Clinical and biological implications of the tumor microenvironment

Bioelectric pharmacology of cancer: A systematic review of ion channel drugs affecting the cancer phenotype

Cancer is a pernicious and pressing medical problem; moreover, it is a failure of multicellular morphogenesis that sheds much light on evolutionary developmental biology. Numerous classes of pharmacological agents have been considered as cancer therapeutics and evaluated as potential carcinogenic agents; however, these are spread throughout the primary literature. Here, we briefly review recent work on ion channel drugs as promising anti-cancer treatments and present a systematic review of the known cancer-relevant effects of 109 drugs targeting ion channels. The roles of ion channels in cancer are consistent with the importance of bioelectrical parameters in cell regulation and with the functions of bioelectric signaling in morphogenetic signals that act as cancer suppressors. We find that compounds that are well-known for having targets in the nervous system, such as voltage-gated ion channels, ligand-gated ion channels, proton pumps, and gap junctions are especially relevant to cancer. Our review suggests further opportunities for the repurposing of numerous promising candidates in the field of cancer electroceuticals.

Molecular perspectives on systemic priming and concomitant immunity in colorectal carcinoma

The progression of metastasis, a complex systemic disease, is facilitated by interactions between tumor cells and their isolated microenvironments. Over the past few decades, researchers have investigated the metastatic spread of cancer extensively, identifying multiple stages in the process, such as intravasation, extravasation, tumor latency, and the development of micrometastasis and macrometastasis. The premetastatic niche is established in target organs by the accumulation of aberrant immune cells and extracellular matrix proteins. The "seed and soil" idea, which has become widely known and accepted, is being used to this day to guide cancer studies. Changes in the local and systemic immune systems have a major impact on whether an infection spreads or not. The belief that the immune response may play a role in slowing tumor growth and may be beneficial against the metastatic disease underpins the responsiveness shown in the immunological landscape of metastasis. Various hypotheses on the phylogenesis of metastases have been proposed in the past. The primary tumor's secreting factors shape the intratumoral microenvironment and the immune landscape, allowing this progress to be made. Therefore, it is evident that among disseminated tumor cells, there are distinct phenotypes that either carry budding for metastasis or have the ability to obtain this potential or in systemic priming through contact with substantial metastatic niches that have implications for medicinal chemistry. Concurrent immunity signals that the main tumor induces an immune response that may not be strong enough to eradicate the tumor. Immunotherapy's success with some cancer patients shows that it is possible to effectively destroy even advanced-stage tumors by modifying the microenvironment and tumor-immune cell interactions. This review focuses on the metastasome in colorectal carcinoma and the therapeutic implications of site-specific metastasis, systemic priming, tumor spread, and the relationship between the immune system and metastasis.

Long non-coding RNA NBR2 suppresses the progression of colorectal cancer by downregulating miR-19a to regulate M2 macrophage polarization

Colorectal cancer (CRC) is a malignant tumor of the gastrointestinal tract that significantly impacts the health of patients and lacks promising methods of diagnosis. Tumor-associated macrophages (TAMs) are involved in CRC progression, and their function is regulated by long non-coding RNAs (lncRNAs). The lncRNA NBR2 was recently reported as an oncogene, whose function in CRC remains uncertain. The present study aimed to investigate the biological function of lncRNA NBR2 in the progression of CRC and its underlying molecular mechanisms. Ten pairs of clinical CRC and para-carcinoma tissues were collected to determine the expression levels of lncRNA NBR2 and miR-19a, and the polarization state of TAMs. Quantitative reverse transcriptase-polymerase chain reaction was used to evaluate the expression of miR-19a, and western blotting was used to determine the expression levels of tumor necrosis factor-α, human leukocyte antigen-DR, arginase-1, CD163, CD206, interleukin-4, AMP-activated protein kinase (AMPK), p-AMPK, hypoxia-inducible factor-1α (HIF-1α), protein kinase B (AKT), p-AKT, mechanistic target of rapamycin (mTOR), and p-mTOR in TAMs. The proliferative ability of HCT-116 cells was detected using the CCK8 assay, and the migratory ability of HCT-116 cells was evaluated using the Transwell assay. The interaction between lncRNA NBR2 and miR-19a was determined using the luciferase assay. The lncRNA NBR2 was downregulated and miR-19a was highly expressed in CRC cells, accompanied by a high M2 polarization. Downregulated miR-19a promoted M1 polarization, activated AMPK, suppressed HIF-1α and AKT/mTOR signaling pathways, and promoted antitumor properties in NBR2-overexpressed TAMs, which were all reversed by the introduction of the miR-19a mimic. LncRNA NBR2 was verified to target miR-19a in macrophages according to the results of the luciferase assay. Collectively, lncRNA NBR2 may suppress the progression of CRC by downregulating miR-19a to regulate M2 macrophage polarization.

The role of erythrocytes and erythroid progenitor cells in tumors

In the current research context of precision treatment of malignant tumors, the advantages of immunotherapy are unmatched by conventional antitumor therapy, which can prolong progression-free survival and overall survival. The search for new targets and novel combination therapies can improve the efficacy of immunotherapy and reduce adverse effects. Since current research targets for immunotherapy mainly focus on lymphocytes, little research has been done on erythrocytes. Nucleated erythroid precursor stem cells have been discovered to play an essential role in tumor progression. Researchers are exploring new targets and therapeutic approaches for immunotherapy from the perspective of erythroid progenitor cells (EPCs). Recent studies have shown that different subtypes of EPCs have specific surface markers and distinct biological roles in tumor immunity. CD45⁺ EPCs are potent myeloid-derived suppressor cell-like immunosuppressants that reduce the patient's antitumor immune response. CD45^- EPCs promote tumor invasion and metastasis by secreting artemin. A specific type of EPC also promotes angiogenesis and provides radiation protection. Therefore, EPCs may be involved in tumor growth, infiltration, and metastasis. It may also be an important cause of anti-angiogenesis and immunotherapy resistance. This review summarizes recent research advances in erythropoiesis, EPC features, and their impacts and processes on tumors.

Three-dimensional (3D) cell culture: a valuable step in advancing treatments for human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common malignant cancer and the third most frequent cause of tumour-related mortality worldwide. Currently, several surgical and medical therapeutic strategies are available for HCCs; however, the interaction between neoplastic cells and non-neoplastic stromal cells within the tumour microenvironment (TME) results in strong therapeutic resistance of HCCs to conventional treatment. Therefore, the development of novel treatments is urgently needed to improve the survival of patients with HCC. The first step in developing efficient chemotherapeutic drugs is the establishment of an appropriate system for studying complex tumour culture and microenvironment interactions. Three-dimensional (3D) culture model might be a crucial bridge between in vivo and in vitro due to its ability to mimic the naturally complicated in vivo TME compared to conventional two-dimensional (2D) cultures. In this review, we shed light on various established 3D culture models of HCC and their role in the investigation of tumour-TME interactions and HCC-related therapeutic resistance.

Organ on Chip Technology to Model Cancer Growth and Metastasis

Organ on chip (OOC) has emerged as a major technological breakthrough and distinct model system revolutionizing biomedical research and drug discovery by recapitulating the crucial structural and functional complexity of human organs in vitro. OOC are rapidly emerging as powerful tools for oncology research. Indeed, Cancer on chip (COC) can ideally reproduce certain key aspects of the tumor microenvironment (TME), such as biochemical gradients and niche factors, dynamic cell-cell and cell-matrix interactions, and complex tissue structures composed of tumor and stromal cells. Here, we review the state of the art in COC models with a focus on the microphysiological systems that host multicellular 3D tissue engineering models and can help elucidate the complex biology of TME and cancer growth and progression. Finally, some examples of microengineered tumor models integrated with multi-organ microdevices to study disease progression in different tissues will be presented.

Bioelectrical approaches to cancer as a problem of the scaling of the cellular self

One lens with which to understand the complex phenomenon of cancer is that of developmental biology. Cancer is the inevitable consequence of a breakdown of the communication that enables individual cells to join into computational networks that work towards large-scale, morphogenetic goals instead of more primitive, unicellular objectives. This perspective suggests that cancer may be a physiological disorder, not necessarily due to problems with the genetically-specified protein hardware. One aspect of morphogenetic coordination is bioelectric signaling, and indeed an abnormal bioelectric signature non-invasively reveals the site of incipient tumors in amphibian models. Functionally, a disruption of resting potential states triggers metastatic melanoma phenotypes in embryos with no genetic defects or carcinogen exposure. Conversely, optogenetic or molecular-biological modulation of bioelectric states can override powerful oncogenic mutations and prevent or normalize tumors. The bioelectrically-mediated information flows that harness cells toward body-level anatomical outcomes represent a very attractive and tractable endogenous control system, which is being targeted by emerging approaches to cancer.

Narrative review on serous primary peritoneal carcinoma of unknown primary site: four questions to be answered

Serous peritoneal papillary carcinoma (SPPC) represents a particular cancer of unknown primary (CUP) entity that arises in the peritoneal surface lining the abdomen and pelvis without a discriminative primary tumor site. In this review, we discuss the validity of SPPC as a distinct entity. Clinically, patients with SPPC are older, have higher parity and later menarche, are more often obese and probably have poorer survival compared to those with primary ovarian cancer. Pathologically, SPPC is more anaplastic and multifocal, unlike primary ovarian cancer which is commonly unifocal. Biologically, it presents a higher expression of proliferative signals and similar cell cycle and DNA repair protein expression. These differences hint towards SPPC and primary ovarian cancer being as a spectrum of disease. Patients with SPPC are traditionally managed similarly to stage III–IV ovarian cancer. The recommended approach integrates aggressive cytoreductive surgery, hyperthermic intraperitoneal chemotherapy, and systemic chemotherapy to remove the macroscopic tumor, eradicate the microscopic residual disease, and control the microscopic metastasis. However, the available evidence lacks proper randomized or prospective studies on SPPC and is limited to retrospective series. The diligent identification of SPPC is warranted to design specific clinical trials that eventually evaluate the impact of the new therapeutics on this distinct entity.

Preparation of liposomes containing IFN-gamma and their potentials in cancer immunotherapy: In vitro and in vivo studies in a colon cancer mouse model

The purpose of this study was to prepare non-PEGylated (HSPC/DSPG/Chol, LIPF1) and PEGylated (HSPC/DSPG/Chol/mPEG2000-DSPE, LIPF2) liposomal formulations containing Interferon-gamma (IFN-γ) and evaluation their effects on macrophages and their antitumor properties. The results showed that the size of liposomal formulations LIP-F1 and LIP-F2 was 120 and 135 nm, respectively. The encapsulation efficiencies of LIP-F1 and LIP-F2 were 52.79% and 49.2%, respectively. Nitric Oxide Synthase (INOS) and arginase assays showed an increase in nitric oxide (NO) level and a reduction in arginase level after the treatment of M2 phenotype macrophage cell line with IFN-γ liposomes. The biodistribution study illustrated the amplitude of iodinated-IFN-γ liposomal formulations in the tumor site, the circulation time and tumor accumulation of LIP-F2 was significantly more than LIPF1. As a result, PEGylated liposomes containing IFN-γ induced significant antitumor responses due to the increased delivery of the cargo to the immune cells and induction of antitumor immune responses.

The diagnostic challenges of patients with carcinoma of unknown primary

INTRODUCTION

Cancer of unknown primary (CUP) is a disease entity encompassing heterogeneous malignancies without a clinically-detectable anatomical primary. It is usually a poor prognosis malignancy with dismal prognosis where molecular and genetic testing were expected to be a major breakthrough.

AREAS COVERED

In this review, we provide an overview of the advances in the understanding of the carcinogenesis, biology, diagnosis and treatment of patients with CUP. This review focuses on the advantages and inconveniences of immunohistochemistry and CUP classifiers in assessing the progress in the management of CUP.

EXPERT OPINION

CUP classifiers were expected to gradually replace the classical multistep approach in identifying the culprit tumors to guide site-specific therapy. Immunohistochemistry staining led to the prediction of a single tissue of origin in 10.8-51%. CUP classifiers identified the primary site in 61-89% of these cases and were concordant with immunohistochemistry in 57.1-100%. Immunohistochemistry is cheap, fast and broadly available whereas CUP classifiers are less widely available and have not been validated in randomized control trials. The diagnostic recommendations consist of a standard pathology evaluation based on morphology and algorithmic immunohistochemistry assessment. Physicians should weigh in the input of the CUP classifier to the clinical picture and pathology investigations before performing additional investigations.

Impact of Site-Specific Metastases on Surgical Value and Survival among Metastatic Colorectal Cancer Patients

We aimed to explore the potential prognostic impact of the metastatic site on the management approach and prognosis of stage IV colorectal cancer patients with synchronous metastases. Synchronous metastatic colorectal cancer patients reported to the Surveillance, Epidemiology, and End Results Program database between 2010 and 2013 were included in this study. Overall survival (OS) was compared between patients with different treatment options using risk-adjusted Cox proportional hazard regression models. Overall, 17,776 patients with stage IV colorectal cancer were identified. Of these patients, 2,052 (11.5%) underwent surgical resection for tumors at both the primary and meta-static sites. Patients who underwent surgical resection of both primary and metastatic sites with liver, lung, and simultaneous liver and lung metastases had a longer median OS ( P < 0.001) than patients who underwent nonsurgical treatments. Cox regression analysis revealed that surgical resection of both primary and metastatic sites was associated with a significantly enhanced OS ( P < 0.001). Colorectal cancer patients with hepatic or pulmonary metastases, who underwent metastasectomy, even in selected patients with both hepatic and pulmonary metastases after multidisciplinary evaluation, could have a better survival benefit than patients who underwent nonsurgical treatments.

Cancer associated fibroblast: Mediators of tumorigenesis

It is well accepted that the tumor microenvironment plays a pivotal role in cancer onset, development, and progression. The majority of clinical interventions are designed to target either cancer or stroma cells. These emphases have been directed by one of two prevailing theories in the field, the Somatic Mutation Theory and the Tissue Organization Field Theory, which represent two seemingly opposing concepts. This review proposes that the two theories are mutually inclusive and should be concurrently considered for cancer treatments. Specifically, this review discusses the dynamic and reciprocal processes between stromal cells and extracellular matrices, using pancreatic cancer as an example, to demonstrate the inclusivity of the theories. Furthermore, this review highlights the functions of cancer associated fibroblasts, which represent the major stromal cell type, as important mediators of the known cancer hallmarks that the two theories attempt to explain.

Progress in refining the clinical management of cancer of unknown primary in the molecular era

Cancer of unknown primary (CUP) is an enigmatic disease entity encompassing heterogeneous malignancies without a detectable primary tumour, despite a thorough diagnostic workup. A minority of patients with CUP (15-20%) can be assigned a putative primary tissue of origin according to clinical and histopathological findings and typically have a more favourable prognosis with the use of corresponding tumour type-specific therapies. Thus, the majority of patients with CUP have disease that cannot be assigned to a culprit primary tumour, are treated with empirical chemotherapy and have a poor prognosis. In the molecular era, the use of (epi)genomic or transcriptomic CUP classifiers and DNA or RNA sequencing offers two, sometimes overlapping, therapeutic strategies: tumour type-specific therapy and biomarker-guided therapy. Published data reveal that the accuracy of site-of-origin predictions made using CUP classifiers ranges between 54% and 98% when compared with the assignment made according to the recommended clinicopathological criteria. These advances have led to promising results in non-randomized prospective studies evaluating the efficacy of tumour type-specific therapy; however, the favourable outcomes were not confirmed in randomized controlled studies comparing this approach with standard empirical chemotherapy. Currently, the evidence supporting the use of biomarker-guided therapies is limited to case reports and small case series. In this Review, we discuss the clinical management of CUP in the era of precision medicine. We focus on the advances in understanding the biology of CUP, the implications for the diagnosis and classification of CUP according to the tissue of origin and the shift away from empirical therapy towards tailored therapy.

Exploring the biological hallmarks of cancer of unknown primary: where do we stand today?

Cancer of unknown primary (CUP) affects a small percentage of the general population. Nonetheless, a substantial number of these patients have a poor prognosis and consequently succumb to their illness within a year of diagnosis. The natural history of CUP is characterised by early metastasis from the unknown primary site, aggressive course and resistance to conventional chemotherapy. Unfortunately, the processes by which this orphan disease originates and progresses have not been fully elucidated and its biology remain unclear. Despite the conceptual progress in genetic and molecular profiling made over the past decade, recognition of the genetic and molecular abnormalities involved in CUP, as well as the identification of the tissue of origin remain unresolved issues. This review will outline the biology of CUP by exploring the hallmarks of cancer in order to rationalise the complexities of this enigmatic syndrome. This approach will help the reader to understand where research efforts currently stand and the pitfalls of this quest.

Ion Channel and Neurotransmitter Modulators as Electroceutical Approaches to the Control of Cancer

The activities of individual cells must be tightly coordinated in order to build and maintain complex 3-dimensional body structures during embryogenesis and regeneration. Thus, one way to view cancer is within systems biology as a network disorder affecting the ability of cells to properly interact with a morphodynamic field of instructive signals that keeps proliferation and migration orchestrated toward the anatomical needs of the host or-ganism. One layer of this set of instructive microenvironmental cues is bioelectrical. Voltage gradients among all somatic cells (not just excitable nerve and muscle) control cell behavior, and the ionic coupling of cells into networks via electrochemical synapses allows them to implement tissue-level patterning decisions. These gradients have been increasingly impli-cated in the induction and suppression of tumorigenesis and metastasis, in the emerging links between developmental bioelectricity to the cancer problem. Consistent with the well-known role of neurotransmitter molecules in transducing electrical activity to downstream cascades in the brain, serotonergic signaling has likewise been implicated in cancer. Here, we review these recent data and propose new approaches for manipulating bioelectric and neurotransmitter pathways in cancer biology based on a bioelectric view of cancer. To sup-port this methodology, we present new data on the effects of the SSRI Prozac and its analog (ZINC ID = ZINC06811610) on survival of both cancer (MCF7) and normal (MCF10A) breast cells exposed to these compounds. We found an IC50 concentration (25 μM for Pro-zac and 100 μM for the Prozac analog) at which these compounds inhibited tumor cell sur-vival and proliferation. Additionally, at these concentrations, we did not observe alterations in a non-tumoral cell line. This constitutes a proof-of-concept demonstration for our hy-pothesis that the use of both existing and novel drugs as electroceuticals could serve as an alternative to highly toxic chemotherapy strategies replacing or augmenting them with less toxic alternatives. We believe this new approach forms an exciting roadmap for future bio-medical advances.

Relationship between infiltrating lymphocytes in cancerous ascites and dysfunction of Cajal mesenchymal cells in the small intestine

Malignant ascites changes the microenvironment of the peritoneal cavity and damages abdominal functional host cells such as interstitial cells of Cajal (ICC), causing gastrointestinal dysfunction and poor prognosis. Besides tumor cells, malignant ascites contains large numbers of lymphocytes and macrophagocytes. These inflammatory cells act as a 'double arrow' and it is not clear whether they cause injury to ICCs. Our study demonstrates the presence of T lymphocytes in malignant ascites and shows that these cells may have a critical role in inducing damage to ICC via Caspases and Fas/FasL. These inflammatory cells were contributory to gastric dysfunction in our GI tumor-induced ascites mouse models.

Halfway between 2D and Animal Models: Are 3D Cultures the Ideal Tool to Study Cancer-Microenvironment Interactions?

An area that has come to be of tremendous interest in tumor research in the last decade is the role of the microenvironment in the biology of neoplastic diseases. The tumor microenvironment (TME) comprises various cells that are collectively important for normal tissue homeostasis as well as tumor progression or regression. Seminal studies have demonstrated the role of the dialogue between cancer cells (at many sites) and the cellular component of the microenvironment in tumor progression, metastasis, and resistance to treatment. Using an appropriate system of microenvironment and tumor culture is the first step towards a better understanding of the complex interaction between cancer cells and their surroundings. Three-dimensional (3D) models have been widely described recently. However, while it is claimed that they can bridge the gap between in vitro and in vivo, it is sometimes hard to decipher their advantage or limitation compared to classical two-dimensional (2D) cultures, especially given the broad number of techniques used. We present here a comprehensive review of the different 3D methods developed recently, and, secondly, we discuss the pros and cons of 3D culture compared to 2D when studying interactions between cancer cells and their microenvironment.

Use of genetically encoded, light-gated ion translocators to control tumorigenesis

It has long been known that the resting potential of tumor cells is depolarized relative to their normal counterparts. More recent work has provided evidence that resting potential is not just a readout of cell state: it regulates cell behavior as well. Thus, the ability to control resting potential in vivo would provide a powerful new tool for the study and treatment of tumors, a tool capable of revealing living-state physiological information impossible to obtain using molecular tools applied to isolated cell components. Here we describe the first use of optogenetics to manipulate ion-flux mediated regulation of membrane potential specifically to prevent and cause regression of oncogene-induced tumors. Injection of mutant-KRAS mRNA induces tumor-like structures with many documented similarities to tumors, in Xenopus tadpoles. We show that expression and activation of either ChR2^D156A, a blue-light activated cation channel, or Arch, a green-light activated proton pump, both of which hyperpolarize cells, significantly lowers the incidence of KRAS tumor formation. Excitingly, we also demonstrate that activation of co-expressed light-activated ion translocators after tumor formation significantly increases the frequency with which the tumors regress in a process called normalization. These data demonstrate an optogenetic approach to dissect the biophysics of cancer. Moreover, they provide proof-of-principle for a novel class of interventions, directed at regulating cell state by targeting physiological regulators that can over-ride the presence of mutations.

Gap junctional signaling in pattern regulation: Physiological network connectivity instructs growth and form

Gap junctions (GJs) are aqueous channels that allow cells to communicate via physiological signals directly. The role of gap junctional connectivity in determining single-cell functions has long been recognized. However, GJs have another important role: the regulation of large-scale anatomical pattern. GJs are not only versatile computational elements that allow cells to control which small molecule signals they receive and emit, but also establish connectivity patterns within large groups of cells. By dynamically regulating the topology of bioelectric networks in vivo, GJs underlie the ability of many tissues to implement complex morphogenesis. Here, a review of recent data on patterning roles of GJs in growth of the zebrafish fin, the establishment of left-right patterning, the developmental dysregulation known as cancer, and the control of large-scale head-tail polarity, and head shape in planarian regeneration has been reported. A perspective in which GJs are not only molecular features functioning in single cells, but also enable global neural-like dynamics in non-neural somatic tissues has been proposed. This view suggests a rich program of future work which capitalizes on the rapid advances in the biophysics of GJs to exploit GJ-mediated global dynamics for applications in birth defects, regenerative medicine, and morphogenetic bioengineering. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 643-673, 2017.

Genetic traits for hematogeneous tumor cell dissemination in cancer patients

Metastatic relapse in patients with solid tumors is the consequence of cancer cells that disseminated to distant sites, adapted to the new microenvironment, and escaped systemic adjuvant therapy. There is increasing evidence that hematogeneous dissemination starts at an early stage of cancer progression with single tumor cells or cell clusters leaving the primary site and entering the blood circulation. These circulating tumor cells (CTCs) can extravasate into secondary tissues where they become disseminated tumor cells (DTCs). Patients might relapse years after initial resection of the primary tumor when DTCs become overt metastases. Current diagnostic strategies for stratification of therapies against metastatic cells focus on the primary tumor tissue. This approach is based on the availability of stored primary tumors obtained at primary surgery, but it ignores that the DTCs might have evolved over years, which can affect the antimetastatic drug response. However, taking biopsies from metastatic tissues is an invasive procedure, and multiple metastases located at different sites in an individual patient show marked genomic heterogeneity. Thus, capturing CTCs from the peripheral blood as a "liquid biopsy" has obvious advantages in particular when repeated sampling is required for monitoring therapies in cancer patients. However, the biology behind tumor cell dissemination and its contribution to metastatic progression in cancer patients is still subject to controversial discussions. This manuscript reviews current theories on the genetic traits behind the spread of CTCs and progression of DTCs into overt metastases.

Insulin-like growth factor (IGF) axis in cancerogenesis

Determination of the role of insulin-like growth factor (IGF) family components in carcinogenesis of several human tumors is based on numerous epidemiological and pre-clinical studies, experiments in vivo and in vitro and on attempts at application of drugs affecting the IGF axis. Investigative hypotheses in original studies were based on biological functions manifested by the entire family of IGF (ligands, receptors, linking proteins, adaptor molecules). In the context of carcinogenesis the most important functions of IGF family involve intensification of proliferation and inhibition of cell apoptosis and effect on cell transformation through synthesis of several regulatory proteins. IGF axis controls survival and influences on metastases of cells. Interactions of IGF axis components may be of a direct or indirect nature. The direct effects are linked to activation of PI3K/Akt signaling pathway, in which the initiating role is first of all played by IGF-1 and IGF-1R. Activity of this signaling pathway leads to an increased mitogenesis, cell cycle progression, and protection against different apoptotic stresses. Indirect effects of the axis depend on interactions between IGF and other molecules important for cancer etiology (e.g. sex hormones, products of suppressor genes, viruses, and other GFs) and the style of life (nutrition, physical activity). From the clinical point of view, components of IGF system are first of all considered as diagnostic serous and/or tissue biomarkers of a given cancer, prognostic factors and attractive target of modern anti-tumor therapies. Several mechanisms in which IGF system components act in the process of carcinogenesis need to be clarified, mainly due to multifactorial etiology of the neoplasms. Pin-pointing of the role played in carcinogenesis by any single signaling pathway remains particularly difficult. The aim of this review is to summarize the current data of several epidemiological studies, experiments in vitro and on animal models, to increase our understanding of the complex role of IGF family components in the most common human cancers.

Stromal dynamic reciprocity in cancer: intricacies of fibroblastic-ECM interactions

Stromal dynamic reciprocity (SDR) consists of the biophysical and biochemical interplay between connective tissue elements that regulate and maintain organ homeostasis. In epithelial cancers, chronic alterations of SDR result in the once tumor-restrictive stroma evolving into a 'new' tumor-permissive environment. This altered stroma, known as desmoplasia, is initiated and maintained by cancer associated fibroblasts (CAFs) that remodel the extracellular matrix (ECM). Desmoplasia fuels a vicious cycle of stromal dissemination enriching both CAFs and desmoplastic ECM. Targeting specific drivers of desmoplasia, such as CAFs, either enhances or halts tumor growth and progression. These conflicting effects suggest that stromal interactions are not fully understood. This review highlights known fibroblastic-ECM interactions in an effort to encourage therapies that will restore cancer-restrictive stromal cues.

Molecular profiling reveals primary mesothelioma cell lines recapitulate human disease

Malignant mesothelioma (MM) is an aggressive, fatal tumor strongly associated with asbestos exposure. There is an urgent need to improve MM patient outcomes and this requires functionally validated pre-clinical models. Mesothelioma-derived cell lines provide an essential and relatively robust tool and remain among the most widely used systems for candidate drug evaluation. Although a number of cell lines are commercially available, a detailed comparison of these commercial lines with freshly derived primary tumor cells to validate their suitability as pre-clinical models is lacking. To address this, patient-derived primary mesothelioma cell lines were established and characterized using complementary multidisciplinary approaches and bioinformatic analysis. Clinical markers of mesothelioma, transcriptional and metabolic profiles, as well as the status of p53 and the tumor suppressor genes CDKN2A and NF2, were examined in primary cell lines and in two widely used commercial lines. Expression of MM-associated markers, as well as the status of CDKN2A, NF2, the ‘gatekeeper' in MM development, and their products demonstrated that primary cell lines are more representative of the tumor close to its native state and show a degree of molecular diversity, thus capturing the disease heterogeneity in a patient cohort. Molecular profiling revealed a significantly different transcriptome and marked metabolic shift towards a greater glycolytic phenotype in commercial compared with primary cell lines. Our results highlight that multiple, appropriately characterised, patient-derived tumor cell lines are required to enable concurrent evaluation of molecular profiles versus drug response. Furthermore, application of this approach to other difficult-to-treat tumors would generate improved cellular models for pre-clinical evaluation of novel targeted therapies.

Pathogenesis of Breast Cancer Metastasis to Brain: a Comprehensive Approach to the Signaling Network

There is a general consensus that breast cancer is a rising trend disease in the world. It is one of the most common cancer types and is the leading cause of death among women's cancers. There are several reasons for this high rate of mortality including metastasis which is responsible for about 90 % of cancer-related mortality. Therefore, recognition and understanding of metastatic process is important, and by considering the key role of pathophysiological route in metastasis as a multistep cascade of "invasion-metastasis," it might modify and improve our insight toward this complex phenomenon. Moreover, it can provide novel approaches for designing advanced targeted therapies. The present work aimed to review the published papers regarding molecular basis of metastatic process of breast cancer to brain metastasis, especially related genes and signaling network. Furthermore, the use of molecular aspects of metastatic breast cancer to brain was discussed in horizon of future treatment of breast cancer.

The impact of inflammatory cells in malignant ascites on small intestinal ICCs' morphology and function

Malignant ascites is one of the common complication at the late stage of abdominal cancers, which may deteriorate the environment of abdominal cavity and lead to potential damage of functional cells. Interstitial cells of Cajal (ICCs) are mesoderm-derived mesenchymal cells that function normal gastrointestinal motility. The pathological changes of ICCs or the reduced number may lead to the motility disorders of gastrointestinal tract. In this study, through analysis of malignant ascites which were obtained from cancer patients, we found that inflammatory cells, including tumour-infiltrating lymphocytes, accounted for 17.26 ± 1.31% and tumour-associated macrophages, occupied 19.06 ± 2.27% of total cells in the ascites, suggesting these inflammatory cells, in addition to tumour cells, may exert important influence on the tumour environment of abdominal cavity. We further demonstrated that the number of mice ICCs were significant decreased, as well as morphological and functional damage when ICCs were in the simulated tumour microenvironment in vitro. Additionally, we illustrated intestinal myoelectrical activity reduced and irregular with morphological changes of ICCs using the mice model of malignant ascites. In conclusion, our data suggested that inflammatory cells in malignant ascites may damage ICCs of the small intestine and lead to intestinal motility disorders.

Modelling breast cancer requires identification and correction of a critical cell lineage-dependent transduction bias

Clinically relevant human culture models are essential for developing effective therapies and exploring the biology and etiology of human cancers. Current breast tumour models, such as those from oncogenically transformed primary breast cells, produce predominantly basal-like properties, whereas the more common phenotype expressed by the vast majority of breast tumours are luminal. Reasons for this puzzling, yet important phenomenon, are not understood. We show here that luminal epithelial cells are significantly more resistant to viral transduction than their myoepithelial counterparts. We suggest that this is a significant barrier to generating luminal cell lines and experimental tumours in vivo and to accurate interpretation of results. We show that the resistance is due to lower affinity of luminal cells for virus attachment, which can be overcome by pretreating cells—or virus—with neuraminidase. We present an analytical method for quantifying transductional differences between cell types and an optimized protocol for transducing unsorted primary human breast cells in context.

Clinical breast cancers predominantly present luminal features, but experimental models are essentially basal. Here the authors show that luminal cells are significantly less susceptible to viral transduction, and present methods to analyse and overcome the bias in heterogeneous populations.

Breast cancer cells promote a notch-dependent mesenchymal phenotype in endothelial cells participating to a pro-tumoral niche

Background

Endothelial cells (ECs) are responsible for creating a tumor vascular niche as well as producing angiocrine factors. ECs demonstrate functional and phenotypic heterogeneity when located under different microenvironments. Here, we describe a tumor-stimulated mesenchymal phenotype in ECs and investigate its impact on tumor growth, stemness, and invasiveness.

Methods

Xenograft tumor assay in NOD/SCID mice and confocal imaging were conducted to show the acquisition of mesenchymal phenotype in tumor-associated ECs in vivo. Immunocytochemistry, qPCR and flow cytometry techniques showed the appearance of mesenchymal traits in ECs after contact with breast tumor cell lines MDA-MB231 or MCF-7. Cell proliferation, cell migration, and sphere formation assays were applied to display the functional advantages of mesenchymal ECs in tumor growth, invasiveness, and enrichment of tumor initiating cells. qPCR and western blotting were used to investigate the mechanisms underlying EC mesenchymal transition.

Results

Our results showed that co-injection of ECs and tumor cells in NOD/SCID mice significantly enhanced tumor growth in vivo with tumor-associated ECs expressing mesenchymal markers while maintaining their intrinsic endothelial trait. We also showed that a mesenchymal phenotype is possibly detectable in human neoplastic breast biopsies as well as ECs pre-exposed to tumor cells (ECs^Mes) in vitro. The ECs^Mes acquired prolonged survival, increased migratory behavior and enhanced angiogenic properties. In return, ECs^Mes were capable of enhancing tumor survival and invasiveness. The mesenchymal phenotypes in ECs^Mes were the result of a contact-dependent transient phenomenon and reversed upon removal of the neoplastic contexture. We showed a synergistic role for TGFβ and notch pathways in this phenotypic change, as simultaneous inhibition of notch and TGFβ down-regulated Smad1/5 phosphorylation and Jag1^KD tumor cells were unable to initiate the process.

Conclusions

Overall, our data proposed a crosstalk mechanism between tumor and microenvironment where tumor-stimulated mesenchymal modulation of ECs enhanced the constitution of a transient mesenchymal/endothelial niche leading to significant increase in tumor proliferation, stemness, and invasiveness. The possible involvement of notch and TGFβ pathways in the initiation of mesenchymal phenotype may propose new stromal targets.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0386-3) contains supplementary material, which is available to authorized users.

Transmembrane voltage potential of somatic cells controls oncogene-mediated tumorigenesis at long-range

The microenvironment is increasingly recognized as a crucial aspect of cancer. In contrast and complement to the field's focus on biochemical factors and extracellular matrix, we characterize a novel aspect of host:tumor interaction - endogenous bioelectric signals among non-excitable somatic cells. Extending prior work focused on the bioelectric state of cancer cells themselves, we show for the first time that the resting potentials of distant cells are critical for oncogene-dependent tumorigenesis. In the Xenopus laevis tadpole model, we used human oncogenes such as mutant KRAS to drive formation of tumor-like structures that exhibited overproliferation, increased nuclear size, hypoxia, acidity, and leukocyte attraction. Remarkably, misexpression of hyperpolarizing ion channels at distant sites within the tadpole significantly reduced the incidence of these tumors. The suppression of tumorigenesis could also be achieved by hyperpolarization using native CLIC1 chloride channels, suggesting a treatment modality not requiring gene therapy. Using a dominant negative approach, we implicate HDAC1 as the mechanism by which resting potential changes affect downstream cell behaviors. Based on published data on the voltage-mediated changes of butyrate flux through the SLC5A8 transporter, we present a model linking resting potentials of host cells to the ability of oncogenes to initiate tumorigenesis. Antibiotic data suggest that the relevant butyrate is generated by a native bacterial species, identifying a novel link between the microbiome and cancer that is mediated by alterations in bioelectric signaling.

Long-range gap junctional signaling controls oncogene-mediated tumorigenesis in Xenopus laevis embryos

In addition to the immediate microenvironment, long-range signaling may be an important component of cancer. Molecular-genetic analyses have implicated gap junctions-key mediators of cell-cell communication-in carcinogenesis. We recently showed that the resting voltage potential of distant cell groups is a key determinant of metastatic transformation and tumor induction. Here, we show in the Xenopus laevis model that gap junctional communication (GJC) is a modulator of the long-range bioelectric signaling that regulates tumor formation. Genetic disruption of GJC taking place within tumors, within remote host tissues, or between the host and tumors significantly lowers the incidence of tumors induced by KRAS mutations. The most pronounced suppression of tumor incidence was observed upon GJC disruption taking place farther away from oncogene-expressing cells, revealing a role for GJC in distant cells in the control of tumor growth. In contrast, enhanced GJC communication through the overexpression of wild-type connexin Cx26 increased tumor incidence. Our data confirm a role for GJC in tumorigenesis, and reveal that this effect is non-local. Based on these results and on published data on movement of ions through GJs, we present a quantitative model linking the GJC coupling and bioelectrical state of cells to the ability of oncogenes to initiate tumorigenesis. When integrated with data on endogenous bioelectric signaling during left-right patterning, the model predicts differential tumor incidence outcomes depending on the spatial configurations of gap junction paths relative to tumor location and major anatomical body axes. Testing these predictions, we found that the strongest influence of GJ modulation on tumor suppression by hyperpolarization occurred along the embryonic left-right axis. Together, these data reveal new, long-range aspects of cancer control by the host's physiological parameters.

Role of the host stroma in cancer and its therapeutic significance

Current cancer research focuses mainly upon the cancer cells in malignant tumours and is providing a growing database about aberrations in their genetic composition. However, tumours also contain non-cancerous host tissue, referred to as the stroma, which plays an active and indispensable role in tumour growth and influences the virulence of the neoplasm towards the host. Many cell types inhabit the stroma, amidst apparently inert fibrous and viscous matrix material, composed of complex polysaccharides, proteins and other molecules. Actually, all of these elements are in constant turnover, causing unpredictable evolution in the properties of the community. This article provides pathologic observations and data on reciprocal interactions between these stromal and neoplastic components of tumours and how they change during the course of the disease. Malignant progression depends upon dauntingly intricate communications between different specialised lineages within the cellular society, which enable rapid adaptation to changing circumstances. Opportunistic misuse of such communication networks enables tumour cells to recruit and incorporate adjacent normal stroma into their midst, so that they may grow, infiltrate and parasitise the host. The absolute dependency of primary tumours and metastases on their diverse stromal components for survival and their insatiable need to continuously recruit more stroma to support expansion, renders them vulnerable to strategies capable of disrupting the cellular interactions involved. This dependency is of critical importance for cancer therapy research, and proposed methods for turning this parasitic behaviour of tumours against themselves are suggested below.

Tumor-associated macrophages promote tumor cell proliferation in nasopharyngeal NK/T-cell lymphoma

OBJECTIVE

To explore the relationship between the number of tumor-associated macrophages (TAMs) and proliferative activity of tumor cells and the relationship between two macrophage biomarkers CD68 and CD163 in nasopharyngeal NK/T-cell lymphoma.

METHODS

Immunohistochemistry was used to reconfirm the diagnosis of nasal NK/T-cell lymphoma and detect the numbers of TAMs and the ki-67 label index of the tumor cells in all 31 cases. In addition, 12 cases of inflammatory cases were collected as controls, for which the immunostaining of CD68 and CD163 were done as well. Then staining results were analyzed with Pearson correlation and t test.

RESULTS

The number of TAMs was positively correlated with tumor proliferative activity (P = 0.024) in nasopharyngeal NK/T-cell lymphoma. The expression of CD68 and CD163 was closely related (P = 0.009), and the positive rate of CD68 was generally higher than CD163, however there is no statistical significance.

CONCLUSION

The increase in numbers of TAMs in nasopharyngeal NK/T-cell lymphoma is related to higher proliferative index, indicating the TAMs play an important role in tumor proliferation. Meanwhile both CD68 and CD163 might be the markers for TAMs but CD163 would be the better one.

The role of gene regulatory networks in promoting cancer progression and metastasis

ABSTRACT: 

The majority of deaths owing to cancer are ultimately caused by metastatic disease. However, most research, to date, has focused on the molecular features of cancers at their primary sites rather than on understanding disseminated malignancy in its systemic form. The dynamic nature of metastatic malignancy and its behavior as a co-ordinated systemic disease require a cancer progression paradigm that is integrative and can incorporate both the proximate causes of cancer and the broader ultimate causes in an evolutionary and developmental context. The study of robust cellular attractor states that arise directly from the architectural patterns contained within gene regulatory networks is proposed as a conceptual framework through which many of the other disparate models of cancer metastasis can be more clearly viewed and, ultimately, unified, thus providing a new conceptual framework in which to understand cancer progression and metastasis.

Miniaturized pre-clinical cancer models as research and diagnostic tools

Cancer is one of the most common causes of death worldwide. Consequently, important resources are directed towards bettering treatments and outcomes. Cancer is difficult to treat due to its heterogeneity, plasticity and frequent drug resistance. New treatment strategies should strive for personalized approaches. These should target neoplastic and/or activated microenvironmental heterogeneity and plasticity without triggering resistance and spare host cells. In this review, the putative use of increasingly physiologically relevant microfabricated cell-culturing systems intended for drug development is discussed. There are two main reasons for the use of miniaturized systems. First, scaling down model size allows for high control of microenvironmental cues enabling more predictive outcomes. Second, miniaturization reduces reagent consumption, thus facilitating combinatorial approaches with little effort and enables the application of scarce materials, such as patient-derived samples. This review aims to give an overview of the state-of-the-art of such systems while predicting their application in cancer drug development.

Chemical mapping of the colorectal cancer microenvironment via MALDI imaging mass spectrometry (MALDI-MSI) reveals novel cancer-associated field effects

Matrix-assisted laser desorption ionisation imaging mass spectrometry (MALDI-MSI) is a rapidly advancing technique for intact tissue analysis that allows simultaneous localisation and quantification of biomolecules in different histological regions of interest. This approach can potentially offer novel insights into tumour microenvironmental (TME) biochemistry. In this study we employed MALDI-MSI to evaluate fresh frozen sections of colorectal cancer (CRC) tissue and adjacent healthy mucosa obtained from 12 consenting patients undergoing surgery for confirmed CRC. Specifically, we sought to address three objectives: (1) To identify biochemical differences between different morphological regions within the CRC TME; (2) To characterise the biochemical differences between cancerous and healthy colorectal tissue using MALDI-MSI; (3) To determine whether MALDI-MSI profiling of tumour-adjacent tissue can identify novel metabolic 'field effects' associated with cancer. Our results demonstrate that CRC tissue harbours characteristic phospholipid signatures compared with healthy tissue and additionally, different tissue regions within the CRC TME reveal distinct biochemical profiles. Furthermore we observed biochemical differences between tumour-adjacent and tumour-remote healthy mucosa. We have referred to this 'field effect', exhibited by the tumour locale, as cancer-adjacent metaboplasia (CAM) and this finding builds on the established concept of field cancerisation.

Origin and pharmacological modulation of tumor-associated regulatory dendritic cells

Protumorigenic activity of immune regulatory cells has been proven to play a major role in precluding immunosurveillance and limiting the efficacy of anticancer therapies. Although several approaches have been offered to deplete myeloid-derived suppressor cells (MDSC) and regulatory T cells, there are no data on how to control suppressive dendritic cell (DC) accumulation or function in the tumor environment. Although immunosuppressive function of DC in cancer was implicated to immature and plasmacytoid DC, details of how conventional DC (cDC) develop immunosuppressive properties remain less understood. Here, we show that the development of lung cancer in mice was associated with fast accumulation of regulatory DC (regDC) prior to the appearance of MDSC. Using the in vitro and in vivo approaches, we demonstrated that (i)both cDC and MDSC could be polarized into protumor regDC in the lung cancer environment; (ii) cDC → regDC polarization was mediated by the small Rho GTPase signaling, which could be controlled by noncytotoxic doses of paclitaxel; and (iii) prevention of regDC appearance increased the antitumor potential of DC vaccine in lung cancer. These findings not only bring new players to the family of myeloid regulatory cells and provide new targets for cancer therapy, but offer novel insights into the immunomodulatory capacity of chemotherapeutic agents used in low, noncytotoxic doses.

Enzyme-directed assembly of nanoparticles in tumors monitored by in vivo whole animal imaging and ex vivo super-resolution fluorescence imaging

Matrix metalloproteinase enzymes, overexpressed in HT-1080 human fibrocarcinoma tumors, were used to guide the accumulation and retention of an enzyme-responsive nanoparticle in a xenograft mouse model. The nanoparticles were prepared as micelles from amphiphilic block copolymers bearing a simple hydrophobic block and a hydrophilic peptide brush. The polymers were end-labeled with Alexa Fluor 647 dyes leading to the formation of labeled micelles upon dialysis of the polymers from DMSO/DMF to aqueous buffer. This dye-labeling strategy allowed the presence of the retained material to be visualized via whole animal imaging in vivo and in ex vivo organ analysis following intratumoral injection into HT-1080 xenograft tumors. We propose that the material is retained by virtue of an enzyme-induced accumulation process whereby particles change morphology from 20 nm spherical micelles to micrometer-scale aggregates, kinetically trapping them within the tumor. This hypothesis is tested here via an unprecedented super-resolution fluorescence analysis of ex vivo tissue slices confirming a particle size increase occurs concomitantly with extended retention of responsive particles compared to unresponsive controls.

Enzyme-directed assembly of a nanoparticle probe in tumor tissue

Enzyme-directed assembly in vivo: A targeting strategy is demonstrated, which leads to an active accumulation of nanoparticles by virtue of an assembly event specific to endogenous, enzymatic biochemical signals associated with tumor tissue. The viability of this approach is examined through a proof-of-concept study showing enzyme-directed particle targeting and accumulation in human xenograft tumors in mice following intravenous injection, and the retention of particles is demonstrated within tumors for extended periods of time.

Anti-tumour strategies aiming to target tumour-associated macrophages

Tumour-associated macrophages (TAMs) represent a predominant population of inflammatory cells that present in solid tumours. TAMs are mostly characterized as alternatively activated M2-like macrophages and are known to orchestrate nearly all stages of tumour progression. Experimental investigations indicate that TAMs contribute to drug-resistance and radio-protective effects, and clinical evidence shows that an elevated number of TAMs and their M2 profile are correlated with therapy failure and poor prognosis in cancer patients. Recently, many studies on TAM-targeted strategies have made significant progress and some pilot works have achieved encouraging results. Among these, connections between some anti-tumour drugs and their influence on TAMs have been suggested. In this review, we will summarize recent advances in TAM-targeted strategies for tumour therapy. Based on the proposed mechanisms, those strategies are grouped into four categories: (i) inhibiting macrophage recruitment; (ii) suppressing TAM survival; (iii) enhancing M1-like tumoricidal activity of TAMs; (iv) blocking M2-like tumour-promoting activity of TAMs. It is desired that further attention be drawn to this research field and more effort be made to promote TAM-targeted tumour therapy.

Integrative analyses identify osteopontin, LAMB3 and ITGB1 as critical pro-metastatic genes for lung cancer

OBJECTIVE

To explore the key regulatory genes associated with lung cancer in order to reduce its occurrence and progress through silencing these key genes.

METHODS

To identify the key regulatory genes involved in lung cancer, we performed a combination of gene array and bioinformatics analyses to compare gene transcription profiles in 3 monoclonal cell strains with high, medium or low metastatic abilities, which were separated from the SPC-A-1sci and SPC-A-1 cell lines by limiting dilution monoclone assay. We then analyzed those genes' biological activities by knocking down their expression in SPC-A-1sci cells using siRNA and lenti-viral shRNA vectors, followed by determinations of the invasion and migration capabilities of the resulting cell lines in vitro as well as their potential for inducing occurrence and metastasis of lung cancer in vivo. To examine the clinical relevance of these findings, we analyzed the expression levels of the identified genes in human lung cancer tissues (n = 135) and matched adjacent normal tissues by immunohistochemical (IHC) staining.

RESULTS

Three monoclonal cell strains characterized with high, medium or low metastatic abilities were successfully selected. Gene array and bioinformatics analyses implied that osteopontin, LAMB3 and ITGB1 were key genes involved in lung cancer. Knockdown of these genes suppressed human lung cancer cell invasion and metastasis in vitro and in vivo. Clinical sample analyses indicated that osteopontin, LAMB3 and ITGB1 protein expression levels were higher in lung cancer patients, compared to non-cancerous adjacent tissues, and correlated with lymphatic metastasis.

CONCLUSIONS

We confirmed that osteopontin, LAMB3 and ITGB1 played important roles in the occurrence and metastasis of lung cancer, thus provided important clues to understanding the molecular mechanism of metastasis and contributing to the therapeutic treatment of lung cancer.

Olfactory receptor 51E1 protein as a potential novel tissue biomarker for small intestine neuroendocrine carcinomas

OBJECTIVE

Late diagnosis hinders proper management of small intestine neuroendocrine carcinoma (SI-NEC) patients. The olfactory receptor, family 51, subfamily E, member 1 (OR51E1) has been reported as a potential novel SI-NEC marker, without protein expression recognition. Thus, we further studied whether the encoded protein may be a novel SI-NEC clinical biomarker.

DESIGN

OR51E1 coding sequence was cloned using total RNA from SI-NEC patient specimens. Quantitative real-time PCR analysis explored OR51E1 expression in laser capture microdissected SI-NEC cells and adjacent microenvironment cells. Moreover, immunohistochemistry investigated OR51E1 protein expression on operation and biopsy material from primary SI-NECs, mesentery, and liver metastases from 70 patients. Furthermore, double immunofluorescence studies explored the potential co-localization of the vesicular monoamine transporter 1 (SLC18A1, generally referred to as VMAT1) and OR51E1 in the neoplastic cells and in the intestinal mucosa adjacent to the tumor.

RESULTS

OR51E1 coding sequence analysis showed absence of mutation in SI-NEC patients at different stages of disease. OR51E1 expression was higher in microdissected SI-NEC cells than in the adjacent microenvironment cells. Furthermore, both membranous and cytoplasmic OR51E1 immunostaining patterns were detected in both primary SI-NECs and metastases. Briefly, 18/43 primary tumors, 7/28 mesentery metastases, and 6/18 liver metastases were 'positive' for OR51E1 in more than 50% of the tumor cells. In addition, co-localization studies showed that OR51E1 was expressed in >50% of the VMAT1 immunoreactive tumor cells and of the enterochromaffin cells in the intestinal mucosa adjacent to the tumor.

CONCLUSION

OR51E1 protein is a potential novel clinical tissue biomarker for SI-NECs. Moreover, we suggest its potential therapeutic molecular target development using solid tumor radioimmunotherapy.

Endogenous Voltage Potentials and the Microenvironment: Bioelectric Signals that Reveal, Induce and Normalize Cancer

Cancer may be a disease of geometry: a misregulation of the field of information that orchestrates individual cells' activities towards normal anatomy. Recent work identified molecular mechanisms underlying a novel system of developmental control: bioelectric gradients. Endogenous spatio-temporal differences in resting potential of non-neural cells provide instructive cues for cell regulation and complex patterning during embryogenesis and regeneration. It is now appreciated that these cues are an important layer of the dysregulation of cell: cell interactions that leads to cancer. Abnormal depolarization of resting potential (Vmem) is a convenient marker for neoplasia and activates a metastatic phenotype in genetically-normal cells in vivo. Moreover, oncogene expression depolarizes cells that form tumor-like structures, but is unable to form tumors if this depolarization is artificially prevented by misexpression of hyperpolarizing ion channels. Vmem triggers metastatic behaviors at considerable distance, mediated by transcriptional and epigenetic effects of electrically-modulated flows of serotonin and butyrate. While in vivo data on voltages in carcinogenesis comes mainly from the amphibian model, unbiased genetic screens and network profiling in rodents and human tissues reveal several ion channel proteins as bona fide oncogene and promising targets for cancer drug development. However, we propose that a focus on specific channel genes is just the tip of the iceberg. Bioelectric state is determined by post-translational gating of ion channels, not only from genetically-specified complements of ion translocators. A better model is a statistical dynamics view of spatial Vmem gradients. Cancer may not originate at the single cell level, since gap junctional coupling results in multi-cellular physiological networks with multiple stable attractors in bioelectrical state space. New medical applications await a detailed understanding of the mechanisms by which organ target morphology stored in real-time patterns of ion flows is perceived or mis-perceived by cells. Mastery of somatic voltage gradients will lead to cancer normalization or rebooting strategies, such as those that occur in regenerating and embryonic organs, resulting in transformative advances in basic biology and oncology.