Peptidergic innervation of human esophageal and cardiac carcinoma

Involvement of neuronal factors in tumor angiogenesis and the shaping of the cancer microenvironment

Emerging evidence suggests that nerves within the tumor microenvironment play a crucial role in regulating angiogenesis. Neurotransmitters and neuropeptides released by nerves can interact with nearby blood vessels and tumor cells, influencing their behavior and modulating the angiogenic response. Moreover, nerve-derived signals may activate signaling pathways that enhance the production of pro-angiogenic factors within the tumor microenvironment, further supporting blood vessel growth around tumors. The intricate network of communication between neural constituents and the vascular system accentuates the potential of therapeutically targeting neural-mediated pathways as an innovative strategy to modulate tumor angiogenesis and, consequently, neoplastic proliferation. Hereby, we review studies that evaluate the precise molecular interplay and the potential clinical ramifications of manipulating neural elements for the purpose of anti-angiogenic therapeutics within the scope of cancer treatment.

The association between the neuroendocrine system and the tumor immune microenvironment: Emerging directions for cancer immunotherapy

This review summarizes emerging evidence that the neuroendocrine system is involved in the regulation of the tumor immune microenvironment (TIME) to influence cancer progression. The basis of the interaction between the neuroendocrine system and cancer is usually achieved by the infiltration of nerve fibers into the tumor tissue, which is called neurogenesis; the migration of cancer cells toward nerve fibers, which is called perineural invasion (PNI), and the neurotransmitters. In addition to the traditional role of neurotransmitters in neural communications, neurotransmitters are increasingly recognized as mediators of crosstalk between the nervous system, cancer cells, and the immune system. Recent studies have revealed that not only nerve fibers but also cancer cells and immune cells within the TIME can secrete neurotransmitters, exerting influence on both neurons and themselves. Furthermore, immune cells infiltrating the tumor environment have been found to express a wide array of neurotransmitter receptors. Hence, targeting these neurotransmitter receptors may promote the activity of immune cells in the tumor microenvironment and exert anti-tumor immunity. Herein, we discuss the crosstalk between the neuroendocrine system and tumor-infiltrating immune cells, which may provide feasible cancer immunotherapy options.

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.

The Galaninergic System: A Target for Cancer Treatment

Simple Summary

Peptidergic systems play an important role in cancer progression. The galaninergic system (the peptide galanin and its receptors: galanin 1, 2 and 3) is involved in tumorigenesis, the invasion and migration of tumor cells and angiogenesis and it has been correlated with tumor stage/subtypes, metastasis and recurrence rate in many types of cancer. Galanin exerts a dual action in tumor cells: a proliferative or an antiproliferative effect depending on the galanin receptor involved in these mechanisms. Galanin receptors could be used in certain tumors as therapeutic targets and diagnostic markers for treatment, prognosis and surgical outcome. This review shows the importance of the galaninergic system in the development of tumors and suggests future promising clinical antitumor applications using galanin agonists or antagonists.

Abstract

The aim of this review is to show the involvement of the galaninergic system in neuroendocrine (phaeochromocytomas, insulinomas, neuroblastic tumors, pituitary tumors, small-cell lung cancer) and non-neuroendocrine (gastric cancer, colorectal cancer, head and neck squamous cell carcinoma, glioma) tumors. The galaninergic system is involved in tumorigenesis, invasion/migration of tumor cells and angiogenesis, and this system has been correlated with tumor size/stage/subtypes, metastasis and recurrence rate. In the galaninergic system, epigenetic mechanisms have been related with carcinogenesis and recurrence rate. Galanin (GAL) exerts both proliferative and antiproliferative actions in tumor cells. GAL receptors (GALRs) mediate different signal transduction pathways and actions, depending on the particular G protein involved and the tumor cell type. In general, the activation of GAL₁R promoted an antiproliferative effect, whereas the activation of GAL₂R induced antiproliferative or proliferative actions. GALRs could be used in certain tumors as therapeutic targets and diagnostic markers for treatment, prognosis and surgical outcome. The current data show the importance of the galaninergic system in the development of certain tumors and suggest future potential clinical antitumor applications using GAL agonists or antagonists.

Tumor Innervation: History, Methodologies, and Significance

Simple Summary

This comprehensive review of tumor innervation summarizes the literature from the earliest publications on the topic to the most recent. It addresses the positive and negative evidence of tumor innervation and the historical developments in thought and methodology that have led to the consensus that tumors are innervated. The role of the immune response is described, as are some important biochemical and physiological mechanisms relevant to regulation of cancer development.

Abstract

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.

Many Voices in a Choir: Tumor-Induced Neurogenesis and Neuronal Driven Alternative Splicing Sound Like Suspects in Tumor Growth and Dissemination

Simple Summary

Significant progress has recently been made in understanding the role of the neuronal system in cancer biology, in many solid tumors such as prostate, breast, pancreatic, gastric and brain cancers. Solid tumors and the nervous system appear to influence each other’s development both directly and indirectly. A recurring element in such interactions is constituted by nerve-related substances such as neurotransmitters and neurotrophins, to which the first part of the current review is devoted. The second part of the review focuses on the potential role played by alternative splicing in cancer progression associated with neural signaling. Alternative splicing is the process where pre-mRNA is cut and re-ligated in different ways to give rise to multiple protein isoforms whose expression profile is often cancer specific. Alternative splicing is known to take place in the mRNA of genes that code for proteins involved in neuronal development and the creation of new nerve fibers. The change in alternative splicing patterns that occur as tumors develop and progress may make these splice variants potential targets for the development of drug treatments. They may also serve as diagnostic or prognostic biomarkers.

Abstract

During development, as tissues expand and grow, they require circulatory, lymphatic, and nervous system expansion for proper function and support. Similarly, as tumors arise and develop, they also require the expansion of these systems to support them. While the contribution of blood and lymphatic systems to the development and progression of cancer is well known and is targeted with anticancer drugs, the contribution of the nervous system is less well studied and understood. Recent studies have shown that the interaction between neurons and a tumor are bilateral and promote metastasis on one hand, and the formation of new nerve structures (neoneurogenesis) on the other. Substances such as neurotransmitters and neurotrophins being the main actors in such interplay, it seems reasonable to expect that alternative splicing and the different populations of protein isoforms can affect tumor-derived neurogenesis. Here, we report the different, documented ways in which neurons contribute to the development and progression of cancer and investigate what is currently known regarding cancer-neuronal interaction in several specific cancer types. Furthermore, we discuss the incidence of alternative splicing that have been identified as playing a role in tumor-induced neoneurogenesis, cancer development and progression. Several examples of changes in alternative splicing that give rise to different isoforms in nerve tissue that support cancer progression, growth and development have also been investigated. Finally, we discuss the potential of our knowledge in alternative splicing to improve tumor diagnosis and treatment.

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.

Clinicopathological Significance of Nerves in Esophageal Cancer

Nerves are emerging promoters of cancer progression, but the innervation of esophageal cancer and its clinicopathologic significance remain unclear. In this study, nerves were analyzed by immunohistochemistry in a cohort of 260 esophageal cancers, including 40 matched lymph node metastases and 137 normal adjacent esophageal tissues. Nerves were detected in 38% of esophageal cancers and were more associated with squamous cell carcinomas (P = 0.04). The surrounding or invasion of nerves by cancer cells (perineural invasion) was detected in 12% of esophageal cancers and was associated with reduced survival (P = 0.04). Nerves were found to express the following receptors for nerve growth factor (NGF): neurotrophic receptor tyrosine kinase 1 and nerve growth factor receptor. An association was suggested between high production of NGF by cancer cells and the presence of nerves (P = 0.02). In vitro, NGF production in esophageal cancer cells was shown by Western blot, and esophageal cancer cells were able to induce neurite outgrowth in the PC12 neuronal cells. The neurotrophic activity of esophageal cancer cells was inhibited by anti-NGF blocking antibodies. Together, these data suggest that innervation is a feature in esophageal cancers that may be driven by cancer cell-released NGF.

Profiling of how nociceptor neurons detect danger - new and old foes

The host evolves redundant mechanisms to preserve physiological processing and homeostasis. These functions range from sensing internal and external threats, creating a memory of the insult and generating reflexes, which aim to resolve inflammation. Impairment in such functioning leads to chronic inflammatory diseases. By interacting through a common language of ligands and receptors, the immune and sensory nervous systems work in concert to accomplish such protective functions. Whilst this bidirectional communication helps to protect from danger, it can contribute to disease pathophysiology. Thus, the somatosensory nervous system is anatomically positioned within primary and secondary lymphoid tissues and mucosa to modulate immunity directly. Upstream of this interplay, neurons detect danger, which prompts the release of neuropeptides initiating (i) defensive reflexes (ranging from withdrawal response to coughing) and (ii) chemotaxis, adhesion and local infiltration of immune cells. The resulting outcome of such neuro-immune interplay is still ill-defined, but consensual findings start to emerge and support neuropeptides not only as blockers of T_H 1-mediated immunity but also as drivers of T_H 2 immune responses. However, the modalities detected by nociceptors revealed broader than mechanical pressure and temperature sensing and include signals as various as cytokines and pathogens to immunoglobulins and even microRNAs. Along these lines, we aggregated various dorsal root ganglion sensory neuron expression profiling datasets supporting such wide-ranging sensing capabilities to help identifying new danger detection modalities of these cells. Thus, revealing unexpected aspects of nociceptor neuron biology might prompt the identification of novel drivers of immunity, means to resolve inflammation and strategies to safeguard homeostasis.

Schwann cells: a new player in the tumor microenvironment

Cancerous cells must cooperate with the surrounding stroma and non-malignant cells within the microenvironment to support the growth and invasion of the tumor. The nervous system is a component of every organ system of the body, and therefore, is invariably at the front line of the tumor invasion. Due to the complexity of the nervous system physiology, this review separately discusses the contributions of the central and peripheral nervous systems to the tumorigenesis and tumor progression. We further focus the discussion on the evidence that Schwann cells aid in tumor growth and invasion. Schwann cells, a largely unexplored element of the tumor microenvironment, may participate in the creation of tumor-favorable conditions through both bi-directional interaction with cancer cells and the facilitation of the immune-suppressive microenvironment through the mechanism of neural repair and immunomodulation.

Impact of the Sensory Neurons on Melanoma Growth In Vivo

Nerve endings are often identified within solid tumors, but their impact on the tumor growth and progression remains poorly understood. Emerging data suggests that the central nervous system may affect cancer development and spreading via the hypothalamic-pituitary-adrenal axis and autonomous nervous system. However, the role of the afferent sensory neurons in tumor growth is unclear, except some reports on perineural invasion in prostate and pancreatic cancer and cancer-related pain syndrome. Here, we provide the results of primary testing of the concept that the interaction between melanoma cells and sensory neurons may induce the formation of tumor-supporting microenvironment via attraction of immune regulatory cells by the tumor-activated dorsal root ganglion (DRG) neurons. We report that despite DRG cells not directly up-regulating proliferation of melanoma cells in vitro, presence of DRG neurons allows tumors to grow significantly faster in vivo. This effect has been associated with increased production of chemokines by tumor-activated DRG neurons and attraction of myeloid-derived suppressor cells both in vitro and in vivo. These initial proof-of-concept results justify further investigations of the sensory (afferent) nervous system in the context of tumorigenesis and the local protumorigenic immunoenvironment.

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.

The role of stress and beta-adrenergic system in melanoma: current knowledge and possible therapeutic options

PURPOSE

The aim of the present review was to discuss recent findings on the role of beta-adrenergic system in melanoma, in order to provide information on the biological responses elicited by its activation and its potential application for melanoma treatment.

METHODS

A literature search was performed, and evidences regarding the involvement of stress and beta-adrenergic system in cancer and melanoma were found and discussed.

RESULTS

Our search pointed out that beta-adrenergic system is a key regulator of important biological processes involved in the onset and progression of some solid tumors. In the last decade, functional beta-adrenoceptors have been also identified on melanoma cells, as well as on their microenvironment cells. Similarly to other common cancers too, the activation of such adrenoceptors by catecholamines, usually released under stress conditions, has been found to trigger pro-tumorigenic pathways contributing to cell proliferation and motility, immune system regulation, apoptosis, epithelial-mesenchymal transition, invasion and neoangiogenesis.

CONCLUSIONS

The biological evidences we found clarify and sustain the clinical evidences reporting the involvement of chronic stress in melanoma onset and progression. In such scenario, it is conceivable that a therapeutic approach targeting beta-adrenergic system could constitute a novel and promising strategy for melanoma treatment.

Elevated SP/NK-1R in esophageal carcinoma promotes esophageal carcinoma cell proliferation and migration

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) remains one of the most lethal malignant tumors, and currently there is no effective ways to manage the late stage disease. Therefore clarifying the mechanisms underlying the development of ESCC is of great importance to develop novel therapeutic agents. The present study focuses on the interaction between neurotransmitter substance P (SP) together with its receptor NK-1R and ESCC progression.

METHODS

The distribution of SP positive nerve fibers and expression of NK-1R were detected in ESCC tissue using immunohistochemistry. The effects of SP stimulation and blocking on the growth and migration of ESCC cells were measured by in vitro and in vivo assay.

RESULTS

A higher density of SP positive nerve fibers and elevated NK-1R expression on ESCC cells were observed. More importantly, the SP positive fiber density was correlated with tumor size and lymph node metastasis. SP promoted ESCC cell proliferation and migration by modulation of intracellular calcium levels.

CONCLUSION

NK-1R activation by SP stimulation promotes growth and migration of ESCC cells.

The clinicopathological significance of neurogenesis in breast cancer

Background

Recent reports support a novel biological phenomenon about cancer related neurogenesis. However, little is known about the clinicopathological significance of neurogenesis in breast cancer.

Methods

A total of 196 cases, including 20 of normal tissue, 14 of fibroadenoma, 18 of ductal carcinoma in situ (DCIS) and 144 of invasive ductal carcinoma (IDC) of the breast were used. The tissue slides were immunostained for protein gene product (PGP) 9.5 and S 100 to identify nerves. The correlation between the expression of PGP 9.5 and clinicopathological characteristics in IDC of the breast was assessed.

Results

While the PGP 9.5 positive nerve fibers are identified in all cases of normal breast tissue controls and in the tumor stroma of 61% (89/144) cases of invasive ductal carcinomas, PGP 9.5 positive nerve fibers are not seen in the tumor stroma of cases of fibroadenoma and DCIS. The percentage of tumors that exhibited neurogenesis increased from tumor grade I to tumor grade II and III (29.4% vs 71.8%, p < 0.0001). In addition, patients with less than 3 years of disease-free survival tended to have a higher positive expression of PGP 9.5 compared to patients with an equal or more than 3 years of disease-free survival (64.8% vs 46.7%, p = 0.035). Furthermore, moderate/strong expression of PGP 9.5 was found to be significantly related to microvessel density (MVD, p = 0.014). Interestingly, PGP 9.5 expression was significantly associated with higher MVD in the ER-negative (p = 0.045) and node-negative (p = 0.039) subgroups of IDC of the breast.

Conclusions

This data indicates that neurogenesis is associated with some aggressive features of IDC including tumor grade and patient survival as well as angiogenesis, especially in ER-negative and node-negative subtypes of IDC of the breast. Thus, neurogenesis appears to be associated with breast cancer progression and may play a role in therapeutic guidance for patients with ER-negative and node-negative invasive breast cancer.

Role of the nervous system in cancer metastasis

The notion that tumors lack innervation was proposed several years ago. However, nerve fibers are irregulatedly found in some tumor tissues. Their terminals interaction with cancer cells are considered to be neuro-neoplastic synapses. Moreover, neural-related factors, which are important players in the development and activity of the nervous system, have been found in cancer cells. Thus, they establish a direct connection between the nervous system and tumor cells. They modulate the process of metastasis, including degradation of base membranes, cancer cell invasion, migration, extravasation and colonization. Peripheral nerve invasion provides another pathway for the spread of cancer cells when blood and lymphatic metastases are absent, which is based on the interactions between the microenvironments of nerve fibers and tumor cells. The nervous system also modulates angiogenesis, the tumor microenvironment, bone marrow, immune functions and inflammatory pathways to influence metastases. Denervation of the tumor has been reported to enhance cancer metastasis. Stress, social isolation and other emotional factors may increase distant metastasis through releasing hormones from the brain, the hypothalamic-pituitary-adrenal axis and autonomic nervous system. Disruption of circadian rhythms will also promote cancer metastasis through direct and indirect actions of the nervous system. Therefore, the nervous system plays an important role in cancer metastasis.

Neurogenesis in colorectal cancer is a marker of aggressive tumor behavior and poor outcomes

BACKGROUND

Colorectal cancer staging criteria do not rely on examination of neuronal tissue. The authors previously demonstrated that perineural invasion is an independent prognostic factor of outcomes in colorectal cancer. For the current study, they hypothesized that neurogenesis occurs in colorectal cancer and portends an aggressive tumor phenotype.

METHODS

In total, samples from 236 patients with colorectal cancer were used to create a tissue array and database. Tissue array slides were immunostained for protein gene product 9.5 (PGP9.5) to identify nerve tissue. The correlation between markers of neurogenesis and oncologic outcomes was determined. The effect of colorectal cancer cells on stimulating neurogenesis in vitro was evaluated using a dorsal root ganglia coculture model.

RESULTS

Patients whose tumors exhibited high degrees of neurogenesis had 50% reductions in 5-year overall survival and disease-free survival compared with patients whose tumors contained no detectable neurogenesis (P = .002 and P = .006, respectively). Patients with stage II disease and high degrees of neurogenesis had greater reductions in 5-year overall survival and disease-free survival compared with lymph node-negative patients with no neurogenesis (P = .002 and P = .008, respectively). Patients with stage II disease and high degrees of neurogenesis had lower 5-year overall survival and disease-free survival compared with patients who had stage III disease with no neurogenesis (P = .01 and P = .008, respectively). Colorectal cancer cells stimulated neurogenesis and exhibited evidence of neuroepithelial interactions between nerves and tumor cells in vitro.

CONCLUSIONS

Neurogenesis in colorectal cancer appeared to play a critical role in colorectal cancer progression. Furthermore, the current results indicated that neurogenesis functions as an independent predictor of outcomes and may play a role in therapy stratification for patients with lymph node-negative disease.

Neurotransmitters, more than meets the eye--neurotransmitters and their perspectives in cancer development and therapy

The neurotransmitter/receptor system has been shown to modulate various aspects of tumor development including cell proliferation, angiogenesis, invasion, migration and metastasis. It has been found that tumor tissues can not only synthesize and release a wide range of neurotransmitters but also produce different biological effects via respective receptors. These tissues are also innervated by nerve fibers but the biological significance is unknown. Nevertheless neurotransmitters can produce either stimulatory or inhibitory effect in normal and tumor tissues. These effects are dependent on the types of tissues and the kinds of neurotransmitter as well as the subtypes of corresponding receptors being involved. These findings clearly extend the conventional role of neurotransmitters in nervous system to the actions in oncogenesis. In this regard, intervention or stimulation of these neuronal pathways in different cancer diseases would have significant clinical implications in cancer treatments. Here, we summarize the influences of various well-characterized neurotransmitters and their receptors on tumor growth and further discuss the respective possible strategies and perspectives for cancer therapy in the future.

The neuronal influence on tumor progression

Nerve fibers accompany blood and lymphatic vessels all over the body. An extensive amount of knowledge has been obtained with regard to tumor angiogenesis and tumor lymphangiogenesis, yet little is known about the potential biological effects of "neoneurogenesis". Cancer cells can exploit the advantage of the factors released by the nerve fibers to generate a positive microenvironment for cell survival and proliferation. At the same time, they can stimulate the formation of neurites by secreting neurotrophic factors and axon guidance molecules. The neuronal influence on the biology of a neoplasm was initially described several decades ago. Since then, an increasing amount of experimental evidence strongly suggests the existence of reciprocal interactions between cancer cells and nerves in humans. Moreover, researchers have been able to demonstrate a crosstalk between cancer cells and nerve fibers as a strategy for survival. Despite all these evidence, a lot remains to be done in order to clarify the role of neurotransmitters, neuropeptides, and their associated receptor-initiated signaling pathways in the development and progression of cancer, and response to therapy. A global-wide characterization of the neurotransmitters or neuropeptides present in the tumor microenvironment would provide insights into the real biological influences of the neuronal tissue on tumor progression. This review is intended to discuss our current understanding of neurosignaling in cancer and its potential implications on cancer prevention and therapy. The review will focus on the soluble factors released by cancer cells and nerve endings, their biological effects and their potential relevance in the treatment of cancer.

Somatostatin, substance P and calcitonin gene-related peptide-positive intramural nerve structures of the human large intestine affected by carcinoma

The aim of this study was to investigate the arrangement and chemical coding of enteric nerve structures in the human large intestine affected by cancer. Tissue samples comprising all layers of the intestinal wall were collected during surgery form both morphologically unchanged and pathologically altered segments of the intestine (n=15), and fixed by immersion in buffered paraformaldehyde solution. The cryostat sections were processed for double-labelling immunofluorescence to study the distribution of the intramural nerve structures (visualized with antibodies against protein gene-product 9.5) and their chemical coding using antibodies against somatostatin (SOM), substance P (SP) and calcitonin gene-related peptide (CGRP). The microscopic observations revealed distinct morphological differences in the enteric nerve system structure between the region adjacent to the cancer invaded area and the intact part of the intestine. In general, infiltration of the cancer tissue resulted in the gradual (depending on the grade of invasion) first decomposition and reduction to final partial or complete destruction and absence of the neuronal elements. A comparative analysis of immunohistochemically labeled sections (from the unchanged and pathologically altered areas) revealed a statistically significant decrease in the number of CGRP-positive neurons and nerve fibres in both submucous and myenteric plexuses in the transitional zone between morphologically unchanged and cancer-invaded areas. In this zone, a decrease was also observed in the density of SP-positive nerve fibres in all intramural plexuses. Conversely, the investigations demonstrated statistically insignificant differences in number of SP- and SOM-positive neurons and a similar density of SOM-positive nerve fibres in the plexuses of the intact and pathologically changed areas. The differentiation between the potential adaptive changes in ENS or destruction of its elements by cancer invasion should be a subject of further investigations.

Loss of sympathetic nerve fibers around intratumoral arterioles reflects malignant potential of gastric cancer

BACKGROUND

The role and clinical significance of the alteration of sympathetic nerve fibers (SNF) was assessed in gastric cancer. Loss of nerve fibers in malignant tumors has previously been described; however, how dysfunction of the nervous system is involved in cancer progression has not been clarified in clinical studies.

MATERIALS AND METHODS

The distribution of SNF was examined in 82 surgically resected gastric cancer specimens with immunohistochemical staining of tyrosine hydroxylase (TH), and the association with clinicopathological findings as well as the clinical outcome of the patients was retrospectively evaluated.

RESULTS

Arterioles in the normal gastric wall were totally covered with SNF, while the immunoreactivity to TH was markedly reduced around arterioles in cancer tissue. The degree of loss of SNF was significantly correlated with the depth of invasion (P < .0001) and lymph node metastasis (P < .0001) as well as microvessel density (MVD) (P = .0043). Moreover, patients who had tumors with marked loss of SNF showed a markedly worse clinical outcome, with an independent association by multivariate analysis.

CONCLUSIONS

Loss of periarteriolar SNF is associated with aggressive phenotype of gastric cancer possibly through enhanced angiogenesis and thus could be a useful marker to predict the clinical outcome.

Changes in vasoactive intestinal peptide, pituitary adenylate cyclase-activating polypeptide and neuropeptide Y-ergic structures of the enteric nervous system in the carcinoma of the human large intestine

This investigation was aimed at immunohistochemical analysis of potential changes in the enteric nervous system caused by cancer of the large intestine. In this purpose, neurons and nerve fibers of intestinal plexuses containing neuropeptides: vasoactive intestinal peptide (VIP), pituitary adenylate cyclase-activating polypeptide (PACAP) and neuropeptide Y (NPY), in pathologically changed part of the large intestine were microscpically observed and compared. Samples were taken from patients operated due to cancer of the sigmoid colon and rectum. The number of neurons and density of nerve fibres containing neuropeptides found in sections with cancer tissues were compared to those observed in sections from the uninvolved intestinal wall. Changes relating to reductions in the number of NPY-ergic neurons and density of nerve fibres in submucous and myenteric plexuses in the sections with cancer tissues (pathological sections) were statistically significant. A statistically similar presence of VIP-ergic and PACAP-ergic neurons in the submucosal and myenteric plexuses was observed in both the pathological and control sections. On the other hand, in the pathological sections, VIP-ergic nerve fibres in the myenteric plexuses and PACAP-ergic nerve fibres in the submucosal and myenteric plexuses were found to be less dense. Analysis revealed changes in pathologically affected part of the large intestine may caused disruption of proper intestinal function. Observed changes in the neural elements which are responsible for relaxation of the intestine may suggest dysfunction in the innervation of this part of the colon.

Tumor interactions with soluble factors and the nervous system

In the genomic era of cancer research, the development of metastases has been attributed to mutations in the tumor that enable the cells to migrate. However, gene analyses revealed that primary tumors and metastases were in some cases genetically identical and the question was raised whether metastasis formation might be an inherent feature of certain tumor cells. In contradiction to this view, the last decade of cancer research has brought to light, that tumor cell migration, similar to leukocyte and fibroblast migration, is a highly regulated process. The nervous system plays an important role in this regulation, at least in two respects: firstly, neurotransmitters are known to regulate the migratory activity of tumor cells, and secondly, nerve fibers are used as routes for perineural invasion. We also summarize here the current knowledge on the innervation of tumors. Such a process might establish a neuro-neoplastic synapse, with the close interaction of tumor cells and nerve cells supporting metastasis formation.

PC-3 prostate carcinoma cells release signal substances that influence the migratory activity of cells in the tumor's microenvironment

Background

Tumor cells interact with the cells of the microenvironment not only by cell-cell-contacts but also by the release of signal substances. These substances are known to induce tumor vascularization, especially under hypoxic conditions, but are also supposed to provoke other processes such as tumor innervation and inflammatory conditions. Inflammation is mediated by two organ systems, the neuroendocrine system and the immune system. Therefore, we investigated the influence of substances released by PC-3 human prostate carcinoma cells on SH-SY5Y neuroblastoma cells as well as neutrophil granulocytes and cytotoxic T lymphocytes, especially with regard to their migratory activity.

Results

PC-3 cells express several cytokines and growth factors including vascular endothelial growth factors, fibroblast growth factors, interleukins and neurotrophic factors. SH-SY5Y cells are impaired in their migratory activity by PC-3 cell culture supernatant, but orientate chemotactically towards the source. Neutrophil granulocytes increase their locomotory activity only in response to cell culture supernantant of hypoxic but not of normoxic PC-3 cells. In contrast, cytotoxic T lymphocytes do not change their migratory activity in response to either culture supernatant, but increase their cytotoxicity, whereas supernatant of normoxic PC-3 cells leads to a stronger increase than that of hypoxic PC-3 cells.

Conclusions

PC-3 cells release several signal substances that influence the behavior of the cells in the tumor's microenvironment, whereas no clear pattern towards proinflammatory or immunosuppressive conditions can be seen.

Chromogranin A-positive tumor cells in human esophageal squamous cell carcinomas

Gastrointestinal cancers have frequently shown neuroendocrine (NE) differentiation, but whether NE differentiation occurs in esophageal squamous cell carcinoma (ESCC) remains unclear. In this study, tissue sections obtained from 43 patients with ESCC from a high-incidence area of Northern China were used for the assessing of NE differentiation by immunohistochemistry using antibody against chromogranin A (CGA). In addition, the malignant characteristics and proliferation capacity of CGA-positive cells were also examined by immunohistochemistry. The clinicopathological significance of these CGA-positive tumor cells in ESCC was assessed. Of 43 ESCC samples, CGAimmunoreactive tumor cells were detected in 10 cases (23.26%). However, the CGA-positive tumor cells were scattered at a very low number among non-immunoreactive tumor cells and were rarely constituted a major part of cancer cell nests. Only 4.65% (2/43) cases showed a high density (>10 cells but <1% of total tumor cell mass) of CGA-positive tumor cells. P53 immunoreactivity was frequently shown, while Ki67 was hard to detect in these CGApositive cells. In addition, no relationship between CGA positivity rate and clinicopathological parameters was found. Thus, we concluded that lowdensity CGA-positive tumor cells can be detected in ESCC, supporting the notion that heterogeneous NE differentiation also exists in tumors that lack neuroendocrine cells in their normal epithelial counterparts.

Inhibition of axonal outgrowth in the tumor environment: involvement of class 3 semaphorins

That tumors lack innervation is dogma in the field of pathology, but the molecular determinants of this phenomenon remain elusive. We studied the effects of conditioned media from Colon 26 and B16 mouse tumor cell lines on the axonal outgrowth and cellular differentiation of embryonic Institute of Cancer Research (ICR) mouse dorsal root ganglion cells. Tumor-conditioned media suppressed dorsal root ganglion axonal extension but had no effect on neuronal or glial differentiation. We found that the tumor cells expressed most of the class 3 semaphorins - axon guidance molecules. Blocking the activity of class 3 semaphorins with the soluble receptor neuropilin-1 significantly counteracted the tumor-induced inhibition of axonal extension. Together, these results suggest a role for tumor-secreted class 3 semaphorins in selectively inhibiting axonal outgrowth of dorsal root ganglion neurons.

Tumor immune escape mechanisms: impact of the neuroendocrine system

Tumor cells act upon, and react to both their proximate and more distant environment, the mechanisms by which this is achieved being both autocrine and paracrine in nature. This interaction, however, takes place not only between adjacent malignant cells, but also non-malignant cells such as those of the immune system, the latter also partaking in the modeling of the tumor environment. Although tumor cells descend from normal tissue cells and thus bear in classical immunological terms 'self signals', it is evident that the immune system is able to recognize tumor cells as a harassment for the body and in consequence tries to eliminate these cells. On the counterpart, tumor cells acquire various characteristics which allow them to evade this immunological surveillance, and have been collectively coined with the term "tumor escape mechanisms". This review will describe and summarize current understanding of tumor escape strategies, and also more closely elaborate on the modulatory role of the neuroendocrine system in the immune system-tumor cell interaction.

Tumour-cell migration, invasion, and metastasis: navigation by neurotransmitters

Cancer starts as a localised disease, which, if detected early, can often be treated successfully by removal of the primary tumour. A pernicious progression is the invasion of tumour cells into surrounding tissues, resulting in development of distant metastases. Because active migration of tumour cells is a prerequisite for tumour-cell invasion and metastasis, a pressing goal in tumour biology has been the elucidation of factors regulating the migratory activity of these cells. The most prominent regulatory factors are ligands to serpentine receptors-eg, chemokines and neurotransmitters. Many types of neurotransmitter receptors are expressed on tumour cells, supporting the theory that psychosocial factors are involved in the progression of cancer. Understanding how such receptors regulate migration and the availability of specific receptor antagonists could open up new avenues for chemoprevention of tumour-cell migration and metastatic development.