Activation of the glutamate receptor GRM1 enhances angiogenic signaling to drive melanoma progression

Effect of conditioned media on the angiogenic activity of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are promising candidates for use in novel cell therapies, although such live cell products are highly complex compared with traditional drugs. For example, difficulties such as the control of manufacturing conditions hinder the manufacture of stable cell populations that maintain their therapeutic potency. Here, assuming that medium selection significantly affects cell potency, we focused on the culture media as a critical manufacturing factor influencing the therapeutic efficacy of MSCs. We therefore performed a tube formation assay to quantify the angiogenic activities of conditioned media used to culture human umbilical vein endothelial cells compared with unconditioned media. Comprehensive molecular genetic analysis using microarrays was applied to determine the effects of these media on signal transduction pathways. We found that activation of the vascular endothelial growth factor (VEGF) signaling pathway differed, and that VEGF concentration was dependent on the composition of the conditioned media. These results indicate that the activation level of cell signaling pathways which contribute to therapeutic efficacy may vary depending on the media components affecting MSCs during their cultivation. Moreover, they indicate that therapeutic efficacy will likely depend on how cells are handled during manufacture. These findings will enhance our understanding of the quality control measures required to ensure the efficacy and safety of cell therapy products.

Current State of Melanoma Therapy and Next Steps: Battling Therapeutic Resistance

Melanoma is the most aggressive and deadly form of skin cancer due to its high propensity to metastasize to distant organs. Significant progress has been made in the last few decades in melanoma therapeutics, most notably in targeted therapy and immunotherapy. These approaches have greatly improved treatment response outcomes; however, they remain limited in their abilities to hinder disease progression due, in part, to the onset of acquired resistance. In parallel, intrinsic resistance to therapy remains an issue to be resolved. In this review, we summarize currently available therapeutic options for melanoma treatment and focus on possible mechanisms that drive therapeutic resistance. A better understanding of therapy resistance will provide improved rational strategies to overcome these obstacles.

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

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

Riluzole-Loaded Nanostructured Lipid Carriers for Hyperproliferative Skin Diseases

Nanocarriers, and especially nanostructured lipid carriers (NLC), represent one of the most effective systems for topical drug administration. NLCs are biodegradable, biocompatible and provide a prolonged drug release. The glutamate release inhibitor Riluzole (RLZ) is a drug currently used for amyotrophic lateral sclerosis (ALS), with anti-proliferative effects potentially beneficial for diseases with excessive cell turnover. However, RLZ possesses low water solubility and high light-sensibility. We present here optimized NLCs loaded with RLZ (RLZ-NLCs) as a potential topical treatment. RLZ-NLCs were prepared by the hot-pressure homogenization method using active essential oils as liquid lipids, and optimized using the design of experiments approach. RLZ-NLCs were developed obtaining optimal properties for dermal application (mean size below 200 nm, negative surface charge and high RLZ entrapment efficacy). In vitro release study demonstrates that RLZ-NLCs allow the successful delivery of RLZ in a sustained manner. Moreover, RLZ-NLCs are not angiogenic and are able to inhibit keratinocyte cell proliferation. Hence, a NLCs delivery system loading RLZ in combination with natural essential oils constitutes a promising strategy against keratinocyte hyperproliferative conditions.

A phase I trial of riluzole and sorafenib in patients with advanced solid tumors: CTEP #8850

BACKGROUND

Overexpression of metabotropic glutamate receptor 1 (GRM1) has been implicated in the pathogenesis of multiple cancers. Riluzole, an inhibitor of glutamate release, showed synergistic antitumor activity in combination with the multi-kinase inhibitor sorafenib in preclinical models. This phase I trial identified the toxicity profile, dose-limiting toxicities, maximum tolerated dose (MTD), and pharmacokinetic and pharmacodynamic properties of riluzole combined with sorafenib in patients with advanced cancers.

PATIENTS AND METHODS

Patients with refractory solid tumors were enrolled utilizing a 3+3 dose-escalation design. Riluzole was given at 100 mg PO BID in combination with sorafenib, beginning at 200 mg PO daily and escalating in 200 mg increments per level in 28-day cycles. Restaging evaluations were performed every 2 cycles.

RESULTS

35 patients were enrolled over 4 dose levels. The MTD was declared at dose level 3 (riluzole: 100 mg PO BID; sorafenib: 400 mg AM/200 mg PM). Pharmacokinetic analyses did not reveal definitive evidence of drug-drug interactions. Consistent decreases in phospho-forms of ERK and AKT in tumor tissue analyses with accompanying decrease in GRM1 expression and increase in pro-apoptotic BIM suggest target engagement by the combination. Best responses included a partial response in 1 (2.9%) patient with pancreatic acinar cell carcinoma with a KANK4-RAF1 fusion, and stable disease in 11 (36%) patients.

CONCLUSION

Combination therapy with riluzole and sorafenib was safe and tolerable in patients with advanced solid tumors. The partial response in a patient with a RAF1 fusion suggests that further exploration in a genomically selected cohort may be warranted.

A 211At-labelled mGluR1 inhibitor induces cancer senescence to elicit long-lasting anti-tumor efficacy

Metabotropic glutamate receptor 1 (mGluR1), a key mediator of glutamatergic signaling, is frequently overexpressed in tumor cells and is an attractive drug target for most cancers. Here, we present a targeted radiopharmaceutical therapy strategy that antagonistically recognizes mGluR1 and eradicates mGluR1⁺ human tumors by harnessing a small-molecule alpha (α)-emitting radiopharmaceutical, ²¹¹At-AITM. A single dose of ²¹¹At-AITM (2.96 MBq) in mGluR1⁺ cancers exhibits long-lasting in vivo antitumor efficacy across seven subtypes of four of the most common tumors, namely, breast cancer, pancreatic cancer, melanoma, and colon cancers, with little toxicity. Moreover, complete regression of mGluR1⁺ breast cancer and pancreatic cancer is observed in approximate 50% of tumor-bearing mice. Mechanistically, the functions of ²¹¹At-AITM are uncovered in downregulating mGluR1 oncoprotein and inducing senescence of tumor cells with a reprogrammed senescence-associated secretory phenotype. Our findings suggest α-radiopharmaceutical therapy with ²¹¹At-AITM can be a useful strategy for mGluR1⁺ pan-cancers, regardless of their tissue of origin.

Blocked metabotropic glutamate receptor 5 enhances chemosensitivity in hepatocellular carcinoma and attenuates chemotoxicity in the normal liver by regulating DNA damage

DNA damaging agents are used as chemotherapeutics in many cancers, including hepatocellular carcinoma (HCC). However, they are associated with problems such as low sensitivity to chemotherapy and the induction of liver injury, underscoring the need to identify new therapies. Here, we investigated the differential regulatory effect of metabotropic glutamate receptor 5 (mGlu5) on chemosensitivity in HCC and chemotoxicity to the normal liver. The expression of mGlu5 was higher in HCC than in the normal liver, and correlated with poor prognosis according to The Cancer Genome Atlas database and Integrative Molecular Database of Hepatocellular Carcinoma. Cisplatin, oxaliplatin or methyl methanesulfonate (MMS) caused cell death by decreasing mGlu5 expression in HCC cells and increased mGlu5 expression in hepatic cells. In HCC cells, inhibition of mGlu5 aggravated MMS-induced DNA damage by increasing intracellular Ca2+ overload and mitogen-activated protein kinase (MAPK) activation, thereby promoting cell death, and activation of mGlu5 rescued the effect of MMS. However, in hepatic cells, mGlu5 inhibition alleviated MMS-induced DNA damage by downregulating Ca2+-derived MAPK pathways to advance hepatic cell survival. The opposite effects of mGlu5 overexpression or knockdown on MMS-induced DNA damage supported that cell death is a result of the differential regulation of mGlu5 expression. Inhibition of mGlu5 increased chemosensitivity and decreased chemotoxicity in a rat tumor model. This study suggests that mGlu5 inhibition could act synergistically with HCC chemotherapeutics with minimal side effects, which may improve the treatment of patients with HCC in the future.

Implications of a Neuronal Receptor Family, Metabotropic Glutamate Receptors, in Cancer Development and Progression

Cancer is the second leading cause of death, and incidences are increasing globally. Simply defined, cancer is the uncontrolled proliferation of a cell, and depending on the tissue of origin, the cancer etiology, biology, progression, prognosis, and treatment will differ. Carcinogenesis and its progression are associated with genetic factors that can either be inherited and/or acquired and are classified as an oncogene or tumor suppressor. Many of these genetic factors converge on common signaling pathway(s), such as the MAPK and PI3K/AKT pathways. In this review, we will focus on the metabotropic glutamate receptor (mGluR) family, an upstream protein that transmits extracellular signals into the cell and has been shown to regulate many aspects of tumor development and progression. We explore the involvement of members of this receptor family in various cancers that include breast cancer, colorectal cancer, glioma, kidney cancer, melanoma, oral cancer, osteosarcoma, pancreatic cancer, prostate cancer, and T-cell cancers. Intriguingly, depending on the member, mGluRs can either be classified as oncogenes or tumor suppressors, although in general most act as an oncogene. The extensive work done to elucidate the role of mGluRs in various cancers suggests that it might be a viable strategy to therapeutically target glutamatergic signaling.

Glutamatergic system components as potential biomarkers and therapeutic targets in cancer in non-neural organs

Glutamate is one of the most abundant amino acids in the blood. Besides its role as a neurotransmitter in the brain, it is a key substrate in several metabolic pathways and a primary messenger that acts through its receptors outside the central nervous system (CNS). The two main types of glutamate receptors, ionotropic and metabotropic, are well characterized in CNS and have been recently analyzed for their roles in non-neural organs. Glutamate receptor expression may be particularly important for tumor growth in organs with high concentrations of glutamate and might also influence the propensity of such tumors to set metastases in glutamate-rich organs, such as the liver. The study of glutamate transporters has also acquired relevance in the physiology and pathologies outside the CNS, especially in the field of cancer research. In this review, we address the recent findings about the expression of glutamatergic system components, such as receptors and transporters, their role in the physiology and pathology of cancer in non-neural organs, and their possible use as biomarkers and therapeutic targets.

The new role of riluzole in the treatment of pancreatic cancer through the apoptosis and autophagy pathways

Pancreatic cancer is always diagnosed at an advanced stage. Hence, chemotherapy becomes the best choice for patients. Therefore, new anticancer drugs for pancreatic cancer are needed. Riluzole (RIL) is mainly used to treat amyotrophic lateral sclerosis clinically, but many previous studies have shown that RIL could inhibit tumors. However, no report has explored the association between RIL and pancreatic cancer. To validate this association, we performed this study. Our data showed that RIL could induce cytotoxicity, block the cell cycle, and inhibit clone formation, apoptosis, and migration in pancreatic cancer cells. Moreover, we demonstrated that RIL could suppress autophagy. However, more experiments will be needed to validate the reliability of our conclusions. In summary, our data suggest that RIL might provide clues for the development of a treatment for human pancreatic cancer in the future.

Glutamatergic Signaling a Therapeutic Vulnerability in Melanoma

Like other cancers, melanomas are associated with the hyperactivation of two major cell signaling cascades, the MAPK and PI3K/AKT pathways. Both pathways are activated by numerous genes implicated in the development and progression of melanomas such as mutated BRAF, RAS, and NF1. Our lab was the first to identify yet another driver of melanoma, Metabotropic Glutamate Receptor 1 (protein: mGluR1, mouse gene: Grm1, human gene: GRM1), upstream of the MAPK and PI3K/AKT pathways. Binding of glutamate, the natural ligand of mGluR1, activates MAPK and PI3K/AKT pathways and sets in motion the deregulated cellular responses in cell growth, cell survival, and cell metastasis. In this review, we will assess the proposed modes of action that mediate the oncogenic properties of mGluR1 in melanoma and possible application of anti-glutamatergic signaling modulator(s) as therapeutic strategy for the treatment of melanomas.

Neuroendocrine Factors in Melanoma Pathogenesis

Simple Summary

Melanoma is a very aggressive and fatal malignant tumor. While curable if diagnosed in its early stages, advanced melanoma, despite the complex therapeutic approaches, is associated with one of the highest mortality rates. Hence, more and more studies have focused on mechanisms that may contribute to melanoma development and progression. Various studies suggest a role played by neuroendocrine factors which can act directly on tumor cells, modulating their proliferation and metastasis capability, or indirectly through immune or inflammatory processes that impact disease progression. However, there are still multiple areas to explore and numerous unknown features to uncover. A detailed exploration of the mechanisms by which neuroendocrine factors can influence the clinical course of the disease could open up new areas of biomedical research and may lead to the development of new therapeutic approaches in melanoma.

Abstract

Melanoma is one of the most aggressive skin cancers with a sharp rise in incidence in the last decades, especially in young people. Recognized as a significant public health issue, melanoma is studied with increasing interest as new discoveries in molecular signaling and receptor modulation unlock innovative treatment options. Stress exposure is recognized as an important component in the immune-inflammatory interplay that can alter the progression of melanoma by regulating the release of neuroendocrine factors. Various neurotransmitters, such as catecholamines, glutamate, serotonin, or cannabinoids have also been assessed in experimental studies for their involvement in the biology of melanoma. Alpha-MSH and other neurohormones, as well as neuropeptides including substance P, CGRP, enkephalin, beta-endorphin, and even cellular and molecular agents (mast cells and nitric oxide, respectively), have all been implicated as potential factors in the development, growth, invasion, and dissemination of melanoma in a variety of in vitro and in vivo studies. In this review, we provide an overview of current evidence regarding the intricate effects of neuroendocrine factors in melanoma, including data reported in recent clinical trials, exploring the mechanisms involved, signaling pathways, and the recorded range of effects.

Exome hits demystified: The next frontier

Severe mental illnesses such as schizophrenia and bipolar disorder have complex inheritance patterns, involving both common and rare variants. Whole exome sequencing is a promising approach to find out the rare genetic variants. We had previously reported several rare variants in multiplex families with severe mental illnesses. The current article tries to summarise the biological processes and pattern of expression of genes harbouring the aforementioned variants, linking them to known clinical manifestations through a methodical narrative review. Of the 28 genes considered for this review from 7 families with multiple affected individuals, 6 genes are implicated in various neuropsychiatric manifestations including some variations in the brain morphology assessed by magnetic resonance imaging. Another 15 genes, though associated with neuropsychiatric manifestations, did not have established brain morphological changes whereas the remaining 7 genes did not have any previously recorded neuropsychiatric manifestations at all. Wnt/b-catenin signaling pathway was associated with 6 of these genes and PI3K/AKT, calcium signaling, ERK, RhoA and notch signaling pathways had at least 2 gene associations. We present a comprehensive review of biological and clinical knowledge about the genes previously reported in multiplex families with severe mental illness. A 'disease in dish approach' can be helpful to further explore the fundamental mechanisms.

Hypoxia and Extracellular Acidification as Drivers of Melanoma Progression and Drug Resistance

Hypoxia and elevated extracellular acidification are prevalent features of solid tumors and they are often shown to facilitate cancer progression and drug resistance. In this review, we have compiled recent and most relevant research pertaining to the role of hypoxia and acidification in melanoma growth, invasiveness, and response to therapy. Melanoma represents a highly aggressive and heterogeneous type of skin cancer. Currently employed treatments, including BRAF V600E inhibitors and immune therapy, often are not effective due to a rapidly developing drug resistance. A variety of intracellular mechanisms impeding the treatment were discovered. However, the tumor microenvironment encompassing stromal and immune cells, extracellular matrix, and physicochemical conditions such as oxygen level or acidity, may also influence the therapy effectiveness. Hypoxia and acidification are able to reprogram the metabolism of melanoma cells, enhance their survival and invasiveness, as well as promote the immunosuppressive environment. For this reason, these physicochemical features of the melanoma niche and signaling pathways related to them emerge as potential therapeutic targets.

2-Aminothiazole: A privileged scaffold for the discovery of anti-cancer agents

Cancer has been the second heath killer being next only to cardiovascular diseases in human society. Although many efforts have been taken for cancer therapy and many achievements have been yielded in the diagnosis and treatment of cancer, the current first-line anti-cancer agents are insufficient owing to the emergence of multi-drug resistance and side effects. Therefore, it is urgent to develop new anti-cancer agents with high activity and low toxicity. 2-Aminothiazole is a class of important scaffold which widely distributes in many natural and synthetic compounds with many pharmacological effects including the potential anti-cancer activity. In this review, we summarized the recent progress of 2-aminothiazole as a privileged scaffold for the discovery of anti-cancer agents based on biological targets, such as tubulin protein, histone acetylase/histone deacetylase (HAT/HDAC), phosphatidylinositol 3-kinases (PI3Ks), Src/Abl kinase, BRAF kinase, epidermal growth factor receptor (EGFR) kinase and sphingosine kinase (SphK), and also investigated the structure-activity relationships (SARs) of most compounds. It is believed that this review could be helpful for medicinal chemists in the discovery of more anti-cancer agents bearing 2-aminothiazole scaffold with excellent activity and high therapeutic index.

Metabolic Signaling Cascades Prompted by Glutaminolysis in Cancer

Simple Summary

Within the last few years, accumulating evidences suggest the involvement of altered metabolisms in human diseases including cancer. Metabolism is defined as the sum of biochemical processes in living organisms that produce and consume energy. Tumor growth requires restructuring of cellular metabolism to meet the increasing demand for building blocks to support the ever-increasing cancer cell numbers. The principle of perturbed metabolism in tumors is known for 50–60 years, it regains greater appreciation within the last few years with the realization that there is interdependency between metabolism and all aspects of cellular function including regulation and control of cell growth. Tumor cells do not need stimulation signals from the surrounding environment to promote cell proliferation; in some cases, the tumor cells can generate their own growth signals. In order to support the continuous tumor cell growth even under stressful conditions, a change in metabolism is necessary to fulfill the continuous demand for energy and building blocks. A better understanding of the relationship between tumor environment and altered cell metabolisms will provide valuable insights to design innovative approaches to limit the supply of energy and macromolecules for the treatment of cancer including melanoma.

Abstract

Aberrant glutamatergic signaling has been implicated in altered metabolic activity and the demand to synthesize biomass in several types of cancer including melanoma. In the last decade, there has been a significant contribution to our understanding of metabolic pathways. An increasing number of studies are now emphasizing the importance of glutamate functioning as a signaling molecule and a building block for cancer progression. To that end, our group has previously illustrated the role of glutamatergic signaling mediated by metabotropic glutamate receptor 1 (GRM1) in neoplastic transformation of melanocytes in vitro and spontaneous development of metastatic melanoma in vivo. Glutamate, the natural ligand of GRM1, is one of the most abundant amino acids in humans and the predominant excitatory neurotransmitter in the central nervous system. Elevated levels of glutaminolytic mitochondrial tricarboxylic acid (TCA) cycle intermediates, especially glutamate, have been reported in numerous cancer cells. Herein, we highlight and critically review metabolic bottlenecks that are prevalent during tumor evolution along with therapeutic implications of limiting glutamate bioavailability in tumors.

Discovery of a Novel Hybrid of Vorinostat and Riluzole as a Potent Antitumor Agent

Vorinostat (suberoylanilide hydroxamic acid) was the first approved histone deacetylase (HDAC) inhibitor in a group of validated cancer therapeutic agents targeting epigenetics. Riluzole is a drug used to treat amyotrophic lateral sclerosis, the antitumor potency of which has been recently revealed. Herein, a novel hybrid of vorinostat and riluzole (compound 1) was rationally designed, synthesized, and evaluated. Compared with vorinostat, compound 1 exhibited superior total HDAC inhibitory activity and similar HDAC isoform selective profiles. The intracellular HDAC inhibition of compound 1 was confirmed by Western blot analysis. Moreover, compound 1 possessed more potent in vitro antiproliferative activity against all tested solid and hematological tumor cell lines than vorinostat. In vitro metabolic stability evaluation of compound 1 revealed better human plasma stability and comparable human liver microsomal stability than vorinostat. Additionally, compound 1 demonstrated more significant in vivo antitumor activity in a MDA-MB-231 xenograft model than vorinostat, which could be attributed to its superior in vitro antiproliferative activity and metabolic stability. Taken together, the results presented here support further research and development of compound 1 as a promising antitumor agent.

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

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

GRM4 inhibits the proliferation, migration, and invasion of human osteosarcoma cells through interaction with CBX4

In recent years, the survey of metabolic glutamate receptor 4 (GRM4) in tumor biology has been gradually concerned. There are currently few studies on GRM4 in osteosarcoma, and the biological function is not clear. Analysis of TCGA database showed that there was no substantial deviation in the expression of GRM4 between osteosarcoma and normal tissues. In the subsequent experiments, there is no significant difference in either mRNA or protein levels among immortalized human osteoblasts and various osteosarcoma cells. With the overexpression of GRM4, cell proliferation, migration and invasion were inhibited obviously. It was further revealed that GRM4 can interact with CBX4 to restrict the nuclear localization of CBX4 and affect the transcriptional activity of HIF-1α. This is the evidence supporting the interaction between GRM4 and CBX4, which could inhibit the malignant behavior of osteosarcoma cells through the GRM4/CBX4/HIF-1α signaling pathway.

Schwann cell reprogramming and lung cancer progression: a meta-analysis of transcriptome data

Schwann cells were identified in the tumor surrounding area prior to initiate the invasion process underlying connective tissue. These cells promote cancer invasion through direct contact, while paracrine signaling and matrix remodeling are not sufficient to proceed. Considering the intertwined structure of signaling, regulatory, and metabolic processes within a cell, we employed a genome-scale biomolecular network. Accordingly, a meta-analysis of Schwann cells associated transcriptomic datasets was performed, and the core information on differentially expressed genes (DEGs) was obtained by statistical analyses. Gene set over-representation analyses was performed on core DEGs to identify significantly functional and pathway enrichment analysis between Schwann cells and, lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC). DEGs were further integrated with genome-scale human biomolecular networks. miRNAs were proposed by the reconstruction of a transcriptional and post-transcriptional regulatory network. Moreover, microarray-based transcriptome profiling was performed, and the prognostic power of selected dedifferentiated Schwann cell biomolecules was predicted. We observed that pathways associated with Schwann cells dedifferentiation was overexpressed in lung cancer samples. However, genes associated with Schwann cells migration inhibition system were downregulated. Besides, miRNA targeting those pathways were also deregulated. In this study, we report valuable data for further experimental and clinical analysis, because the proposed biomolecules have significant potential as systems biomarkers for screening or for therapeutic purposes in perineural invasion of lung cancer.

Concurrent Targeting of Glutaminolysis and Metabotropic Glutamate Receptor 1 (GRM1) Reduces Glutamate Bioavailability in GRM1+ Melanoma

Aberrant glutamatergic signaling has been implicated in altered metabolic activity in many cancer types, including malignant melanoma. Previously, we have illustrated the role of metabotropic glutamate receptor 1 (GRM1) in neoplastic transformation of melanocytes in vitro and spontaneous metastatic melanoma in vivo. In this study, we showed that autocrine stimulation constitutively activates the GRM1 receptor and its downstream mitogenic signaling. GRM1-activated (GRM1+) melanomas exhibited significantly increased expression of glutaminase (GLS), which catalyzes the first step in the conversion of glutamine to glutamate. In cultured GRM1+ melanoma cell lines, CB-839, a potent, selective, and orally bioavailable inhibitor of GLS, suppressed cell proliferation, while riluzole, an inhibitor of glutamate release, promoted apoptotic cell death in vitro and in vivo. Combined treatment with CB-839 and riluzole treatment proved to be superior to single-agent treatment, restricting glutamate bioavailability and leading to effective suppression of tumor cell proliferation in vitro and tumor progression in vivo. Hyperactivation of GRM1 in malignant melanoma is an oncogenic driver, which acts independently of canonical melanoma proto-oncogenes, BRAF or NRAS. Overall, these results indicate that expression of GRM1 promotes a metabolic phenotype that supports increased glutamate production and autocrine glutamatergic signaling, which can be pharmacologically targeted by decreasing glutamate bioavailability and the GLS-dependent glutamine to glutamate conversion. SIGNIFICANCE: These findings demonstrate that targeting glutaminolytic glutamate bioavailability is an effective therapeutic strategy for GRM1-activated tumors.

Glutamate triggers intracellular Ca2+ oscillations and nitric oxide release by inducing NAADP- and InsP3 -dependent Ca2+ release in mouse brain endothelial cells

The neurotransmitter glutamate increases cerebral blood flow by activating postsynaptic neurons and presynaptic glial cells within the neurovascular unit. Glutamate does so by causing an increase in intracellular Ca²⁺ concentration ([Ca²⁺ ]_i ) in the target cells, which activates the Ca²⁺ /Calmodulin-dependent nitric oxide (NO) synthase to release NO. It is unclear whether brain endothelial cells also sense glutamate through an elevation in [Ca²⁺ ]_i and NO production. The current study assessed whether and how glutamate drives Ca²⁺ -dependent NO release in bEND5 cells, an established model of brain endothelial cells. We found that glutamate induced a dose-dependent oscillatory increase in [Ca²⁺ ]_i , which was maximally activated at 200 μM and inhibited by α-methyl-4-carboxyphenylglycine, a selective blocker of Group 1 metabotropic glutamate receptors. Glutamate-induced intracellular Ca²⁺ oscillations were triggered by rhythmic endogenous Ca²⁺ mobilization and maintained over time by extracellular Ca²⁺ entry. Pharmacological manipulation revealed that glutamate-induced endogenous Ca²⁺ release was mediated by InsP₃ -sensitive receptors and nicotinic acid adenine dinucleotide phosphate (NAADP) gated two-pore channel 1. Constitutive store-operated Ca²⁺ entry mediated Ca²⁺ entry during ongoing Ca²⁺ oscillations. Finally, glutamate evoked a robust, although delayed increase in NO levels, which was blocked by pharmacologically inhibition of the accompanying intracellular Ca²⁺ signals. Of note, glutamate induced Ca²⁺ -dependent NO release also in hCMEC/D3 cells, an established model of human brain microvascular endothelial cells. This investigation demonstrates for the first time that metabotropic glutamate-induced intracellular Ca²⁺ oscillations and NO release have the potential to impact on neurovascular coupling in the brain.

Integrated molecular analysis of Tamoxifen-resistant invasive lobular breast cancer cells identifies MAPK and GRM/mGluR signaling as therapeutic vulnerabilities

Invasive lobular breast cancer (ILC) is an understudied malignancy with distinct clinical, pathological, and molecular features that distinguish it from the more common invasive ductal carcinoma (IDC). Mounting evidence suggests that estrogen receptor-alpha positive (ER+) ILC has a poor response to Tamoxifen (TAM), but the mechanistic drivers of this are undefined. In the current work, we comprehensively characterize the SUM44/LCCTam ILC cell model system through integrated analysis of gene expression, copy number, and mutation, with the goal of identifying actionable alterations relevant to clinical ILC that can be co-targeted along with ER to improve treatment outcomes. We show that TAM has several distinct effects on the transcriptome of LCCTam cells, that this resistant cell model has acquired copy number alterations and mutations that impinge on MAPK and metabotropic glutamate receptor (GRM/mGluR) signaling networks, and that pharmacological inhibition of either improves or restores the growth-inhibitory actions of endocrine therapy.

Diet-induced obesity alters the maternal metabolome and early placenta transcriptome and decreases placenta vascularity in the mouse

Maternal obesity is associated with an increased risk of obesity and metabolic disease in offspring. Increasing evidence suggests that the placenta plays an active role in fetal programming. In this study, we used a mouse model of diet-induced obesity to demonstrate that the abnormal metabolic milieu of maternal obesity sets the stage very early in pregnancy by altering the transcriptome of placenta progenitor cells in the preimplantation (trophectoderm [TE]) and early postimplantation (ectoplacental cone [EPC]) placenta precursors, which is associated with later changes in placenta development and function. Sphingolipid metabolism was markedly altered in the plasma of obese dams very early in pregnancy as was expression of genes related to sphingolipid processing in the early placenta. Upregulation of these pathways inhibits angiogenesis and causes endothelial dysfunction. The expression of many other genes related to angiogenesis and vascular development were disrupted in the TE and EPC. Other key changes in the maternal metabolome in obese dams that are likely to influence placenta and fetal development include a marked decrease in myo and chiro-inositol. These early metabolic and gene expression changes may contribute to phenotypic changes in the placenta, as we found that exposure to a high-fat diet decreased placenta microvessel density at both mid and late gestation. This is the first study to demonstrate that maternal obesity alters the transcriptome at the earliest stages of murine placenta development.

Targeting metabotropic glutamate receptors in the treatment of primary brain tumors

In spite of the recent advancement in the molecular characterization of malignant gliomas and medulloblastomas, the treatment of primary brain tumors remains suboptimal. The use of small molecule inhibitors of intracellular signaling pathways, inhibitors of angiogenesis, and immunotherapic agents is limited by systemic adverse effects, limited brain penetration, and, in some cases, lack of efficacy. Thus, adjuvant chemo-therapy and radiotherapy still remain the gold standard in the treatment of grade-IV astrocytoma (glioblastoma multiforme) and medulloblastoma. We review evidence that supports the development of mGlu3 receptor antagonists as add-on drugs in the treatment of malignant gliomas. These drugs appear to display pleiotropic effect on tumor cells, affecting proliferation, differentiation, and response to chemotherapy. mGlu1 and mGlu4 receptors could also be targeted by potential anticancer agents in the treatment of malignant gliomas and medulloblastoma, but extensive research is required for target validation.

Role of the Nervous System in Tumor Angiogenesis

The development of cancer involves an intricate process, wherein many identified and unidentified factors play a role. Tumor angiogenesis, growth of new blood vessels, is one of the major prerequisites for tumor growth as tumor cells rely on adequate oxygen and nutrient supply as well as the removal of waste products. Growth factors including VEGF orchestrate the development of angiogenesis. In addition, nervous system via the release of neurotransmitters contributes to tumor angiogenesis. 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 via regulating tumor angiogenesis. Various neurotransmitters have been reported to play an important role in tumor angiogenesis.

Optical coherence tomography angiography in choroidal melanoma and nevus

Synopsis

In optical coherence tomography angiography, the choroidal vascular flow rate in choroidal melanoma is significantly lower than that in choroidal nevus.

Objective

The objective of this study was to describe the choriocapillaris and retinal features imaged by optical coherence tomography angiography (OCTA) in eyes with choroidal nevus from small malignant choroidal melanoma.

Methods

In this retrospective, noninvasive, observational study, 11 patients diagnosed with small choroidal mass (five with choroidal nevus and six with malignant melanoma) who underwent dilated fundus examination, ocular ultrasonography and OCTA images were compared.

Results

In choroidal nevus of all patients, OCTA demonstrated a hyporeflective mass with no significant deformity of choroidal vasculature and an intact retinal pigment epithelium (RPE)–Bruch’s membrane complex. The flow void mass was surrounded by an intense vascular rim named as surface microvasculature (SMV) that had an approximately similar flow rate median of 63.68 mm² (60.42–67.62 mm²), comparable with the median of the contralateral normal eye of 61.77 mm² (60.42–64.53 mm²; P>0.09) for nevi. OCTA showed an obscured Bruch’s membrane–RPE–Bruch’s membrane complex and outer retinal layer in choroidal melanomas. Choriocapillaris flow rate over the melanomas was 55.73% (41.93%–60.82%), and the corresponding normal areas had a flow area of 62.75% (61.99%–63.10%; P=0.01). A flow rate difference between choroidal melanoma and nevus was significant (P=0.006). Axial and peripheral feeding vessels were more dilated and tortuous compared with benign nevi.

Conclusion

Decreased flow rate of SMV of choroidal melanoma cases compared with nevi was a significant finding. Detection of characteristic vascular features of choroidal melanoma by OCTA could make OCTA an assuring diagnostic modality to differentiate malignant lesions.

Exosomes released by metabotropic glutamate receptor 1 (GRM1) expressing melanoma cells increase cell migration and invasiveness

Exosomes are naturally occurring membrane-bound nanovesicles generated constitutively and released by various cell types, and often in higher quantities by tumor cells. Exosomes may facilitate communication between the primary tumor and its local microenvironment, supporting cell invasion and other early events in metastasis. A neuronal receptor, metabotropic glutamate receptor 1 (GRM1), when ectopically expressed in melanocytes, induces in vitro melanocytic transformation and spontaneous malignant melanoma development in vivo in a transgenic mouse model. Our earlier studies showed that genetic modulation in GRM1 expression by siRNA or disruption of GRM1-mediated glutamate signaling interfere with downstream effectors resulting in a decrease in both cell proliferation in vitro and tumor progression in vivo. In this study, we sought to determine whether exosome formation might play a role in GRM1 mediated melanoma development and progression. To test this, we utilized in vitro cultured cells in which GRM1 expression and function could be modulated by pharmacological and genetic means and determined effects on exosome production. We also tested the effects of exosomes from GRM1 expressing melanoma cells on growth, migration and invasion of GRM1 negative cells. Our results show that although GRM1 expression has no influence on exosome quantity, exosomes produced by GRM1-positive cells modulate the ability of the recipient cell to migrate, invade and exhibit anchorage-independent cell growth.

Adapt, Recycle, and Move on: Proteostasis and Trafficking Mechanisms in Melanoma

Melanoma has emerged as a paradigm of a highly aggressive and plastic cancer, capable to co-opt the tumor stroma in order to adapt to the hostile microenvironment, suppress immunosurveillance mechanisms, and disseminate. In particular, oncogene- and aneuploidy-driven dysregulations of proteostasis in melanoma cells impose a rewiring of central proteostatic processes, such as the heat shock and unfolded protein responses, autophagy, and the endo-lysosomal system, to avoid proteotoxicity. Research over the past decade has indicated that alterations in key nodes of these proteostasis pathways act in conjunction with crucial oncogenic drivers to increase intrinsic adaptations of melanoma cells against proteotoxic stress, modulate the high metabolic demand of these cancer cells and the interface with other stromal cells, through the heightened release of soluble factors or exosomes. Here, we overview and discuss how key proteostasis pathways and vesicular trafficking mechanisms are turned into vital conduits of melanoma progression, by supporting cancer cell's adaptation to the microenvironment, limiting or modulating the ability to respond to therapy and fueling melanoma dissemination.

Computational Identification of Novel Stage-Specific Biomarkers in Colorectal Cancer Progression

It is well-known that the conversion of normal colon epithelium to adenoma and then to carcinoma stems from acquired molecular changes in the genome. The genetic basis of colorectal cancer has been elucidated to a certain extent, and much remains to be known about the identity of specific cancer genes that are associated with the advancement of colorectal cancer from one stage to the next. Here in this study we attempted to identify novel cancer genes that could underlie the stage-specific progression and metastasis of colorectal cancer. We conducted a stage-based meta-analysis of the voluminous tumor genome-sequencing data and mined using multiple approaches for novel genes driving the progression to stage-II, stage-III and stage-IV colorectal cancer. The consensus of these driver genes seeded the construction of stage-specific networks, which were then analyzed for the centrality of genes, clustering of subnetworks, and enrichment of gene-ontology processes. Our study identified three novel driver genes as hubs for stage-II progression: DYNC1H1, GRIN2A, GRM1. Four novel driver genes were identified as hubs for stage-III progression: IGF1R, CPS1, SPTA1, DSP. Three novel driver genes were identified as hubs for stage-IV progression: GSK3B, GGT1, EIF2B5. We also identified several non-driver genes that appeared to underscore the progression of colorectal cancer. Our study yielded potential diagnostic biomarkers for colorectal cancer as well as novel stage-specific drug targets for rational intervention. Our methodology is extendable to the analysis of other types of cancer to fill the gaps in our knowledge.

Metabotropic glutamate receptors in cancer

Metabotropic glutamate receptors (mGluRs) are widely known for their roles in synaptic signaling. However, accumulating evidence suggests roles of mGluRs in human malignancies in addition to synaptic transmission. Somatic cell homeostasis presents intriguing possibilities of mGluRs and glutamate signaling as novel targets for human cancers. More recently, aberrant glutamate signaling has been shown to participate in the transformation and maintenance of various cancer types, including glioma, melanoma skin cancer, breast cancer, and prostate cancer, indicating that genes encoding mGluRs, GRMs, can function as oncogenes. Here, we provide a review on the interactions of mGluRs and their ligand, glutamate, in processes that promote the growth of tumors of neuronal and non-neuronal origins. Further, we discuss the evolution of riluzole, a glutamate release inhibitor approved for amyotrophic lateral sclerosis (ALS), but now fashioned as an mGluR1 inhibitor for melanoma therapy and as a radio-sensitizer for tumors that have metastasized to the brain. With the success of riluzole, it is not far-fetched to believe that other drugs that may act directly or indirectly on other mGluRs can be beneficial for multiple applications. This article is part of the Special Issue entitled 'Metabotropic Glutamate Receptors, 5 years on'.

Genetics of melanoma progression: the rise and fall of cell senescence

There are many links between cell senescence and the genetics of melanoma, meaning both familial susceptibility and somatic-genetic changes in sporadic melanoma. For example, CDKN2A, the best-known melanoma susceptibility gene, encodes two effectors of cell senescence, while other familial melanoma genes are related to telomeres and their maintenance. This article aimed to analyze our current knowledge of the genetic or epigenetic driver changes necessary to generate a cutaneous metastatic melanoma, the commonest order in which these occur, and the relation of these changes to the biology and pathology of melanoma progression. Emphasis is laid on the role of cell senescence and the escape from senescence leading to cellular immortality, the ability to divide indefinitely.

Atypical signaling of metabotropic glutamate receptor 1 in human melanoma cells

The metabotropic glutamate 1 (mGlu1) receptor has emerged as a novel target for the treatment of metastatic melanoma and various other cancers. Our laboratory has demonstrated that a selective, non-competitive mGlu1 receptor antagonist slows human melanoma growth in vitro and in vivo. In this study, we sought to determine if the activation of a canonical G protein-dependent signal transduction cascade, which is often used as an output of mGlu1 receptor activity in neuronal cells, correlated with mGlu1 receptor-mediated melanoma cell viability. Glutamate, the endogenous ligand of mGlu1 receptors, significantly increased melanoma cell viability, but did not stimulate phosphoinositide (PI) hydrolysis in several human melanoma cell lines. In contrast, melanoma cell viability was not increased by quisqualate, a highly potent mGlu1 receptor agonist, or DHPG, a selective group I mGlu receptor agonist. Similarly to glutamate, quisqualate also failed to stimulate PI hydrolysis in mGlu1 receptor-expressing melanoma cells. These results suggest that the canonical G protein-dependent signal transduction cascade is not coupled to mGlu1 receptors in all human melanoma cells. On the other hand, dynamin inhibition selectively decreased viability of mGlu1 receptor-expressing melanoma cells, suggesting that a mechanism requiring internalization may control melanoma cell viability. Taken together, these data demonstrate that the approaches commonly used to study mGlu1 receptor function and signaling in other systems may be inappropriate for studying mGlu1 receptor-mediated melanoma cell viability.

The current management of brain metastasis in melanoma: a focus on riluzole

Brain metastasis is a common endpoint in human malignant melanoma, and the prognosis for patients remains poor despite advancements in therapy. Current treatment for melanoma metastatic to the brain is grouped into those providing symptomatic relief such as corticosteroids and antiepileptic agents, to those that are disease modifying. Related to the latter group, recent studies have demonstrated that aberrant glutamate signaling plays a role in the transformation and maintenance of various cancer types, including melanoma. Glutamate secretion from these and surrounding cells have been found to stimulate regulatory pathways that control tumor growth, proliferation and survival in vitro and in vivo. The antiglutamatergic actions of an inhibitor of glutamate release, riluzole, have been detected by its ability to clear glutamate from the synapse, and it has been shown to inhibit glutamate release rather than directly inhibiting glutamate receptors. Preclinical studies have demonstrated the ability of riluzole to act as a radiosensitizing agent in melanoma. The effect of riluzole on downstream glutamatergic signaling has pointed to cross talk between the metabotropic G-protein-coupled glutamate receptors implicated in a subset of human melanomas with other signaling pathways, including apoptotic, angiogenic, ROS and cell invasion mechanisms, thus establishing its potential to be further explored in combination therapy regimens for both primary human melanoma and melanoma metastatic to the brain.

Metabotropic glutamate receptor 1 acts as a dependence receptor creating a requirement for glutamate to sustain the viability and growth of human melanomas

Metabotropic glutamate 1 (mGlu) receptor has been proposed as a target for the treatment of metastatic melanoma. Studies have demonstrated that inhibiting the release of glutamate (the natural ligand of mGlu1 receptors), results in a decrease of melanoma tumor growth in mGlu1 receptor-expressing melanomas. Here we demonstrate that mGlu1 receptors, which have been previously characterized as oncogenes, also behave like dependence receptors by creating a dependence on glutamate for sustained cell viability. In the mGlu1 receptor-expressing melanoma cell lines SK-MEL-2 (SK2) and SK-MEL-5 (SK5), we show that glutamate is both necessary and sufficient to maintain cell viability, regardless of underlying genetic mutations. Addition of glutamate increased DNA synthesis, whereas removal of glutamate not only suppressed DNA synthesis but also promoted cell death in SK2 and SK5 melanoma cells. Using genetic and pharmacological inhibitors, we established that this effect of glutamate is mediated by the activation of mGlu1 receptors. The stimulatory potential of mGlu1 receptors was further confirmed in vivo in a melanoma cell xenograft model. In this model, subcutaneous injection of SK5 cells with short hairpin RNA-targeted downregulation of mGlu1 receptors resulted in a decrease in the rate of tumor growth relative to control. We also demonstrate for the first time that a selective mGlu1 receptor antagonist JNJ16259685 ((3,4-Dihydro-2H-pyrano[2,3-b]quinolin-7-yl)-(cis-4-methoxycyclohexyl)-methanone) slows SK2 and SK5 melanoma tumor growth in vivo. Taken together, these data suggest that pharmacological inhibition of mGlu1 receptors may be a novel approach for the treatment of metastatic melanoma.

Pharmacological characterization of mGlu1 receptors in cerebellar granule cells reveals biased agonism

The majority of existing research on the function of metabotropic glutamate (mGlu) receptor 1 focuses on G protein-mediated outcomes. However, similar to other G protein-coupled receptors (GPCR), it is becoming apparent that mGlu1 receptor signaling is multi-dimensional and does not always involve G protein activation. Previously, in transfected CHO cells, we showed that mGlu1 receptors activate a G protein-independent, β-arrestin-dependent signal transduction mechanism and that some mGlu1 receptor ligands were incapable of stimulating this response. Here we set out to investigate the physiological relevance of these findings in a native system using primary cultures of cerebellar granule cells. We tested the ability of a panel of compounds to stimulate two mGlu1 receptor-mediated outcomes: (1) protection from decreased cell viability after withdrawal of trophic support and (2) G protein-mediated phosphoinositide (PI) hydrolysis. We report that the commonly used mGlu1 receptor ligands quisqualate, DHPG, and ACPD are completely biased towards PI hydrolysis and do not induce mGlu1 receptor-stimulated neuroprotection. On the other hand, endogenous compounds including glutamate, aspartate, cysteic acid, cysteine sulfinic acid, and homocysteic acid stimulate both responses. These results show that some commonly used mGlu1 receptor ligands are biased agonists, stimulating only a fraction of mGlu1 receptor-mediated responses in neurons. This emphasizes the importance of utilizing multiple agonists and assays when studying GPCR function.