Synthetic Cannabinoids Influence the Invasion of Glioblastoma Cell Lines in a Cell- and Receptor-Dependent Manner

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.

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.

Cannabinoid-mediated targeting of mitochondria on the modulation of mitochondrial function and dynamics

Mitochondria play a critical role in the regulation of several biological processes (e.g., programmed cell death, inflammation, neurotransmission, cell differentiation). In recent years, accumulating findings have evidenced that cannabinoids, a group of endogenous and exogenous (synthetic and plant-derived) psychoactive compounds that bind to cannabinoid receptors, may modulate mitochondrial function and dynamics. As such, mitochondria have gained increasing interest as central mediators in cannabinoids' pharmacological and toxicological signatures. Here, we review the mechanisms underlying the cannabinoids' modulation of mitochondrial activity and dynamics, as well as the potential implications of such mitochondrial processes' disruption on cell homeostasis and disease. Interestingly, cannabinoids may target different mitochondrial processes (e.g., regulation of intracellular calcium levels, bioenergetic metabolism, apoptosis, and mitochondrial dynamics, including mitochondrial fission and fusion, transport, mitophagy, and biogenesis), by modulating multiple and complex signaling pathways. Of note, the outcome may depend on the experimental models used, as well as the chemical structure, concentration, and exposure settings to the cannabinoid, originating equivocal data. Notably, this interaction seems to represent not only an important feature of cannabinoids' toxicological signatures, with potential implications for the onset of distinct pathological conditions (e.g., cancer, neurodegenerative diseases, metabolic syndromes), but also an opportunity to develop novel therapeutic strategies for such pathologies, which is also discussed in this review.

The strengths and limits of cannabinoids and their receptors in cancer: Insights into the role of tumorigenesis-underlying mechanisms and therapeutic aspects

Cancer, as a mysterious and complex disease, has a multi-stage molecular process that uses the cellular molecular machine and multiple signaling pathways to its advantage. Cannabinoids, as terpenophenolic compounds and their derivatives, showed influences on immune system responses, inflammation, and cell growth that have sparked a growing interest in exploring their effects on cancer cell fate, as well. A large body of evidence in experimental models indicating the involvement of cannabinoids and their related receptors in cancer cell growth, development, and fate. In accordance, the present study provided insights regarding the strengths and limits of cannabinoids and their receptors in critical steps of tumorigenesis and its underlying molecular pathways such as; cancer cell proliferation, type of cell death pathway, angiogenesis, invasion, metastasis and, immune system response. Based on the results of the present study and due to the contribution of cannabinoids in various cancer cell growth control processes, these compounds cancer can be considered worthwhile in finding new alternatives for cancer therapy.

Preparation and Culture of Organotypic Hippocampal Slices for the Analysis of Brain Metastasis and Primary Brain Tumor Growth

Brain metastasis is a major challenge for therapy and defines the end stage of tumor progression with a very limited patients' prognosis. Experimental setups that faithfully mimic these processes are necessary to understand the mechanism of brain metastasis and to develop new improved therapeutic strategies. Here, we describe an in vitro model, which closely resembles the in vivo situation. Organotypic hippocampal brain slice cultures (OHSCs) prepared from 3- to 8-day-old mice are well suited for neuro-oncology research including brain metastasis. The original morphology is preserved in OHSCs even after culture periods of several days to weeks. Tumor cells or cells of metastatic origin can be seeded onto OHSCs to evaluate micro-tumor formation, tumor cell invasion, or treatment response. We describe preparation and culture of OHSCs including the seeding of tumor cells. Finally, we show examples of how to treat the OHSCs for life-dead or immunohistochemical staining.

Bioscaffolds embedded with regulatory modules for cell growth and tissue formation: A review

The demand for artificial organs has greatly increased because of various aging-associated diseases and the wide need for organ transplants. A recent trend in tissue engineering is the precise reconstruction of tissues by the growth of cells adhering to bioscaffolds, which are three-dimensional (3D) structures that guide tissue and organ formation. Bioscaffolds used to fabricate bionic tissues should be able to not only guide cell growth but also regulate cell behaviors. Common regulation methods include biophysical and biochemical stimulations. Biophysical stimulation cues include matrix hardness, external stress and strain, surface topology, and electromagnetic field and concentration, whereas biochemical stimulation cues include growth factors, proteins, kinases, and magnetic nanoparticles. This review discusses bioink preparation, 3D bioprinting (including extrusion-based, inkjet, and ultraviolet-assisted 3D bioprinting), and regulation of cell behaviors. In particular, it provides an overview of state-of-the-art methods and devices for regulating cell growth and tissue formation and the effects of biophysical and biochemical stimulations on cell behaviors. In addition, the fabrication of bioscaffolds embedded with regulatory modules for biomimetic tissue preparation is explained. Finally, challenges in cell growth regulation and future research directions are presented.

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.

Cannabinoids as anticancer therapeutic agents

The recent announcement of marijuana legalization in Canada spiked many discussions about potential health benefits of Cannabis sativa. Cannabinoids are active chemical compounds produced by cannabis, and their numerous effects on the human body are primarily exerted through interactions with cannabinoid receptor types 1 (CB1) and 2 (CB2). Cannabinoids are broadly classified as endo-, phyto-, and synthetic cannabinoids. In this review, we will describe the activity of cannabinoids on the cellular level, comprehensively summarize the activity of all groups of cannabinoids on various cancers and propose several potential mechanisms of action of cannabinoids on cancer cells.

Opposite Effects of Neuroprotective Cannabinoids, Palmitoylethanolamide, and 2-Arachidonoylglycerol on Function and Morphology of Microglia

Various studies performed in cultured cells and in in vivo models of neuronal damage showed that cannabinoids exert a neuroprotective effect. The increase in cannabinoids and cannabinoid like substances after stroke has been postulated to limit the content of neuronal injury. As well-accepted, inflammation, and neuronal damage are coupled processes and microglial cells as the main intrinsic immunological effector within the brain play a central role in their regulation. Treatment with the endocannabinoid, 2-arachidonoylglycerol (2-AG) or the endocannabinoid-like substance, palmitoylethanolamide (PEA) affected microglial cells and led to a decrease in the number of damaged neurons after excitotoxical lesion in organotypic hippocampal slice cultures (OHSC). 2-AG activated abnormal cannabidiol (abn-CBD) receptor, PEA was shown to mediate neuroprotection via peroxisome proliferator-activated receptor (PPAR)α. Despite the known neuroprotective and anti-inflammatory properties, the potential synergistic effect, namely possible entourage effect after treatment with the combination of these two protective cannabinoids has not been examined yet. After excitotoxical lesion OHSC were treated with PEA, 2-AG or a combination of both and the number of damaged neurons was evaluated. To investigate the role of microglial cells in PEA and 2-AG mediated protection, primary microglial cell cultures were treated with lipopolysaccharide (LPS) and 2-AG, PEA or a combination of those. Thereafter, we measured NO production, ramification index, proliferation and PPARα distribution in microglial cells. While PEA or 2-AG alone were neuroprotective, their co-application vanished the protective effect. This behavior was independent of microglial cells. Furthermore, PEA and 2-AG had contrary effects on ramification index and on NO production. No significant changes were observed in the proliferation rate of microglial cells after treatment. The expression of PPARα was not changed upon stimulation with PEA or 2-AG, but the distribution was significantly altered. 2-AG and PEA mediated neuroprotection was abolished when co-applied. Both cannabinoids exert contrary effects on morphology and function of microglial cells. Co-application of both cannabinoids with different targets did not lead to a positive additive effect as expected, presumably due to the contrary polarization of microglial cells.