI difficult in orthotopic murine models. Here, we describe a heterotopic in vivo model of PNI, where we inject syngeneic pancreatic cancer cell line Panc02-H7 into the murine sciatic nerve. In this model, sciatic nerves of anesthetized mice are exposed and injected with cancer cells. The cancer cells invade in the nerves proximally toward the spinal cord from the point of injection. The invaded sciatic nerves are then extracted and processed with OCT for frozen sectioning. H&E and immunofluorescence staining of these sections allow quantification of both the degree of invasion and changes in protein expression. This model can be applied to a variety of studies on PNI given its versatility. Using mice with different genetic modifications and/or different types of cancer cells allows for investigation of the cellular and molecular mechanisms of PNI and for different cancer types. Furthermore, the effects of therapeutic agents on nerve invasion can be studied by applying treatment to these mice.

Functions of chemokines in the perineural invasion of tumors (Review)

The perineural invasion (PNI) of malignant tumors is a form of tumor progression in which cancer cells encroach along nerves. PNI hinders curative resection. Residual tumor cells in or around nerves can bring about local recurrence, infiltration and metastasis. This behavior is usually associated with a poor clinical prognosis. Therefore, it is necessary to investigate novel ligand-receptor crosstalk between nerves and tumor cells that promote the process of PNI. Chemokines are regarded as one of pivotal factors involved in the process of PNI. The present review collates information provided by previous studies with regard to the role of chemokines in PNI. The study presents a definition of PNI in cancer, generalizes the biological characteristics and the expression of chemokines and their receptors in cancer types associated with PNI, and discusses the underlying molecular mechanisms of chemokines, the reciprocal interactions between chemokines and other factors in PNI, and the interconnectivity of the microenvironment and chemokines. The aim of the review is to thoroughly illustrate the molecular cues of chemokines in cancer with PNI and to identify novel antitumor targets.

The CCL5/CCR5 Chemotactic Pathway Promotes Perineural Invasion in Salivary Adenoid Cystic Carcinoma

PURPOSE

Perineural invasion (PNI) is a hallmark of salivary adenoid cystic carcinoma (SACC) and represents an important risk factor for local recurrence and poor survival. However, the mechanism of PNI has yet to be explored. We sought to examine the CCL5-CCR5 ligand-receptor interaction between nerves and SACC cells.

MATERIALS AND METHODS

CCL5/CCR5 expression was determined by immunohistochemistry in SACC tissue specimens. The correlations between CCL5/CCR5 expression and clinicopathologic features were investigated. Dorsal root ganglia (DRG) and SACC cells cocultured in vitro were used to evaluate the effects of CCL5/CCR5 on PNI progression and pathogenesis.

RESULTS

CCR5 expression was significantly elevated in SACC tissues and associated with distant metastasis, PNI, and TNM grade (P < .05). DRG and SACC cells cocultured in vitro showed that the activation of the CCL5/CCR5 axis significantly increased SACC cell invasion and promoted the outgrowth of the DRG. SACC cell lines expressing CCR5 migrated in response to CCL5 derived from DRG, eventually leading to PNI. More importantly, further study showed that blocking of CCL5 or CCR5 effectively inhibited the invasive capacity and PNI activity of SACC cells (P < .05).

CONCLUSIONS

Our results suggest a pivotal role of CCL5/CCR5 axis in tumor-nerve interactions during PNI of SACC. The CCL5/CCR5 pathway might prove to be an attractive new target for the treatment of SACC with PNI.

Inflammatory Monocytes Promote Perineural Invasion via CCL2-Mediated Recruitment and Cathepsin B Expression

Perineural invasion (PNI) is an ominous event strongly linked to poor clinical outcome. Cells residing within peripheral nerves collaborate with cancer cells to enable PNI, but the contributing conditions within the tumor microenvironment are not well understood. Here, we show that CCR2-expressing inflammatory monocytes (IM) are preferentially recruited to sites of PNI, where they differentiate into macrophages and potentiate nerve invasion through a cathepsin B-mediated process. A series of adoptive transfer experiments with genetically engineered donors and recipients demonstrated that IM recruitment to nerves was driven by CCL2 released from Schwann cells at the site of PNI, but not CCL7, an alternate ligand for CCR2. Interruption of either CCL2-CCR2 signaling or cathepsin B function significantly impaired PNI in vivo Correlative studies in human specimens demonstrated that cathepsin B-producing macrophages were enriched in invaded nerves, which was associated with increased local tumor recurrence. These findings deepen our understanding of PNI pathogenesis and illuminate how PNI is driven in part by corruption of a nerve repair program. Further, they support the exploration of inhibiting IM recruitment and function as a targeted therapy for PNI. Cancer Res; 77(22); 6400-14. ©2017 AACR.

RNA sequencing reveals resistance of TLR4 ligand-activated microglial cells to inflammation mediated by the selective jumonji H3K27 demethylase inhibitor

Persistent microglial activation is associated with the production and secretion of various pro-inflammatory genes, cytokines and chemokines, which may initiate or amplify neurodegenerative diseases. A novel synthetic histone 3 lysine 27 (H3K27) demethylase JMJD3 inhibitor, GSK-J4, was proven to exert immunosuppressive activities in macrophages. However, a genome-wide search for GSK-J4 molecular targets has not been undertaken in microglia. To study the immuno-modulatory effects of GSK-J4 at the transcriptomic level, triplicate RNA sequencing and quantitative real-time PCR analyses were performed with resting, GSK-J4-, LPS- and LPS + GSK-J4-challenged primary microglial (PM) and BV-2 microglial cells. Among the annotated genes, the transcriptional sequencing of microglia that were treated with GSK-J4 revealed a selective effect on LPS-induced gene expression, in which the induction of cytokines/chemokines, interferon-stimulated genes, and prominent transcription factors TFs, as well as previously unidentified genes that are important in inflammation was suppressed. Furthermore, we showed that GSK-J4 controls are important inflammatory gene targets by modulating STAT1, IRF7, and H3K27me3 levels at their promoter sites. These unprecedented results demonstrate that the histone demethylase inhibitor GSK-J4 could have therapeutic applications for neuroinflammatory diseases.

How Schwann cells facilitate cancer progression in nerves

Recent studies have demonstrated a critical role for nerves in enabling tumor progression. The association of nerves with cancer cells is well established for a variety of malignant tumors, including pancreatic, prostate and the head and neck cancers. This association is often correlated with poor prognosis. A strong partnership between cancer cells and nerve cells leads to both cancer progression and expansion of the nerve network. This relationship is supported by molecular pathways related to nerve growth and repair. Peripheral nerves form complex tumor microenvironments, which are made of several cell types including Schwann cells. Recent studies have revealed that Schwann cells enable cancer progression by adopting a de-differentiated phenotype, similar to the Schwann cell response to nerve trauma. A detailed understanding of the molecular and cellular mechanisms involved in the regulation of cancer progression by the nerves is essential to design strategies to inhibit tumor progression.

Selective inhibition of EZH2 by a small molecule inhibitor regulates microglial gene expression essential for inflammation

Multiple studies have documented that Enhancer of zeste homolog 2 (EZH2) could play a role in inflammation and a wide range of malignancies; however, the underlying mechanisms remain largely unaddressed. Microglial activation is a key process in the production and release of numerous pro-inflammatory mediators that play important roles in inflammation and neurodegeneration in the central nervous system (CNS). Therefore, our aim was to investigate whether inhibition of EZH2 with the selective small molecule inhibitor EPZ-6438 protects against neonatal microglial activation. First, in mouse primary microglial cells and a microglial cell line, we found that LPS can rapidly increase EZH2 mRNA level and we subsequently performed gene expression profiling and constructed networks in resting, EPZ-6438-treated, LPS-treated and LPS+EPZ-6438-treated primary microglial cells and a microglial cell line using transcriptome RNA sequencing and bioinformatics analyses. By examining the RNA sequencing, we identified EPZ-6438 target genes and co-regulated modules that were critical for inflammation. We also identified unexpected relationships between the inducible transcription factors (TFs), motif strength, and the transcription of key inflammatory mediators. Furthermore, we showed that EPZ-6438 controls important inflammatory gene targets by modulating interferon regulatory factor (IRF) 1, IRF8, and signal transducer and activator of transcription (STAT) 1 levels at their promoter sites. Our unprecedented findings demonstrate that pharmacological interventions built upon EZH2 inhibition by EPZ-6438 could be a useful therapeutic approach for the treatment of neuroinflammatory diseases associated with microglial activation.