Novel role of cannabinoid receptor 2 in inhibiting EGF/EGFR and IGF-I/IGF-IR pathways in breast cancer

Combinatorial effects of cannabinoid receptor 1 and 2 agonists on characteristics and proteomic alteration in MDA-MB-231 breast cancer cells

Breast cancer is the most common cancer diagnosed in women worldwide. However, the effective treatment for breast cancer progression is still being sought. The activation of cannabinoid receptor (CB) has been shown to negatively affect breast cancer cell survival. Our previous study also reported that breast cancer cells responded to various combinations of CB1 and CB2 agonists differently. Nonetheless, the mechanism underlying this effect and whether this phenomenon can be seen in other cancer characteristics remain unknown. Therefore, this study aims to further elucidate the effects of highly selective CB agonists and their combination on triple-negative breast cancer proliferation, cell cycle progression, invasion, lamellipodia formation as well as proteomic profile of MDA-MB-231 breast cancer cells. The presence of CB agonists, specifically a 2:1 (ACEA: GW405833) combination, prominently inhibited colony formation and induced the S-phase cell cycle arrest in MDA-MB-231 cells. Furthermore, cell invasion ability and lamellipodia formation of MDA-MB-231 were also attenuated by the exposure of CB agonists and their 2:1 combination ratio. Our proteomic analysis revealed proteomic profile alteration in MDA-MB-231 upon CB exposure that potentially led to breast cancer suppression, such as ZPR1/SHC1/MAPK-mediated cell proliferation and AXL/VAV2/RAC1-mediated cell motility pathways. Our findings showed that selective CB agonists and their combination suppressed breast cancer characteristics in MDA-MB-231 cells. The exposure of CB agonists also altered the proteomic profile of MDA-MB-231, which could lead to cell proliferation and motility suppression.

Investigation of the regulation of EGF signaling by miRNAs, delving into the underlying mechanism and signaling pathways in cancer

The EGF receptors (EGFRs) signaling pathway is essential for tumorigenesis and progression of cancer. Emerging evidence suggests that miRNAs are essential regulators of EGF signaling, influencing various pathway components and tumor behavior. This article discusses the underlying mechanisms and clinical implications of miRNA-mediated regulation of EGF signaling in cancer. miRNAs utilize multiple mechanisms to exert their regulatory effects on EGF signaling. They can target EGF ligands, including EGF and TGF-directly, inhibiting their expression and secretion. In addition, miRNAs can modulate EGF signaling indirectly by targeting EGF receptors, downstream signaling molecules, and transcription factors implicated in regulating the EGF pathway. These miRNAs can disrupt the delicate equilibrium of EGF signaling, resulting in aberrant activation and fostering tumor cell proliferation, survival, angiogenesis, and metastasis. The dysregulation of the expression of specific miRNAs has been linked to clinical outcomes in numerous types of cancer. Specific profiles of miRNA expression have been identified as prognostic markers, reflecting tumor characteristics, invasiveness, metastatic potential, and therapeutic response. These miRNAs can serve as potential therapeutic targets for interventions that modulate EGF signaling and improve patient outcomes. Understanding the intricate relationship between miRNAs and EGF signaling in cancer can transform cancer diagnosis, prognosis, and treatment. The identification of specific miRNAs involved in the regulation of the EGF pathway opens the door to the development of targeted therapies and personalized medicine approaches. In addition, miRNA-based interventions promise to overcome therapeutic resistance and improve the efficacy of existing treatments. miRNAs are crucial regulators of EGF signaling in cancer, affecting tumor behavior and clinical outcomes. Further research is required to decipher the complex network of miRNA-mediated EGF signaling regulation and translate these findings into clinically applicable strategies for enhanced cancer treatment.

Overexpression of cannabinoid receptor 2 is associated with human breast cancer proliferation, apoptosis, chemosensitivity and prognosis via the PI3K/Akt/mTOR signaling pathway

INTRODUCTION

The cannabinoid receptor 2 (CB2) is mainly involved in the immune system. However, although CB2 has been reported to play an anti-tumor function in breast cancer (BC), its specific mechanism in BC remains unclear.

METHODS

We examined the expression and prognostic significance of CB2 in BC tissues by qPCR, second-generation sequencing, western blot, and immunohistochemistry. We assessed the impacts of overexpression and a specific agonist of CB2 on the growth, proliferation, apoptosis, and drug resistance of BC cells in vitro and in vivo using CCK-8, flow cytometry, TUNEL staining, immunofluorescence, tumor xenografts, western blot, and colony formation assays.

RESULTS

CB2 expression was significantly lower in BC compared with paracancerous tissues. It was also highly expressed in benign tumors and ductal carcinoma in situ, and its expression was correlated with prognosis in BC patients. CB2 overexpression and treatment of BC cells with a CB2 agonist inhibited proliferation and promoted apoptosis, and these actions were achieved by suppressing the PI3K/Akt/mTOR signaling pathway. Moreover, CB2 expression was increased in MDA-MB-231 cell treated with cisplatin, doxorubicin, and docetaxel, and sensitivity to these anti-tumor drugs was increased in BC cells overexpressing CB2.

CONCLUSIONS

These findings reveal that CB2 mediates BC via the PI3K/Akt/mTOR signaling pathway. CB2 could be a novel target for the diagnosis and treatment of BC.

Lipids as Targets for Renal Cell Carcinoma Therapy

Kidney cancer is among the top ten most common cancers to date. Within the kidney, renal cell carcinoma (RCC) is the most common solid lesion occurring. While various risk factors are suspected, including unhealthy lifestyle, age, and ethnicity, genetic mutations seem to be a key risk factor. In particular, mutations in the von Hippel-Lindau gene (Vhl) have attracted a lot of interest since this gene regulates the hypoxia inducible transcription factors HIF-1α and HIF-2α, which in turn drive the transcription of many genes that are important for renal cancer growth and progression, including genes involved in lipid metabolism and signaling. Recent data suggest that HIF-1/2 are themselves regulated by bioactive lipids which make the connection between lipids and renal cancer obvious. This review will summarize the effects and contributions of the different classes of bioactive lipids, including sphingolipids, glycosphingolipids, eicosanoids, free fatty acids, cannabinoids, and cholesterol to renal carcinoma progression. Novel pharmacological strategies interfering with lipid signaling to treat renal cancer will be highlighted.

Cannabinoids as Prospective Anti-Cancer Drugs: Mechanism of Action in Healthy and Cancer Cells

Endogenous and exogenous cannabinoids modulate many physiological and pathological processes by binding classical cannabinoid receptors 1 (CB1) or 2 (CB2) or non-cannabinoid receptors. Cannabinoids are known to exert antiproliferative, apoptotic, anti-migratory and anti-invasive effect on cancer cells by inducing or inhibiting various signaling cascades. In this chapter, we specifically emphasize the latest research works about the alterations in endocannabinoid system (ECS) components in malignancies and cancer cell proliferation, migration, invasion, angiogenesis, autophagy, and death by cannabinoid administration, emphasizing their mechanism of action, and give a future perspective for clinical use.

Endocannabinoid-Binding Receptors as Drug Targets

Cannabis plant has been used from ancient times with therapeutic purposes for treating human pathologies, but the identification of the cellular and molecular mechanisms underlying the therapeutic properties of the phytocannabinoids, the active compounds in this plant, occurred in the last years of the past century. In the late 1980s and early 1990s, seminal studies demonstrated the existence of cannabinoid receptors and other elements of the so-called endocannabinoid system. These G protein-coupled receptors (GPCRs) are a key element in the functions assigned to endocannabinoids and appear to serve as promising pharmacological targets. They include CB₁, CB₂, and GPR55, but also non-GPCRs can be activated by endocannabinoids, like ionotropic receptor TRPV₁ and even nuclear receptors of the PPAR family. Their activation, inhibition, or simply modulation have been associated with numerous physiological effects at both central and peripheral levels, which may have therapeutic value in different human pathologies, then providing a solid experimental explanation for both the ancient medicinal uses of Cannabis plant and the recent advances in the development of cannabinoid-based specific therapies. This chapter will review the scientific knowledge generated in the last years around the research on the different endocannabinoid-binding receptors and their signaling mechanisms. Our intention is that this knowledge may help readers to understand the relevance of these receptors in health and disease conditions, as well as it may serve as the theoretical basis for the different experimental protocols to investigate these receptors and their signaling mechanisms that will be described in the following chapters.

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.

Expression of cannabinoid receptors CB1 and CB2 in canine cutaneous mast cell tumours

Cannabinoid receptors (CB1 and CB2) belong to endocannabinoid system (ECS), which is also composed from endocannabinoids and the enzymatic systems involved in their biosynthesis and degradation. The expression of CB1 and CB2 have been previously identified in normal canine mast cell and in atopic dermatitis. Canine cutaneous mast cell tumours (cMCTs) are among the most common cutaneous neoplasms in dogs and have a highly variable clinical behaviour. Expression of CB1-CB2 was assessed by means of immunohistochemistry in thirty-seven dogs (from 2019 to 2021) with proven histological diagnosis of cMCT. Dogs were divided in two groups according to the Kiupel's grading system: high-grade (HG) cMCT and low-grade (LG) cMCT. A semiquantitative (score 0-3) and quantitative assessment of immunoreactivity (IR) was performed for each case. Our results show that there CB1 and CB2 are highly expressed in LG- cMCT, in contrast to HG- cMCT.

Cannabinoid Receptor-1 suppresses M2 macrophage polarization in colorectal cancer by downregulating EGFR

Cannabinoid receptors, CB1 and CB2, have been implicated as emerging targets for cancer therapy. Herein, we investigated the potential regulation mechanism of CB1 and its implications in colorectal cancer. CB1 and EGFR expression were examined in colorectal cancer cell lines. The effects of CB1 agonist ACEA and its antagonist AM251 on the proliferation, migration and invasion of colorectal cancer cells and the expression of M1 and M2 macrophage markers were examined. EGFR overexpression was performed with plasmids containing EGFR gene. Tumor xenografts were constructed to explore the effects of CB1 activation on tumorigenesis. We showed that CB1 was downregulated while EGFR was upregulated in colorectal cancer cells. The activation of CB1 suppressed the proliferation, migration and invasion of colorectal cancer cells and the differentiation of M2 macrophages, while CB1 inhibition had opposite effects. Moreover, the alterations in tumorigenesis and M2 macrophage activation induced by CB1 activation were counteracted by EGFR overexpression. Besides, CB1 silencing promoted tumor cell proliferation and M2 polarization which was counteracted by EGFR knockdown. In vivo, CB1 activation also repressed tumorigenesis and M2 macrophage activation. The present study demonstrated that CB1 activation suppressed M2 macrophage through EGFR downregulation in colorectal cancers. These findings first unveiled the potential avenue of CB1 as a targeted therapy for colorectal cancer.

Chronic Administration of Cannabinoid Receptor 2 Agonist (JWH-133) Increases Ectopic Ovarian Tumor Growth and Endocannabinoids (Anandamide and 2-Arachidonoyl Glycerol) Levels in Immunocompromised SCID Female Mice

Cannabinoid-based therapies are increasingly being used by cancer patients to treat chemotherapy-induced nausea and vomiting. Recently, cannabinoids have gained increased attention for their effects on cancer growth. Indeed, the effect of CB₂ (JWH-015, JWH-133) agonists on breast cancer models have shown to reduce the size of breast cancer tumors. However, these studies assessing breast cancer progression were using CB₂ agonist administered early into the cancer progression therefore assessing their effects on already established tumors is a critical need. In our study, we evaluate tumor growth using an ectopic xenograft ovarian (SKOV-3 and OVCAR-5) cancer model. The impact of chronic (30 days) administration of CB₂ (JWH-133) agonist will be evaluated and started on 30 days of ectopic ovarian tumors. We will then evaluate and determine the mechanisms involved in ovarian cancer tumor growth by measuring levels of anandamide and 2-arachidonoyl glycerol as well as protein levels of CB₁, CB₂, ERα, ERβ, GPER, TNFα, IL-1β and IL-6 in ovarian and tumor tissues. Our results demonstrate a significant increase in ectopic ovarian tumor growth following chronic administration of JWH-133. Ovarian cancer tumor tissues chronically (30 days) treated with JWH-133 in comparison to vehicle treated groups showed an increase in endocannabinoid (AEA and 2-AG) and protein (CB₂ and TNFα) levels with a decrease in GPER protein levels. Interestingly, our study emphasizes the importance of studying the impact of cannabinoid compounds on already established tumors to improve our understanding of cannabinoid-based therapies and, therefore better address clinical needs in cancer patients.

Cannabinoids, their cellular receptors, and effects on the invasive phenotype of carcinoma and metastasis

BACKGROUND

The morbidity and mortality of cancer are significantly impacted by the invasive and metastatic potential of particular subgroups of malignant cells within a tumor. The particular pre-metastatic properties of cancerous cells are thus a critical target for novel therapeutics in the oncology field. Cannabinoid molecules have been investigated in recent years in the context of invasion and metastasis of various malignancies, with varying effects reported in the literature.

RECENT FINDINGS

There was substantial variability in the findings reported by the literature of the effects of cannabinoid molecules on cancer cell invasion and metastasis. These effects varied depending on which ligand and which of the CB1, CB2, or GPR55 receptors were investigated. These findings suggest a role for the phenomenon of biased signaling in explaining the diversity of effects of cannabinoid molecules on cancer cell invasion.

CONCLUSION

While substantially more investigation is required into the effects of cannabinoid molecules on cancer cell invasion and metastasis, we describe in this review the significant diversity in the responses of cancer cells to cannabinoid molecules in terms of their invasive and metastatic capacities.

Cannabinoid receptors promote chronic intermittent hypoxia-induced breast cancer metastasis via IGF-1R/AKT/GSK-3β

The progression of breast cancer is closely related to obstructive sleep apnea-hypopnea syndrome (OSAHS). Low concentrations of cannabinoids promote tumor proliferation. However, the role of cannabinoid receptors (CBs) in chronic intermittent hypoxia (CIH)-induced breast cancer has not been reported. The migration and invasion of breast cancer cell lines (MCF-7 and T47D) were measured by scratch assay and transwell assay. Gene and protein expressions were analyzed by qPCR and western blotting. Tumor xenograft mice model were established to evaluate the function of CBs. We observed that chronic hypoxia (CH) and CIH increased CBs expression and promoted migration and invasion in breast cancer. Mice grafted with MCF-7 exhibited obvious tumor growth, angiogenesis, and lung metastasis in CIH compared with CH and control. In addition, CIH induced CBs expression, which subsequently activated insulin-like growth factor-1 receptor (IGF-1R)/AKT/glycogen synthase kinase-3β (GSK-3β) axis. Knockdown of CBs alleviated CIH-induced migration and invasion of breast cancer in vitro. Furthermore, CIH exaggerated the malignancy of breast cancer and silencing of CBs suppressed tumor growth and metastasis in vivo. Our study contributed to understanding the role of CIH in breast cancer development modulation.

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.

Chelation-Tamoxifen Conjugates for Imaging of Estrogen Receptors

Background: The differential diagnosis of estrogen receptor-positive (ER+) pathway-activated systems by using a labeled antiestrogen helps to select the patients for optimal response to endocrine therapy and to discontinue the treatment when resistance occurs. The authors' purpose was to synthesize chelator-tamoxifen conjugates for imaging ER (+) diseases. Materials and Methods: A hydroxypropyl linker was incorporated between either cyclam or cyclam diacetic acid and tamoxifen analog to produce SC-05-L-1 (Z-1-(1,4,8,11-tetraazacyclotetradecan-1-yl)-3-((5-(4-(2-(diethylamino)ethoxy) phenyl) -4,5-diphenylpent-4-en-1-yl)oxy)propan-2-ol) and SC-05-N-1 (Z-2,2'-(4-(3-((5-(4-(2-(diethylamino)ethoxy)phenyl)-4,5-diphenylpent-4-en-1-yl)oxy)-2-hydroxy-propyl) -1,4,8,11-tetraazacyclotetradecane-1,8-diyl)diacetic acid), respectively. In vitro cell uptake and cell/media ratios of ^99mTc-SC-05-L-1 and ^99mTc- SC-05-N-1 in ER (+) ovarian cancer cells (TOV-112D and OVCAR3) were performed. To ascertain the specificity of cell uptake, the cell uptake was blocked with estrone. In vivo ^99mTc-SC-05-L-1 or ^99mTc-SC-05-N-1 single-photon emission computed tomography/computed tomography was conducted in tumor-bearing rodents and compared to ¹⁸F-fluoro-2-deoxy-d-glucose (¹⁸F-FDG) positron emission tomography/magnetic resonance imaging (a reference technology). Results: The radiochemical purities of ^99mTc-SC-05-L-1 and ^99mTc-SC-05-N-1 were greater than 99% (n = 10). ^99mTc-SC-05-L-1 had higher cell/media ratios than ^99mTc-SC-05-N-1 in OVCAR-3 ER (+) cells. The cell uptake of ^99mTc-SC-05-L-1 was blocked 80% by estrone indicating an ER-mediated process occurred. ^99mTc-SC-05-N-1 was further selected for in vivo imaging studies due to higher maximum tolerated dose and superior water solubility than ^99mTc-SC-05-L-1. ^99mTc-SC-05-N-1 showed higher tumor uptake and tumor/muscle count density ratios than ¹⁸F-FDG in tumor-bearing rodents. Conclusion: ^99mTc-SC-05-N-1 showed better differential diagnosis of ovarian tumors than ¹⁸F-FDG, indicating great promising in chelator-tamoxifen conjugate for ER pathway-directed systems imaging.

Pharmacological Properties, Therapeutic Potential and Molecular Mechanisms of JWH133, a CB2 Receptor-Selective Agonist

The endocannabinoid system has attracted attention as a pharmacological target for several pathological conditions. Cannabinoid (CB2)-selective agonists have been the focus of pharmacological studies because modulation of the CB2 receptor (CB2R) can be useful in the treatment of pain, inflammation, arthritis, addiction, and cancer among other possible therapeutic applications while circumventing CNS-related adverse effects. Increasing number of evidences from different independent preclinical studies have suggested new perspectives on the involvement of CB2R signaling in inflammation, infection and immunity, thus play important role in cancer, cardiovascular, renal, hepatic and metabolic diseases. JWH133 is a synthetic agonist with high CB2R selectivity and showed to exert CB2R mediated antioxidant, anti-inflammatory, anticancer, cardioprotective, hepatoprotective, gastroprotective, nephroprotective, and immunomodulatory activities. Cumulative evidences suggest that JWH133 protects against hepatic injury, renal injury, cardiotoxicity, fibrosis, rheumatoid arthritis, and cancer as well as against oxidative damage and inflammation, inhibits fibrosis and apoptosis, and acts as an immunosuppressant. This review provides a comprehensive overview of the polypharmacological properties and therapeutic potential of JWH133. This review also presents molecular mechanism and signaling pathways of JWH133 under various pathological conditions except neurological diseases. Based on the available data, this review proposes the possibilities of developing JWH133 as a promising therapeutic agent; however, further safety and toxicity studies in preclinical studies and clinical trials in humans are warranted.

Adiponectin and Thyroid Cancer: Insight into the Association between Adiponectin and Obesity

In recent decades, the incidence and diagnosis of thyroid cancer have risen dramatically, and thyroid cancer has now become the most common endocrine cancer in the world. The onset of thyroid cancer is insidious, and its progression is slow and difficult to detect. Therefore, early prevention and treatment have important strategic significance. Moreover, an in-depth exploration of the pathogenesis of thyroid cancer is key to early prevention and treatment. Substantial evidence supports obesity as an independent risk factor for thyroid cancer. Adipose tissue dysfunction in the obese state is accompanied by dysregulation of a variety of adipocytokines. Adiponectin (APN) is one of the most pivotal adipocytokines, and its connection with obesity and obesity-related disease has gradually become a hot topic in research. Recently, the association between APN and thyroid cancer has received increasing attention. The purpose of this review is to systematically review previous studies, give prominence to APN, focus on the relationship between APN, obesity and thyroid cancer, and uncover the underlying pathogenic mechanisms.

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.

Cannabidiol induces antidepressant and anxiolytic-like effects in experimental type-1 diabetic animals by multiple sites of action

Cannabidiol (CBD), a phytocannabinoid compound, presents antidepressant and anxiolytic-like effects in the type-1 diabetes mellitus(DM1) animal model. Although the underlying mechanism remains unknown, the type-1A serotonin receptor (5-HT1A) and cannabinoids type-1 (CB1) and type-2 (CB2) receptors seem to play a central role in mediating the beneficial effects on emotional responses. We aimed to study the involvement of these receptors on an antidepressant- and anxiolytic-like effects of CBD and on some parameters of the diabetic condition itself. After 2 weeks of the DM1 induction in male Wistar rats by streptozotocin (60 mg/kg; i.p.), animals were treated continuously for 2-weeks with the 5-HT1A receptor antagonist WAY100635 (0.1 mg/kg, i.p.), CB1 antagonist AM251 (1 mg/kg i.p.) or CB2 antagonist AM630 (1 mg/kg i.p.) before the injection of CBD (30 mg/kg, i.p.) or vehicle (VEH, i.p.) and then, they were submitted to the elevated plus-maze and forced swimming tests. Our findings show the continuous treatment with CBD improved all parameters evaluated in these diabetic animals. The previous treatment with the antagonists - 5-HT1A, CB1, or CB2 - blocked the CBD-induced antidepressant-like effect whereas only the blockade of 5-HT1A or CB1 receptors was able to inhibit the CBD-induced anxiolytic-like effect. Regarding glycemic control, only the blockade of CB2 was able to inhibit the beneficial effect of CBD in reducing the glycemia of diabetic animals. These findings indicated a therapeutic potential for CBD in the treatment of depression/anxiety associated with diabetes pointing out a complex intrinsic mechanism in which 5-HT1A, CB1, and/or CB2 receptors are differently recruited.

Unraveling the Molecular Nexus between GPCRs, ERS, and EMT

G protein-coupled receptors (GPCRs) represent a large family of transmembrane proteins that transduce an external stimulus into a variety of cellular responses. They play a critical role in various pathological conditions in humans, including cancer, by regulating a number of key processes involved in tumor formation and progression. The epithelial-mesenchymal transition (EMT) is a fundamental process in promoting cancer cell invasion and tumor dissemination leading to metastasis, an often intractable state of the disease. Uncontrolled proliferation and persistent metabolism of cancer cells also induce oxidative stress, hypoxia, and depletion of growth factors and nutrients. These disturbances lead to the accumulation of misfolded proteins in the endoplasmic reticulum (ER) and induce a cellular condition called ER stress (ERS) which is counteracted by activation of the unfolded protein response (UPR). Many GPCRs modulate ERS and UPR signaling via ERS sensors, IRE1α, PERK, and ATF6, to support cancer cell survival and inhibit cell death. By regulating downstream signaling pathways such as NF-κB, MAPK/ERK, PI3K/AKT, TGF-β, and Wnt/β-catenin, GPCRs also upregulate mesenchymal transcription factors including Snail, ZEB, and Twist superfamilies which regulate cell polarity, cytoskeleton remodeling, migration, and invasion. Likewise, ERS-induced UPR upregulates gene transcription and expression of proteins related to EMT enhancing tumor aggressiveness. Though GPCRs are attractive therapeutic targets in cancer biology, much less is known about their roles in regulating ERS and EMT. Here, we will discuss the interplay in GPCR-ERS linked to the EMT process of cancer cells, with a particular focus on oncogenes and molecular signaling pathways.

Identification of an extracellular vesicle-related gene signature in the prediction of pancreatic cancer clinical prognosis

Although extracellular vesicles (EVs) in body fluid have been considered to be ideal biomarkers for cancer diagnosis and prognosis, it is still difficult to distinguish EVs derived from tumor tissue and normal tissue. Therefore, the prognostic value of tumor-specific EVs was evaluated through related molecules in pancreatic tumor tissue. NA sequencing data of pancreatic adenocarcinoma (PAAD) were acquired from The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC). EV-related genes in pancreatic cancer were obtained from exoRBase. Protein–protein interaction (PPI) network analysis was used to identify modules related to clinical stage. CIBERSORT was used to assess the abundance of immune and non-immune cells in the tumor microenvironment. A total of 12 PPI modules were identified, and the 3-PPI-MOD was identified based on the randomForest package. The genes of this model are involved in DNA damage and repair and cell membrane-related pathways. The independent external verification cohorts showed that the 3-PPI-MOD can significantly classify patient prognosis. Moreover, compared with the model constructed by pure gene expression, the 3-PPI-MOD showed better prognostic value. The expression of genes in the 3-PPI-MOD had a significant positive correlation with immune cells. Genes related to the hypoxia pathway were significantly enriched in the high-risk tumors predicted by the 3-PPI-MOD. External databases were used to verify the gene expression in the 3-PPI-MOD. The 3-PPI-MOD had satisfactory predictive performance and could be used as a prognostic predictive biomarker for pancreatic cancer.

Anti-Metastatic Activity of an Anti-EGFR Monoclonal Antibody against Metastatic Colorectal Cancer with KRAS p.G13D Mutation

The now clinically-used anti-epidermal growth factor receptor (EGFR) monoclonal antibodies have demonstrated significant efficacy only in patients with metastatic colorectal cancer (mCRC), with wild-type Kirsten rat sarcoma viral oncogene homolog (KRAS). However, no effective treatments for patients with mCRC with KRAS mutated tumors have been approved yet. Therefore, a new strategy for targeting mCRC with KRAS mutated tumors is desired. In the present study, we examined the anti-tumor activities of a novel anti-EGFR monoclonal antibody, EMab-17 (mouse IgG_2a, kappa), in colorectal cancer (CRC) cells with the KRAS p.G13D mutation. This antibody recognized endogenous EGRF in CRC cells with or without KRAS mutations, and showed a high sensitivity for CRC cells in flow cytometry, indicating that EMab-17 possesses a high binding affinity to the endogenous EGFR. In vitro experiments showed that EMab-17 exhibited antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity activities against CRC cells. In vivo analysis revealed that EMab-17 inhibited the metastases of HCT-15 and HCT-116 cells in the livers of nude mouse metastatic models, unlike the anti-EGFR monoclonal antibody EMab-51 of subtype mouse IgG₁. In conclusion, EMab-17 may be useful in an antibody-based therapy against mCRC with the KRAS p.G13D mutation.

Vitamin D and Its Potential Interplay With Pain Signaling Pathways

About 50 million of the U.S. adult population suffer from chronic pain. It is a complex disease in its own right for which currently available analgesics have been deemed woefully inadequate since ~20% of the sufferers derive no benefit. Vitamin D, known for its role in calcium homeostasis and bone metabolism, is thought to be of clinical benefit in treating chronic pain without the side-effects of currently available analgesics. A strong correlation between hypovitaminosis D and incidence of bone pain is known. However, the potential underlying mechanisms by which vitamin D might exert its analgesic effects are poorly understood. In this review, we discuss pathways involved in pain sensing and processing primarily at the level of dorsal root ganglion (DRG) neurons and the potential interplay between vitamin D, its receptor (VDR) and known specific pain signaling pathways including nerve growth factor (NGF), glial-derived neurotrophic factor (GDNF), epidermal growth factor receptor (EGFR), and opioid receptors. We also discuss how vitamin D/VDR might influence immune cells and pain sensitization as well as review the increasingly important topic of vitamin D toxicity. Further in vitro and in vivo experimental studies will be required to study these potential interactions specifically in pain models. Such studies could highlight the potential usefulness of vitamin D either alone or in combination with existing analgesics to better treat chronic pain.

Can Hemp Help? Low-THC Cannabis and Non-THC Cannabinoids for the Treatment of Cancer

Cannabis has been used to relieve the symptoms of disease for thousands of years. However, social and political biases have limited effective interrogation of the potential benefits of cannabis and polarised public opinion. Further, the medicinal and clinical utility of cannabis is limited by the psychotropic side effects of ∆⁹-tetrahydrocannabinol (∆⁹-THC). Evidence is emerging for the therapeutic benefits of cannabis in the treatment of neurological and neurodegenerative diseases, with potential efficacy as an analgesic and antiemetic for the management of cancer-related pain and treatment-related nausea and vomiting, respectively. An increasing number of preclinical studies have established that ∆⁹-THC can inhibit the growth and proliferation of cancerous cells through the modulation of cannabinoid receptors (CB1R and CB2R), but clinical confirmation remains lacking. In parallel, the anti-cancer properties of non-THC cannabinoids, such as cannabidiol (CBD), are linked to the modulation of non-CB1R/CB2R G-protein-coupled receptors, neurotransmitter receptors, and ligand-regulated transcription factors, which together modulate oncogenic signalling and redox homeostasis. Additional evidence has also demonstrated the anti-inflammatory properties of cannabinoids, and this may prove relevant in the context of peritumoural oedema and the tumour immune microenvironment. This review aims to document the emerging mechanisms of anti-cancer actions of non-THC cannabinoids.

Genetic landscape of prognostic value in pancreatic ductal adenocarcinoma microenvironment

Background

The prognosis of pancreatic ductal adenocarcinoma (PDAC) remains dismally poor and is widely considered as an intricate genetic disorder. The mutational landscape of PDAC may directly reflect cancer immunogenicity and dictate the extent and phenotype of immune cell infiltration. In adverse, the microenvironment may also effect the gene expression of cancer cells, which is associated with clinical prognosis. Thus, it is crucial to identify genomic alterations in PDAC microenvironment and its impacts on clinical prognosis.

Methods

The gene expression profiles, mutation data and clinical information of 179 pancreatic cancer patients with an initial pathologic diagnosis ranging from 2001 to 2013 were retrieved from The Cancer Genome Atlas (TCGA) database. The MAlignant Tumor tissues using Expression data (ESTIMATE) algorithm for calculating immune scores and stromal scores and Tumor IMmune Estimation Resource (TIMER) resource for cell infiltrations were applied in this study.

Results

The average immune score or stromal score of PDAC subtype was significantly higher than that of other specific subtypes. KRAS mutant cases had significantly lower immune scores (P=0.001) and stromal scores (P=0.007), in concert with lower immune scores in TP53 mutant cases (P=0.030). However, no significant difference was found in SMAD4 and CDKN2A mutations. In the cohort OS/RFS, the infiltration levels of CD8+ T cells, B cells, Macrophages, Neutrophils and DCs in high stromal score group were higher than those in the low score group (all P<0.001), as well as in immune score groups except for Macrophages in the cohort RFS. In the cohort OS/RFS, 317/379 upregulated genes and 9/6 downregulated genes were observed in the high immune score group, while 227/205 upregulated genes and 17/6 downregulated genes in the high stromal score group. With the analysis for prognostic value of DEGs, 82 and 58 DEGs respectively in the high immune and stromal score group were verified to be significantly associated with better OS (P<0.05), while 53 and 17 DEGs respectively with longer RFS (P<0.05). Functional enrichment analysis showed genes of prognostic values were significantly related to immune response.

Conclusions

A list of genes with prognostic value in PDAC microenvironment were obtained from functional enrichment analysis based on immune and stromal scores, which indicates a series of potential auxiliary prognostic biomarkers for PDAC are available. Further research on these genes may be valuable and helpful to understand the crosstalk between tumor and microenvironment, new immune evasion mechanisms and underlying novel therapeutic targets in an integrated manner.

Therapeutic potential of cannabinoid receptor 2 in the treatment of diabetes mellitus and its complications

The biological effects of endocannabinoid system are mediated by two types of receptors, cannabinoid 1 (CB₁) and cannabinoid 2 receptor (CB₂). They play a pivotal role in the management of pain, inflammation, cancer, obesity and diabetes mellitus. CB₂ receptor activity downregulation is hallmark of inflammation and oxidative stress. Strong evidence display the relation between activation of CB₂ receptors with decrease in the pro-inflammatory cytokines and pro-apoptotic factors. Numerous in vitro and in vivo studies have been validated to confirm the role of CB₂ receptor in the management of obesity, hyperlipidemia and diabetes mellitus by regulating glucose and lipid metabolism. Activation of CB₂ receptor has led to reduction of inflammatory cytokines; tumor necrosis factor-alpha (TNF-α), Interleukin 6 (IL-6), Nuclear factor kappa beta (NF-κβ) and also amelioration of reactive oxygen species and reactive nitrogen species playing role in apoptosis. Many studies confirmed the role of CB₂ receptors in the insulin secretion via facilitating calcium entry into the pancreatic β-cells. CB₂ receptors also displayed improvement in the neuronal and renal functions by decreasing the oxidative stress and downregulating inflammatory cascade. The present review addresses, potential role of CB₂ receptor activation in management of diabetes and its complications. It also includes the role of CB₂ receptors as an anti-oxidant, anti-apoptotic and anti-inflammatory for the treatment of DM and its complications. Also, an informative summary of CB₂ receptor agonist drugs is provided with their potential role in the reduction of glucose levels, increment in the insulin levels, decrease in the hyperglycaemic oxidative stress and inflammation.

Inhibitory role of Gi-coupled receptors on cAMP-driven cancers with focus on opioid receptors in lung adenocarcinoma and its stem cells

The development, progression, metastasis and drug resistance of the most common human cancers are driven by cyclic adenosine monophosphate (cAMP)-signaling downstream of beta-adrenergic receptors (β-Ars) coupled to the stimulatory G-protein G_s. Receptors coupled to the inhibitory G-protein G_i inhibit this signaling cascade by blocking the activation of the enzyme adenylyl cyclase that catalyzes the formation of cAMP and function as the physiological inhibitors of this signaling cascade. Members of the G_i-coupled receptor family widely expressed in the mammalian organism are GABA B receptors (GABA_B-Rs) for the inhibitory neurotransmitter γ-aminobutyric acid (GABA), opioid receptors for endogenous opioid peptides and cannabinoid receptors for endogenous cannabinoids. This review summarizes current evidence for the concept that the activation of G_i-receptor signaling by pharmacological and psychological means is a promising tool for the long-term management of cAMP-driven cancers with special emphasis on the inhibitory effects of opioids on lung adenocarcinoma and its stem cells.

Current Evidence on miRNAs as Potential Theranostic Markers for Detecting Chemoresistance in Colorectal Cancer: A Systematic Review and Meta-Analysis of Preclinical and Clinical Studies

BACKGROUND

Findings from observational clinical studies examining the relationship between biomarker expression and theranosis in colorectal cancer (CRC) have been conflicting.

OBJECTIVE

We conducted this systematic review and meta-analysis to summarise the existing evidence to demonstrate the involvement of microRNAs (miRNAs) in chemoresistance and sensitivity in CRC through drug genetic pathways.

METHODS

Using PRISMA guidelines, we systematically searched PubMed and Science Direct for relevant studies that took place between 2012 and 2017. A random-effects model of meta-analysis was applied to evaluate the pooled effect size of hazard ratios (HRs) across the included studies. Cochran's Q test and the I² statistic were used to detect heterogeneity. A funnel plot was used to assess potential publication bias.

RESULTS

Of the 4700 studies found, 39 studies comprising 2822 patients with CRC met the inclusion criteria. The included studies used one or a combination of 14 chemotherapy drugs, including 5-fluorouracil and oxaliplatin. Of the 60 miRNAs, 28 were associated with chemosensitivity, 20 with chemoresistance, and one with differential expression and radiosensitivity; ten miRNAs were not associated with any impact on chemotherapy. The results outline the importance of 34 drug-regulatory pathways of chemoresistance and sensitivity in CRC. The mean effect size was 0.689 (95% confidence interval 0.428-1.110), indicating that the expression of miRNAs decreased the likelihood of death by about 32%.

CONCLUSION

Studies have consistently shown that multiple miRNAs could act as clinical predictors of chemoresistance and sensitivity. An inclusion of supplementary miRNA estimation in CRC routine practice needs to be considered to evaluate the efficacy of chemotherapy after confirming our findings with large-scale prospective cohort studies.

PROSPERO REGISTRATION NUMBER

CRD42017082196.

Cannabinoid Receptor 2 Agonist JWH-015 Inhibits Interleukin-1β-Induced Inflammation in Rheumatoid Arthritis Synovial Fibroblasts and in Adjuvant Induced Arthritis Rat via Glucocorticoid Receptor

Management of pain in the treatment of rheumatoid arthritis (RA) is a priority that is not fully addressed by the conventional therapies. In the present study, we evaluated the efficacy of cannabinoid receptor 2 (CB2) agonist JWH-015 using RA synovial fibroblasts (RASFs) obtained from patients diagnosed with RA and in a rat adjuvant-induced arthritis (AIA) model of RA. Pretreatment of human RASFs with JWH-015 (10–20 μM) markedly inhibited the ability of pro-inflammatory cytokine interleukin-1β (IL-1β) to induce production of IL-6 and IL-8 and cellular expression of inflammatory cyclooxygenase-2 (COX-2). JWH-015 was effective in reducing IL-1β-induced phosphorylation of TAK1 (Thr^184/187) and JNK/SAPK in human RASFs. While the knockdown of CB2 in RASFs using siRNA method reduced IL-1β-induced inflammation, JWH-015 was still effective in eliciting its anti-inflammatory effects despite the absence of CB2, suggesting the role of non-canonical or an off-target receptor. Computational studies using molecular docking and molecular dynamics simulations showed that JWH-105 favorably binds to glucocorticoid receptor (GR) with the binding pose and interactions similar to its well-known ligand dexamethasone. Furthermore, knockdown of GR using siRNA abrogated JWH-015's ability to reduce IL-1β-induced IL-6 and IL-8 production. In vivo, administration of JWH-015 (5 mg/kg, daily i.p. for 7 days at the onset of arthritis) significantly ameliorated AIA in rats. Pain assessment studies using von Frey method showed a marked antinociception in AIA rats treated with JWH-015. In addition, JWH-015 treatment inhibited bone destruction as evident from micro-CT scanning and bone analysis on the harvested joints and modulated serum RANKL and OPG levels. Overall, our findings suggest that CB2 agonist JWH-015 elicits anti-inflammatory effects partly through GR. This compound could further be tested as an adjunct therapy for the management of pain and tissue destruction as a non-opioid for RA.

Therapeutic targeting of HER2-CB2R heteromers in HER2-positive breast cancer

Although human epidermal growth factor receptor 2 (HER2)-targeted therapies have dramatically improved the clinical outcome of HER2-positive breast cancer patients, innate and acquired resistance remains an important clinical challenge. New therapeutic approaches and diagnostic tools for identification, stratification, and treatment of patients at higher risk of resistance and recurrence are therefore warranted. Here, we unveil a mechanism controlling the oncogenic activity of HER2: heteromerization with the cannabinoid receptor CB₂R. We show that HER2 physically interacts with CB₂R in breast cancer cells, and that the expression of these heteromers correlates with poor patient prognosis. The cannabinoid Δ⁹-tetrahydrocannabinol (THC) disrupts HER2-CB₂R complexes by selectively binding to CB₂R, which leads to (i) the inactivation of HER2 through disruption of HER2-HER2 homodimers, and (ii) the subsequent degradation of HER2 by the proteasome via the E3 ligase c-CBL. This in turn triggers antitumor responses in vitro and in vivo. Selective targeting of CB₂R transmembrane region 5 mimicked THC effects. Together, these findings define HER2-CB₂R heteromers as new potential targets for antitumor therapies and biomarkers with prognostic value in HER2-positive breast cancer.

Cannabis for cancer - illusion or the tip of an iceberg: a review of the evidence for the use of Cannabis and synthetic cannabinoids in oncology

INTRODUCTION

A flowering plant of variegated ingredients and psychoactive qualities, Cannabis has long been used for medicinal and recreational purposes. Regulatory approvals have been gained across a broad range of palliative and therapeutic indications, and in some cases, included in standard treatment guidelines.

AREAS COVERED

The use of Cannabis and cannabinoid-based-medicines in oncology is summarized in this article. Cannabinoids are classified according to natural and synthetic subtypes and their mechanisms of action expounded. The variability of available products is discussed in the clinical context and data regarding chemotherapy-induced nausea and vomiting, cancer-related pain, anorexia, insomnia, and anxiety are presented. Moreover, immunological and antineoplastic effects in preclinical and clinical trials are addressed. Concepts such as synergism or opposition with conventional treatment modalities, the sequence of administration and dosage, molecular cross-talk and malignancy-cannabinoid congruence, are explored. Finally, side-effects, limitations in trial design and legislation barriers are related.

EXPERT OPINION

Sufficient evidence supports the use of Cannabis for palliative indications in oncology; however, patients should be carefully selected, guided and followed. Promising research suggests the potent antineoplastic activity, but more data must be accrued before conclusions can be drawn.

Cholinergic Signaling via Muscarinic Receptors Directly and Indirectly Suppresses Pancreatic Tumorigenesis and Cancer Stemness

In many solid tumors, parasympathetic input is provided by the vagus nerve, which has been shown to modulate tumor growth. However, whether cholinergic signaling directly regulates progression of pancreatic ductal adenocarcinoma (PDAC) has not been defined. Here, we found that subdiaphragmatic vagotomy in LSL-Kras +/G12D;Pdx1-Cre (KC) mice accelerated PDAC development, whereas treatment with the systemic muscarinic agonist bethanechol restored the normal KC phenotype, thereby suppressing the accelerated tumorigenesis caused by vagotomy. In LSL-Kras +/G12D;LSL-Trp53 +/R172H;Pdx1-Cre mice with established PDAC, bethanechol significantly extended survival. These effects were mediated in part through CHRM1, which inhibited downstream MAPK/EGFR and PI3K/AKT pathways in PDAC cells. Enhanced cholinergic signaling led to a suppression of the cancer stem cell (CSC) compartment, CD11b+ myeloid cells, TNFα levels, and metastatic growth in the liver. Therefore, these data suggest that cholinergic signaling directly and indirectly suppresses growth of PDAC cells, and therapies that stimulate muscarinic receptors may be useful in the treatment of PDAC.Significance: Subdiaphragmatic vagotomy or Chrm1 knockout accelerates pancreatic tumorigenesis, in part via expansion of the CSC compartment. Systemic administration of a muscarinic agonist suppresses tumorigenesis through MAPK and PI3K/AKT signaling, in early stages of tumor growth and in more advanced, metastatic disease. Therefore, CHRM1 may represent a potentially attractive therapeutic target. Cancer Discov; 8(11); 1458-73. ©2018 AACR. This article is highlighted in the In This Issue feature, p. 1333.

Overexpression of Epidermal Growth Factor Receptor (EGFR) and HER-2 in Bladder Carcinoma and Its Association with Patients' Clinical Features

BACKGROUND The aim of this study was to determine the expression of EGFR/HER-2 and investigate their association with patients' clinical features in bladder transitional cell carcinoma (BTCC). MATERIAL AND METHODS Immunohistochemistry was utilized in our study to explore the expression of EGFR/HER-2 of 56 human bladder cancer samples and 10 normal bladder samples. RESULTS EGFR and HER-2 expressions were both significantly higher in bladder transitional cell carcinoma (BTCC) than that in non-cancer bladder samples; the EGFR positivity rate was 55.4% among BTCC samples and 37.5% for HER-2a. A statistically significant correlation was also present between the increasing EGFR or HER-2 expression levels and the clinical stages, pathologic grades, and tumor recurrence. The expression level of EGFR increased along with higher clinical stages and pathologic grades of BTCC, and the obviously increased expression of HER-2 was statistically associated with clinical stages and tumor recurrence. In addition, the expression level of HER-2 increased along with the higher clinical stage of BTCC. EGFR expression and HER-2 levels were positively associated in BTCC samples. CONCLUSIONS Our findings demonstrate that high EGFR and HER-2 expressions are dramatically increased in the BTCC tissues and are closely related to the clinical stages, pathologic grades, and tumor recurrence. Therefore, the evaluation of EGFR and HER-2 expression in BTCC may contribute to identifying patients who are at increased risk of disease progression and recurrence.

Insights into the effects of the endocannabinoid system in cancer: a review

In the last few decades, the endocannabinoid system has attracted a great deal of interest in terms of its applications to clinical medicine. In particular, its applications in cancer probably represent one of the therapeutic areas with most promise. On the one hand, expression of the endocannabinoid system is altered in numerous types of tumours, compared to healthy tissue, and this aberrant expression has been related to cancer prognosis and disease outcome, suggesting a role of this system in tumour growth and progression that depends on cancer type. On the other hand, cannabinoids exert an anticancer activity by inhibiting the proliferation, migration and/or invasion of cancer cells and also tumour angiogenesis. However, some cannabinoids, at lower concentrations, may increase tumour proliferation, inducing cancer growth. Enough data has been provided to consider the endocannabinoid system as a new therapeutic target in cancer, although further studies to fully establish the effect of cannabinoids on tumour progression are still needed.

Cannabinoid receptor 2 as a novel target for promotion of renal cell carcinoma prognosis and progression

PURPOSE

Renal cell carcinoma (RCC) is the most common malignancy of urogenital system, and patients with RCC may face a poor prognosis. However, limited curable therapeutic options are currently available. The aim of this study is to investigate the role of Cannabinoid receptor 2 (CB2) in RCC progression.

METHODS

Immunohistochemistry was to investigate the expression pattern of CB2 in 418 RCC tissues and explore its prognostic function in RCC patients. Furthermore, the role of used CB2 si-RNA knockdown and inhibited by AM630, a CB2 inverse agonist, on cell proliferation, migration, and cell cycle of RCC cell lines in vitro was also investigated.

RESULTS

We observed that CB2 was up-regulated in RCC tissues, and presented as an independent prognostic factor for overall survival of RCC patients and higher CB2 expression tends to have poor clinical outcomes in survival analyses. Moreover, we also observed that CB2, incorporated with pN stage, pathological grade, and recurrence or distant metastasis after surgery, could obviously enhance their prognostic accuracy in a predictive nomogram analysis. In addition, knockdown or inhibition by AM630 for the expression of CB2 in vitro could significantly decreased cell proliferation and migration, and obviously induced cell cycle arrest in G2/M of RCC cells.

CONCLUSIONS

CB2 expression is functionally related to cellular proliferation, migration, and cell cycle of RCC cells. Our data suggest that CB2 might be a potential therapeutic target for RCC.

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.