Role of the autonomic nervous system in tumorigenesis and metastasis

Spotting the clues: cluster of differentiation-a perspective of immune response intertwined with dysautonomia in colon cancer - a prospective cohort study

Dysautonomia, a parasympathetic-sympathetic imbalance, has clinical and public health consequences. Colon neoplasm is linked to dysautonomia through a complex interplay between the two conditions. In this prospective cohort study, we evaluated 18 patients divided into three groups: six patients with both colon cancer and dysautonomia, six patients with colon cancer without dysautonomia, and six patients with dysautonomia only (control group). Dysautonomia was defined by the presence of orthostatic hypotension, a non-increased or dropped heart rate, and various autonomic symptoms. During abdominal surgery, tissue samples from the celiac ganglion were collected and analyzed using immunohistochemistry (IHC). Our findings revealed a significant correlation between IHC marker expression in colon cancer and dysautonomia (control) (r = 0.927, P = 0.008). ANOVA results confirmed that the model was significant and that the dysautonomia group (control) had a significant effect on the independent variables (colon cancer or colon cancer + dysautonomia). The study proposes that a shared immunological mechanism underlies both dysautonomia and colon cancer, suggesting that the immune system plays a crucial role in the development or progression of these two conditions.

Association of Sympathovagal Imbalance with Increased Inflammation and Impaired Adaptive Immunity in Bladder Cancer Patients

Stress responses can impact bladder cancer (BC) outcomes via immune-inflammatory pathway modulation. This study explores heart rate variability (HRV) associations with serum immune-inflammatory biomarkers, blood count inflammatory markers, and psychosocial self-report measures in patients versus healthy controls. The TREM-1 and TREM-2 expressions on peripheral blood monocytes were analysed via flow cytometry; serum inflammatory biomarkers by ELISA; HRV (5-min ECG) pre-tumour resection; blood counts by haematology analyser; and psychosocial factors by validated questionnaires. Patients exhibited altered immune-inflammatory profiles with increased TREM-1/TREM-2, sTREM-1, sTREM-1/sTREM-2 ratio, BDNF, MCP-1, and NLR, and reduced IFN-γ, IL-10, LMR, and PMR. HRV analysis indicated sympathetic dominance (SNS, Stress indices, ACmod) and reduced parasympathetic modulation (PNS index, SDNN, RMSSD, 2UV%, DCmod, SD1). Sympathetic HRV indices correlated positively with sTREM-1, sTREM-1/sTREM-2 ratio, fractalkine, and inflammatory markers (SII, NLR, PLR) and negatively with parasympathetic HRV indices-correlations absent in controls. Only in patients, reduced physical function and social support, and higher anxiety, depression, and fatigue, associated positively with sympathetic HRV indices and inflammatory markers. This study links immune-inflammatory markers, HRV parameters, and psychosocial factors in BC, suggesting that immune and autonomic variations may relate to unfavourable outcomes. Incorporating these assessments could help tailor more personalised treatment strategies for BC patients.

Neural landscape is associated with functional outcomes in irradiated patients with oropharyngeal squamous cell carcinoma

The incidence of human papilloma virus-mediated oropharyngeal squamous cell carcinoma (OPSCC) has increased over the past 40 years, particularly among young individuals with a favorable prognosis; however, current therapy often leads to unfortunate side effects, such as dysphagia. Despite the emphasis on dysphagia in previous studies, there is an important research gap in understanding the correlation between neuronal changes and patient-reported and functional outcomes in patients with OPSCC. To address this issue, we examined pathologic tissue samples from patients with OPSCC using multiplex immunofluorescence staining and machine learning to correlate tumor-associated neuronal changes with prospectively collected patient-reported and functional outcomes. We found that tumor enrichment of adrenergic (TH+) and CGRP+ sensory-afferent nerves correlated with poorer swallowing outcomes. Functional electromyography recordings showed correlations between growing (GAP43+) and immature cholinergic (ChAT+DCX+) nerves and denervation patterns in survivors of OPSCC. A murine model of radiation-induced dysphagia further confirmed that immature cholinergic and CGRP+ nerves were correlated with impaired swallowing. Preclinical interventional studies also supported the independent contributions of CGRP+ and cholinergic (ChAT+) nerves to dysphagia in treated mouse models of OPSCC. Our results suggest that CGRP+ and ChAT+ neuronal signaling play distinct roles in tumor- and radiation-induced dysphagia in OPSCC and offer a comprehensive dataset on the neural landscape of OPSCC. These insights may guide early interventions for swallow preservation and the repurposing of neurology-related drugs, such as CGRP blockers, in clinical oncology and survivorship.

Hallmarks of perineural invasion in pancreatic ductal adenocarcinoma: new biological dimensions

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignant tumor with a high metastatic potential. Perineural invasion (PNI) occurs in the early stages of PDAC with a high incidence rate and is directly associated with a poor prognosis. It involves close interaction among PDAC cells, nerves and the tumor microenvironment. In this review, we detailed discuss PNI-related pain, six specific steps of PNI, and treatment of PDAC with PNI and emphasize the importance of novel technologies for further investigation.

The Neuroimmune Axis and Its Therapeutic Potential for Primary Liver Cancer

The autonomic nervous system plays an integral role in motion and sensation as well as the physiologic function of visceral organs. The nervous system additionally plays a key role in primary liver diseases. Until recently, however, the impact of nerves on cancer development, progression, and metastasis has been unappreciated. This review highlights recent advances in understanding neuroanatomical networks within solid organs and their mechanistic influence on organ function, specifically in the liver and liver cancer. We discuss the interaction between the autonomic nervous system, including sympathetic and parasympathetic nerves, and the liver. We also examine how sympathetic innervation affects metabolic functions and diseases like nonalcoholic fatty liver disease (NAFLD). We also delve into the neurobiology of the liver, the interplay between cancer and nerves, and the neural regulation of the immune response. We emphasize the influence of the neuroimmune axis in cancer progression and the potential of targeted interventions like neurolysis to improve cancer treatment outcomes, especially for hepatocellular carcinoma (HCC).

Targeting beta-adrenergic receptor pathways in melanoma: how stress modulates oncogenic immunity

The intricate pathways of the sympathetic nervous system hold an inherently protective role in the setting of acute stress. This is achieved through dynamic immunomodulatory and neurobiological networks. However, excessive and chronic exposure to these stress-induced stimuli appears to cause physiologic dysfunction through several mechanisms that may impair psychosocial, neurologic, and immunologic health. Numerous preclinical observations have identified the beta-2 adrenergic receptor (β2-AR) subtype to possess the strongest impact on immune dysfunction in the setting of chronic stressful stimuli. This prolonged expression of β2-ARs appears to suppress immune surveillance and promote tumorigenesis within multiple cancer types. This occurs through several pathways, including (1) decreasing the frequency and function of CD8 + T-cells infiltrating the tumor microenvironment (TME) via inhibition of metabolic reprogramming during T cell activation, and (2) establishing an immunosuppressive profile within the TME including promotion of an exhausted T cell phenotype while simultaneously enhancing local and paracrine metastatic potential. The use of nonselective β-AR antagonists appears to reverse many chronic stress-induced tumorigenic pathways and may also provide an additive therapeutic benefit for various immune checkpoint modulating agents including commonly utilized immune checkpoint inhibitors. Here we review the translational and clinical observations highlighting the foundational hypotheses that chronic stress-induced β-AR signaling promotes a pro-tumoral immunophenotype and that blockade of these pathways may augment the therapeutic response of immune checkpoint inhibition within the scope of melanoma.

Tracking Cancer: Exploring Heart Rate Variability Patterns by Cancer Location and Progression

Reduced heart rate variability (HRV) is an autonomic nervous system (ANS) response that may indicate dysfunction in the human body. Consistent evidence shows cancer patients elicit lower HRV; however, only select cancer locations were previously evaluated. Thus, the aim of the current study was to explore HRV patterns in patients diagnosed with and in varying stages of the most prevalent cancers. At a single tertiary academic medical center, 798 patients were recruited. HRV was measured via an armband monitor (Warfighter MonitorTM, Tiger Tech Solutions, Inc., Miami, FL, USA) equipped with electrocardiographic capabilities and was recorded for 5 to 7 min with patients seated in an upright position. Three time-domain metrics were calculated: SDNN (standard deviation of the NN interval), rMSSD (the root mean square of successive differences of NN intervals), and the percentage of time in which the change in successive NN intervals exceeds 50ms within a measurement (pNN50). Of the 798 patients, 399 were diagnosed with cancer. Cancer diagnoses were obtained via medical records one week following the measurement. Analysis of variance models were performed comparing the HRV patterns between different cancers, cancer stages (I-IV), and demographic strata. A total of 85% of the cancer patients had breast, gastrointestinal, genitourinary, or respiratory cancer. The cancer patients were compared to a control non-cancer patient population with similar patient size and distributions for sex, age, body mass index, and co-morbidities. For all HRV metrics, non-cancer patients exhibited significantly higher rMSSDs (11.1 to 13.9 ms, p < 0.0001), SDNNs (22.8 to 27.7 ms, p < 0.0001), and pNN50s (6.2 to 8.1%, p < 0.0001) compared to stage I or II cancer patients. This significant trend was consistently observed across each cancer location. Similarly, compared to patients with stage III or IV cancer, non-cancer patients possessed lower HRs (-11.8 to -14.0 bpm, p < 0.0001) and higher rMSSDs (+31.7 to +32.8 ms, p < 0.0001), SDNNs (+45.2 to +45.8 ms), p < 0.0001, and pNN50s (19.2 to 21.6%, p < 0.0001). The HR and HRV patterns observed did not significantly differ between cancer locations (p = 0.96 to 1.00). The depressed HRVs observed uniformly across the most prevalent cancer locations and stages appeared to occur independent of patients' co-morbidities. This finding highlights the potentially effective use of HRV as a non-invasive tool for determining common cancer locations and their respective stages. More studies are needed to delineate the HRV patterns across different ages, between sexes and race/ethnic groups.

Neural recordings can differentiate between spontaneously metastasizing melanomas and melanomas with low metastatic potential

Multiple studies report that melanomas are innervated tumors with sensory and sympathetic fibers where these neural fibers play crucial functional roles in tumor growth and metastasis with branch specificity. Yet there is no study which reports the direct neural recording and its pattern during in-vivo progression of the cancer. We performed daily neural recordings from male and female mice bearing orthotopic metastasizing- melanomas and melanomas with low metastatic poential, derived from B16-F10 and B16-F1 cells, respectively. Further, to explore the origins of neural activity, 6-Hydroxidopamine mediated chemical sympathectomy was performed followed by daily microneurographic recordings. We also performed the daily bioluminescent imaging to track in vivo growth of primary tumors and distant metastasis to the cranial area. Our results show that metastasizing tumors display high levels of neural activity while tumors with low metastatic potential lack it indicating that the presence of neural activity is linked to the metastasizing potential of the tumors. Moreover, the neural activity is not continuous over the tumor progression and has a sex-specific temporal patterns where males have two peaks of high neural activity while females show a single peak. The neural peak activity originated in peripheral sympathetic nerves as sympathectomy completely eliminated the peak activity in both sexes. Peak activities were highly correlated with the distant metastasis in both sexes. These results show that sympathetic neural activity is crucially involved in tumor metastasis and has sex-specific role in malignancy initiation.

Increased sympathetic nervous system impairs prognosis in lung cancer patients: a scoping review of clinical studies

Aim

To summarize current knowledge, gaps, quality of the evidence and show main results related to the role of the autonomic nervous system in lung cancer.

Methods

Studies were identified through electronic databases (PubMed, Scopus, Embase and Cochrane Library) in October 2023, and a descriptive analysis was performed. Twenty-four studies were included, and most were observational.

Results

Our data indicated an increased expression of β-2-adrenergic receptors in lung cancer, which was associated with poor prognosis. However, the use of β-blockers as an add-on to standard treatment promoted enhanced overall survival, recurrence-free survival and reduced metastasis occurrence.

Conclusion

Although the results herein seem promising, future research using high-quality prospective clinical trials is required to draw directions to guide clinical interventions.

Propranolol, Promising Chemosensitizer and Candidate for the Combined Therapy through Disruption of Tumor Microenvironment Homeostasis by Decreasing the Level of Carbonic Anhydrase IX

Resistance to chemotherapy represents a persisting medical problem, ranking among main causes of chemotherapy failure and cancer mortality. There is a possibility to utilize and repurpose already existing therapeutics which were not primarily intended for oncological treatment. Overactivation of adrenergic receptors and signaling dysregulation promotes tumor progression, metastatic potential, immune system evasion, tumor angiogenesis and drug resistance. The non-selective beta-blocker propranolol, approved in infantile haemangioma treatment, has a high potential for use in cancer therapy. We analyzed the effects of propranolol and 5-fluorouracil combination on sensitive and resistant cells derived from colorectal carcinoma in monolayers, single-component and co-culture spheroids and in vivo mouse models. Our results revealed that propranolol is able to exert its effect not only in chemosensitive colorectal cells, but also in 5-fluorouracil resistant cells. Propranolol disrupts the hypoxic adaptation machinery by inhibiting HIF1α, carbonic anhydrase IX, and activates apoptosis, which may be important in the management of chemo-resistant patients. We showed that propranolol slows down the growth of xenografts formed from colorectal cancer cells, even from cells already adapted to the β-blocker. We provide clear evidence that blockade of β-adrenergic receptors affects essential signaling pathways modulating tumor microenvironment and thus the response to anticancer therapy. Our findings indicate that propranolol could be repurposed to serve as chemosensitizer in combined therapy aimed at disrupting homeostasis of tumor microenvironment.

On the origin and nature of nongenetic information in eumetazoans

Nongenetic information implies all the forms of biological information not related to genes and DNA in general. Despite the deep scientific relevance of the concept, we currently lack reliable knowledge about its carriers and origins; hence, we still do not understand its true nature. Given that genes are the targets of nongenetic information, it appears that a parsimonious approach to find the ultimate source of that information is to trace back the sequential steps of the causal chain upstream of the target genes up to the ultimate link as the source of the nongenetic information. From this perspective, I examine seven nongenetically determined phenomena: placement of locus-specific epigenetic marks on DNA and histones, changes in snRNA expression patterns, neural induction of gene expression, site-specific alternative gene splicing, predator-induced morphological changes, and cultural inheritance. Based on the available evidence, I propose a general model of the common neural origin of all these forms of nongenetic information in eumetazoans.

Blocking Muscarinic Receptor 3 Attenuates Tumor Growth and Decreases Immunosuppressive and Cholinergic Markers in an Orthotopic Mouse Model of Colorectal Cancer

Tumor cells have evolved to express immunosuppressive molecules allowing their evasion from the host's immune system. These molecules include programmed death ligands 1 and 2 (PD-L1 and PD-L2). Cancer cells can also produce acetylcholine (ACh), which plays a role in tumor development. Moreover, tumor innervation can stimulate vascularization leading to tumor growth and metastasis. The effects of atropine and muscarinic receptor 3 (M3R) blocker, 1,1-dimethyl-4-diphenylacetoxypiperidinium iodide (4-DAMP), on cancer growth and spread were evaluated in vitro using murine colon cancer cell line, CT-26, and in vivo in an orthotopic mouse model of colorectal cancer. In the in vitro model, atropine and 4-DAMP significantly inhibited CT-26 cell proliferation in a dose dependent manner and induced apoptosis. Atropine attenuated immunosuppressive markers and M3R via inhibition of EGFR/AKT/ERK signaling pathways. However, 4-DAMP showed no effect on the expression of PD-L1, PD-L2, and choline acetyltransferase (ChAT) on CT-26 cells but attenuated M3R by suppressing the phosphorylation of AKT and ERK. Blocking of M3R in vivo decreased tumor growth and expression of immunosuppressive, cholinergic, and angiogenic markers through inhibition of AKT and ERK, leading to an improved immune response against cancer. The expression of immunosuppressive and cholinergic markers may hold potential in determining prognosis and treatment regimens for colorectal cancer patients. This study's results demonstrate that blocking M3R has pronounced antitumor effects via several mechanisms, including inhibition of immunosuppressive molecules, enhancement of antitumor immune response, and suppression of tumor angiogenesis via suppression of the AKT/ERK signaling pathway. These findings suggest a crosstalk between the cholinergic and immune systems during cancer development. In addition, the cholinergic system influences cancer evasion from the host's immunity.

Insights and opportunities at the crossroads of cancer and neuroscience

The biological and pathological importance of mutual interactions between the nervous system and cancer have become increasingly evident. The emerging field of cancer neuroscience aims to decipher key signalling factors of cancer-nervous system crosstalk and to exploit these modulators as targets for improved anticancer therapies. Here we discuss the key achievements in cancer neuroscience research, inspire further interactions on a variety of related research topics, and provide a roadmap for future studies.

The Nervous System as a Regulator of Cancer Hallmarks: Insights into Therapeutic Implications

Simple Summary

The nervous system communicates with the whole organism, regulating several physiological pathways. The modification of nerve activity could deregulate the state of cellular and tissue homeostasis which could drive cancer development. This paper provides the current state of knowledge, in an evidence-oriented manner, that the nervous system is able to participate in the carcinogenesis process by inducing biochemical, physiological, and cellular modifications involved in the hallmarks of cancer.

Abstract

The involvement of the nervous system in the development of cancer is controversial. Several authors have shown opinions and conflicting evidence that support the early effect of the nervous system on the carcinogenic process. For about a century, research has not been enough, questions remain open, ideas are not discarded, and although more research is still needed to answer all the questions, there is now enough evidence to support the theories and give hope of finding one more possible form of treatment. It is clear that malignant neoplasms have endogenous characteristics that allow them to establish and progress. Some of these characteristics known as hallmarks of cancer, are damage mechanisms in the pathology but necessary during other physiological processes which show some nerve dependence. The nervous system communicates with the whole organism, regulating physiological processes necessary to respond to external stimuli and for the maintenance of homeostasis. The modification of nerve activity could generate an overload and deregulate the state of cellular and tissue homeostasis; this could drive cancer development. In this review, we will address the issue in an evidence-oriented manner that supports that the nervous system is able to participate in the initial and progressive process of carcinogenesis by inducing biochemical, physiological, and cellular modifications involved in the hallmarks of cancer.

Identification of a neural development gene expression signature in colon cancer stem cells reveals a role for EGR2 in tumorigenesis

Recent evidence demonstrates that colon cancer stem cells (CSCs) can generate neurons that synapse with tumor innervating fibers required for tumorigenesis and disease progression. Greater understanding of the mechanisms that regulate CSC driven tumor neurogenesis may therefore lead to more effective treatments. RNA-sequencing analyses of ALDHPositive CSCs from colon cancer patient-derived organoids (PDOs) and xenografts (PDXs) showed CSCs to be enriched for neural development genes. Functional analyses of genes differentially expressed in CSCs from PDO and PDX models demonstrated the neural crest stem cell (NCSC) regulator EGR2 to be required for tumor growth and to control expression of homebox superfamily embryonic master transcriptional regulator HOX genes and the neural stem cell and master cell fate regulator SOX2. These data support CSCs as the source of tumor neurogenesis and suggest that targeting EGR2 may provide a therapeutic differentiation strategy to eliminate CSCs and block nervous system driven disease progression.

Tumor Innervation: History, Methodologies, and Significance

The role of the nervous system in cancer development and progression has been under experimental and clinical investigation since nineteenth-century observations in solid tumor anatomy and histology. For the first half of the twentieth century, methodological limitations and opaque mechanistic concepts resulted in ambiguous evidence of tumor innervation. Differential spatial distribution of viable or disintegrated nerve tissue colocalized with neoplastic tissue led investigators to conclude that solid tumors either are or are not innervated. Subsequent work in electrophysiology, immunohistochemistry, pathway enrichment analysis, neuroimmunology, and neuroimmunooncology have bolstered the conclusion that solid tumors are innervated. Regulatory mechanisms for cancer-related neurogenesis, as well as specific operational definitions of perineural invasion and axonogenesis, have helped to explain the consensus observation of nerves at the periphery of the tumor signifying a functional role of nerves, neurons, neurites, and glia in tumor development.

TUMOR CELL MALIGNANCY: A COMPLEX TRAIT BUILT THROUGH RECIPROCAL INTERACTIONS BETWEEN TUMORS AND TISSUE-BODY SYSTEM

Since the discovery of oncogenes and tumor suppressor genes in the late past century, cancer research has been overwhelmingly focused on the genetics and biology of tumor cells and hence has addressed mostly cell-autonomous processes with emphasis on traditional driver/passenger genetic models. Nevertheless, over that same period, multiple seminal observations have accumulated highlighting the role of non-cell autonomous effectors in tumor growth and metastasis. However, given that cell autonomous and non-autonomous events are observed together at the time of diagnosis, it is in fact impossible to know whether the malignant transformation is initiated by cell autonomous oncogenic events or by non-cell autonomous conditions generated by alterations of the tissue-body ecosystem. This review aims at addressing this issue by taking the option of defining malignancy as a complex genetic trait incorporating genetically determined reciprocal interactions between tumor cells and tissue-body ecosystem.

β-Adrenergic signaling in skin cancer

Activation of the sympathetic nervous system releases catecholamines that can interact with β-adrenergic receptors on tumor cells. Preclinical models have shown that the signaling processes initiated by activation of β-adrenergic receptors increase tumorigenesis, stimulate cell proliferation, and inhibit apoptosis. Indeed, preclinical studies have also shown that β-adrenergic blockade can decrease tumor burden. Researchers have been studying the effects of β-adrenergic receptor blockers on tumor cells and how they may slow the progression of melanoma, basal cell carcinoma, and squamous cell carcinoma. Moreover, clinical data have shown improved prognosis in patients with skin cancer who take β-blockers. This review discusses the mechanisms of β-adrenergic signaling in cancer and immune cells, details preclinical models of sympathetic blockade, and considers clinical evidence of the effects of β-adrenergic blockade in skin cancers.

Blockade of beta-adrenergic receptors reduces cancer growth and enhances the response to anti-CTLA4 therapy by modulating the tumor microenvironment

The development of immune checkpoint inhibitors (ICI) marks an important breakthrough of cancer therapies in the past years. However, only a limited fraction of patients benefit from such treatments, prompting the search for immune modulating agents that can improve the therapeutic efficacy. The nonselective beta blocker, propranolol, which for decades has been prescribed for the treatment of cardiovascular conditions, has recently been used successfully to treat metastatic angiosarcoma. These results have led to an orphan drug designation by the European Medicines Agency for the treatment of soft tissue sarcomas. The anti-tumor effects of propranolol are suggested to involve the reduction of cancer cell proliferation as well as angiogenesis. Here, we show that oral administration of propranolol delays tumor progression of MCA205 fibrosarcoma model and MC38 colon cancer model and increases the survival rate of tumor bearing mice. Propranolol works by reducing tumor angiogenesis and facilitating an anti-tumoral microenvironment with increased T cell infiltration and reduced infiltration of myeloid-derived suppressor cells (MDSCs). Using T cell deficient mice, we demonstrate that the full anti-tumor effect of propranolol requires the presence of T cells. Flow cytometry-based analysis and RNA sequencing of FACS-sorted cells show that propranolol treatment leads to an upregulation of PD-L1 on tumor associated macrophages (TAMs) and changes in their chemokine expression profile. Lastly, we observe that the co-administration of propranolol significantly enhances the efficacy of anti-CTLA4 therapy. Our results identify propranolol as an immune modulating agent, which can improve immune checkpoint inhibitor therapies in soft tissue sarcoma patients and potentially in other cancers.

Comparative transcriptome analysis between patient and endometrial cancer cell lines to determine common signaling pathways and markers linked to cancer progression

The rising incidence and mortality of endometrial cancer (EC) in the United States calls for an improved understanding of the disease's progression. Current methodologies for diagnosis and treatment rely on the use of cell lines as models for tumor biology. However, due to inherent heterogeneity and differential growing environments between cell lines and tumors, these comparative studies have found little parallels in molecular signatures. As a consequence, the development and discovery of preclinical models and reliable drug targets are delayed. In this study, we established transcriptome parallels between cell lines and tumors from The Cancer Genome Atlas (TCGA) with the use of optimized normalization methods. We identified genes and signaling pathways associated with regulating the transformation and progression of EC. Specifically, the LXR/RXR activation, neuroprotective role for THOP1 in Alzheimer's disease, and glutamate receptor signaling pathways were observed to be mostly downregulated in advanced cancer stage. While some of these highlighted markers and signaling pathways are commonly found in the central nervous system (CNS), our results suggest a novel function of these genes in the periphery. Finally, our study underscores the value of implementing appropriate normalization methods in comparative studies to improve the identification of accurate and reliable markers.

Adrenergic-Angiogenic Crosstalk in Head and Neck Cancer: Mechanisms and Therapeutic Implications

Head and neck squamous cell carcinomas (HNSCC) are loco-regionally aggressive tumors that often lead to debilitating changes in appearance, speech, swallowing and respiratory function in patients. It is therefore critical to develop novel targeted treatment strategies that can effectively target multiple components within the tumor microenvironment. In this regard, there has been an increased recognition of the role of neural signaling networks as mediators of disease progression in HNSCC. Here, we summarize the current knowledge on the mechanisms of adrenergic signaling in HNSCC specifically focusing on neurovascular crosstalk and the potential of targeting the adrenergic-angiogenic axis through repurposing of FDA-approved drugs against HNSCC.

Melanoma Immunotherapy and Precision Medicine in the Era of Tumor Micro-Tissue Engineering: Where Are We Now and Where Are We Going?

Malignant melanoma still remains a cancer with very poor survival rates, although it is at the forefront of personalized medicine. Most patients show partial responses and disease progressed due to adaptative resistance mechanisms, preventing long-lasting clinical benefits to the current treatments. The response to therapies can be shaped by not only taking into account cancer cell heterogeneity and plasticity, but also by its structural context as well as the cellular component of the tumor microenvironment (TME). Here, we review the recent development in the field of immunotherapy and target-based therapy and how, in the era of tumor micro-tissue engineering, ex-vivo assays could help to enhance our melanoma biology knowledge in its complexity, translating it in the development of successful therapeutic strategies, as well as in the prediction of therapeutic benefits.

Alternations in the Cardiovascular Autonomic Regulation and Growth Factors in Autism

Autism spectrum disorder (ASD) represents a serious neurodevelopmental disorder associated with autonomic nervous system dysregulation. The aim was to study complex cardiovascular autonomic regulation using heart rate variability (HRV) and systolic blood pressure variability (SBPV) linear/non-linear analysis at rest and during orthostasis, and to assess plasma levels of epidermal growth factor (EGF) and vascular endothelial growth factor (VEGF) in autistic children. Twenty-five ASD boys and 25 age and gender-matched children at the age 7-15 years were examined. After venous blood taking, continuous ECG and blood pressure biosignals were recorded at rest and during orthostasis. Evaluated parameters: RR intervals, high- and low-frequency band of HRV spectral analysis (HF-HRV, LF-HRV), symbolic dynamics parameters 0V%, 1V%, 2LV%, 2UV%, low- and high-frequency band of SBPV (LF-SBPV, HF-SBPV), systolic, diastolic, mean blood pressure, EGF, VEGF plasma levels. RR intervals were significantly shortened and the HF-HRV, LF-SBPV, HF-SBPV parameters were significantly lower at rest, the HF-HRV and LF-SBPV remained lower during orthostasis in autistic children compared to controls (p<0.05). EGF plasma levels were significantly lower in ASD compared to controls (p=0.046). No significant differences were found in remaining parameters. Our study revealed tachycardia, cardiovagal underactivity, and blunted sympathetic vasomotor regulation at rest and during orthostasis in autistic children. Additionally, complex heart rate dynamics are similar in autistic children than controls. Furthermore, EGF was reduced in autistic children without significant correlations with any autonomic parameters. We suggest that the abnormal complex cardiovascular reflex control could contribute to understanding the pathway linking autonomic features and autism.

Emerging roles of microRNA-208a in cardiology and reverse cardio-oncology

Cardiovascular diseases (CVDs) and cancer, which are the leading causes of mortality globally, have been viewed as two distinct diseases. However, the fact that cancer and CVDs may coincide has been noted by cardiologists when taking care of patients with CVDs caused by cancer chemotherapy; this entity is designated cardio-oncology. More recently, patients with CVDs have also been found to have increased risk of cancers, termed reverse cardio-oncology. Although reverse cardio-oncology has been highlighted as an important disease state in recent studies, how the diseased heart affects cancer and the potential mediators of the crosstalk between CVDs and cancer are largely unknown. Here, we focus on the roles of cardiac-specific microRNA-208a (miR-208a) in cardiac and cancer biology and explore its essential roles in reverse cardio-oncology. Accumulating evidence has shown that within the heart, increased miR-208a promotes myocardial injury, arrhythmia, cardiac remodeling, and dysfunction and that secreted miR-208a in the circulation may have novel roles in promoting tumor proliferation and invasion. This review, therefore, provides insights into the novel roles of miR-208a in reverse cardio-oncology and strategies to prevent secondary carcinogenesis in patients with early- or late-stage heart failure.

Cancer-Associated Neurogenesis and Nerve-Cancer Cross-talk

In this review, we highlight recent discoveries regarding mechanisms contributing to nerve-cancer cross-talk and the effects of nerve-cancer cross-talk on tumor progression and dissemination. High intratumoral nerve density correlates with poor prognosis and high recurrence across multiple solid tumor types. Recent research has shown that cancer cells express neurotrophic markers such as nerve growth factor, brain-derived neurotrophic factor, and glial cell-derived neurotrophic factor and release axon-guidance molecules such as ephrin B1 to promote axonogenesis. Tumor cells recruit new neural progenitors to the tumor milieu and facilitate their maturation into adrenergic infiltrating nerves. Tumors also rewire established nerves to adrenergic phenotypes via exosome-induced neural reprogramming by p53-deficient tumors. In turn, infiltrating sympathetic nerves facilitate cancer progression. Intratumoral adrenergic nerves release noradrenaline to stimulate angiogenesis via VEGF signaling and enhance the rate of tumor growth. Intratumoral parasympathetic nerves may have a dichotomous role in cancer progression and may induce Wnt-β-catenin signals that expand cancer stem cells. Importantly, infiltrating nerves not only influence the tumor cells themselves but also impact other cells of the tumor stroma. This leads to enhanced sympathetic signaling and glucocorticoid production, which influences neutrophil and macrophage differentiation, lymphocyte phenotype, and potentially lymphocyte function. Although much remains unexplored within this field, fundamental discoveries underscore the importance of nerve-cancer cross-talk to tumor progression and may provide the foundation for developing effective targets for the inhibition of tumor-induced neurogenesis and tumor progression.

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.

Mathematical Model and Numerical Simulation for Electric Field Induced Cancer Cell Migration

A mathematical model describing the interaction of cancer cells with the urokinase plasminogen activation system is represented by a system of partial differential equations, in which cancer cell dynamics accounts for diffusion, chemotaxis, and haptotaxis contributions. The mutual relations between nerve fibers and tumors have been recently investigated, in particular, the role of nerves in the development of tumors, as well neurogenesis induced by cancer cells. Such mechanisms are mediated by neurotransmitters released by neurons as a consequence of electrical stimuli flowing along the nerves, and therefore electric fields can be present inside biological tissues, in particular, inside tumors. Considering cancer cells as negatively charged particles immersed in the correct biological environment and subjected to an external electric field, the effect of the latter on cancer cell dynamics is still unknown. Here, we implement a mathematical model that accounts for the interaction of cancer cells with the urokinase plasminogen activation system subjected to a uniform applied electric field, simulating the first stage of cancer cell dynamics in a three-dimensional axial symmetric domain. The obtained numerical results predict that cancer cells can be moved along a preferred direction by an applied electric field, suggesting new and interesting strategies in cancer therapy.

Neural Networks Recapitulation by Cancer Cells Promotes Disease Progression: A Novel Role of p73 Isoforms in Cancer-Neuronal Crosstalk

Simple Summary

Cancer is initiated by alterations in specific genes. However, at late stages, cancer cells become metastatic not necessarily through continuous accumulation of additional mutations, but by hijacking programs of normal embryonic development and reactivating them in an unusual place, at the wrong time. Here, we applied computational and experimental approaches to show that these malignant reactivations include genes that are crucial for the development and function of the nervous system. We use the paradigm of melanoma transition from less invasive to highly aggressive stages in order to show that major players of metastasis, such as TP73 gene products, are implicated in this process. This work provides evidence for interactions between cancer cells and the neuronal system, which may have important future implications for metastasis prevention and cancer management.

Abstract

Mechanisms governing tumor progression differ from those of initiation. One enigmatic prometastatic process is the recapitulation of pathways of neural plasticity in aggressive stages. Cancer and neuronal cells develop reciprocal interactions via mutual production and secretion of neuronal growth factors, neurothrophins and/or axon guidance molecules in the tumor microenvironment. Understanding cancer types where this process is active, as well as the drivers, markers and underlying mechanisms, has great significance for blocking tumor progression and improving patient survival. By applying computational and systemic approaches, in combination with experimental validations, we provide compelling evidence that genes involved in neuronal development, differentiation and function are reactivated in tumors and predict poor patient outcomes across various cancers. Across cancers, they co-opt genes essential for the development of distinct anatomical parts of the nervous system, with a frequent preference for cerebral cortex and neural crest-derived enteric nerves. Additionally, we show that p73, a transcription factor with a dual role in neuronal development and cancer, simultaneously induces neurodifferentiation and stemness markers during melanoma progression. Our data yield the basis for elucidating driving forces of the nerve–tumor cell crosstalk and highlight p73 as a promising regulator of cancer neurobiology.

Norepinephrine-CREB1-miR-373 axis promotes progression of colon cancer

The adrenergic system contributes to the stress‐induced onset and progression of cancer. Adrenergic fibers are the primary source of norepinephrine (NE). The underlying mechanisms involved in NE‐induced colon cancer remain to be understood. In this study, we describe the function and regulatory network of NE in the progression of colon cancer. We demonstrate that NE‐induced phosphorylation of cAMP response element‐binding protein 1 (CREB1) promotes proliferation, migration, and invasion of human colon cancer cells. The downstream effector of NE, CREB1, bound to the promoter of miR‐373 and transcriptionally activated its expression. miR‐373 expression was shown to be necessary for NE‐induced cell proliferation, invasion, and tumor growth. We confirmed that proliferation and invasion of colon cancer cells are regulated in vitro and in vivo by miR‐373 through targeting of the tumor suppressors TIMP2 and APC. Our data suggest that NE promotes colon cancer cell proliferation and metastasis by activating the CREB1–miR‐373 axis. The study of this novel signaling axis may provide mechanistic insights into the neural regulation of colon cancer and help in the design of future clinical studies on stress biology in colorectal cancer.

Neural Functions Play Different Roles in Triple Negative Breast Cancer (TNBC) and non-TNBC

Triple negative breast cancer (TNBC) represents the most malignant subtype of breast cancer, and yet our understanding about its unique biology remains elusive. We have conducted a comparative computational analysis of transcriptomic data of TNBC and non-TNBC (NTNBC) tissue samples from the TCGA database, focused on genes involved in neural functions. Our main discoveries are: (1) while both subtypes involve neural functions, TNBC has substantially more up-regulated neural genes than NTNBC, suggesting that TNBC is more complex than NTNBC; (2) non-neural functions related to cell-microenvironment interactions and intracellular damage processing are key inducers of the neural genes in both TNBC and NTNBC, but the inducer-responder relationships are different in the two cancer subtypes; (3) key neural functions such as neural crest formation are predicted to enhance adaptive immunity in TNBC while glia development, along with a few other neural functions, induce both innate and adaptive immunity in NTNBC. These results reveal key differences in the biology between the two cancer subtypes, particularly in terms of the roles that neural functions play. Our findings may open new doors for further investigation of the distinct biology of TNBC vs. NTNBC.

Correlations Between Clinicopathological Features and the Vegetative Nervous System in Gastric Cancer

Gastric cancer currently represents one of the most important public health problems. Recent studies have demonstrated the existence of strong correlations between the vegetative nervous system and the role it plays in the initiation of the oncogenetic process and the progression of cancer. The purpose of this paper is to demonstrate the involvement of the sympathetic and parasympathetic vegetative nervous system in the evolution of gastric cancer, according to the stage of tumor differentiation. In this current paper we have included a number of four patients diagnosed with gastric cancer post UGI (Upper Gastrointestinal Endoscopy) and have analyzed relations that exist between the tumor differentiation degree and the metanephrine and normetanephrine serum level in the blood of the patients. Following the research, we have observed an increased value of the metanephrine and normetanephrine serum level in the patient which displayed the lowest degree of differentiation.

Schwann cells shape the neuro-immune environs and control cancer progression

At present, significant experimental and clinical data confirm the active involvement of the peripheral nervous system (PNS) in different phases of cancer development and progression. Most of the research effort focuses on the impact of distinct neuronal types, e.g., adrenergic, cholinergic, dopaminergic, etc. in carcinogenesis, generally ignoring neuroglia. The very fact that these cells far outnumber the other cellular types may also play an important role worthy of study in this context. The most prevalent neuroglia within the PNS consists of Schwann cells (SCs). These cells play a substantial role in maintaining homeostasis within the nervous system. They possess distinct immunomodulatory, inflammatory and regenerative capacities-also, one should consider their broad distribution throughout the body; this makes them a perfect target for malignant cells during the initial stages of cancer development and the very formation of the tumor microenvironment itself. We show that SCs in the tumor milieu attract different subsets of immune regulators and augment their ability to suppress effector T cells. SCs may also up-regulate invasiveness of tumor cells and support metastatic disease. We outline the interactive potential of SCs juxtaposed with cancerous cells, referring to data from various external sources alongside data of our own.

Muscarinic acetylcholine receptor M1 mediates prostate cancer cell migration and invasion through hedgehog signaling

The autonomic nervous system contributes to prostate cancer proliferation and metastasis. However, the exact molecular mechanism remains unclear. In this study, muscarinic acetylcholine receptor M1 (CHRM1) expression was measured via immunohistochemical analysis in human prostate cancer tissue array slides. PC-3, LNCaP, and A549 cells were treated with pirenzepine or carbachol, and the cell migration and invasion abilities were evaluated. Western blotting and quantitative real-time PCR were performed to measure GLI family zinc finger 1 (GLI1), patched 1 (PTCH1), and sonic hedgehog (SHH) expression levels. High expression of CHRM1 was found in early-stage human prostate cancer tissues. In addition, the selective CHRM1 antagonist pirenzepine inhibited PC-3, LNCaP, and A549 cell migration and invasion, but the agonist carbachol promoted the migration and invasion of these three cell lines. Muscarinic signaling can be relayed by hedgehog signaling. These data show that CHRM1 is involved in the regulation of prostate cancer migration and invasion through the hedgehog signaling pathway.

Progenitors from the central nervous system drive neurogenesis in cancer

Autonomic nerve fibres in the tumour microenvironment regulate cancer initiation and dissemination, but how nerves emerge in tumours is currently unknown. Here we show that neural progenitors from the central nervous system that express doublecortin (DCX⁺) infiltrate prostate tumours and metastases, in which they initiate neurogenesis. In mouse models of prostate cancer, oscillations of DCX⁺ neural progenitors in the subventricular zone-a neurogenic area of the central nervous system-are associated with disruption of the blood-brain barrier, and with the egress of DCX⁺ cells into the circulation. These cells then infiltrate and reside in the tumour, and can generate new adrenergic neurons. Selective genetic depletion of DCX⁺ cells inhibits the early phases of tumour development in our mouse models of prostate cancer, whereas transplantation of DCX⁺ neural progenitors promotes tumour growth and metastasis. In humans, the density of DCX⁺ neural progenitors is strongly associated with the aggressiveness and recurrence of prostate adenocarcinoma. These results reveal a unique crosstalk between the central nervous system and prostate tumours, and indicate neural targets for the treatment of cancer.

Neuroendocrine regulation of innate lymphoid cells

The activities of the immune system in repairing tissue injury and combating pathogens were long thought to be independent of the nervous system. However, a major regulatory role of immunomodulatory molecules released locally or systemically by the neuroendocrine system has recently emerged. A number of observations and discoveries support indeed the notion of the nervous system as an immunoregulatory system involved in immune responses. Innate lymphoid cells (ILCs), including natural killer (NK) cells and tissue-resident ILCs, form a family of effector cells present in organs and mucosal barriers. ILCs are involved in the maintenance of tissue integrity and homeostasis. They can also secrete effector cytokines rapidly, and this ability enables them to play early roles in the immune response. ILCs are activated by multiple pathways including epithelial and myeloid cell-derived cytokines. Their functions are also regulated by mediators produced by the nervous system. In particular, the peripheral nervous system, through neurotransmitters and neuropeptides, works in parallel with the hypothalamic-pituitary-adrenal and gonadal axis to modulate inflammatory events and maintain homeostasis. We summarize here recent findings concerning the regulation of ILC activities by neuroendocrine mediators in homeostatic and inflammatory conditions.

Schwann Cells Augment Cell Spreading and Metastasis of Lung Cancer

Although lungs are densely innervated by the peripheral nervous system (PNS), the role of the PNS in the progression of lung cancer is unknown. In this study, we report that mouse adult Schwann cells (SC), the principal glial cells of the PNS, can regulate the motility of lung cancer cells in vitro and the formation of metastases in vivo SCs promoted epithelial-to-mesenchymal transition (EMT) and the motility of two lung cancer cell lines by increasing expression of Snail and Twist in tumor cells; blocking of Snail and Twist expression abolished SC-induced motility of tumor cells. SC-derived CXCL5 was responsible for EMT in lung cancer cells, as the inhibition of CXCL5 or its receptor CXCR2 reduced SC-induced expression of Snail and Twist and reduced motility in tumor cells. CXCL5/CXCR2 binding activated the PI3K/AKT/GSK-3β/Snail-Twist signaling pathway in lung cancer cells, and the PI3K inhibitor blocked CXCL5-dependent phosphorylation of AKT and GSK-3β, reduced expression of Snail/Twist, and limited tumor cell invasiveness. SC conditioning of tumor cells prior to their injection into mice significantly increased the formation of metastases in the regional lymph nodes. In summary, SCs can regulate the CXCL5/CXCR2/PI3K/AKT/GSK-3β/Snail-Twist pathway to promote EMT, invasiveness, and metastatic potential of lung cancer cells. Our results reveal a new role of the PNS in the functional organization of the tumor microenvironment and tumor progression.Significance: This study increases our understanding of how nerves and, in particular, specific glial cells, Schwann cells, in the peripheral nervous system, may help promote tumor growth and metastasis. Cancer Res; 78(20); 5927-39. ©2018 AACR.

Modulation of anti-tumor immunity by the brain's reward system

Regulating immunity is a leading target for cancer therapy. Here, we show that the anti-tumor immune response can be modulated by the brain's reward system, a key circuitry in emotional processes. Activation of the reward system in tumor-bearing mice (Lewis lung carcinoma (LLC) and B16 melanoma) using chemogenetics (DREADDs), resulted in reduced tumor weight. This effect was mediated via the sympathetic nervous system (SNS), manifested by an attenuated noradrenergic input to a major immunological site, the bone marrow. Myeloid derived suppressor cells (MDSCs), which develop in the bone marrow, became less immunosuppressive following reward system activation. By depleting or adoptively transferring the MDSCs, we demonstrated that these cells are both necessary and sufficient to mediate reward system effects on tumor growth. Given the central role of the reward system in positive emotions, these findings introduce a physiological mechanism whereby the patient's psychological state can impact anti-tumor immunity and cancer progression.

Adrenergic Signaling: A Targetable Checkpoint Limiting Development of the Antitumor Immune Response

An immune response must be tightly controlled so that it will be commensurate with the level of response needed to protect the organism without damaging normal tissue. The roles of cytokines and chemokines in orchestrating these processes are well known, but although stress has long been thought to also affect immune responses, the underlying mechanisms were not as well understood. Recently, the role of nerves and, specifically, the sympathetic nervous system, in regulating immune responses is being revealed. Generally, an acute stress response is beneficial but chronic stress is detrimental because it suppresses the activities of effector immune cells while increasing the activities of immunosuppressive cells. In this review, we first discuss the underlying biology of adrenergic signaling in cells of both the innate and adaptive immune system. We then focus on the effects of chronic adrenergic stress in promoting tumor growth, giving examples of effects on tumor cells and immune cells, explaining the methods commonly used to induce stress in preclinical mouse models. We highlight how this relates to our observations that mandated housing conditions impose baseline chronic stress on mouse models, which is sufficient to cause chronic immunosuppression. This problem is not commonly recognized, but it has been shown to impact conclusions of several studies of mouse physiology and mouse models of disease. Moreover, the fact that preclinical mouse models are chronically immunosuppressed has critical ramifications for analysis of any experiments with an immune component. Our group has found that reducing adrenergic stress by housing mice at thermoneutrality or treating mice housed at cooler temperatures with β-blockers reverses immunosuppression and significantly improves responses to checkpoint inhibitor immunotherapy. These observations are clinically relevant because there are numerous retrospective epidemiological studies concluding that cancer patients who were taking β-blockers have better outcomes. Clinical trials testing whether β-blockers can be repurposed to improve the efficacy of traditional and immunotherapies in patients are on the horizon.

Role of the nervous system in cancer metastasis

Cancer remains as one of the leading cause of death worldwide. The development of cancer involves an intricate process, wherein many identified and unidentified factors play a role. Although most studies have focused on the genetic abnormalities which initiate and promote cancer, there is overwhelming evidence that tumors interact within their environment by direct cell-to-cell contact and with signaling molecules, suggesting that cancer cells can influence their microenvironment and bidirectionally communicate with other systems. However, only in recent years the role of the nervous system has been recognized as a major contributor to cancer development and metastasis. The nervous system governs functional activities of many organs, and, as tumors are not independent organs within an organism, this system is integrally involved in tumor growth and progression.

Tumorigenesis as a process of gradual loss of original cell identity and gain of properties of neural precursor/progenitor cells

Cancer is a complex disease without a unified explanation for its cause so far. Our recent work demonstrates that cancer cells share similar regulatory networks and characteristics with embryonic neural cells. Based on the study, I will address the relationship between tumor and neural cells in more details. I collected the evidence from various aspects of cancer development in many other studies, and integrated the information from studies on cancer cell properties, cell fate specification during embryonic development and evolution. Synthesis of the information strongly supports that cancer cells share much more similarities with neural progenitor/stem cells than with mesenchymal-type cells and that tumorigenesis represents a process of gradual loss of cell or lineage identity and gain of characteristics of neural cells. I also discuss cancer EMT, a concept having been under intense debate, and possibly the true meaning of EMT in cancer initiation and development. This synthesis provides fresh insights into a unified explanation for and a previously unrecognized nature of tumorigenesis, which might not be revealed by studies on individual molecular events. The review will also present some brief suggestions for cancer research based on the proposed model of tumorigenesis.

Neurons generated from carcinoma stem cells support cancer progression

Recent evidences show that nervous system acts as a crucial part of cancer microenvironment. Infiltration of nerve fibers into cancer microenvironment has an important active role in cancer progression. The stimulations of both cancer growth and metastasis by members of nervous system such as neurons and glial cells have been demonstrated. However, how the nervous system is built in cancer is largely unknown. Here we show that a fraction of cancer stem cells (CSCs) derived from patients with gastric carcinoma and colorectal carcinoma are capable of producing neurons that are involved in tumor neurogenesis and tumor growth. Cancer stem cell monoclone derived from a single cancer stem cell was able to generate neurons including sympathetic and parasympathetic neurons to take part in the nervous system in cancer tissues. Knocking down the neural cell generating capability of the human CSCs inhibited the growth of xenograft tumors in mouse model. Our data demonstrate that human CSCs are able to produce one of most important components in the cancer microenvironment that are required for cancer development and progression.

Putative Links Between Sleep Apnea and Cancer: From Hypotheses to Evolving Evidence

In recent years, the potentially adverse role of sleep-disordered breathing in cancer incidence and outcomes has emerged. In parallel, animal models of intermittent hypoxia (IH) and sleep fragmentation (SF) emulating the two major components of OSA have lent support to the notion that OSA may enhance the proliferative and invasive properties of solid tumors. Based on several lines of evidence, we propose that OSA-induced increases in sympathetic outflow and alterations in immune function are critically involved in modifying oncologic processes including angiogenesis. In this context, we suggest that OSA, via IH (and potentially SF), promotes changes in several signaling pathways and transcription factors that coordinate malignant transformation and expansion, disrupts host immunologic surveillance, and consequently leads to increased probability of oncogenesis, accelerated tumor proliferation, and invasion, ultimately resulting in adverse outcomes.

Tumour-induced neoneurogenesis and perineural tumour growth: a mathematical approach

It is well-known that tumours induce the formation of a lymphatic and a blood vasculature around themselves. A similar but far less studied process occurs in relation to the nervous system and is referred to as neoneurogenesis. The relationship between tumour progression and the nervous system is still poorly understood and is likely to involve a multitude of factors. It is therefore relevant to study tumour-nerve interactions through mathematical modelling: this may reveal the most significant factors of the plethora of interacting elements regulating neoneurogenesis. The present work is a first attempt to model the neurobiological aspect of cancer development through a system of differential equations. The model confirms the experimental observations that a tumour is able to promote nerve formation/elongation around itself, and that high levels of nerve growth factor and axon guidance molecules are recorded in the presence of a tumour. Our results also reflect the observation that high stress levels (represented by higher norepinephrine release by sympathetic nerves) contribute to tumour development and spread, indicating a mutually beneficial relationship between tumour cells and neurons. The model predictions suggest novel therapeutic strategies, aimed at blocking the stress effects on tumour growth and dissemination.