Anandamide exerts its antiproliferative actions on cholangiocarcinoma by activation of the GPR55 receptor

Discovery of Novel Peptide Antagonists Targeting GPR55 for Liver Inflammation and Fibrosis

Liver fibrosis is a condition characterized by aberrant proliferation of connective tissue in the liver resulting from diverse etiological factors. G protein-coupled receptor GPR55 has recently been identified as a regulator of liver diseases. Herein, we report the discovery of a cyclic peptide P1-1 that antagonizes GPR55 and suppresses collagen secretion in hepatic stellate cells. The alanine scanning and docking study was carried out to predict the binding mode and allowed for further structural optimization of peptide antagonists for GPR55. The subsequent in vivo study demonstrated that P1-1 ameliorates CCl4-induce and MCD-diet-induce acute liver inflammation and fibrosis. Further study indicates that P1-1 reduces reactive oxygen species (ROS) production, attenuates ER stress, and inhibits mitochondria-associated hepatocyte apoptosis. In this work, we provided the first successful example of antagonizing GPR55 for liver inflammation and fibrosis, which validates GPR55 as a promising target for the treatment of liver fibrosis and affords a high-potent GPR55 antagonist P1-1 as a potential therapeutic candidate.

Modulation of neuroinflammation and oxidative stress by targeting GPR55 - new approaches in the treatment of psychiatric disorders

Pharmacological treatment of psychiatric disorders remains challenging in clinical, pharmacological, and scientific practice. Even if many different substances are established for treating different psychiatric conditions, subgroups of patients show only small or no response to the treatment. The neuroinflammatory hypothesis of the genesis of psychiatric disorders might explain underlying mechanisms in these non-responders. For that reason, recent research focus on neuroinflammatory processes and oxidative stress as possible causes of psychiatric disorders. G-protein coupled receptors (GPCRs) form the biggest superfamily of membrane-bound receptors and are already well known as pharmacological targets in various diseases. The G-protein coupled receptor 55 (GPR55), a receptor considered part of the endocannabinoid system, reveals promising modulation of neuroinflammatory and oxidative processes. Different agonists and antagonists reduce pro-inflammatory cytokine release, enhance the synthesis of anti-inflammatory mediators, and protect cells from oxidative damage. For this reason, GPR55 ligands might be promising compounds in treating subgroups of patients suffering from psychiatric disorders related to neuroinflammation or oxidative stress. New approaches in drug design might lead to new compounds targeting different pathomechanisms of those disorders in just one molecule.

Bioactive signalling lipids as drivers of chronic liver diseases

Lipids are important in multiple cellular functions, with most having structural or energy storage roles. However, a small fraction of lipids exert bioactive roles through binding to G protein-coupled receptors and induce a plethora of processes including cell proliferation, differentiation, growth, migration, apoptosis, senescence and survival. Bioactive signalling lipids are potent modulators of metabolism and energy homeostasis, inflammation, tissue repair and malignant transformation. All these events are involved in the initiation and progression of chronic liver diseases. In this review, we focus specifically on the roles of bioactive lipids derived from phospholipids (lyso-phospholipids) and poly-unsaturated fatty acids (eicosanoids, pro-resolving lipid mediators and endocannabinoids) in prevalent chronic liver diseases (alcohol-associated liver disease, non-alcoholic fatty liver disease, viral hepatitis and hepatocellular carcinoma). We discuss the balance between pathogenic and beneficial bioactive lipids as well as potential therapeutic targets related to the agonism or antagonism of their receptors.

Elucidation of GPR55-Associated Signaling behind THC and LPI Reducing Effects on Ki67-Immunoreactive Nuclei in Patient-Derived Glioblastoma Cells

GPR55 is involved in many physiological and pathological processes. In cancer, GPR55 has been described to show accelerating and decelerating effects in tumor progression resulting from distinct intracellular signaling pathways. GPR55 becomes activated by LPI and various plant-derived, endogenous, and synthetic cannabinoids. Cannabinoids such as THC exerted antitumor effects by inhibiting tumor cell proliferation or inducing apoptosis. Besides its effects through CB1 and CB2 receptors, THC modulates cellular responses among others via GPR55. Previously, we reported a reduction in Ki67-immunoreactive nuclei of human glioblastoma cells after GPR55 activation in general by THC and in particular by LPI. In the present study, we investigated intracellular mechanisms leading to an altered number of Ki67+ nuclei after stimulation of GPR55 by LPI and THC. Pharmacological analyses revealed a strongly involved PLC-IP3 signaling and cell-type-specific differences in Gα-, Gβγ-, RhoA-ROCK, and calcineurin signaling. Furthermore, immunochemical visualization of the calcineurin-dependent transcription factor NFAT revealed an unchanged subcellular localization after THC or LPI treatment. The data underline the cell-type-specific diversity of GPR55-associated signaling pathways in coupling to intracellular G proteins. Furthermore, this diversity might determine the outcome and the individual responsiveness of tumor cells to GPR55 stimulation by cannabin oids.

FAAH inhibition ameliorates breast cancer in a murine model

Breast cancer is the leading cancer among females worldwide. Disease outcome depends on the hormonal status of the cancer and whether or not it is metastatic, but there is a need for more efficacious therapeutic strategies where first line treatment fails. In this study, Fatty Acid Amide Hydrolase (FAAH) inhibition and endocannabinoids were examined as therapeutic alternatives. FAAH is an integral membrane enzyme that hydrolyzes endocannabinoids, rendering them inactive, and FAAH inhibition is predicted to increase cancer cell death. To test this, breast cancer cells were probed for FAAH expression using Western blot analysis, treated with FAAH inhibitors, exogenous endocannabinoids, and combinations of the two treatments, and assessed for viability. High levels of FAAH were observed in different breast cancer cell lines. FAAH inhibition was more effective than exogenous endocannabinoid treatment, and the combination of FAAH inhibitors and endocannabinoids was the most effective in inducing apoptosis of breast cancer cells in vitro. In addition, in vivo FAAH inhibition reduced breast cancer growth in immunodeficient mice. FAAH inhibition is a promising approach, and tremendous progress has been made in the field to validate this mechanism as an alternative to chemotherapy. Further research exploring the therapeutic potential and impact of FAAH expression on cancer cells is warranted.

DAGLβ is the principal synthesizing enzyme of 2-AG and promotes aggressive phenotype of intrahepatic cholangiocarcinoma via AP-1/DAGLβ/miR4516 feedforward circuitry

The endocannabinoid system (ECS) is dysregulated in various liver diseases. Previously, we had shown that the major endocannabinoid 2-arachidonoyl glycerol (2-AG) promoted tumorigenesis of intrahepatic cholangiocarcinoma (ICC). However, biosynthesis regulation and clinical significance of 2-AG remain elusive. In the present study, we quantified 2-AG by gas chromatography/mass spectrometry (GC/MS) and showed that 2-AG was enriched in patients with ICC samples as well as in thioacetamide-induced orthotopic rat ICC model. Moreover, we found that diacylglycerol lipase β (DAGLβ) was the principal synthesizing enzyme of 2-AG that significantly upregulated in ICC. DAGLβ promoted tumorigenesis and metastasis of ICC in vitro and in vivo and positively correlated with clinical stage and poor survival in patients with ICC. Functional studies showed that activator protein-1 (AP-1; heterodimers of c-Jun and FRA1) directly bound to the promoter and regulated transcription of DAGLβ, which can be enhanced by lipopolysaccharide (LPS). miR-4516 was identified as the tumor-suppressing miRNA of ICC that can be significantly suppressed by LPS, 2-AG, or ectopic DAGLβ overexpression. FRA1 and STAT3 were targets of miR-4516 and overexpression of miRNA-4516 significantly suppressed expression of FRA1, SATA3, and DAGLβ. Expression of miRNA-4516 was negatively correlated with FRA1, SATA3, and DAGLβ in patients with ICC samples. Our findings identify DAGLβ as the principal synthesizing enzyme of 2-AG in ICC. DAGLβ promotes oncogenesis and metastasis of ICC and is transcriptionally regulated by a novel AP-1/DAGLβ/miR4516 feedforward circuitry.NEW & NOTEWORTHY Dysregulated endocannabinoid system (ECS) had been confirmed in various liver diseases. However, regulation and function of 2-arachidonoyl glycerol (2-AG) and diacylglycerol lipase β (DAGLβ) in intrahepatic cholangiocarcinoma (ICC) remain to be elucidated. Here, we demonstrated that 2-AG was enriched in ICC, and DAGLβ was the principal synthesizing enzyme of 2-AG in ICC. DAGLβ promotes tumorigenesis and metastasis in ICC via a novel activator protein-1 (AP-1)/DAGLβ/miR4516 feedforward circuitry.

The Mechanisms of GPR55 Receptor Functional Selectivity during Apoptosis and Proliferation Regulation in Cancer Cells

GPR55 is a non-canonical cannabinoid receptor, important for cancer proliferation. Depending on the ligand, it induces either cell proliferation or death. The objective of the study was to establish the mechanisms of this multidirectional signaling. Using the CRISPR-Cas9 system, the GPR55, CB1, CB2, and GPR18 receptor knockouts of the MDA-MB-231 line were obtained. After the CB2 receptor knockout, the pro-apoptotic activity of the pro-apoptotic ligand docosahexaenoyl dopamine (DHA-DA) slightly increased, while the pro-proliferative activity of the most active synthetic ligand of the GPR55 receptor (ML-184) completely disappeared. On the original cell line, the stimulatory effect of ML-184 was removed by the CB2 receptor blocker and by GPR55 receptor knockout. Thus, it can be confidently assumed that when proliferation is stimulated with the participation of the GPR55 receptor, a signal is transmitted from the CB2 receptor to the GPR55 receptor due to the formation of a heterodimer. GPR18 was additionally involved in the implementation of the pro-apoptotic effect of DHA-DA, while the CB1 receptor is not involved. In the implementation of the pro-apoptotic action of DHA-DA, the elimination of Gα13 led to a decrease in cytotoxicity. The obtained data provide novel details to the mechanism of the pro-proliferative action of GPR55.

A zebrafish HCT116 xenograft model to predict anandamide outcomes on colorectal cancer

Colon cancer is one of the leading causes of death worldwide. In recent years, cannabinoids have been extensively studied for their potential anticancer effects and symptom management. Several in vitro studies reported anandamide's (AEA) ability to block cancer cell proliferation and migration, but evidence from in vivo studies is still lacking. Thus, in this study, the effects of AEA exposure in zebrafish embryos transplanted with HCT116 cells were evaluated. Totally, 48 hpf xenografts were exposed to 10 nM AEA, 10 nM AM251, one of the cannabinoid 1 receptor (CB1) antagonist/inverse agonists, and to AEA + AM251, to verify the specific effect of AEA treatment. AEA efficacy was evaluated by confocal microscopy, which demonstrated that these xenografts presented a smaller tumor size, reduced tumor angiogenesis, and lacked micrometastasis formation. To gain deeper evidence into AEA action, microscopic observations were completed by molecular analyses. RNA seq performed on zebrafish transcriptome reported the downregulation of genes involved in cell proliferation, angiogenesis, and the immune system. Conversely, HCT116 cell transcripts resulted not affected by AEA treatment. In vitro HCT116 culture, in fact, confirmed that AEA exposure did not affect cell proliferation and viability, thus suggesting that the reduced tumor size mainly depends on direct effects on the fish rather than on the transplanted cancer cells. AEA reduced cell proliferation and tumor angiogenesis, as suggested by socs3 and pcnp mRNAs and Vegfc protein levels, and exerted anti-inflammatory activity, as indicated by the reduction of il-11a, mhc1uba, and csf3b mRNA. Of note, are the results obtained in groups exposed to AM251, which presence nullifies AEA's beneficial effects. In conclusion, this study promotes the efficacy of AEA in personalized cancer therapy, as suggested by its ability to drive tumor growth and metastasis, and strongly supports the use of zebrafish xenograft as an emerging model platform for cancer studies.

Use of Cannabis and Cannabinoids for Treatment of Cancer

The endocannabinoid system (ECS) is an ancient homeostasis mechanism operating from embryonic stages to adulthood. It controls the growth and development of many cells and cell lineages. Dysregulation of the components of the ECS may result in uncontrolled proliferation, adhesion, invasion, inhibition of apoptosis and increased vascularization, leading to the development of various malignancies. Cancer is the disease of uncontrolled cell division. In this review, we will discuss whether the changes to the ECS are a cause or a consequence of malignization and whether different tissues react differently to changes in the ECS. We will discuss the potential use of cannabinoids for treatment of cancer, focusing on primary outcome/care-tumor shrinkage and eradication, as well as secondary outcome/palliative care-improvement of life quality, including pain, appetite, sleep, and many more factors. Finally, we will complete this review with the chapter on sex- and gender-specific differences in ECS and response to cannabinoids, and equality of the access to treatments with cannabinoids.

Anti-Tumorigenic Effect of a Novel Derivative of 2-Hydroxyoleic Acid and the Endocannabinoid Anandamide on Neuroblastoma Cells

Modulation of the endogenous cannabinoid system has been suggested as a potential anticancer strategy. In the search for novel and less toxic therapeutic options, structural modifications of the endocannabinoid anandamide and the synthetic derivative of oleic acid, Minerval (HU-600), were done to obtain 2-hydroxy oleic acid ethanolamide (HU-585), which is an HU-600 derivative with the anandamide side chain. We showed that treatment of SK-N-SH neuroblastoma cells with HU-585 induced a better anti-tumorigenic effect in comparison to HU-600 as evidenced by 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide assay, colony-forming assay, and migration assay. Moreover, HU-585 demonstrated pro-apoptotic properties shown by increased levels of activated caspase-3 following treatment and a better senescence induction effect in comparison to HU-600, as demonstrated by increased activity of lysosomal β-galactosidase. Finally, we observed that combined treatment of HU-585 with the senolytic drugs ABT-263 in vitro, and ABT-737 in vivo resulted in enhanced anti-proliferative effects and reduced neuroblastoma xenograft growth in comparison to treatment with HU-585 alone. Based on these results, we suggest that HU-585 is a pro-apoptotic and senescence-inducing compound, better than HU-600. Hence, it may be a beneficial option for the treatment of resistant neuroblastoma especially when combined with senolytic drugs that enhance its anti-tumorigenic effects.

The oncogenic lysophosphatidylinositol (LPI)/GPR55 signaling

GPR55 is a class A orphan G protein-coupled receptor that has drawn important therapeutic attention in the last decade because of its role in pathophysiological processes including vascular functions, metabolic dysfunction, neurodegenerative disorders, or bone turnover among others. Several cannabinoids of phytogenic, endogenous, and synthetic nature have shown to modulate this receptor leading to propose it as a member of the endocannabinoid system. The putative endogenous GPR55 ligand is L-α-lysophosphatidylinositol (LPI) and it has been associated with several processes that control cell survival and tumor progression. The relevance of GPR55 in cancer is currently being extensively studied in vitro and in vivo using diverse cancer models. The LPI/GPR55 axis has been reported to participate in pro-oncogenic processes including cellular proliferation, differentiation, migration, invasion, and metastasis being altered in several cancer cells via G_12/13 and G_q signaling. Moreover, GRP55 and its bioactive lipid have been proposed as potential biomarkers for cancer diagnosis. Indeed, GPR55 overexpression or high expression has been shown to correlate with cancer aggressiveness in specific tumors including acute myeloid leukemia, uveal melanoma, low grade glioma and renal cancer. This review aims to analyze and summarize current evidence on the cancerogenic role of the LPI/GPR55 axis providing a critical view of the therapeutic prospects of this promising target.

Prognostic Significance of GPR55 mRNA Expression in Colon Cancer

G protein-coupled receptor 55 (GPR55) probably plays a role in innate immunity and tumor immunosurveillance through its effect on immune cells, such as T cells and NK cells. In this study, the prognostic value of GPR55 in colon cancer (CC) was investigated. mRNA expression levels of GPR55 were determined in 382 regional lymph nodes of 121 CC patients with 12 years observation time after curative surgery. The same clinical material had previously been analyzed for expression levels of CEA, CXCL16, CXCL17, GPR35 V2/3 and LGR5 mRNAs. Clinical cutoffs of 0.1365 copies/18S rRNA unit for GPR55 and 0.1481 for the GPR55/CEA ratio were applied to differentiate between the high- and low-GPR55 expression groups. Kaplan–Meier survival analysis and Cox regression risk analysis were used to determine prognostic value. Improved discrimination between the two groups was achieved by combining GPR55 with CEA, CXCL16 or CXCL17 compared with GPR55 alone. The best result was obtained using the GPR55/CEA ratio, with an increased mean survival time of 14 and 33 months at 5 and 12 years observation time, respectively (p = 0.0003 and p = 0.003) for the high-GPR55/CEA group. The explanation for the observed improvement is most likely that GPR55 is a marker for T cells and B cells in lymph nodes, whereas CEA, CXCL16 and CXCL17, are markers for tumor cells of epithelial origin.

Prognostic Significance of GPR55 mRNA Expression in Colon Cancer

G protein-coupled receptor 55 (GPR55) probably plays a role in innate immunity and tumor immunosurveillance through its effect on immune cells, such as T cells and NK cells. In this study, the prognostic value of GPR55 in colon cancer (CC) was investigated. mRNA expression levels of GPR55 were determined in 382 regional lymph nodes of 121 CC patients with 12 years observation time after curative surgery. The same clinical material had previously been analyzed for expression levels of CEA, CXCL16, CXCL17, GPR35 V2/3 and LGR5 mRNAs. Clinical cutoffs of 0.1365 copies/18S rRNA unit for GPR55 and 0.1481 for the GPR55/CEA ratio were applied to differentiate between the high- and low-GPR55 expression groups. Kaplan–Meier survival analysis and Cox regression risk analysis were used to determine prognostic value. Improved discrimination between the two groups was achieved by combining GPR55 with CEA, CXCL16 or CXCL17 compared with GPR55 alone. The best result was obtained using the GPR55/CEA ratio, with an increased mean survival time of 14 and 33 months at 5 and 12 years observation time, respectively (p = 0.0003 and p = 0.003) for the high-GPR55/CEA group. The explanation for the observed improvement is most likely that GPR55 is a marker for T cells and B cells in lymph nodes, whereas CEA, CXCL16 and CXCL17, are markers for tumor cells of epithelial origin.

Cannabinoids as anticancer drugs: current status of preclinical research

Drugs that target the endocannabinoid system are of interest as pharmacological options to combat cancer and to improve the life quality of cancer patients. From this perspective, cannabinoid compounds have been successfully tested as a systemic therapeutic option in a number of preclinical models over the past decades. As a result of these efforts, a large body of data suggests that the anticancer effects of cannabinoids are exerted at multiple levels of tumour progression via different signal transduction mechanisms. Accordingly, there is considerable evidence for cannabinoid-mediated inhibition of tumour cell proliferation, tumour invasion and metastasis, angiogenesis and chemoresistance, as well as induction of apoptosis and autophagy. Further studies showed that cannabinoids could be potential combination partners for established chemotherapeutic agents or other therapeutic interventions in cancer treatment. Research in recent years has yielded several compounds that exert promising effects on tumour cells and tissues in addition to the psychoactive Δ9-tetrahydrocannabinol, such as the non-psychoactive phytocannabinoid cannabidiol and inhibitors of endocannabinoid degradation. This review provides an up-to-date overview of the potential of cannabinoids as inhibitors of tumour growth and spread as demonstrated in preclinical studies.

Endocannabinoid System and Tumour Microenvironment: New Intertwined Connections for Anticancer Approaches

The tumour microenvironment (TME) is now recognised as a hallmark of cancer, since tumour:stroma crosstalk supports the key steps of tumour growth and progression. The dynamic co-evolution of the tumour and stromal compartments may alter the surrounding microenvironment, including the composition in metabolites and signalling mediators. A growing number of evidence reports the involvement of the endocannabinoid system (ECS) in cancer. ECS is composed by a complex network of ligands, receptors, and enzymes, which act in synergy and contribute to several physiological but also pathological processes. Several in vitro and in vivo evidence show that ECS deregulation in cancer cells affects proliferation, migration, invasion, apoptosis, and metastatic potential. Although it is still an evolving research, recent experimental evidence also suggests that ECS can modulate the functional behaviour of several components of the TME, above all the immune cells, endothelial cells and stromal components. However, the role of ECS in the tumour:stroma interplay remains unclear and research in this area is particularly intriguing. This review aims to shed light on the latest relevant findings of the tumour response to ECS modulation, encouraging a more in-depth analysis in this field. Novel discoveries could be promising for novel anti-tumour approaches, targeting the microenvironmental components and the supportive tumour:stroma crosstalk, thereby hindering tumour development.

Molecular Mechanism of Cannabinoids in Cancer Progression

Cannabinoids are a family of heterogeneous compounds that mostly interact with receptors eliciting several physiological effects both in the central and peripheral nervous systems and in peripheral organs. They exert anticancer action by modulating signaling pathways involved in cancer progression; furthermore, the effects induced by their use depend on both the type of tumor and their action on the components of the endocannabinoid system. This review will explore the mechanism of action of the cannabinoids in signaling pathways involved in cancer proliferation, neovascularisation, migration, invasion, metastasis, and tumor angiogenesis.

THC Reduces Ki67-Immunoreactive Cells Derived from Human Primary Glioblastoma in a GPR55-Dependent Manner

Glioblastoma (GBM) is the most frequent malignant tumor of the central nervous system in humans with a median survival time of less than 15 months. ∆⁹-Tetrahydrocannabinol (THC) and cannabidiol (CBD) are the best-characterized components of Cannabis sativa plants with modulating effects on cannabinoid receptors 1 and 2 (CB₁ and CB₂) and on orphan receptors such as GPR18 or GPR55. Previous studies have demonstrated anti-tumorigenic effects of THC and CBD in several tumor entities including GBM, mostly mediated via CB₁ or CB₂. In this study, we investigated the non-CB₁/CB₂ effects of THC on the cell cycle of GBM cells isolated from human tumor samples. Cell cycle entry was measured after 24 h upon exposure by immunocytochemical analysis of Ki67 as proliferation marker. The Ki67-reducing effect of THC was abolished in the presence of CBD, whereas CBD alone did not cause any changes. To identify the responsible receptor for THC effects, we first characterized the cells regarding their expression of different cannabinoid receptors: CB₁, CB₂, GPR18, and GPR55. Secondly, the receptors were pharmacologically blocked by application of their selective antagonists AM281, AM630, O-1918, and CID16020046 (CID), respectively. All examined cells expressed the receptors, but only in presence of the GPR55 antagonist CID was the THC effect diminished. Stimulation with the GPR55 agonist lysophosphatidylinositol (LPI) revealed similar effects as obtained for THC. The LPI effects were also inhibited by CBD and CID, confirming a participation of GPR55 and suggesting its involvement in modifying the cell cycle of patient-derived GBM cells.

GPR55 Receptor Activation by the N-Acyl Dopamine Family Lipids Induces Apoptosis in Cancer Cells via the Nitric Oxide Synthase (nNOS) Over-Stimulation

GPR55 is a GPCR of the non-CB1/CB2 cannabinoid receptor family, which is activated by lysophosphatidylinositol (LPI) and stimulates the proliferation of cancer cells. Anandamide, a bioactive lipid endocannabinoid, acts as a biased agonist of GPR55 and induces cancer cell death, but is unstable and psychoactive. We hypothesized that other endocannabinoids and structurally similar compounds, which are more hydrolytically stable, could also induce cancer cell death via GPR55 activation. We chemically synthesized and tested a set of fatty acid amides and esters for cell death induction via GPR55 activation. The most active compounds appeared to be N-acyl dopamines, especially N-docosahexaenoyl dopamine (DHA-DA). Using a panel of cancer cell lines and a set of receptor and intracellular signal transduction machinery inhibitors together with cell viability, Ca2+, NO, ROS (reactive oxygen species) and gene expression measurement, we showed for the first time that for these compounds, the mechanism of cell death induction differed from that published for anandamide and included neuronal nitric oxide synthase (nNOS) overstimulation with concomitant oxidative stress induction. The combination of DHA-DA with LPI, which normally stimulates cancer proliferation and is increased in cancer setting, had an increased cytotoxicity for the cancer cells indicating a therapeutic potential.

The Endocannabinoid System: A Target for Cancer Treatment

In recent years, the endocannabinoid system has received great interest as a potential therapeutic target in numerous pathological conditions. Cannabinoids have shown an anticancer potential by modulating several pathways involved in cell growth, differentiation, migration, and angiogenesis. However, the therapeutic efficacy of cannabinoids is limited to the treatment of chemotherapy-induced symptoms or cancer pain, but their use as anticancer drugs in chemotherapeutic protocols requires further investigation. In this paper, we reviewed the role of cannabinoids in the modulation of signaling mechanisms implicated in tumor progression.

Antitumor Activity of Abnormal Cannabidiol and Its Analog O-1602 in Taxol-Resistant Preclinical Models of Breast Cancer

Cannabinoids exhibit anti-inflammatory and antitumorigenic properties. Contrary to most cannabinoids present in the Cannabis plant, some, such as O-1602 and abnormal cannabidiol, have no or only little affinity to the CB₁ or CB₂ cannabinoid receptors and instead exert their effects through other receptors. Here, we investigated whether the synthetic regioisomers of cannabidiol, abnormal cannabidiol, and a closely related compound, O-1602, display antitumorigenic effects in cellular models of breast cancer and whether it could reduce tumorigenesis in vivo. Several studies have shown the effects of cannabinoids on chemotherapy-sensitive breast cancer cell lines, but less is known about the antitumorigenic effects of cannabinoids in chemotherapy-resistant cell lines. Paclitaxel-resistant MDA-MB-231 and MCF-7 breast cancer cell lines were used to study the effect of O-1602 and abnormal cannabidiol on viability, apoptosis, and migration. The effects of O-1602 and abnormal cannabidiol on cell viability were completely blocked by the combination of GPR55 and GPR18-specific siRNAs. Both O-1602 and abnormal cannabidiol decreased viability in paclitaxel-resistant breast cancer cells in a concentration-dependent manner through induction of apoptosis. The effect of these cannabinoids on tumor growth in vivo was studied in a zebrafish xenograft model. In this model, treatment with O-1602 and abnormal cannabidiol (2 µM) significantly reduced tumor growth. Our results suggest that atypical cannabinoids, like O-1602 and abnormal cannabidiol, exert antitumorigenic effects on paclitaxel-resistant breast cancer cells. Due to their lack of central sedation and psychoactive effects, these atypical cannabinoids could represent new leads for the development of additional anticancer treatments when resistance to conventional chemotherapy occurs during the treatment of breast and possibly other cancers.

Effect of endocannabinoid signalling on cell fate: life, death, differentiation and proliferation of brain cells

Cell fate events are regulated by different endogenous developmental factors such as the cell micro-environment, external or remote signals and epigenetic factors. Among the many regulatory factors, endocannabinoid-associated signalling pathways are known to conduct several of these events in the developing nervous system and in the adult brain. Interestingly, endocannabinoids exert modulatory actions in both physiological and pathological conditions. Endocannabinoid signalling can promote cell survival by acting on non-transformed brain cells (neurons, astrocytes or oligodendrocytes) and can have either a protumoural or antitumoural effect on transformed cells. Moreover, endocannabinoids are able to attenuate the detrimental effects on neurogenesis and neuroinflammation associated with ageing. Thus, the endocannabinoid system emerges as an important regulator of cell fate, controlling cell survival/cell death decisions depending on the cell type and its environment. LINKED ARTICLES: This article is part of a themed section on 8th European Workshop on Cannabinoid Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.10/issuetoc.

Multiple endocannabinoid-mediated mechanisms in the regulation of energy homeostasis in brain and peripheral tissues

The endocannabinoid (eCB) system is widely expressed in many central and peripheral tissues, and is involved in a plethora of physiological processes. Among these, activity of the eCB system promotes energy intake and storage, which, however, under pathophysiological conditions, can favour the development of obesity and obesity-related disorders. It is proposed that eCB signalling is evolutionary beneficial for survival under periods of scarce food resources. Remarkably, eCB signalling is increased both in hunger and in overnutrition conditions, such as obesity and type-2 diabetes. This apparent paradox suggests a role of the eCB system both at initiation and at clinical endpoint of obesity. This review will focus on recent findings about the role of the eCB system controlling whole-body metabolism in mice that are genetically modified selectively in different cell types. The current data in fact support the notion that eCB signalling is not only engaged in the development but also in the maintenance of obesity, whereby specific cell types in central and peripheral tissues are key sites in regulating the entire body's energy homeostasis.

GPR55 controls functional differentiation of self-renewing epithelial progenitors for salivation

GPR55, a lipid-sensing receptor, is implicated in cell cycle control, malignant cell mobilization, and tissue invasion in cancer. However, a physiological role for GPR55 is virtually unknown for any tissue type. Here, we localize GPR55 to self-renewing ductal epithelial cells and their terminally differentiated progeny in both human and mouse salivary glands. Moreover, we find GPR55 expression downregulated in salivary gland mucoepidermoid carcinomas and GPR55 reinstatement by antitumor irradiation, suggesting that GPR55 controls renegade proliferation. Indeed, GPR55 antagonism increases cell proliferation and function determination in quasiphysiological systems. In addition, Gpr55-/- mice present ~50% enlarged submandibular glands with many more granulated ducts, as well as disordered endoplasmic reticuli and with glycoprotein content. Next, we hypothesized that GPR55 could also modulate salivation and glycoprotein content by entraining differentiated excretory progeny. Accordingly, GPR55 activation facilitated glycoprotein release by itself, inducing low-amplitude Ca2+ oscillations, as well as enhancing acetylcholine-induced Ca2+ responses. Topical application of GPR55 agonists, which are ineffective in Gpr55-/- mice, into adult rodent submandibular glands increased salivation and saliva glycoprotein content. Overall, we propose that GPR55 signaling in epithelial cells ensures both the life-long renewal of ductal cells and the continuous availability of saliva and glycoproteins for oral health and food intake.

Alterations in Gene and Protein Expression of Cannabinoid CB2 and GPR55 Receptors in the Dorsolateral Prefrontal Cortex of Suicide Victims

Recent studies point to the cannabinoid CB2 receptors (CB2r) and the non-cannabinoid receptor GPR55 as potential key targets involved in the response to stress, anxiety, and depression. Considering the close relationship between neuropsychiatric disorders and suicide, the purpose of this study was to evaluate the potential alterations of CB2r and GPR55 in suicide victims. We analyzed gene and protein expression of both receptors by real-time PCR and western blot, respectively, in the dorsolateral prefrontal cortex (DLPFC) of 18 suicide victims with no clinical psychiatric history or treatment with anxiolytics or antidepressants, and 15 corresponding controls. We used in situ proximity ligation assay to evaluate whether the receptors formed heteromeric complexes and to determine the expression level of these heteromers, also assessing the co-expression of heteromers in neurons, astroglia, or microglia cells. CB2r and GPR55 gene expressions were significantly lower (by 33 and 41%, respectively) in the DLPFC of suicide cases. CB2r protein expression was higher, as were CB2-GPR55 heteroreceptor complexes. The results also revealed the presence of CB2-GPR55 receptor heteromers in both neurons and astrocytes, whereas microglial cells showed no expression. We did not observe any significant alterations of GPR55 protein expression. Additional studies will be necessary to evaluate if these alterations are reproducible in suicide victims diagnosed with different psychiatric disorders. Taken together, the results suggest that CB2r and GPR55 may play a relevant role in the neurobiology of suicide.

Lysophosphatidylinositols, from Cell Membrane Constituents to GPR55 Ligands

Lysophosphatidylinositols (LPIs) are membrane constituents that alter the properties of said membranes. However, recent data showing that the once orphan receptor, GPR55, can act as a receptor for LPIs has sparked a renewed interest in LPIs as bioactive lipids. As evidence supporting the importance of LPIs and/or GPR55 is continuously accumulating and because LPI levels are altered in a number of pathologies such as obesity and cancer, the coming years should bring new, exciting discoveries to this field. In this review, we discuss the recent work on LPIs and on their molecular target, the GPR55 receptor. First, we summarize the metabolism of LPIs before outlining the cellular pathways activated by GPR55. Then, we review the actions of LPIs and GPR55 that could have potential pharmacological or therapeutic applications in several pathophysiological settings, such as cancer, obesity, pain, and inflammation.

Activation of the orphan receptor GPR55 by lysophosphatidylinositol promotes metastasis in triple-negative breast cancer

The orphan G protein-coupled receptor GPR55 has been directly or indirectly related to basic alterations that drive malignant growth: uncontrolled cancer cell proliferation, sustained angiogenesis, and cancer cell adhesion and migration. However, little is known about the involvement of this receptor in metastasis. Here, we show that elevated GPR55 expression in human tumors is associated with the aggressive basal/triple-negative breast cancer population, higher probability to develop metastases, and therefore poor patient prognosis. Activation of GPR55 by its proposed endogenous ligand lysophosphatidylinositol confers pro-invasive features on breast cancer cells both in vitro and in vivo. Specifically, this effect is elicited by coupling to Gq/11 heterotrimeric proteins and the subsequent activation, through ERK, of the transcription factor ETV4/PEA3. Together, these data show that GPR55 promotes breast cancer metastasis, and supports the notion that this orphan receptor may constitute a new therapeutic target and potential biomarker in the highly aggressive triple-negative subtype.

Cannabinoids Modulate Neuronal Activity and Cancer by CB1 and CB2 Receptor-Independent Mechanisms

Cannabinoids include the active constituents of Cannabis or are molecules that mimic the structure and/or function of these Cannabis-derived molecules. Cannabinoids produce many of their cellular and organ system effects by interacting with the well-characterized CB1 and CB2 receptors. However, it has become clear that not all effects of cannabinoid drugs are attributable to their interaction with CB1 and CB2 receptors. Evidence now demonstrates that cannabinoid agents produce effects by modulating activity of the entire array of cellular macromolecules targeted by other drug classes, including: other receptor types; ion channels; transporters; enzymes, and protein- and non-protein cellular structures. This review summarizes evidence for these interactions in the CNS and in cancer, and is organized according to the cellular targets involved. The CNS represents a well-studied area and cancer is emerging in terms of understanding mechanisms by which cannabinoids modulate their activity. Considering the CNS and cancer together allow identification of non-cannabinoid receptor targets that are shared and divergent in both systems. This comparative approach allows the identified targets to be compared and contrasted, suggesting potential new areas of investigation. It also provides insight into the diverse sources of efficacy employed by this interesting class of drugs. Obtaining a comprehensive understanding of the diverse mechanisms of cannabinoid action may lead to the design and development of therapeutic agents with greater efficacy and specificity for their cellular targets.

G protein-coupled receptor GPR55 promotes colorectal cancer and has opposing effects to cannabinoid receptor 1

The putative cannabinoid receptor GPR55 has been shown to play a tumor-promoting role in various cancers, and is involved in many physiological and pathological processes of the gastrointestinal (GI) tract. While the cannabinoid receptor 1 (CB₁ ) has been reported to suppress intestinal tumor growth, the role of GPR55 in the development of GI cancers is unclear. We, therefore, aimed at elucidating the role of GPR55 in colorectal cancer (CRC), the third most common cancer worldwide. Using azoxymethane (AOM)- and dextran sulfate sodium (DSS)-driven CRC mouse models, we found that GPR55 plays a tumor-promoting role that involves alterations of leukocyte populations, i.e. myeloid-derived suppressor cells and T lymphocytes, within the tumor tissues. Concomitantly, expression levels of COX-2 and STAT3 were reduced in tumor tissue of GPR55 knockout mice, indicating reduced presence of tumor-promoting factors. By employing the experimental CRC models to CB₁ knockout and CB₁ /GPR55 double knockout mice, we can further show that GPR55 plays an opposing role to CB₁ . We report that GPR55 and CB₁ mRNA expression are differentially regulated in the experimental models and in a cohort of 86 CRC patients. Epigenetic methylation of CNR1 and GPR55 was also differentially regulated in human CRC tissue compared to control samples. Collectively, our data suggest that GPR55 and CB₁ play differential roles in colon carcinogenesis where the former seems to act as oncogene and the latter as tumor suppressor.

N-acyl dopamines induce apoptosis in PC12 cell line via the GPR55 receptor activation

Dopamine amides of arachidonic, docosahexaenoic, and oleic acids were found to induce apoptosis in PC12 cells, which was blocked exclusively by antagonists and preincubation agonists of the receptor GPR55, belonging to the group of non-CB1/CB2 receptors.

Synthesis and Evaluation of the Novel Prostamide, 15-Deoxy, Δ12,14-Prostamide J2, as a Selective Antitumor Therapeutic

15-deoxy, Δ^12,14-prostaglandin J₂-ethanolamide, also known as 15-deoxy, Δ^12,14-prostamide J₂ (15d-PMJ₂) is a novel product of the metabolism of arachidonoyl ethanolamide (AEA) by COX-2. 15d-PMJ₂ preferentially induced cell death and apoptosis in tumorigenic A431 keratinocytes and B16F10 melanoma cells compared with nontumorigenic HaCaT keratinocytes and Melan-A melanocytes. Activation of the ER stress execution proteins, PERK and CHOP10, was evaluated to determine whether this process was involved in 15d-PMJ₂ cell death. 15d-PMJ₂ increased the phosphorylation of PERK and expression of CHOP10 in tumorigenic but not nontumorigenic cells. The known ER stress inhibitors, salubrinal and 4-phenylbutaric acid, significantly inhibited 15d-PMJ₂-mediated apoptosis, suggesting ER stress as a primary apoptotic mediator. Furthermore, the reactive double bond present within the cyclopentenone structure of 15d-PMJ₂ was identified as a required moiety for the induction of ER stress apoptosis. The effect of 15d-PMJ₂ on B16F10 melanoma growth was also evaluated by dosing C57BL/6 mice with 0.5 mg/kg 15d-PMJ₂ Tumors of animals treated with 15d-PMJ₂ exhibited significantly reduced growth and mean weights compared with vehicle and untreated animals. TUNEL and IHC analysis of tumor tissues showed significant cell death and ER stress in tumors of 15d-PMJ₂-treated compared with control group animals. Taken together, these findings suggest that the novel prostamide, 15d-PMJ₂, possesses potent antitumor activity in vitro and in vivoMol Cancer Ther; 16(5); 838-49. ©2017 AACR.

Bladder cancer cell growth and motility implicate cannabinoid 2 receptor-mediated modifications of sphingolipids metabolism

The inhibitory effects demonstrated by activation of cannabinoid receptors (CB) on cancer proliferation and migration may also play critical roles in controlling bladder cancer (BC). CB expression on human normal and BC specimens was tested by immunohistochemistry. Human BC cells RT4 and RT112 were challenged with CB agonists and assessed for proliferation, apoptosis, and motility. Cellular sphingolipids (SL) constitution and metabolism were evaluated after metabolic labelling. CB1-2 were detected in BC specimens, but only CB2 was more expressed in the tumour. Both cell lines expressed similar CB2. Exposure to CB2 agonists inhibited BC growth, down-modulated Akt, induced caspase 3-activation and modified SL metabolism. Baseline SL analysis in cell lines showed differences linked to unique migratory behaviours and cytoskeletal re-arrangements. CB2 activation changed the SL composition of more aggressive RT112 cells by reducing (p < 0.01) Gb3 ganglioside (−50 ± 3%) and sphingosine 1-phosphate (S1P, −40 ± 4%), which ended up to reduction in cell motility (−46 ± 5%) with inhibition of p-SRC. CB2-selective antagonists, gene silencing and an inhibitor of SL biosynthesis partially prevented CB2 agonist-induced effects on cell viability and motility. CB2 activation led to ceramide-mediated BC cell apoptosis independently of SL constitutive composition, which instead was modulated by CB2 agonists to reduce cell motility.

Preclinical and Clinical Assessment of Cannabinoids as Anti-Cancer Agents

Cancer is the second leading cause of death in the United States with 1.7 million new cases estimated to be diagnosed in 2016. This disease remains a formidable clinical challenge and represents a substantial financial burden to the US health care system. Therefore, research and development of novel therapeutics for the treatment of cancer is of high priority. Cannabinoids and their derivatives have been utilized for their medicinal and therapeutic properties throughout history. Cannabinoid activity is regulated by the endocannabinoid system (ECS), which is comprised of cannabinoid receptors, transporters, and enzymes involved in cannabinoid synthesis and breakdown. More recently, cannabinoids have gained special attention for their role in cancer cell proliferation and death. However, many studies investigated these effects using in vitro models which may not adequately mimic tumor growth and metastasis. As such, this article aims to review study results which evaluated effects of cannabinoids from plant, synthetic and endogenous origins on cancer development in preclinical animal models and to examine the current standing of cannabinoids that are being tested in human cancer patients.

Expert consensus document: Cholangiocarcinoma: current knowledge and future perspectives consensus statement from the European Network for the Study of Cholangiocarcinoma (ENS-CCA)

Cholangiocarcinoma (CCA) is a heterogeneous group of malignancies with features of biliary tract differentiation. CCA is the second most common primary liver tumour and the incidence is increasing worldwide. CCA has high mortality owing to its aggressiveness, late diagnosis and refractory nature. In May 2015, the "European Network for the Study of Cholangiocarcinoma" (ENS-CCA: www.enscca.org or www.cholangiocarcinoma.eu) was created to promote and boost international research collaboration on the study of CCA at basic, translational and clinical level. In this Consensus Statement, we aim to provide valuable information on classifications, pathological features, risk factors, cells of origin, genetic and epigenetic modifications and current therapies available for this cancer. Moreover, future directions on basic and clinical investigations and plans for the ENS-CCA are highlighted.

GPR55 promotes migration and adhesion of colon cancer cells indicating a role in metastasis

BACKGROUND AND PURPOSE

Tumour cell migration and adhesion constitute essential features of metastasis. G-protein coupled receptor 55 (GPR55), a lysophospholipid receptor, has been shown to play an important role in carcinogenesis. Here, we investigated the involvement of GPR55 in migration and metastasis of colon cancer cells.

EXPERIMENTAL APPROACH

Adhesion and migration assays using the highly metastatic colon cancer cell line HCT116 and an in vivo assay of liver metastasis were performed. The GPR55 antagonist CID16020046, cannabidiol, a putative GPR55 antagonist and GPR55 siRNA were used to block GPR55 activity in HCT116 colon cancer cells.

KEY RESULTS

HCT116 cells showed a significant decrease in adhesion to endothelial cells and in migration after blockade with CID16020046 or cannabidiol. The inhibitory effects of CID16020046 or cannabidiol were averted by GPR55 siRNA knock down in cancer cells. The integrity of endothelial cell monolayers was increased after pretreatment of HCT116 cells with the antagonists or after GPR55 siRNA knockdown while pretreatment with lysophosphatidylinositol (LPI), the endogenous ligand of GPR55, decreased integrity of the monolayers. LPI also induced migration in GPR55 overexpressing HCT116 cells that was blocked by GPR55 antagonists. In a mouse model of metastasis, the arrest of HCT116 cancer cells in the liver was reduced after treatment with CID16020046 or cannabidiol. Increased levels of LPI (18:0) were found in colon cancer patients when compared with healthy individuals.

CONCLUSIONS AND IMPLICATIONS

GPR55 is involved in the migratory behaviour of colon carcinoma cells and may serve as a pharmacological target for the prevention of metastasis. © 2015 The British Pharmacological Society.

Comprehensive analysis of transcriptome and metabolome analysis in Intrahepatic Cholangiocarcinoma and Hepatocellular Carcinoma

Intrahepatic cholangiocarcinoma (ICC) and hepatocellular carcinoma (HCC) are liver originated malignant tumors. Of the two, ICC has the worse prognosis because it has no reliable diagnostic markers and its carcinogenic mechanism is not fully understood. The aim of this study was to integrate metabolomics and transcriptomics datasets to identify variances if any in the carcinogenic mechanism of ICC and HCC. Ten ICC and 6 HCC who were resected surgically, were enrolled. miRNA and mRNA expression analysis were performed by microarray on ICC and HCC and their corresponding non-tumor tissues (ICC_NT and HCC_NT). Compound analysis was performed using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS). Principle component analysis (PCA) revealed that among the four sample groups (ICC, ICC_NT, HCC, and HCC_NT) there were 14 compounds, 62 mRNAs and 17 miRNAs with two distinct patterns: tumor and non-tumor, and ICC and non-ICC. We accurately (84.38%) distinguished ICC by the distinct pattern of its compounds. Pathway analysis using transcriptome and metabolome showed that several pathways varied between tumor and non-tumor samples. Based on the results of the PCA, we believe that ICC and HCC have different carcinogenic mechanism therefore knowing the specific profile of genes and compounds can be useful in diagnosing ICC.

Potent and selective N-(4-sulfamoylphenyl)thiourea-based GPR55 agonists

To date, many known G protein-coupled receptor 55 (GPR55) ligands are those identified among the cannabinoids. In order to further study the function of GPR55, new potent and selective ligands are needed. In this study, we utilized the screening results from PubChem bioassay AID 1961 which reports the results of Image-based HTS for Selective Agonists of GPR55. Three compounds, CID1792579, CID1252842 and CID1011163, were further evaluated and used as a starting point to create a series of nanomolar potency GPR55 agonists with N-(4-sulfamoylphenyl)thiourea scaffold. The GPR55 activity of the compounds were screened by using a commercial β-arrestin PathHunter assay and the potential compounds were further evaluated by using a recombinant HEK cell line exhibiting GPR55-mediated effects on calcium signalling. The designed compounds were not active when tested against various endocannabinoid targets (CB1R, CB2R, FAAH, MGL, ABHD6 and ABHD12), indicating compounds' selectivity for the GPR55. Finally, structure-activity relationships of these compounds were explored.

Evaluation of cannabinoid CB1 and CB2 receptors expression in mobile tongue squamous cell carcinoma: associations with clinicopathological parameters and patients' survival

Cannabinoid receptors (CB1R and CB2R) constitute essential members of the endocannabinoid system (ECS) which participates in many different functions indispensable to homeostatic regulation in several tissues, exerting also antitumorigenic effects. The present study aimed to assess the clinical significance of CB1R and CB2R protein expression in mobile tongue squamous cell carcinoma (SCC). CB1R and CB2R expression was assessed immunohistochemically on 28 mobile tongue SCC tissue samples and was analyzed in relation with clinicopathological characteristics and overall and disease-free patients' survival. CB1R, CB2R, and concomitant CB1R/CB2R expression was significantly increased in older compared to younger mobile tongue SCC patients (p = 0.0243, p = 0.0079, and p = 0.0366, respectively). Enhanced CB2R and concomitant CB1R/CB2R expression was significantly more frequently observed in female compared to male mobile tongue SCC patients (p = 0.0025 and p = 0.0016, respectively). Elevated CB2R expression was significantly more frequently observed in mobile tongue SCC patients presenting well-defined tumor shape compared to those with diffuse (p = 0.0430). Mobile tongue SCC patients presenting enhanced CB1R, CB2R, or concomitant CB1R/CB2R expression showed significantly longer overall (log-rank test, p = 0.004, p = 0.011, p = 0.018, respectively) and disease-free (log-rank test, p = 0.003, p = 0.007, p = 0.027, respectively) survival times compared to those with low expression. In multivariate analysis, CB1R was identified as an independent prognostic factor for disease-free patients' survival (Cox-regression analysis, p = 0.032). The present study provides evidence that CB1R and CB2R may play a role in the pathophysiological aspects of the mobile tongue SCC and even each molecule may constitute a potential target for the development of novel anti-cancer drugs for this type of malignancy.

Clinical Significance of Cannabinoid Receptors CB1 and CB2 Expression in Human Malignant and Benign Thyroid Lesions

The endocannabinoid system is comprised of cannabinoid receptors (CB1 and CB2), their endogenous ligands (endocannabinoids), and proteins responsible for their metabolism participate in many different functions indispensable to homeostatic regulation in several tissues, exerting also antitumorigenic effects. The present study aimed to evaluate the clinical significance of CB1 and CB2 expression in human benign and malignant thyroid lesions. CB1 and CB2 proteins' expression was assessed immunohistochemically on paraffin-embedded thyroid tissues obtained from 87 patients with benign (n = 43) and malignant (n = 44) lesions and was statistically analyzed with clinicopathological parameters, follicular cells' proliferative capacity, and risk of recurrence rate estimated according to the American Thyroid Association (ATA) staging system. Enhanced CB1 and CB2 expression was significantly more frequently observed in malignant compared to benign thyroid lesions (p = 0.0010 and p = 0.0005, resp.). Enhanced CB1 and CB2 expression was also significantly more frequently observed in papillary carcinomas compared to hyperplastic nodules (p = 0.0097 and p = 0.0110, resp.). In malignant thyroid lesions, elevated CB2 expression was significantly associated with the presence of lymph node metastases (p = 0.0301). Enhanced CB2 expression was also more frequently observed in malignant thyroid cases with presence of capsular (p = 0.1165), lymphatic (p = 0.1989), and vascular invasion (p = 0.0555), as well as in those with increased risk of recurrence rate (p = 0.1165), at a nonsignificant level though, whereas CB1 expression was not associated with any of the clinicopathological parameters examined. Our data suggest that CB receptors may be involved in malignant thyroid transformation and especially CB2 receptor could serve as useful biomarker and potential therapeutic target in thyroid neoplasia.

The evolving role of the endocannabinoid system in gynaecological cancer

BACKGROUND

The 'endocannabinoid system' (ECS), comprising endogenous ligands (endocannabinoids) and their regulating enzymes, together with the cannabinoid receptors, has attracted a great deal of attention because it affects not only all facets of human reproduction, from gametogenesis through to parturition and beyond, but also targets key mechanisms affecting some hallmarks of cancer. Recent evidence showing that cannabinoid receptors play a very important role in the development of malignancies outside of the reproductive organs suggests a similar role for the ECS in the establishment or continued development of gynaecological malignancy.

METHODS

Primary papers and review articles, and primary sources within these papers, up to December 2014, on the evolving role of the ECS in cancer, with a special focus on gynaecological cancers, were obtained by Medline and PubMed searches using the search terms: 'cancer', 'cannabinoid', 'endocannabinoid', 'gynaecology' and 'malignancy'. Non-English manuscripts were excluded.

RESULTS

More than 2100 sources were obtained from which only 112 were specifically important to the topic. Analysis of those articles supports a role of the ECS in gynaecological cancers but leaves many gaps in our knowledge that need to be filled. How some of the relevant receptors are activated and cause changes in cell phenotypes that progress to malignancy remains undiscovered and an area for future research. Increasing evidence suggests that malignant transformation within the female genital tract could be accompanied by deregulation of components of the ECS, acting through rather complex cannabinoid receptor-dependent and receptor-independent mechanisms.

CONCLUSIONS

The paucity of studies in this area suggests that research using animal models is needed to evaluate endocannabinoid signalling in cancer networks. Future randomized clinical studies should reveal whether endocannabinoids or their derivatives prove to be useful therapeutic targets for gynaecological and other cancers.

The therapeutic potential of orphan GPCRs, GPR35 and GPR55

The G protein-coupled receptor (GPCR) superfamily of integral proteins is the largest family of signal transducers, comprised of ∼1000 members. Considering their prevalence and functional importance, it’s not surprising that ∼60% of drugs target GPCRs. Regardless, there exists a subset of the GPCR superfamily that is largely uncharacterized and poorly understood; specifically, more than 140 GPCRs have unknown endogenous ligands—the so-called orphan GPCRs. Orphan GPCRs offer tremendous promise, as they may provide novel therapeutic targets that may be more selective than currently known receptors, resulting in the potential reduction in side effects. In addition, they may provide access to signal transduction pathways currently unknown, allowing for new strategies in drug design. Regardless, orphan GPCRs are an important area of inquiry, as they represent a large gap in our understanding of signal transduction at the cellular level. Here, we focus on the therapeutic potential of two recently deorphanized GPCRs: GPR35/CXCR8 and GPR55. First, GPR35/CXCR8 has been observed in numerous tissues/organ systems, including the gastrointestinal tract, liver, immune system, central nervous system, and cardiovascular system. Not surprisingly, GPR35/CXCR8 has been implicated in numerous pathologies involving these tissues/systems. While several endogenous ligands have been identified, GPR35/CXCR8 has recently been observed to bind the chemokine CXCL17. Second, GPR55 has been observed to be expressed in the central nervous system, adrenal glands, gastrointestinal tract, lung, liver, uterus, bladder, kidney, and bone, as well as, other tissues/organ systems. Likewise, it is not surprising that GPR55 has been implicated in pathologies involving these tissues/systems. GPR55 was initially deorphanized as a cannabinoid receptor and this receptor does bind many cannabinoid compounds. However, the GPR55 endogenous ligand has been found to be a non-cannabinoid, lysophophatidylinositol (LPI) and subsequent high throughput assays have identified other GPR55 ligands that are not cannabinoids and do not bind to either the cannabinoid CB1 and CB2 receptors. Here, we review reports that suggest that GPR35/CXCR8 and GPR55 may be promising therapeutic targets, with diverse physiological roles.

Saturated free fatty acids induce cholangiocyte lipoapoptosis

Recent studies have identified a cholestatic variant of nonalcoholic fatty liver disease (NAFLD) with portal inflammation and ductular reaction. Based on reports of biliary damage, as well as increased circulating free fatty acids (FFAs) in NAFLD, we hypothesized the involvement of cholangiocyte lipoapoptosis as a mechanism of cellular injury. Here, we demonstrate that the saturated FFAs palmitate and stearate induced robust and rapid cell death in cholangiocytes. Palmitate and stearate induced cholangiocyte lipoapoptosis in a concentration-dependent manner in multiple cholangiocyte-derived cell lines. The mechanism of lipoapoptosis relied on the activation of caspase 3/7 activity. There was also a significant up-regulation of the proapoptotic BH3-containing protein, PUMA. In addition, palmitate-induced cholangiocyte lipoapoptosis involved a time-dependent increase in the nuclear localization of forkhead family of transcription factor 3 (FoxO3). We show evidence for posttranslational modification of FoxO3, including early (6 hours) deacetylation and dephosphorylation that coincide with localization of FoxO3 in the nuclear compartment. By 16 hours, nuclear FoxO3 is both phosphorylated and acetylated. Knockdown studies confirmed that FoxO3 and its downstream target, PUMA, were critical for palmitate- and stearate-induced cholangiocyte lipoapoptosis. Interestingly, cultured cholangiocyte-derived cells did not accumulate appreciable amounts of neutral lipid upon FFA treatment.

CONCLUSION

Our data show that the saturated FFAs palmitate and stearate induced cholangiocyte lipoapoptosis by way of caspase activation, nuclear translocation of FoxO3, and increased proapoptotic PUMA expression. These results suggest that cholangiocyte injury may occur through lipoapoptosis in NAFLD and nonalcoholic steatohepatitis patients.

The endocannabinoid anandamide induces apoptosis in cytotrophoblast cells: involvement of both mitochondrial and death receptor pathways

INTRODUCTION

A balanced proliferation, apoptosis and differentiation in trophoblast cells of the human placenta is crucial for a proper placental development. Alteration in trophoblast apoptosis and differentiation are associated with gestational-related complications, such as preeclampsia, intrauterine growth restriction or miscarriages. The endocannabinoids (eCBs) have been recognized as new interveners in pregnancy events such as implantation and decidualization. However, their importance in placentation is poorly understood. We hypothesise that these novel lipid mediators may intervene in cytotrophoblast apoptosis and, concomitantly, have a role during placental development.

METHODS

primary human cytotrophoblasts (hCTs) and the human trophoblast-like choriocarcinoma cell line BeWo cells were exposed to Anandamide (AEA). It was investigated the cellular pathways involved in cell death, by the assessment of cell morphology, caspases activity, mitochondrial membrane potential (Δψm), reactive oxygen/nitrogen species (ROS/RNS) and western blot of cleaved Poly (ADP-ribose) polymerase 1 (PARP-1), truncated Bid (t-Bid) and IκB-α.

RESULTS

AEA decreased hCTs viability and induced morphological features of apoptosis (chromatin condensation and fragmentation), caspase-3/7 activation and PARP-1 cleavage. In BeWo, AEA also increased the activities of caspase-3/7 and 9, induced loss in Δψm and production of ROS/RNS. These effects were reversed by either CB1 or CB2 antagonists, whereas the increase in caspase-3/7 activity was only reversed with CB2 blockage. AEA-treated cells showed increased caspase-8 activation and formation of t-Bid, suggesting the interplay between intrinsic and extrinsic apoptotic pathways. AEA also increased IκB-α expression, a NF-κB regulatory protein.

CONCLUSION

Our results highlight the importance of eCBs in cytotrophoblast cell apoptosis and indicate that a crosstalk between intrinsic and extrinsic apoptotic pathways is involved in AEA-induced effects.

CB2 receptor activation inhibits melanoma cell transmigration through the blood-brain barrier

During parenchymal brain metastasis formation tumor cells need to migrate through cerebral endothelial cells, which form the morphological basis of the blood-brain barrier (BBB). The mechanisms of extravasation of tumor cells are highly uncharacterized, but in some aspects recapitulate the diapedesis of leukocytes. Extravasation of leukocytes through the BBB is decreased by the activation of type 2 cannabinoid receptors (CB2); therefore, in the present study we sought to investigate the role of CB2 receptors in the interaction of melanoma cells with the brain endothelium. First, we identified the presence of CB1, CB2(A), GPR18 (transcriptional variant 1) and GPR55 receptors in brain endothelial cells, while melanoma cells expressed CB1, CB2(A), GPR18 (transcriptional variants 1 and 2), GPR55 and GPR119. We observed that activation of CB2 receptors with JWH-133 reduced the adhesion of melanoma cells to the layer of brain endothelial cells. JWH-133 decreased the transendothelial migration rate of melanoma cells as well. Our results suggest that changes induced in endothelial cells are critical in the mediation of the effect of CB2 agonists. Our data identify CB2 as a potential target in reducing the number of brain metastastes originating from melanoma.

A potential role for GPR55 in the regulation of energy homeostasis

G protein-coupled receptor 55 (GPR55) is a putative cannabinoid receptor that is expressed in several tissues involved in regulating energy homeostasis, including the hypothalamus, gastrointestinal tract, pancreas, liver, white adipose and skeletal muscle. GPR55 has been shown to have a role in cancer and gastrointestinal inflammation, as well as in obesity and type 2 diabetes mellitus (T2DM). Despite this, the (patho)physiological role of GPR55 in cell dysfunction is still poorly understood, largely because of the limited identification of downstream signalling targets. Nonetheless, research has suggested that GPR55 modulation would be a useful pharmacological target in metabolically active tissues to improve treatment of diseases such as obesity and T2DM. Further research is essential to gain a better understanding of the role that this receptor might have in these and other pathophysiological conditions.

Anticancer activity of anandamide in human cutaneous melanoma cells

Cannabinoids are implicated in the control of cell proliferation, but little is known about the role of the endocannabinoid system in human malignant melanoma. This study was aimed at characterizing the in vitro antitumor activity of anandamide (AEA) in A375 melanoma cells. The mRNA expression of genes that code for proteins involved in the metabolism and in the mechanism of AEA action was assessed by RT-PCR. Cell viability was tested using WST-1 assay and the apoptotic cell death was determined by measuring caspase 3/7 activities. A375 cells express high levels of fatty acid amide hydrolase (FAAH), cyclooxygenase (COX)-2, cannabinoid receptor 1 (CB1), transient receptor potential cation channel subfamily V member 1 (TRPV1) and G-protein-coupled receptor 55 (GPR55) genes. AEA induced a concentration-dependent cytotoxicity with an IC50 of 5.8 ± 0.7 µM and such an effect was associated to a caspase-dependent apoptotic pathway. AEA cytotoxicity was potentiated by FAAH inhibition (2-fold increase, p<0.05) and mitigated by COX-2 or lipoxygenase (LOX) inhibition (5- and 3-fold decrease, respectively; p<0.01). Blocking CB1 receptors partially decreased AEA cytotoxicity, whereas selective antagonism on the TRPV1 barely affected the mechanism of AEA action. Finally, methyl-β-cyclodextrin, a membrane cholesterol depletory, completely reversed the cytotoxicity induced by the selective GPR55 agonist, O-1602, and AEA. Overall, these findings demonstrate that AEA induces cytotoxicity against human melanoma cells in the micromolar range of concentrations through a complex mechanism, which involves COX-2 and LOX-derived product synthesis and CB1 activation. Lipid raft modulation, probably linked to GPR55 activation, might also have a role.

Liver carcinogenesis: rodent models of hepatocarcinoma and cholangiocarcinoma

Hepatocellular carcinoma and cholangiocarcinoma are primary liver cancers, both represent a growing challenge for clinicians due to their increasing morbidity and mortality. In the last few years a number of in vivo models of hepatocellular carcinoma and cholangiocarcinoma have been developed. The study of these models is providing a significant contribution in unveiling the pathophysiology of primary liver malignancies. They are also fundamental tools to evaluate newly designed molecules to be tested as new potential therapeutic agents in a pre-clinical set. Technical aspects of each model are critical steps, and they should always be considered in order to appropriately interpret the findings of a study or its planning. The purpose of this review is to describe the technical and experimental features of the most significant rodent models, highlighting similarities or differences between the corresponding human diseases. The first part is dedicated to the discussion of models of hepatocellular carcinoma, developed using toxic agents, or through dietary or genetic manipulations. In the second we will address models of cholangiocarcinoma developed in rats or mice by toxin administration, genetic manipulation and/or bile duct incannulation or surgery. Xenograft or syngenic models are also proposed.

A selective antagonist reveals a potential role of G protein-coupled receptor 55 in platelet and endothelial cell function

The G protein-coupled receptor 55 (GPR55) is a lysophosphatidylinositol (LPI) receptor that is also responsive to certain cannabinoids. Although GPR55 has been implicated in several (patho)physiologic functions, its role remains enigmatic owing mainly to the lack of selective GPR55 antagonists. Here we show that the compound CID16020046 ((4-[4-(3-hydroxyphenyl)-3-(4-methylphenyl)-6-oxo-1H,4H,5H,6H-pyrrolo[3,4-c]pyrazol-5-yl] benzoic acid) is a selective GPR55 antagonist. In yeast cells expressing human GPR55, CID16020046 antagonized agonist-induced receptor activation. In human embryonic kidney (HEK293) cells stably expressing human GPR55, the compound behaved as an antagonist on LPI-mediated Ca²⁺ release and extracellular signal-regulated kinases activation, but not in HEK293 cells expressing cannabinoid receptor 1 or 2 (CB₁ or CB₂). CID16020046 concentration dependently inhibited LPI-induced activation of nuclear factor of activated T-cells (NFAT), nuclear factor κ of activated B cells (NF-κB) and serum response element, translocation of NFAT and NF-κB, and GPR55 internalization. It reduced LPI-induced wound healing in primary human lung microvascular endothelial cells and reversed LPI-inhibited platelet aggregation, suggesting a novel role for GPR55 in platelet and endothelial cell function. CID16020046 is therefore a valuable tool to study GPR55-mediated mechanisms in primary cells and tissues.

The endocannabinoid signaling system in cancer

Changes in lipid metabolism are intimately related to cancer. Several classes of bioactive lipids play roles in the regulation of signaling pathways involved in neoplastic transformation and tumor growth and progression. The endocannabinoid system, comprising lipid-derived endocannabinoids, their G-protein-coupled receptors (GPCRs), and the enzymes for their metabolism, is emerging as a promising therapeutic target in cancer. This report highlights the main signaling pathways for the antitumor effects of the endocannabinoid system in cancer and its basic role in cancer pathogenesis, and discusses the alternative view of cannabinoid receptors as tumor promoters. We focus on new players in the antitumor action of the endocannabinoid system and on emerging crosstalk among cannabinoid receptors and other membrane or nuclear receptors involved in cancer. We also discuss the enzyme MAGL, a key player in endocannabinoid metabolism that was recently recognized as a marker of tumor lipogenic phenotype.