Capsaicin-induced inactivation of sensory neurons promotes a more aggressive gene expression phenotype in breast cancer cells

Striated muscle: an inadequate soil for cancers

Many organs of the body are susceptible to cancer development. However, striated muscles-which include skeletal and cardiac muscles-are rarely the sites of primary cancers. Most deaths from cancer arise due to complications associated with the development of secondary metastatic tumours, for which there are few effective therapies. However, as with primary cancers, the establishment of metastatic tumours in striated muscle accounts for a disproportionately small fraction of secondary tumours, relative to the proportion of body composition. Examining why primary and metastatic cancers are comparatively rare in striated muscle presents an opportunity to better understand mechanisms that can influence cancer cell biology. To gain insights into the incidence and distribution of muscle metastases, this review presents a definitive summary of the 210 case studies of metastasis in muscle published since 2010. To examine why metastases rarely form in muscles, this review considers the mechanisms currently proposed to render muscle an inhospitable environment for cancers. The "seed and soil" hypothesis proposes that tissues' differences in susceptibility to metastatic colonization are due to differing host microenvironments that promote or suppress metastatic growth to varying degrees. As such, the "soil" within muscle may not be conducive to cancer growth. Gaining a greater understanding of the mechanisms that underpin the resistance of muscles to cancer may provide new insights into mechanisms of tumour growth and progression, and offer opportunities to leverage insights into the development of interventions with the potential to inhibit metastasis in susceptible tissues.

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

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

From pain to tumor immunity: influence of peripheral sensory neurons in cancer

The nervous and immune systems are the primary sensory interfaces of the body, allowing it to recognize, process, and respond to various stimuli from both the external and internal environment. These systems work in concert through various mechanisms of neuro-immune crosstalk to detect threats, provide defense against pathogens, and maintain or restore homeostasis, but can also contribute to the development of diseases. Among peripheral sensory neurons (PSNs), nociceptive PSNs are of particular interest. They possess a remarkable capability to detect noxious stimuli in the periphery and transmit this information to the brain, resulting in the perception of pain and the activation of adaptive responses. Pain is an early symptom of cancer, often leading to its diagnosis, but it is also a major source of distress for patients as the disease progresses. In this review, we aim to provide an overview of the mechanisms within tumors that are likely to induce cancer pain, exploring a range of factors from etiological elements to cellular and molecular mediators. In addition to transmitting sensory information to the central nervous system, PSNs are also capable, when activated, to produce and release neuropeptides (e.g., CGRP and SP) from their peripheral terminals. These neuropeptides have been shown to modulate immunity in cases of inflammation, infection, and cancer. PSNs, often found within solid tumors, are likely to play a significant role in the tumor microenvironment, potentially influencing both tumor growth and anti-tumor immune responses. In this review, we discuss the current state of knowledge about the degree of sensory innervation in tumors. We also seek to understand whether and how PSNs may influence the tumor growth and associated anti-tumor immunity in different mouse models of cancer. Finally, we discuss the extent to which the tumor is able to influence the development and functions of the PSNs that innervate it.

Targeting TRPV1 for Cancer Pain Relief: Can It Work?

Chronic intractable pain affects a large proportion of cancer patients, especially those with metastatic bone disease. Blocking sensory afferents for cancer pain relief represents an attractive alternative to opioids and other drugs acting in the CNS in that sensory nerve blockers are not addictive and do not affect the mental state of the patient. A distinct subpopulation of sensory afferents expresses the capsaicin receptor TRPV1. Intrathecal resiniferatoxin, an ultrapotent capsaicin analog, ablates TRPV1-expressing nerve endings exposed to the cerebrospinal fluid, resulting in permanent analgesia in women with cervical cancer metastasis to the pelvic bone. High-dose capsaicin patches are effective pain killers in patients with chemotherapy-induced peripheral neuropathic pain. However, large gaps remain in our knowledge since the mechanisms by which cancer activates TRPV1 are essentially unknown. Most important, it is not clear whether or not sensory denervation mediated by TRPV1 agonists affects cancer progression. In a murine model of breast cancer, capsaicin desensitization was reported to accelerate progression. By contrast, desensitization mediated by resiniferatoxin was found to block melanoma growth. These observations imply that TRPV1 blockade for pain relief may be indicated for some cancers and contraindicated for others. In this review, we explore the current state of this field and compare the analgesic potential of TRPV1 antagonism and sensory afferent desensitization in cancer patients.

Cerebral cavernous malformation proteins, CCM1, CCM2 and CCM3, are decreased in metastatic lesions in a murine breast carcinoma model

Three genes are associated with cerebral cavernous malformations (CCMs): CCM1, CCM2 and CCM3. These genes participate in microvascular angiogenesis, cell-to-cell junctions, migration and apoptosis. We evaluated the expression in vivo of CCM genes in primary tumors and metastastases in a murine model of metastatic breast carcinoma. We used cell lines obtained from metastasis of 4T1, 4TLM and 4THM breast cancer to liver and heart. These cells were injected into the mammary ridge of Balb/C female mice. After 27 days, the primary tumors, liver and lung were removed and CCM proteins were assessed using immunohistochemistry and western blot analysis. CCM proteins were expressed in primary tumor tissues of all tumor-injected animals; however, no CCM protein was expressed in metastatic tumor cells that migrated into other tissues. CCM proteins still were observed in the lung and liver tissue cells. Our findings suggest that CCM proteins are present during primary tumor formation, but when these cells develop metastatic potential, they lose CCM protein expression. CCM protein expression was lost or reduced in metastatic tissues compared to the primary tumor, which indicates that CCM proteins might participate in tumorigenesis and metastasis.

ADAM10 and Neprilysin level decreases in immune cells of mice bearing metastatic breast carcinoma: Possible role in cancer inflammatory response

OBJECTIVE AND DESIGN

ADAM10 and Neprilysin, proteases, play critical role in inflammatory disease, however their role in cancer immune response is not clear. We here evaluated changes in immune response using an experimental model for breast cancer.

MATERIAL AND METHOD

Highly metastatic breast cancer cells (4T1-derived) were injected orthotopically (mammary-pad of Balb-c mice) to induce tumors. Changes in enzyme level and activity as well as alterations in inflammatory cytokine release in the presence or absence of ADAM10 and NEP activity was determined using specific inhibitors and recombinant proteins. Cytokine response was evaluated using mix leucocyte cultures obtained from control and tumor-bearing mice. ANOVA with Dunnett's posttest was used for statistical analysis.

RESULTS

ADAM10 and NEP expression was decreased markedly in lymph nodes and spleens of tumor-bearing mice. ADAM10 activity was reduced together with apparent alterations of ADAM10 processing. ADAM10 and NEP activity decreased TNF-α, IL-6 and IFN-ɣ secretion. Suppression of these inflammatory cytokines were more prominent in cultures obtained from control mice demonstrating counteracting factors that are exist in tumor-bearing mice.

CONCLUSION

Loss of ADAM10 and NEP activity in immune cells during breast cancer metastasis might be one of the main factors involved in induction of chronic inflammation by tumors.

Progress in cancer neuroscience

Cancer of the central nervous system (CNS) can crosstalk systemically and locally in the tumor microenvironment and has become a topic of attention for tumor initiation and advancement. Recently studied neuronal and cancer interaction fundamentally altered the knowledge about glioma and metastases, indicating how cancers invade complex neuronal networks. This review systematically discussed the interactions between neurons and cancers and elucidates new therapeutic avenues. We have overviewed the current understanding of direct or indirect communications of neuronal cells with cancer and the mechanisms associated with cancer invasion. Besides, tumor-associated neuronal dysfunction and the influence of cancer therapies on the CNS are highlighted. Furthermore, interactions between peripheral nervous system and various cancers have also been discussed separately. Intriguingly and importantly, it cannot be ignored that exosomes could mediate the "wireless communications" between nervous system and cancer. Finally, promising future strategies targeting neuronal-brain tumor interactions were reviewed. A great deal of work remains to be done to elucidate the neuroscience of cancer, and future more research should be directed toward clarifying the precise mechanisms of cancer neuroscience, which hold enormous promise to improve outcomes for a wide range of malignancies.

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.

Radical Tumor Denervation Activates Potent Local and Global Cancer Treatment

This preliminary study seeks to determine the effect of R&P denervation on tumor growth and survival in immunocompetent rats bearing an aggressive and metastatic breast solid tumor. A novel microsurgical approach was applied "in situ", aiming to induce R&P denervation through the division of every single nerve fiber connecting the host with the primary tumor via its complete detachment and re-attachment, by resecting and reconnecting its supplying artery and vein (anastomosis). This preparation, known as microsurgical graft or flap, is radically denervated by definition, but also effectively delays or even impedes the return of innervation for a significant period of time, thus creating a critical and therapeutic time window. Mammary adenocarcinoma cells (HH-16.cl4) were injected into immunocompetent Sprague Dawley adult rats. When the tumors reached a certain volume, the subjects entered the study. The primary tumor, including a substantial amount of peritumoral tissue, was surgically isolated on a dominant artery and vein, which was resected and reconnected using a surgical microscope (orthotopic tumor auto-transplantation). Intending to simulate metastasis, two or three tumors were simultaneously implanted and only one was treated, using the surgical technique described herein. Primary tumor regression was observed in all of the microsurgically treated subjects, associated with a potent systemic anticancer effect and prolonged survival. In stark contrast, the subjects received a close to identical surgical operation; however, with the intact neurovascular connection, they did not achieve the therapeutic result. Animals bearing multiple tumors and receiving the same treatment in only one tumor exhibited regression in both the "primary" and remote- untreated tumors at a clinically significant percentage, with regression occurring in more than half of the treated subjects. A novel therapeutic approach is presented, which induces the permanent regression of primary and, notably, remote tumors, as well as, evidently, the naturally occurring metastatic lesions, at a high rate. This strategy is aligned with the impetus that comes from the current translational research data, focusing on the abrogation of the neuro-tumoral interaction as an alternative treatment strategy. More data regarding the clinical significance of this are expected to come up from a pilot clinical trial that is ongoing.

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

Background

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

Methods

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

Results

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

Conclusion

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

Carcinogenesis and Metastasis: Focus on TRPV1-Positive Neurons and Immune Cells

Both sensory neurons and immune cells, albeit at markedly different levels, express the vanilloid (capsaicin) receptor, Transient Receptor Potential, Vanilloid-1 (TRPV1). Activation of TRPV1 channels in sensory afferent nerve fibers induces local effector functions by releasing neuropeptides (most notably, substance P) which, in turn, trigger neurogenic inflammation. There is good evidence that chronic activation or inactivation of this inflammatory pathway can modify tumor growth and metastasis. TRPV1 expression was also demonstrated in a variety of mammalian immune cells, including lymphocytes, dendritic cells, macrophages and neutrophils. Therefore, the effects of TRPV1 agonists and antagonists may vary depending on the prominent cell type(s) activated and/or inhibited. Therefore, a comprehensive understanding of TRPV1 activity on immune cells and nerve endings in distinct locations is necessary to predict the outcome of therapies targeting TRPV1 channels. Here, we review the neuro-immune modulation of cancer growth and metastasis, with focus on the consequences of TRPV1 activation in nerve fibers and immune cells. Lastly, the potential use of TRPV1 modulators in cancer therapy is discussed.

The neuroscience of cancer

The nervous system regulates tissue stem and precursor populations throughout life. Parallel to roles in development, the nervous system is emerging as a critical regulator of cancer, from oncogenesis to malignant growth and metastatic spread. Various preclinical models in a range of malignancies have demonstrated that nervous system activity can control cancer initiation and powerfully influence cancer progression and metastasis. Just as the nervous system can regulate cancer progression, cancer also remodels and hijacks nervous system structure and function. Interactions between the nervous system and cancer occur both in the local tumour microenvironment and systemically. Neurons and glial cells communicate directly with malignant cells in the tumour microenvironment through paracrine factors and, in some cases, through neuron-to-cancer cell synapses. Additionally, indirect interactions occur at a distance through circulating signals and through influences on immune cell trafficking and function. Such cross-talk among the nervous system, immune system and cancer-both systemically and in the local tumour microenvironment-regulates pro-tumour inflammation and anti-cancer immunity. Elucidating the neuroscience of cancer, which calls for interdisciplinary collaboration among the fields of neuroscience, developmental biology, immunology and cancer biology, may advance effective therapies for many of the most difficult to treat malignancies.

Capsaicin shapes gut microbiota and pre-metastatic niche to facilitate cancer metastasis to liver

Dietary factors are fundamental in tumorigenesis throughout our lifetime. A spicy diet has been ambiguous on the development of cancers, especially in the study of colon cancer metastasis. Here, we utilized a mouse metastasis model to test the potential role of capsaicin in influencing metastasis. Long-term continuous administration of capsaicin diet (300 mg/kg) to mice promotes the formation of liver pre-metastatic niche to facilitate the metastasis of colon cancer cells. Bacteria translocation to liver is clearly observed. Capsaicin increases intestinal barrier permeability and disrupts gut vascular barrier by altering the composition of gut microbiota. Capsaicin not only changes the abundance of mucin-related bacteria like Akkermanisa and Muribaculaceae, but also bacteria involved in bile acids metabolism. Dysregulated bile acids profile is related to the recruitment of natural killer T (NKT) cells in pre-metastatic niche, primary bile acid α-Muricholic acid can enhance the recruitment of NKT cells, while secondary bile acids Glycoursodeoxycholic acid and Taurohyodeoxycholic acid impair the recruitment of NKT cells. These findings reveal long term consumption of capsaicin increases the risk of cancer metastasis through modulating the gut microbiota. Capsaicin (300 mg/kg) disrupts gut barrier and promotes the translocation of bacteria to liver, while altered bile acids metabolism affects the recruitment of NKT cells in liver, forming a pre-metastatic niche and promoting cancer metastasis.

Tissue-resident glial cells associate with tumoral vasculature and promote cancer progression

Cancer cells are embedded within the tissue and interact dynamically with its components during cancer progression. Understanding the contribution of cellular components within the tumor microenvironment is crucial for the success of therapeutic applications. Here, we reveal the presence of perivascular GFAP+/Plp1+ cells within the tumor microenvironment. Using in vivo inducible Cre/loxP mediated systems, we demonstrated that these cells derive from tissue-resident Schwann cells. Genetic ablation of endogenous Schwann cells slowed down tumor growth and angiogenesis. Schwann cell-specific depletion also induced a boost in the immune surveillance by increasing tumor-infiltrating anti-tumor lymphocytes, while reducing immune-suppressor cells. In humans, a retrospective in silico analysis of tumor biopsies revealed that increased expression of Schwann cell-related genes within melanoma was associated with improved survival. Collectively, our study suggests that Schwann cells regulate tumor progression, indicating that manipulation of Schwann cells may provide a valuable tool to improve cancer patients' outcomes.

Anti-cancer activity of sustained release capsaicin formulations

Capsaicin (trans-8-methyl-N-vanillyl-6-noneamide) is a hydrophobic, lipophilic vanilloid phytochemical abundantly found in chili peppers and pepper extracts. Several convergent studies show that capsaicin displays robust cancer activity, suppressing the growth, angiogenesis and metastasis of several human cancers. Despite its potent cancer-suppressing activity, the clinical applications of capsaicin as a viable anti-cancer drug have remained problematic due to its poor bioavailability and aqueous solubility properties. In addition, the administration of capsaicin is associated with adverse side effects like gastrointestinal cramps, stomach pain, nausea and diarrhea and vomiting. All these hurdles may be circumvented by encapsulation of capsaicin in sustained release drug delivery systems. Most of the capsaicin-based the sustained release drugs have been tested for their pain-relieving activity. Only a few of these formulations have been investigated as anti-cancer agents. The present review describes the physicochemical properties, bioavailability, and anti-cancer activity of capsaicin-sustained release agents. The asset of such continuous release capsaicin formulations is that they display better solubility, stability, bioavailability, and growth-suppressive activity than the free drug. The encapsulation of capsaicin in sustained release carriers minimizes the adverse side effects of capsaicin. In summary, these capsaicin-based sustained release drug delivery systems have the potential to function as novel chemotherapies, unique diagnostic imaging probes and innovative chemosensitization agents in human cancers.

Regulation of Carcinogenesis by Sensory Neurons and Neuromediators

Simple Summary

Sensory nerve fibers extensively innervate the entire body. They are the first to sense danger signals, including the ones coming from newly formed cancer cells. Various studies have demonstrated that the inactivation of sensory nerve fibers as well as the vagus nerve enhances tumor growth and spread in models including breast, pancreatic, and gastric cancer. On the other hand, there are also contradictory findings that show the opposite, namely that the inactivation of nerve fibers inhibits tumor growth. These discrepancies are likely caused by the stage and the level of aggressiveness of the tumor model used. Hence, further studies are required to determine the factors involved in neuro-immunological mechanisms of tumor growth and spread.

Abstract

Interactions between the immune system and the nervous system are crucial in maintaining homeostasis, and disturbances of these neuro-immune interactions may participate in carcinogenesis and metastasis. Nerve endings have been identified within solid tumors in humans and experimental animals. Although the involvement of the efferent sympathetic and parasympathetic innervation in carcinogenesis has been extensively investigated, the role of the afferent sensory neurons and the neuropeptides in tumor development, growth, and progression is recently appreciated. Similarly, current findings point to the significant role of Schwann cells as part of neuro-immune interactions. Hence, in this review, we mainly focus on local and systemic effects of sensory nerve activity as well as Schwann cells in carcinogenesis and metastasis. Specific denervation of vagal sensory nerve fibers, or vagotomy, in animal models, has been reported to markedly increase lung metastases of breast carcinoma as well as pancreatic and gastric tumor growth, with the formation of liver metastases demonstrating the protective role of vagal sensory fibers against cancer. Clinical studies have revealed that patients with gastric ulcers who have undergone a vagotomy have a greater risk of stomach, colorectal, biliary tract, and lung cancers. Protective effects of vagal activity have also been documented by epidemiological studies demonstrating that high vagal activity predicts longer survival rates in patients with colon, non-small cell lung, prostate, and breast cancers. However, several studies have reported that inhibition of sensory neuronal activity reduces the development of solid tumors, including prostate, gastric, pancreatic, head and neck, cervical, ovarian, and skin cancers. These contradictory findings are likely to be due to the post-nerve injury-induced activation of systemic sensory fibers, the level of aggressiveness of the tumor model used, and the local heterogeneity of sensory fibers. As the aggressiveness of the tumor model and the level of the inflammatory response increase, the protective role of sensory nerve fibers is apparent and might be mostly due to systemic alterations in the neuro-immune response. Hence, more insights into inductive and permissive mechanisms, such as systemic, cellular neuro-immunological mechanisms of carcinogenesis and metastasis formation, are needed to understand the role of sensory neurons in tumor growth and spread.

Olvanil activates sensory nerve fibers, increases T cell response and decreases metastasis of breast carcinoma

BACKGROUND

Inactivation of sensory neurons expressing transient receptor potential vanilloid 1 (TRPV1) enhances breast cancer metastasis. Sensory neurons have profound effects on immune response to a wide range of diseases including cancer. Hence, activation of sensory nerves using feasible approaches such as specific TRPV1 agonists may inhibit breast cancer metastasis through neuroimmune pathways. TRPV1 agonists are considered for the treatment of pain and inflammatory diseases.

METHODS

We here first determined the effects of four different TRPV1 agonists on proliferation of three different metastatic breast carcinoma cells since TRPV1 is also expressed in cancer cells. Based on the results obtained under in-vitro conditions, brain metastatic breast carcinoma cells (4TBM) implanted orthotopically into the mammary-pad of Balb-c mice followed by olvanil treatment (i.p.). Changes in tumor growth, metastasis and immune response to cancer cells were determined.

RESULTS

Olvanil dose-dependently activated sensory nerve fibers and markedly suppressed lung and liver metastasis without altering the growth of primary tumors. Olvanil (5 mg/kg) systemically increased T cell count, enhanced intra-tumoral recruitment of CD8+ T cells and increased IFN-γ response to irradiated cancer cells and Con-A. Anti-inflammatory changes such as increased IL-10 and decrease IL-6 as well as S100A8+ cells were observed following olvanil treatment.

CONCLUSIONS

Our results show that anti-metastatic effects of olvanil is mainly due to activation of neuro-immune pathways since olvanil dose used here is not high enough to directly activate immune cells. Furthermore, olvanil effectively depletes sensory neuropeptides; hence, olvanil is a good non-pungent alternative to capsaicin.

Neurobiology of cancer: Definition, historical overview, and clinical implications

Studies published in the last two decades have clearly demonstrated that the nervous system plays a significant role in carcinogenesis, the progression of cancer, and the development of metastases. These studies, combining oncological and neuroscientific approaches, created the basis for the emergence of a new field in oncology research, the so‐called “neurobiology of cancer.” The concept of the neurobiology of cancer is based on several facts: (a) psychosocial factors influence the incidence and progression of cancer diseases; (b) the nervous system affects DNA mutations and oncogene‐related signaling; (c) the nervous system modulates tumor‐related immune responses; (d) tumor tissues are innervated; (e) neurotransmitters released from nerves innervating tumor tissues affect tumor growth and metastasis; (f) alterations or modulation of nervous system activity affects the incidence and progression of cancers; (g) tumor tissue affects the nervous system. The aim of this review is to characterize the pillars that create the basis of cancer neurobiology, to describe recent research advances of the nervous system's role in cancer diseases, and to depict potential clinical implications for oncology.

Effects of in-vitro modulation of TRPV1 activity on immune response of mice bearing metastatic breast carcinoma: Enhanced inflammatory response may hinder therapeutic potentials of TRPV1 agonists

AIMS

Activation of transient receptor potential vanilloid 1 (TRPV1) ion channels inhibits inflammation, enhance cytotoxic immune response, and may have therapeutic potential in treatment of cancer characterized by increased systemic inflammation. We here determined how activation of TRPV1 alters immune response of tumor-bearing mice.

MAIN METHODS

Three different metastatic subset of 4 T1 breast carcinoma cells were used to induce tumors in Balb-c mice. Mix leukocyte cultures (MLCs) using spleens and draining lymph nodes were prepared and stimulated with various challenges. Effects TRPV1 agonists including capsaicin, antagonist (AMG9810) and Gambogic Amide (GA), a TrkA agonist that sensitizes TRPV1, on secreted levels of cytokines were determined.

KEY FINDINGS

MLCs of tumor-bearing mice secreted markedly higher levels of IL-6 and lower levels of IFN-γ compared to control mice. We observed differential effects of TRPV1 agonists in control and mice bearing different subset of metastatic cells. TRPV1 increased IFN-γ and IL-17 secretion in control mice while they markedly increased IL-6 secretion and suppressed IFN--γ secretion in tumor-bearing mice. Unexpectedly, AMG9810 acted as an inverse agonist and did not antagonize the effects of TRPV1 agonists.

SIGNIFICANCE

Our results demonstrate constitutive activity of TRPV1 in immune cells, suggesting cross activation. To prevent excessive chronic activation of TRPV1 in immune cells in the presence of metastatic breast carcinoma, lower doses of TRPV1 agonist should be considered. Unexpected findings further document that a drug can have multiple intrinsic activities depending on surrounding factors can act on the same receptor as an agonist, antagonist or inverse agonist.

Chemogenetic modulation of sensory neurons reveals their regulating role in melanoma progression

Sensory neurons have recently emerged as components of the tumor microenvironment. Nevertheless, whether sensory neuronal activity is important for tumor progression remains unknown. Here we used Designer Receptors Exclusively Activated by a Designer Drug (DREADD) technology to inhibit or activate sensory neurons' firing within the melanoma tumor. Melanoma growth and angiogenesis were accelerated following inhibition of sensory neurons' activity and were reduced following overstimulation of these neurons. Sensory neuron-specific overactivation also induced a boost in the immune surveillance by increasing tumor-infiltrating anti-tumor lymphocytes, while reducing immune-suppressor cells. In humans, a retrospective in silico analysis of melanoma biopsies revealed that increased expression of sensory neurons-related genes within melanoma was associated with improved survival. These findings suggest that sensory innervations regulate melanoma progression, indicating that manipulation of sensory neurons' activity may provide a valuable tool to improve melanoma patients' outcomes.

Desensitization of Capsaicin-Sensitive Afferents Accelerates Early Tumor Growth via Increased Vascular Leakage in a Murine Model of Triple Negative Breast Cancer

There is growing interest in the role of nerve-driven mechanisms in tumorigenesis and tumor growth. Capsaicin-sensitive afferents have been previously shown to possess antitumoral and immune-regulatory properties, the mechanism of which is currently poorly understood. In this study, we have assessed the role of these terminals in the triple negative 4T1 orthotopic mouse model of breast cancer. The ultrapotent capsaicin-analogue resiniferatoxin (RTX) was used for the selective, systemic desensitization of capsaicin-sensitive afferents. Growth and viability of orthotopically implanted 4T1 tumors were measured by caliper, in vivo MRI, and bioluminescence imaging, while tumor vascularity and protease enzyme activity were assessed using fluorescent in vivo imaging. The levels of the neuropeptides Calcitonin Gene-Related Peptide (CGRP), Substance P (SP), and somatostatin were measured from tumor tissue homogenates using radioimmunoassay, while tumor structure and peritumoral inflammation were evaluated by conventional use of CD31, CD45 and CD3 immunohistology. RTX-pretreated mice demonstrated facilitated tumor growth in the early phase measured using a caliper, which was coupled with increased tumor vascular leakage demonstrated using fluorescent vascular imaging. The tumor size difference dissipated by day seven. The MRI tumor volume was similar, while the intratumoral protease enzyme activity measured by fluorescence imaging was also comparable in RTX-pretreated and non-pretreated animals. Tumor viability or immunohistopathological profile was measured using CD3, CD31, and CD45 stains and did not differ significantly from the non-pretreated control group. Intratumoral somatostatin, CGRP, and SP levels were similar in both groups. Our results underscore the beneficial, antitumoral properties of capsaicin sensitive nerve terminals in this aggressive model of breast cancer, which is presumed to be due to the inhibition of tumor vascular bed disruption. The absence of any difference in intratumoral neuropeptide levels indicates non-neural sources playing a substantial part in their expression.

A Holistic Perspective: Exosomes Shuttle between Nerves and Immune Cells in the Tumor Microenvironment

One of the limitations of cancer research has been the restricted focus on tumor cells and the omission of other non-malignant cells that are constitutive elements of this systemic disease. Current research is focused on the bidirectional communication between tumor cells and other components of the tumor microenvironment (TME), such as immune and endothelial cells, and nerves. A major success of this bidirectional approach has been the development of immunotherapy. Recently, a more complex landscape involving a multi-lateral communication between the non-malignant components of the TME started to emerge. A prime example is the interplay between immune and endothelial cells, which led to the approval of anti-vascular endothelial growth factor-therapy combined with immune checkpoint inhibitors and classical chemotherapy in non-small cell lung cancer. Hence, a paradigm shift approach is to characterize the crosstalk between different non-malignant components of the TME and understand their role in tumorigenesis. In this perspective, we discuss the interplay between nerves and immune cells within the TME. In particular, we focus on exosomes and microRNAs as a systemic, rapid and dynamic communication channel between tumor cells, nerves and immune cells contributing to cancer progression. Finally, we discuss how combinatorial therapies blocking this tumorigenic cross-talk could lead to improved outcomes for cancer patients.

Sympathetic and parasympathetic innervation in cancer: therapeutic implications

PURPOSE

The autonomic nervous system, consisting of sympathetic and parasympathetic/vagal nerves, is known to control the functions of any organ, maintaining whole-body homeostasis under physiological conditions. Recently, there has been increasing evidence linking sympathetic and parasympathetic/vagal nerves to cancers. The present review aimed to summarize recent developments from studies addressing the relationship between sympathetic and parasympathetic/vagal nerves and cancer behavior.

METHODS

Literature review.

RESULTS

Human and animal studies have revealed that sympathetic and parasympathetic/vagal nerves innervate the cancer microenvironment and alter cancer behavior. The sympathetic nerves have cancer-promoting effects on prostate cancer, breast cancer, and melanoma. On the other hand, while the parasympathetic/vagal nerves have cancer-promoting effects on prostate, gastric, and colorectal cancers, they have cancer-suppressing effects on breast and pancreatic cancers. These neural effects may be mediated by β-adrenergic or muscarinic receptors and can be explained by changes in cancer cell behavior, angiogenesis, tumor-associated macrophages, and adaptive antitumor immunity.

CONCLUSIONS

Sympathetic nerves innervating the tumor microenvironment promote cancer progression and are related to stress-induced cancer behavior. The parasympathetic/vagal nerves have variable (promoting or suppressing) effects on different cancer types. Approaches directed toward the sympathetic and parasympathetic/vagal nerves can be developed as a new cancer therapy. In addition to existing pharmacological, surgical, and electrical approaches, a recently developed virus vector-based genetic local neuroengineering technology is a powerful approach that selectively manipulates specific types of nerve fibers innervating the cancer microenvironment and leads to the suppression of cancer progression. This technology will enable the creation of "cancer neural therapy" individually tailored to different cancer types.

Role of the parasympathetic nervous system in cancer initiation and progression

The nervous system plays an important role in cancer initiation and progression. Accumulated evidences clearly show that the sympathetic nervous system exerts stimulatory effects on carcinogenesis and cancer growth. However, the role of the parasympathetic nervous system in cancer has been much less elucidated. Whereas retrospective studies in vagotomized patients and experiments employing vagotomized animals indicate the parasympathetic nervous system has an inhibitory effect on cancer, clinical studies in patients with prostate cancer indicate it has stimulatory effects. Therefore, the aim of this paper is a critical evaluation of the available data related to the role of the parasympathetic nervous system in cancer.

New insight into the role of substance P/neurokinin-1 receptor system in breast cancer progression and its crosstalk with microRNAs

The neuropeptide substance P (SP) triggers a variety of tumor-promoting signaling pathways through the activation of neurokinin-1receptor (NK1R), a class of neurokinin G protein-coupled receptors superfamily. Recent researches in our and other laboratories have shown the overexpression of both SP and NK1R in breast cancer (BC) patients. SP/NK1R signaling is strongly implicated in the pathogenesis of BC through affecting cell proliferation, migration, metastasis, angiogenesis, and resistance. Therefore, SP/NK1R signaling responses must be rigorously regulated; otherwise, they would contribute to a more aggressive BC phenotype. Recently, microRNAs (miRNAs) as a specific class of epigenetic regulators have been shown to regulate NK1R and thus, controlling SP/NK1R signaling responses in BC. This review summarizes the current knowledge of the role of SP/NK1R signaling and its therapeutic potentials in BC. We also provide an overview regarding the effects of miRNA-mediated NK1R regulatory mechanisms in controlling BC tumorigenesis to gain a clearer view and thus better management of cancer.

Nerves in cancer

The contribution of nerves to the pathogenesis of malignancies has emerged as an important component of the tumour microenvironment. Recent studies have shown that peripheral nerves (sympathetic, parasympathetic and sensory) interact with tumour and stromal cells to promote the initiation and progression of a variety of solid and haematological malignancies. Furthermore, new evidence suggests that cancers may reactivate nerve-dependent developmental and regenerative processes to promote their growth and survival. Here we review emerging concepts and discuss the therapeutic implications of manipulating nerves and neural signalling for the prevention and treatment of cancer.

Role of sensory neurons, neuroimmune pathways, and transient receptor potential vanilloid 1 (TRPV1) channels in a murine model of breast cancer metastasis

Sensory nerves sensitive to capsaicin are afferent nerve fibers which contain TRPV1 channels. Activation of these channels induces release of neuropeptides which regulate local blood flow and immune response. Inactivation of sensory neurons either with high-dose capsaicin treatment or local ablation of vagal sensory nerve activity markedly increases metastasis of breast carcinoma formed by 4T1 derivative cells. These cancer cells also induce an extensive systemic inflammatory response. Further findings have documented that lack of local sensory neuromediators alters phenotype of cancer cells within primary tumor leading to overgrowth of metastatic subsets. This might be due to decreases in local and systemic immune response to growing tumor. Specifically, Substance P, one of the most abundant sensory neuropeptides, enhances anti-tumoral immune response evoked by radiotherapy under in vivo conditions. These findings further suggest that activation of TRPV1 channels on sensory neurons may induce an anti-tumoral immune response. We are testing this hypothesis. Our initial results as reported here demonstrate anti-inflammatory consequences of low-dose systemic capsaicin treatment. In conclusion, sensory nerve fibers sensitive to capsaicin have important roles in defense against metastatic breast carcinoma; hence, controlled activation of these neural pathways might be effective in cancer therapy. Specifically, activation of sensory fibers of left vagus nerve using a perineuronal stimulation may inhibit metastasis of breast carcinoma. Likewise, pharmacological modulators of TRPV1 channels may induce anti-tumoral immune response. Exact players of this newly explored defense system are, however, only partly validated, and further studies are required.

Capsaicinoids: Multiple effects on angiogenesis, invasion and metastasis in human cancers

Cancer progression is a complex multistep process comprising of angiogenesis of the primary tumor, its invasion into the surrounding stroma and its migration to distant organs to produce metastases. Nutritional compounds of the "capsaicinoid" family regulate angiogenesis, invasion and metastasis of tumors. Capsaicinoids display robust anti-angiogenic activity in both cell culture and mice models. However, conflicting reports exist about the effect of capsaicinoids on invasion of metastasis of cancers. While some published reports have described an anti-invasive and anti-metastatic role for capsaicinoids, others have argued that capsaicinoids stimulate invasion and metastasis of cancers. The present review article summarizes these findings involving the bioactivity of capsaicin in angiogenesis, invasion and metastasis of cancer. A survey of literature indicate that they are several articles summarizing the growth-inhibitory activity of capsaicinoids but few describe its effects on angiogenesis, invasion and metastasis in detail. Our review article fills this gap of knowledge. The discovery of a second generation of natural and synthetic capsaicin analogs (with anti-tumor activity) will pave the way to improved strategies for the treatment of several human cancers.

HSP90 inhibitor PU-H71 increases radiosensitivity of breast cancer cells metastasized to visceral organs and alters the levels of inflammatory mediators

Heat shock protein 90 (HSP90) inhibitors are considered as new radiosensitizing agents. PU-H71, a novel HSP90 inhibitor, is under evaluation for the treatment of advanced cancer. It is however not known whether PU-H71 alters radiosensitivity of metastatic breast cancer. Hence, we here evaluated mechanisms of possible anti-tumoral and radiosensitizing effects of PU-H71 on breast carcinoma cells metastasized to vital organs such as the liver and brain. The effect of PU-H71 on proliferation of breast carcinoma cells was determined using 4T1 cells and its brain (4TBM), liver (4TLM), and heart (4THM) metastatic subsets as well as non-metastatic 67NR cells. Changes in radiation sensitivity were determined by clonogenic assays. Changes in client proteins and levels of angiogenic and inflammatory mediators from these cancer cell cultures and ex vivo cultures were detected. PU-H71 alone inhibited ERK1/2, p38, and Akt activation and reduced N-cadherin and HER2 which further documented the anti-tumoral effects of PU-H71. The combination of PU-H71 and radiotherapy induced cytotoxic effect than PU-H71 alone, and PU-H71 showed a radiosensitizing effect in vitro. On the other hand, PU-H71 and radiation co-treatment increased p38 phosphorylation which is one of the hallmarks of inflammatory response. Accordingly, IL-6 secretion was increased following PU-H71 and radiotherapy co-treatment ex vivo. Levels of angiogenic and inflammatory factors such as MIP-2, SDF-1, and VEGF were increased under in vitro conditions but not under ex vivo conditions. These results demonstrated for the first time that PU-H71 enhances therapeutic effects of radiotherapy especially in highly metastatic breast carcinoma but a possible increase in inflammatory response should also be considered.

Capsaicinoids enhance chemosensitivity to chemotherapeutic drugs

Cytotoxic chemotherapy is the mainstay of cancer treatment. Conventional chemotherapeutic agents do not distinguish between normal and neoplastic cells. This leads to severe toxic side effects, which may necessitate the discontinuation of treatment in some patients. Recent research has identified key molecular events in the initiation and progression of cancer, promoting the design of targeted therapies to selectively kill tumor cells while sparing normal cells. Although, the side effects of such drugs are typically milder than conventional chemotherapies, some off-target effects still occur. Another serious challenge with all chemotherapies is the acquisition of chemoresistance upon prolonged exposure to the drug. Therefore, identifying supplementary agents that sensitize tumor cells to chemotherapy-induced apoptosis and help minimize drug resistance would be valuable for improving patient tolerance and response to chemotherapy. The use of effective supplementary agents provides a twofold advantage in combination with standard chemotherapy. First, by augmenting the activity of the chemotherapeutic drug it can lower the dose needed to kill tumor cells and decrease the incidence and severity of treatment-limiting side effects. Second, adjuvant therapies that lower the effective dose of chemotherapy may delay/prevent the development of chemoresistance in tumors. Capsaicinoids, a major class of phytochemical compounds isolated from chili peppers, have been shown to improve the efficacy of several anti-cancer drugs in cell culture and animal models. The present chapter summarizes the current knowledge about the chemosensitizing activity of capsaicinoids with conventional and targeted chemotherapeutic drugs, highlighting the potential use of capsaicinoids in novel combination therapies to improve the therapeutic indices of conventional and targeted chemotherapeutic drugs in human cancers.

Neuroendocrine regulation of cholangiocarcinoma: A status quo review

Increasing studies have demonstrated that neuroendocrine system is involved in the development and progression of cholangiocarcinoma. The neuroendocrine hormones, neurotransmitters and neuropeptides regulate cholangiocarcinoma via affecting pathophysiology of tumor cells. The developing interaction and interplay between neuroendocrine-associated factors and tumor cells provide novel insights into neural control of tumorigenesis and reveal potential therapeutic effect on patients with cholangiocarcinoma. Herein we reviewed the latest findings and achievements which demonstrate the close interactions between neuroendocrine regulation and progression of cholangiocarcinoma. Also, future therapeutic approaches targeting neuroendocrine-associated factors are discussed which may help improve management and treatment of cholangiocarcinoma.

Nutrition and Cancercapsaicin Treatment Reduces Tumor Growth, Tumor Cell Proliferation Ex Vivo and Partially Reverses Cancer Cachexia in Walker 256 Tumor-Bearing Rats

Capsaicin (trans-8-methyl-n-vanillyl-6-nonenamide) is the main pungent component found in hot peppers.

AIM

In this study, we investigated the effect of capsaicin treatment on tumor growth and the metabolic indicators of cachexia in Walker 256 tumor-bearing rats.

METHODS

Male Wistar rats were inoculated subcutaneously in the right flank with 1 ml of a sterile suspension of 3 × 10⁷ Walker tumor cells. The treated groups received capsaicin intraperitoneal 5 mg/kg body weight for 13 days.

RESULTS

The tumor weight on Day 14 in the non-treated group was 18 g. The rats also had a body weight loss, hypoglycemia, hyperlactacidemia, hypertriacylglycerolemia, and a depletion in glycogen storage. Treatment with capsaicin decreased tumor growth by 49% and a reversal of triacylglycerol serum. We also found a 32% reduction in tumor cell proliferation ex vivo. Lactate serum concentrations and body weight were lower but did not reach control levels.

CONCLUSION

The treatment with capsaicin reduces tumor growth and cellular proliferation along with increased apoptosis and partial cachexia reversal.

CD200fc enhances anti-tumoral immune response and inhibits visceral metastasis of breast carcinoma

CD200 is a widely expressed cell surface glycoprotein that inhibits excessive inflammation in autoimmunity, transplantation, and viral infections. We previously observed that visceral metastasis of highly aggressive and inflammatory 4THM breast carcinoma cells was markedly decreased in CD200 transgenic mice. The goal of this study was to determine whether exogenous exposure to CD200fc mimics the effects of endogenously over expressed CD200. Female BALB/c mice were injected with CD200fc two times a week for five times. Injection was started two days after orthotopic injection of 4THM cells. Tumor infiltrating Gr1+Cd11b+ cells were decreased while CD8+ cells were increased in CD200fc-treated animals. CD200fc injection significantly decreased lung and liver metastasis and the growth of primary tumors. CD200fc injection enhanced the tumor-induced IFN-g response while suppressing the IL-10 response. We observed excessive basal IL-6 secretion in MLC which was significantly decreased in CD200fc treated mice 12 days after injection of 4TM cells. These results are in accord with previous data from CD200 transgenic mice, and demonstrate for the first time that CD200 analogues might have therapeutic potential in the treatment of aggressive breast carcinoma which induces excessive systemic inflammation.

Secretomes reveal several novel proteins as well as TGF-β1 as the top upstream regulator of metastatic process in breast cancer

PURPOSE

Metastatic breast cancer is resistant to many conventional treatments and novel therapeutic targets are needed. We previously isolated subsets of 4T1 murine breast cancer cells which metastasized to liver (4TLM), brain (4TBM), and heart (4THM). Among these cells, 4TLM is the most aggressive one, demonstrating mesenchymal phenotype. Here we compared secreted proteins from 4TLM, 4TBM, and 4THM cells and compared with that of hardly metastatic 67NR cells to detect differentially secreted factors involved in organ-specific metastasis.

METHOD AND RESULTS

Label-free LC-MS/MS proteomic technique was used to detect the differentially secreted proteins. Eighty-five of over 500 secreted proteins were significantly altered in metastatic breast cancer cells. Differential expression of several proteins such as fibulin-4, Bone Morphogenetic Protein 1, TGF-β1 MMP-3, MMP-9, and Thymic Stromal Lymphopoietin were further verified using ELISA or Western blotting. Many of these identified proteins were also present in human metastatic breast carcinomas. Annexin A1 and A5, laminin beta 1, Neutral alpha-glucosidase AB were commonly found at least in three out of six studies examined here. Ingenuity Pathway Analysis showed that proteins differentially secreted from metastatic cells are involved primarily in carcinogenesis and TGF-β1 is the top upstream regulator in all metastatic cells.

CONCLUSIONS

Cells metastasized to different organs displayed significant differences in several of secreted proteins. Proteins differentially altered were fibronectin, insulin-like growth factor-binding protein 7, and Procollagen-lysine, 2-oxoglutarate 5-dioxygenase 1. On the other hand, many exosomal proteins were also common to all metastatic cells, demonstrating involvement of key universal factors in distant metastatic process.

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.

Nephronectin is Decreased in Metastatic Breast Carcinoma and Related to Metastatic Organs

Breast cancer causes death mostly due to distant metastasis. During metastasis, cancer cells create new conditions in which normal tissue structure can be disturbed. Nephronectin, which is the primary ligand for α8β1 integrin, plays an important role in kidney development. There are conflicting findings regarding its role in cancer progression and metastasis, especially in breast carcinoma. The aim of this study was to determine changes in nephronectin expression in primary tumor tissues and metastatic visceral organs, using metastatic and non-metastatic cell lines in a mouse model of breast cancer. In our study, 4T1-Liver Metastatic and 4T1-Heart Metastatic cells, originally derived from 4T1-murine breast carcinoma, and non-metastatic 67NR carcinoma cells were used. Cancer cells were injected orthotopically into the mammary gland of 8-10 week-old Balb-c mice. Primary tumors, lung, liver tissues were collected on 12th and 25th days after the tumor injection. Immunohistochemistry was used to determine expression of nephronectin in tissues. We also investigated the expression levels of the protein by using western blot technique. We found that lung and liver tissue of control animals (not-injected with tumor cells) expressed nephronectin which was lost in animals bearing metastatic tumor for 25 days. In accordance, nephronectin staining of lung and liver was preserved in animals injected with non-metastatic 67NR tumors. These results demonstrate that loss of nephronectin may play an important role in formation metastatic milieu for cancer cells. This is the first study demonstrating that tumor-induced loss of nephronectin expression in visceral organs in which metastatic growth takes place.

An updated review on molecular mechanisms underlying the anticancer effects of capsaicin

The quest for developing anticancer principles from natural sources has a long historical track record and remarkable success stories. The pungent principle of hot chili pepper, capsaicin, has been a subject of research for anticancer drug discovery for more than three decades. However, the majority of research has revealed that capsaicin interferes with various hallmarks of cancer, such as increased cell proliferation, evasion from apoptosis, inflammation, tumor angiogenesis and metastasis, and tumor immune escape. Moreover, the compound has been reported to inhibit carcinogen activation and chemically induced experimental tumor growth. Capsaicin has also been reported to inhibit the activation of various kinases and transcription that are involved in tumor promotion and progression. The compound activated mitochondria-dependent and death receptor-mediated tumor cell apoptosis. Considering the growing interest in capsaicin, this review provides an update on the molecular targets of capsaicin in modulating oncogenic signaling.

Neuropeptide Levels as well as Neprilysin Activity Decrease in Renal Cell Carcinoma

Calcitonin Gene-related Peptide (CGRP), Vasoactive Intestinal Peptide (VIP) and Substance P (SP) are sensory neuropeptides which may alter cancer growth through modulation of chronic inflammation. We recently reported that SP suppresses breast cancer growth and metastasis through neuroimmune modulation. These neuropeptides are hydrolyzed by Neprilysin (NEP) to bioactive fragments. Decreased activity of NEP was reported in clear cell and chromophobe type renal cell carcinoma (RCC). It is however not known how the levels of neuropeptides hydrolyzed with NEP changes in RCC. Decrease activity of SP and CGRP containing sensory nerve endings was previously reported to increase cancer metastasis in animal models. It is however not known how peptidergic nerve endings are altered in RCC. Hence we here evaluated the levels of neuronal and non-neuronal neuropeptides and NEP activity in RCC including papillary type as well as neighboring uninvolved kidney. A cross-sectional study was conducted in 57 patients undergoing radical nephrectomy and diagnosed with RCC. NEP activity, levels and expression were determined using flourogenic substrate, western blot and qPCR respectively in freshly-frozen tissues. Immunohistochemical analyses were also performed. Neuronal and non-neuronal levels of CGRP, SP and VIP levels were determined using two-step acetic acid extraction. Levels and activity of NEP were markedly decreased in RCC regardless of subtype. Similar levels of VIP were detected in first and second extractions. VIP levels were higher in clear cell and papillary RCC compared to nearby kidney tissue. VIP levels of neighboring kidney tissue of papillary type RCC was significantly lower compared to kidney samples from clear cell RCC. CGRP levels were higher in second extraction. Similar to VIP levels, CGRP levels of neighboring kidney tissue from clear cell and chromophobe type RCC was significantly lower compared to corresponding tumor samples, an effect observed in the second extraction. VIP and CGRP levels of nearby kidney tissue varied subtype dependently demonstrating that different subtypes of RCC alter their local environment differently. Furthermore NEP-induce hydrolysis of VIP creates selective VPAC-1 receptor agonist which has anti-proliferative and anti-inflammatory effects. Hence loss of NEP activity may prevent anti-tumoral effects of VIP on RCC.

Changes in expressions of ADAM9, 10, and 17 as well as α-secretase activity in renal cell carcinoma

BACKGROUND

ADAM9, 10, and 17 are a class of disintegrins and metallproteinases with α-secretase activity. There are conflicting results regarding the role(s) of ADAM9, 10, and 17 in carcinogenesis, and only a few studies have examined their levels and cellular localization in renal cell carcinoma (RCC). Studies examining changes in α-secretase activity in RCC compared to enzymatic activity of the uninvolved kidney are lacking.

METHOD

A cross-sectional study was conducted in 56 patients undergoing radical nephrectomy after the diagnosis of RCC. α-Secretase activity was determined using flourogenic substrate in freshly frozen tumor tissues as well as similarly treated tissues from the neighboring kidney. Immunohistochemical analyses of ADAM9, 10, and 17 were also performed.

RESULTS

α-Secretase activity decreased markedly in all types of RCC as compared to neighboring uninvolved kidney tissue having 5 to 10 times higher levels of α-secretase activity. Although type-dependent variations were observed, tumoral expressions of ADAMs, except for ADAM17, were lower in the tumors compared to that of neighboring tissues, but the changes in α-secretase activity were greater. In RCC tissue, ADAM9 expressions were localized in nuclear and cytoplasmic compartments, whereas ADAM10 and 17 were present predominately in the cytoplasm potentially explaining the markedly decreased enzyme activity. Membranous localization of ADAMs was noted in uninvolved kidney tissue.

CONCLUSIONS

The loss of α-secretase activity observed here in conjunction with previous findings argue against tumorigenic effects of ADAM9, 10, and 17 supporting that increased nuclear and cytoplasmic expression may be an attempt to compensate for loss of function.

Gingerol Reverses the Cancer-Promoting Effect of Capsaicin by Increased TRPV1 Level in a Urethane-Induced Lung Carcinogenic Model

Both gingerol and capsaicin are agonists of TRPV1, which can negatively control tumor progression. This study observed the long-term effects of oral administration of 6-gingerol alone or in combination with capsaicin for 20 weeks in a urethane-induced lung carcinogenic model. We showed that lung carcinoma incidence and multiplicity were 70% and 21.2 ± 3.6, respectively, in the control versus 100% and 35.6 ± 5.2 in the capsaicin group (P < 0.01) and 50% and 10.8 ± 3.1 in the 6-gingerol group (P < 0.01). The combination of 6-gingerol and capsaicin reversed the cancer-promoting effect of capsaicin (carcinoma incidence of 100% versus 20% and multiplicity of 35.6 ± 5.2 versus 4.7 ± 2.3; P < 0.001). The cancer-promoting effect of capsaicin was due to increased epidermal growth-factor receptor (EGFR) level by decreased transient receptor potential vanilloid type-1 (TRPV1) level (P < 0.01) . The capsaicin-decreased EGFR level subsequently reduced levels of nuclear factor-κB (NF-κB) and cyclin D1 that favored enhanced lung epithelial proliferation and epithelial-mesenchymal transition (EMT) during lung carcinogenesis (P < 0.01). In contrast, 6-gingerol promoted TRPV1 level and drastically decreased the levels of EGFR, NF-κB, and cyclin D1 that favored reduced lung epithelial proliferation and EMT (P < 0.01). This study provides valuable information for the long-term consumption of chili-pepper-rich diets to decrease the risk of cancer development.

Endostatin and irradiation modifies the activity of ADAM10 and neprilysin in breast cancer cells

Angiogenesis, the formation of new blood vessels, is regarded as a key cancer cell property. Endostatin (ES) is a potential antiangiogenic agent and it may be useful when implemented in combination with other cancer therapeutic strategies. The present study investigated the in vitro effects of ES, radiotherapy (RT) or combination therapy (ES + RT) on two important proteases, a disintegrin and metalloproteinase domain‑containing protein 10 (ADAM10) and neprilysin (NEP) in 4T1 mouse breast cancer cells and the more metastatic phenotype of 4THMpc breast cancer cells. 4T1 and 4THMpc cells were treated with recombinant murine ES (4 µg/ml) alone, RT (45 Gy) alone or with ES + RT. ADAM10 enzyme activity was determined using a tumor necrosis factor‑α converting enzyme (α‑secretase) activity assay kit, and NEP enzyme activity was measured with a fluorometric assay based on the generation of free dansyl‑D‑Ala‑Gly from N-dansyl-Ala-Gly-D-nitro-Phe-Gly, the substrate of NEP. Western blotting analysis was performed to determine whether the altered enzyme activity levels of the two cell lines occurred due to changes in expression level. These data indicate that ES independently potentiates the activity of ADAM10 and NEP enzymes in 4T1 and 4THMpc breast cancer cells.

Non-pungent long chain capsaicin-analogs arvanil and olvanil display better anti-invasive activity than capsaicin in human small cell lung cancers

The nutritional compound capsaicin inhibits the invasion of many types of human cancers. The clinical development of capsaicin as an anti-cancer drug is limited due to its unfavorable side effects like burning sensation, stomach cramps, gut pain and nausea. This study compared the anti-invasive activity of capsaicin to non-pungent long chain capsaicin analogs, namely arvanil and olvanil, in human small cell lung cancer cells. Boyden chamber invasion assays revealed that arvanil and olvanil displayed improved anti-invasive activity relative to capsaicin in human SCLC cells. The results of the Boyden chamber assay were confirmed by the spherical invasion assay, and similar results were obtained. The anti-invasive activity of arvanil, olvanil and capsaicin were independent of TRPV and CB1 receptors. Furthermore, the anti-invasive activity of arvanil, olvanil and capsaicin was mediated by the AMPK pathway. Depletion of AMPK levels by siRNA methodology abrogated the anti-invasive activity of arvanil, olvanil and capsaicin. The non-pungent capsaicin analogs arvanil and olvanil display improved anti-invasive activity relative to capsaicin in human SCLC cells. These agents may represent the second generation of capsaicin-like compounds which are more potent than the parent molecule and have a better side effect profile.

Serum-derived exosomes from mice with highly metastatic breast cancer transfer increased metastatic capacity to a poorly metastatic tumor

Altered interaction between CD200 and CD200R represents an example of “checkpoint blockade” disrupting an effective, tumor‐directed, host response in murine breast cancer cells. In CD200R1KO mice, long‐term cure of EMT6 breast cancer, including metastatic spread to lung and liver, was achieved in BALB/c mice. The reverse was observed with 4THM tumors, an aggressive, inflammatory breast cancer, with increased tumor metastasis in CD200R1KO. We explored possible explanations for this difference. We measured the frequency of circulating tumor cells (CTCs) in peripheral blood of tumor bearers, as well as lung/liver and draining lymph nodes. In some cases mice received infusions of exosomes from nontumor controls, or tumor bearers, with/without additional infusions of anticytokine antibodies. The measured frequency of circulating tumor cells (CTCs) in peripheral blood was equivalent in the two models in WT and CD200R1KO mice. Increased metastasis in EMT6 tumor bearers was seen in vivo following adoptive transfer of serum, or serum‐derived exosomes, from 4THM tumor bearers, an effect which was attenuated by anti‐IL‐6, and anti‐IL‐17, but not anti‐TNFα, antibody. Anti‐IL‐6 also attenuated enhanced migration of EMT6 cells in vitro induced by 4THM serum or exosomes, or recombinant IL‐6. Exosome cytokine proteomic profiles responses in 4THM and EMT6 tumor‐bearing mice were regulated by CD200:CD200R interactions, with attenuation of both IL‐6 and IL‐17 in 4THM CD200^tg mice, and enhanced levels in 4THM CD200R1KO mice. We suggest these cytokines act on the microenvironment at sites within the host, and/or directly on tumor cells themselves, to increase metastatic potential.

Sirtuin 1 (SIRT1) Deacetylase Activity and NAD⁺/NADH Ratio Are Imperative for Capsaicin-Mediated Programmed Cell Death

Capsaicin is considered a chemopreventive agent by virtue of its selective antigrowth activity, commonly associated with apoptosis, against cancer cells. However, noncancerous cells possess relatively higher tolerance to capsaicin, although the underlying mechanism for this difference remains unclear. Hence, this study aimed to elucidate the differential effects of capsaicin on cell lines from lung tissues by addressing the signal pathway leading to two types of cell death. In MRC-5 human fetal lung cells, capsaicin augmented silent mating type information regulation 1 (SIRT1) deacetylase activity and the intracellular NAD(+)/NADH ratio, decreasing acetylation of p53 and inducing autophagy. In contrast, capsaicin decreased the intracellular NAD(+)/NADH ratio, possibly through inhibition of tumor-associated NADH oxidase (tNOX), and diminished SIRT1 expression leading to enhanced p53 acetylation and apoptosis. Moreover, SIRT1 depletion by RNA interference attenuated capsaicin-induced apoptosis in A549 cancer cells and autophagy in MRC-5 cells, suggesting a vital role for SIRT1 in capsaicin-mediated cell death. Collectively, these data not only explain the differential cytotoxicity of capsaicin but shed light on the distinct cellular responses to capsaicin in cancerous and noncancerous cell lines.

Activation of neuroimmune pathways increases therapeutic effects of radiotherapy on poorly differentiated breast carcinoma

Recent studies document the importance of neuronal dysfunction in cancer development and metastasis. We reported previously that both depletion of neuropeptides in capsaicin-sensitive sensory nerve endings and vagotomy increases metastasis of triple negative breast carcinoma. Of the sensory neuropeptides, Substance P (SP) is distributed widely for regulation of immune functions. We therefore examined the affects of continuous exposure to low doses of SP on brain metastatic cells of the mouse breast carcinoma (4TBM) in the presence of radiotherapy (RT) thought to increase antigenicity of cancer cells. 4TBM cells have a cancer stem cell phenotype and induce extensive visceral metastasis after orthotopic inoculation into the mammary pad. Results demonstrated that SP treatment decreases the number of tumor-infiltrating myeloid-derived suppressor cells as well as the TNF-α response to LPS challenge. SP also increased CD4+Cd25(bright) cells in draining lymph nodes of tumor-bearing animals and IFN-γ secretion from leukocyte culture prepared from lymph nodes and spleens of tumor-bearing animals. SP also prevented tumor-induced degeneration of sensory nerve endings and altered release of angiogenic factors from cancer-associated fibroblasts (CAF) and tumor explants. In accordance with these observed immunological effects, combination treatment of continuous SP with a single dose of RT induced complete tumor regression and significantly reduced or prevented metastasis in 50% of the animals while suppressing primary tumor growth and metastasis in the remaining mice. These original findings demonstrate that SP through neuroimmune modulation can prevent formation of immune suppression in the tumor microenvironment, enhance cytotoxic immunity in the presence of RT and prevent metastatic growth.

Exercise training improves heart rate recovery in women with breast cancer

PURPOSE

To determine whether exercise training improves autonomic function in women with breast cancer (BC).

METHODS

Fifty-one patients (aged between 39 and 72 years) with a history of primary invasive BC within the previous 5 years and enrolled in the Mediterranean diet-based DIANA (Diet and Androgens)-5 Trial were subdivided in two groups: a ET group (n = 25) followed a formal ET program of moderate intensity (3 session/week on a bicycle at 60-70% VO2peak for 3 months, followed by one session/week until 1-year follow-up), while a control group (n = 26) did not perform any formal ET. At baseline and after 1-year, all patients underwent cardiopulmonary exercise stress test (CPET). Heart rate recovery (HRR) was calculated as the difference between heart rate at peak exercise and heart rate at first minute of the cool-down period.

RESULTS

There were no significant differences between groups in baseline anthropometrical, BC characteristics, metabolic profile, CPET parameters and HRR. Compared to controls, at 1-year follow-up ET group showed a significant improvement in VO2peak (from 12.6 ± 3.0 to 14.5 ± 3.3 ml/kg/min, p < 0.001; p < 0.001 between groups); and in HRR (from 17.6 ± 6.4 to 23.0 ± 8.3 beats/min, p < 0.001; p < 0.001 between groups). In ET group the changes in HRR directly correlated with changes in VO2peak (r = 0.58, p = 0.002).

CONCLUSIONS

Moderate intensity exercise training in BC survivors is associated with improvement of autonomic function. Whether the improvement of sympatho-vagal balance may favorably modulate some of the pathophysiological mechanisms implied in cancer evolution need further investigation.

Comparison of immunity in mice cured of primary/metastatic growth of EMT6 or 4THM breast cancer by chemotherapy or immunotherapy

PURPOSE

We have compared cure from local/metastatic tumor growth in BALB/c mice receiving EMT6 or the poorly immunogenic, highly metastatic 4THM, breast cancer cells following manipulation of immunosuppressive CD200:CD200R interactions or conventional chemotherapy.

METHODS

We reported previously that EMT6 tumors are cured in CD200R1KO mice following surgical resection and immunization with irradiated EMT6 cells and CpG oligodeoxynucleotide (CpG), while wild-type (WT) animals developed pulmonary and liver metastases within 30 days of surgery. We report growth and metastasis of both EMT6 and a highly metastatic 4THM tumor in WT mice receiving iv infusions of Fab anti-CD200R1 along with CpG/tumor cell immunization. Metastasis was followed both macroscopically (lung/liver nodules) and microscopically by cloning tumor cells at limiting dilution in vitro from draining lymph nodes (DLN) harvested at surgery. We compared these results with local/metastatic tumor growth in mice receiving 4 courses of combination treatment with anti-VEGF and paclitaxel.

RESULTS

In WT mice receiving Fab anti-CD200R, no tumor cells are detectable following immunotherapy, and CD4+ cells produced increased TNFα/IL-2/IFNγ on stimulation with EMT6 in vitro. No long-term cure was seen following surgery/immunotherapy of 4THM, with both microscopic (tumors in DLN at limiting dilution) and macroscopic metastases present within 14 d of surgery. Chemotherapy attenuated growth/metastases in 4THM tumor-bearers and produced a decline in lung/liver metastases, with no detectable DLN metastases in EMT6 tumor-bearing mice-these latter mice nevertheless showed no significantly increased cytokine production after restimulation with EMT6 in vitro. EMT6 mice receiving immunotherapy were resistant to subsequent re-challenge with EMT6 tumor cells, but not those receiving curative chemotherapy. Anti-CD4 treatment caused tumor recurrence after immunotherapy, but produced no apparent effect in either EMT6 or 4THM tumor bearers after chemotherapy treatment.

CONCLUSION

Immunotherapy, but not chemotherapy, enhances CD4+ immunity and affords long-term control of breast cancer growth and resistance to new tumor foci.