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Inhibition of ATM kinase upregulates levels of cell death induced by cannabidiol and γ-irradiation in human glioblastoma cells

Abstract

Despite advances in glioblastoma (GBM) therapy, prognosis of the disease remains poor with a low survival rate. Cannabidiol (CBD) can induce cell death and enhance radiosensitivity of GBM but not normal astrocytes. Inhibition of ATM kinase is an alternative mechanism for radiosensitization of cancer cells. In this study, we increased the cytotoxic effects of the combination of CBD and γ-irradiation in GBM cells through additional inhibition of ATM kinase with KU60019, a small molecule inhibitor of ATM kinase. We observed in GBM cells treated by CBD, γ-irradiation and KU60019 high levels of apoptosis together with strong upregulation of the percentage of G2/M-arrested cells, blockade of cell proliferation and a massive production of pro-inflammatory cytokines. Overall, these changes caused both apoptotic and non-apoptotic inflammation-linked cell death. Furthermore, via JNK-AP1 activation in concert with active NF-κB, CBD upregulated gene and protein expression of DR5/TRAIL-R2 and sensitize GBM cells to TRAIL-induced apoptosis. In contrast, CBD notably decreased in GBM surface levels of PD-L1, a critical immune checkpoint agent for T-lymphocytes. We also used in the present study TS543 human proneural glioma cells that were grown as spheroid culture. TS543 neurospheres exhibited dramatic sensitivity to CBD-mediated killing that was additionally increased in combination with γ-irradiation and KU60019. In conclusion, treatment of human GBM by the triple combination (CBD, γ-irradiation and KU60019) could significantly increase cell death levels in vitro and potentially improve the therapeutic ratio of GBM.

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Can cannabidiol inhibit angiogenesis in colon cancer?

Abstract

Colon cancer is the third most common human malignancy and a main cause of death worldwide. The current study was carried out to investigate the effects of cannabidiol, a cannabinoid, on angiogenesis and cell death in mice with experimental colon cancer induced by injection of CT26 cell line. Fifty male BALB/c mice were assigned randomly to five study groups, including: (1) negative control, (2) cancer control, (3) cancer vehicle control, (3) cancer treatment (1 mg/kg cannabidiol), and (5) cancer treatment (5 mg/kg cannabidiol). Treatment responses were evaluated based on histopathological examination, the expression of vascular endothelial growth factor (VEGF) gene, measurement of interleukins (ILs 6 and 8), oxidative stress parameters (glutathione peroxidase, glutathione reductase, superoxide dismutase serum activities, total antioxidant capacity, and malondialdehyde levels). In the present study, CBD reduced VEGF gene expression, decreased serum levels of IL6, IL8, and malondialdehyde, and increased antioxidant enzyme activity in mice with colon cancer. Moreover, cannabidiol induced apoptosis and reduced cellular pleomorphism. Cannabidiol can be potentially considered as an anti-colon cancer medicine as it exerts an inhibitory effect on angiogenesis, tumor growth, and metastasis through reducing VEGF gene expression, decreasing cytokines, and increasing antioxidant enzyme activities.

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Identifying the Cannabis Compounds that Kill Cancer

In our latest CannMed speaker interview, David Meiri provides some amazing insight into how he and his team are working to understand the specific cannabis compounds that can be used to kill cancer cells. What they have found so far is fascinating.

By testing different cannabis extracts on cancer cells with specific genetic mutations, they can identify which cannabis strains are effective in killing a certain type of cancer cell. From there, they dig deeper into the cell’s mechanisms to figure out how the cannabis compounds block, activate, or change the pathways and determine the minimum compounds needed to produce the effect.

Using this approach Dr. Meiri and his team have found a specific combination of three compounds that kills leukemia cells. Interestingly, if one of those compounds is excluded from the extract, it will not kill the cell. This finding seems to confirm the theory of an entourage effect; however, all 100+ compounds found in the cannabis plant are not needed in this case. What’s even more interesting is that the effective compounds they identified are not the major cannabinoids or terpenes we are all familiar with. In fact, one compound hasn’t even been named in the literature!

Watch the video above to learn more about Dr. Meiri’s work

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Regulation of human glioblastoma cell death by combined treatment of cannabidiol, γ-radiation and small molecule inhibitors of cell signaling pathways

Abstract

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults. The challenging problem in cancer treatment is to find a way to upregulate radiosensitivity of GBM while protecting neurons and neural stem/progenitor cells in the brain. The goal of the present study was upregulation of the cytotoxic effect of γ-irradiation in GBM by non-psychotropic and non-toxic cannabinoid, cannabidiol (CBD). We emphasized three main aspects of signaling mechanisms induced by CBD treatment (alone or in combination with γ-irradiation) in human GBM that govern cell death: 1) CBD significantly upregulated the active (phosphorylated) JNK1/2 and MAPK p38 levels with the subsequent downregulation of the active phospho-ERK1/2 and phospho-AKT1 levels. MAPK p38 was one of the main drivers of CBD-induced cell death, while death levels after combined treatment of CBD and radiation were dependent on both MAPK p38 and JNK. Both MAPK p38 and JNK regulate the endogenous TRAIL expression. 2) NF-κB p65-P(Ser536) was not the main target of CBD treatment and this transcription factor was found at high levels in CBD-treated GBM cells. Additional suppression of p65-P(Ser536) levels using specific small molecule inhibitors significantly increased CBD-induced apoptosis. 3) CBD treatment substantially upregulated TNF/TNFR1 and TRAIL/TRAIL-R2 signaling by modulation of both ligand and receptor levels followed by apoptosis. Our results demonstrate that radiation-induced death in GBM could be enhanced by CBD-mediated signaling in concert with its marginal effects for neural stem/progenitor cells and astrocytes. It will allow selecting efficient targets for sensitization of GBM and overcoming cancer therapy-induced severe adverse sequelae.

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Inhibition of cervical cancer cell proliferation by cannabidiol

Seventy phytocannabinoids are now known to be synthesized by Cannabis sativa (marijuana) [1]. The major non-psychoactive cannabinoid cannabidiol (CBD) exhibits antiproliferative effects against breast, cervix, colon, glioma, leukemia, ovary, prostate, and thyroid cancer cells [2]. In this study, we investigated the antiproliferative effect of CBD on the ME-180 cervical cancer cell line. The cells were plated at subconfluent density in DMEM-F12 medium containing 10% fetal bovine serum (FBS), and the experiments were carried out in the serum-free medium. CBD inhibited the proliferation of these cells with an IC50 value of approximately 6µM. At 10µM, CBD induced apoptosis of nearly all cells within 24 hours (figure below). However, within few hours of treatment with CBD, the cells also exhibited numerous cytoplasmic vacuoles, reminiscent of paraptosis. Significant reversal of the CBD-induced inhibition of proliferation was observed in the presence of antioxidant α-tocopherol (200µM), Trolox (200µM), peroxisome proliferator-activated receptor-γ antagonist GW9662 (2µM), and ceramidase inhibitor L-cycloserine (100µM). Limited reversal of inhibition of proliferation was also observed in the presence of 2µM of cannabinoid receptor (CB) antagonist AM251 (CB1). Nevertheless, the cytoplasmic vacuoles observed in the presence of CBD persisted in the presence of these compounds, with the exception of α-tocopherol and Trolox. The results of our study suggest that CBD exerts its antiproliferative effect via multiple mechanisms, and it could be a potential treatment for cervical cancer.

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Quantitative Analyses of Synergistic Responses between Cannabidiol and DNA-Damaging Agents on the Proliferation and Viability of Glioblastoma and Neural Progenitor Cells in Culture

Abstract

Evidence suggests that the nonpsychotropic cannabis-derived compound, cannabidiol (CBD), has antineoplastic activity in multiple types of cancers, including glioblastoma multiforme (GBM). DNA-damaging agents remain the main standard of care treatment available for patients diagnosed with GBM. Here we studied the antiproliferative and cell-killing activity of CBD alone and in combination with DNA-damaging agents (temozolomide, carmustine, or cisplatin) in several human GBM cell lines and in mouse primary GBM cells in cultures. This activity was also studied in mouse neural progenitor cells (NPCs) in culture to assess for potential central nervous system toxicity. We found that CBD induced a dose-dependent reduction of both proliferation and viability of all cells with similar potencies, suggesting no preferential activity for cancer cells. Hill plot analysis indicates an allosteric mechanism of action triggered by CBD in all cells. Cotreatment regimens combining CBD and DNA-damaging agents produced synergistic antiproliferating and cell-killing responses over a limited range of concentrations in all human GBM cell lines and mouse GBM cells as well as in mouse NPCs. Remarkably, antagonistic responses occurred at low concentrations in select human GBM cell lines and in mouse GBM cells. Our study suggests limited synergistic activity when combining CBD and DNA-damaging agents in treating GBM cells, along with little to no therapeutic window when considering NPCs.

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Cannabidiol rather than Cannabis sativa extracts inhibit cell growth and induce apoptosis in cervical cancer cells

This research was done in vitro, results in vitro do not always carry over to human trials.

Results

Results obtained indicate that both cannabidiol and Cannabis sativa extracts were able to halt cell proliferation in all cell lines at varying concentrations. They further revealed that apoptosis was induced by cannabidiol as shown by increased subG0/G1 and apoptosis through annexin V. Apoptosis was confirmed by overexpression of p53, caspase 3 and bax. Apoptosis induction was further confirmed by morphological changes, an increase in Caspase 3/7 and a decrease in the ATP levels.

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Isolated cannabidiol from Cannabis sativa plant extracts inhibit growth and induce apoptosis in cervical cancer cells

Abstract

Cervical cancer remains a global health related issue among females of Sub-Saharan Africa, with over half a million new cases reported each year. Different therapeutic regimens have been suggested in various regions of Africa, however, over a quarter of a million women die of cervical cancer, annually. Therefore, it is important to search for new drugs through effective screening of medicinal plant extracts to identify lead anti-cervical cancer drugs. The aim of this study was to evaluate for the anti-growth effects of Cannabis sativa extracts and its isolate, cannabidiol on cervical cancer cell lines HeLa, SiHa, and ME-180. To determine for the presence of important constituents and evaluate for the anti-growth effects, phytochemical screening, MTT assay, cell growth analysis, flow cytometry, morphology analysis, Western blot, caspase 3/7 assay, and ATP measurement assay were conducted were conducted. Results obtained indicate that both plant extracts induced cell death at an IC50 of 50 – 100μg/ml and the Inhibition of cell growth was cell line dependent. Flow cytometry confirmed that, with or without cell cycle arrest, the type of induced cell death was apoptosis. Cannabis sativa extracts led to the up-regulation of apoptosis proteins (p53, Bax, caspase-3, and caspase-9) and the down regulation of anti-apoptosis proteins (Bcl-2 and RBBP6), signalling the execution of apoptosis. Apoptosis induction was further confirmed by morphological changes, an increase in Caspase 3/7 and a decrease in the ATP levels. In conclusion, this data implies Cannabis sativa crude extracts has the potential to inhibit growth and induce apoptosis in cervical cancer cell lines, which may be due to the presence of cannabidiol.

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Cannabis Extract Treatment for Terminal Acute Lymphoblastic Leukemia with a Philadelphia Chromosome Mutation

Abstract

Acute lymphoblastic leukemia (ALL) is a cancer of the white blood cells and is typically well treated with combination chemotherapy, with a remission state after 5 years of 94% in children and 30-40% in adults. To establish how aggressive the disease is, further chromosome testing is required to determine whether the cancer is myeloblastic and involves neutrophils, eosinophils or basophils, or lymphoblastic involving B or T lymphocytes. This case study is on a 14-year-old patient diagnosed with a very aggressive form of ALL (positive for the Philadelphia chromosome mutation). A standard bone marrow transplant, aggressive chemotherapy and radiation therapy were revoked, with treatment being deemed a failure after 34 months. Without any other solutions provided by conventional approaches aside from palliation, the family administered cannabinoid extracts orally to the patient. Cannabinoid resin extract is used as an effective treatment for ALL with a positive Philadelphia chromosome mutation and indications of dose-dependent disease control. The clinical observation in this study revealed a rapid dose-dependent correlation.
© 2013 S. Karger AG, Basel

Presentation of the Case

A 14-year-old female, P.K., presented with symptoms of weakness, shortness of breath and bruising when she was taken to the Hospital for Sick Children, Toronto, Canada, on the 10th March 2006. She was diagnosed with acute lymphoblastic leukemia (ALL), with >300,000 blast cells present. Acute chemotherapy followed by a standard chemotherapy regimen went on for 6 months after the diagnosis. Upon further analysis, she was found to be positive for the Philadelphia chromosome mutation. A mutation in the Philadelphia chromosome is a much more aggressive form of ALL. When standard treatment options were unsuccessful, a bone marrow transplant was pursued. She successfully received the transplant in August 2006 and was able to be released from isolation 45 days later. She was observed posttransplant by following the presence of blast cells, noted 6 months after treatment. Consequently, in February 2007, aggressive chemotherapy procedures (AALL0031) were administered along with a tyrosine kinase inhibitor, imatinib mesylate (Gleevac), 500 mg orally twice a day. In November 2007, 9 months after the transplant, the presence of premature blast cells was observed and it was determined that another bone marrow transplant would not be effective. In February 2008, in an effort to sustain the patient, another tyrosine kinase inhibitor, disatinib (Sprycel), was administered at 78 mg twice a day with no additional rounds of chemotherapy. The patient experienced increased migraine-like headaches in June 2008. After conducting a CT scan of the head in July 2008, cerebellitis was noted. It was assumed by the primary oncologist that the blast cells could have infiltrated the CNS and be present in the brain, although none were noted in the blood. By October 2008, ten treatments of radiation therapy had been administered to the brain.

On the 4th February 2009, blood was noted in the patient’s stools and a blood cell count revealed the presence of blast cells. As a result, all treatment including the disatinib was suspended and the patient’s medical staff acknowledged failure in treating her cancer. It was charted by the patient’s hematologist/oncologist that the patient ‘suffers from terminal malignant disease. She has been treated to the limits of available therapy… no further active intervention will be undertaken’. She was placed in palliative home care and told to prepare for her disease to overwhelm her body and from which she would suffer a stroke within the next 2 months.

Cannabinoid Treatment

After this, disease progression was observed with rising counts of blast cells. The patient was receiving frequent blood transfusions and platelets during this period. Through research conducted by the patient’s family, it was observed, in a particular paper by Guzman [1] published in Nature Reviews Cancer, that cannabinoids have been shown to inhibit the growth of tumor cells in culture and in animal models by modulating key cell-signaling pathways. Cannabinoids are usually well tolerated and do not produce the generalized toxic effects of conventional chemotherapies. The family found promise in an organization known as Phoenix Tears, led by Rick Simpson who had treated several cancers with hemp oil, an extract from the cannabis plant. Rick worked with the family to help them prepare the extract.

From the 4th to the 20th of February, the patient’s blast cell count had risen from 51,490 to 194,000. The first dose of cannabinoid resin, also referred to as ‘hemp oil’, was administered orally (1 drop about the size of half a grain of rice) at 6:30 a.m. on the 21st February 2009 (day 0 in fig. 1). A 2-ounce Cannabis indica strain (known as ‘Chronic Strain’) was used to extract 7.5 ml of hemp oil using 1.2 liters of 99%-isopropyl-alcohol solution, which was boiled off in a rice cooker. Immediately after the dosing, the patient attempted to vomit; nausea had been observed previously and is common with this condition. To deal with the bitter taste and viscous nature of the hemp oil, it was suspended in honey, a known natural digestive aid, and then administered to the patient in daily doses. The objective was to quickly increase the frequency and amount of the dose and to hopefully build up the patient’s tolerance to cannabinoid resin (refer to fig. 1). The patient was observed to have periods of panic early on during administration of the hemp oil, along with increased appetite and fatigue.

Fig 1: Blast cell counts, days 0-15: Chronic Strain.

The blast cell count reached a peak of 374,000 on the 25th February 2009 (day 5), followed by a decrease, which correlated with the increasing dose. The daily dosing is the amount administered per dose; the doses were initially given once per day up to a total of 3 times per day by day 15, and were continued with the same average frequency throughout the treatment. A decreased use of morphine for pain, an increase in euphoria symptoms, a disoriented memory and an increase in alertness were observed; these are typical with cannabinoid use.

After day 15, the original Chronic Strain had been consumed and administration of a new strain (referred to as Hemp Oil #2) was started. This was obtained by the family from an outside source. It was noted that administering the same dose yielded a decreased response in terms of the side effects of euphoria and appetite, and the patient suffered more nausea with this hemp oil. The blast cells began to increase, demonstrated in figure 2.

Fig 2: Blast cell counts, days 18-39: Hemp Oil #2.

There is a wide amount of variance in cannabinoid concentration amongst different strains and even in the same strain with changes in growing conditions. The amount of each dose was increased to match the response of the blast cells that had been declining previously (fig. 1). After day 27, there was another peak blast cell count of 66,000 followed by a rapid decrease. There were elevated levels of urate present in the blood with corresponding joint pain; it was established that this was caused by tumor lysis syndrome of the blast cells. Allopurinol was administered.

On the 1st April 2009 (day 41), an infected central line with tunnel infection was noted on a blood test and the patient was admitted with a heavy antibiotic regimen of intravenous tazocin, gentamicin and vancomycin. On day 43, a new batch of hemp oil from an Afghan/Thai strain (referred to as Hemp Oil #3) prepared by the family was administered. A stronger psychosomatic response and increased fatigue were observed, so dosing was adjusted to 0.5 ml, shown in figure 3. Due to hospital restrictions, dosing was limited to twice a day.

Fig 3: Blast cell counts, days 44-49: Hemp Oil #3.

A new batch of hemp oil was obtained by the family from an outside source and the dosing regimen continued twice a day, shown in figure 4.

Fig 4: Blast cell counts, days 50-67: Hemp Oil #4.

After returning home from the hospital on the 11th April (day 51), the patient suffered from intense nausea, an inability to eat and overall weakness. On the 13th April, the patient was readmitted to the SickKids Hospital and was treated for refeeding syndrome. This was the outcome of stopping total parenteral nutrition too quickly and causing shock to the patient’s body while she was being treated for the infection. The dosing regimen was intermittent until day 59, remaining at 1-2 doses per day of 0.5 ml. As the blast cells began to increase and the patient’s appetite increased, the dosing frequency was again increased to 3 times per day starting on day 62, and the amount administered was increased from day 65.

On day 68, a new batch of medicine was obtained by the family from an outside source (referred to as Hemp Oil #5), shown in figure 5.

Fig 5: Blast cell counts, days 69-78: Hemp Oil #5.

Dosing was maintained 3 times a day at 1.0 ml. On day 78, the patient had stomach pain in the morning and was admitted to hospital. Upon X-ray, it was noted that gastrointestinal bleeding had occurred. The patient was under a DNR order and ultimately passed away due to the bowel perforation. A prior history of pancolitis documented by CT scan in March 2009 pointed to neutropenic colitis with perforation as the cause of death. Furthermore, prior to starting on the hemp oil treatment, the patient had been extremely ill, severely underweight and had endured numerous sessions of chemotherapy and radiation therapy in the course of 34 months.

As reported by Hematology/Oncology at SickKids:

‘At admission her total WBC was 1.4, hemoglobin was 82, platelet count 8,000. She was profoundly neutropenic… a prior history of pancolitis documented by CT scan in March 2009 was neutropenic colitis with perforation… her abdomen was distended and obviously had some signs of diffuse peritonitis. The abdomen X-ray was in favour a perforation…she passed away at 10:05 in the present (sic) of family…’.

Discussion

Figure 6 is a summary of dose response to all the batches of hemp oil administered over a total of 78 days.

Fig 6: Response to hemp oil treatment over 78 days.

The results shown here cannot be attributed to the phenomenon of ‘spontaneous remission’ because a dose response curve was achieved. Three factors, namely frequency of dosing, amount given (therapeutic dosing) and the potency of the cannabis strains, were critical in determining response and disease control. By viewing figure 6, it can be seen that introducing strains that were less potent, dosing at intervals >8 h and suboptimal therapeutic dosing consistently showed increases in the leukemic blast cell count. It could not be determined which cannabinoid profiles constituted a ‘potent’ cannabis strain because the resin was not analyzed. Research is needed to determine the profile and ratios of cannabinoids within the strains that exhibit antileukemic properties.

These results cannot be explained by any other therapies, as the child was under palliative care and was solely on cannabinoid treatment when the response was documented by the SickKids Hospital. The toxicology reports ruled out chemotherapeutic agents, and only showed her to be positive for THC (tetrahydrocannabinol) when she had ‘a recent massive decrease of WBC from 350,000 to 0.3′ inducing tumor lysis syndrome, as reported by the primary hematologist/oncologist at the SickKids Hospital.

This therapy has to be viewed as polytherapy, as many cannabinoids within the resinous extract have demonstrated targeted, antiproliferative, proapoptotic and antiangiogenic properties. This also needs to be explored further, as there is potential that cannabinoids might show selectivity when attacking cancer cells, thereby reducing the widespread cytotoxic effects of conventional chemotherapeutic agents. It must be noted that where our most advanced chemotherapeutic agents had failed to control the blast counts and had devastating side effects that ultimately resulted in the death of the patient, the cannabinoid therapy had no toxic side effects and only psychosomatic properties, with an increase in the patient’s vitality.

The nontoxic side effects associated with cannabis may be minimized by slowly titrating the dosing regimen upwards, building up the patient’s tolerance. The possibility of bypassing the psychoactive properties also exists, by administering nonpsychoactive cannabinoids such as cannabidiol that have demonstrated antiproliferative properties. Furthermore, future therapies could examine the possibility of upregulating a patient’s endogenous cannabinoids to help combat leukemic cells. It goes without saying that much more research and, even more importantly, phase clinical trials need to be implemented to determine the benefits of such therapies. Laboratory analysis is critical to figure out the constituents/profiles/ratios of the vast cannabis strains that show the most favored properties for exerting possible anticancer effects. Despite the nonstandardization of the medicines, the dose was readily titrated according to the biological response of the patient and produced a potentially life-saving response, namely, the drop in the leukemic blast cell count.

There has been an abundance of research exhibiting the cytotoxic effects of cannabinoids on leukemic cell lines in the form of in vitro and in vivo studies [1,2,3,4]. An oncology and hematology journal, Blood, has published numerous papers [2] over the years constructing the biochemical pathway to be elicited by the anticancer properties of cannabinoids. Our goal, upon examination of this significant case study which demonstrated complete disease control and a dose response curve, is to invest effort in and to focus on research and development to advance this therapy. An emphasis needs to be placed on determining the correct cannabinoid ratios for different types of cancer, the best method of administration, quality control and standardization of the cannabis strains and their growing conditions as well as therapeutic dosing ranges for various cancers contingent on staging and ages. Toxicity profiles favor therapies deriving from cannabis because toxicity within the body is greatly reduced and the devastating side effects of chemoradiation (i.e. secondary cancers or death) can be eliminated. It is unfortunate that this therapy does come with some unwanted psychosomatic properties; however, these might be eliminated by target therapies of nonpsychoactive cannabinoids such as cannabidiol which has garnered much attention as being a potent anti-inflammatory and possible antileukemic and anticancer agent. It is acknowledged that significant research needs to be conducted to reproduce these results and that in vitro studies cannot always be reproduced in clinical trials and the human physiological microenvironment. However, the numerous research studies and this particular clinical case are powerful enough to warrant implementing clinical trials to determine dose ranges, cannabinoid profiles and ratios, the methods of administration that produce the most efficacious therapeutic responses and the reproducibility of the results. It is tempting to speculate that, with integration of this care in a setting of full medical and laboratory support, a better outcome may indeed be achieved in the future.

References

  1. Guzman M: Cannabinoids: potential anti-cancer agent. Nat Rev Cancer 2003;3:745-755.
  2. Powles T, Poele RT, Shamash J, Chaplin T, Propper D, Joel S, Oliver T, Liu WM: Cannabis-induced cytotoxicity in leukemic cell lines: the role of the cannabinoid receptors and the MAPK pathway. Blood 2005;105:1214-1221.
  3. McKallip RJ, Jia W, Schlomer J, Warren JW, Nagarkatti PS, Nagarkatti M: Cannabidiol-induced apoptosis in human leukemia cells: a novel role of cannabidiol in the regulation of p22phox and Nox4 expression. Mol Pharmacol 2006;70:897-908.
  4. Murison G, Chubb C, Maeda S, Gemmell MA, Huberman E: Cannabinoids induce incomplete maturation of cultured human leukemia cells. Proc Natl Acad Sci 1987;84:5414-5418.

Author Contacts

Yadvinder Singh
44 Don Minaker Drive
Brampton, ON, L6P1R3 (Canada)
E-Mail [email protected]

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Id-1 is a Key Transcriptional Regulator of Glioblastoma Aggressiveness and a Novel Therapeutic Target

Abstract

Glioblastoma (GBM) is the most common form of primary adult brain tumors. A majority of GBMs grow invasively into distant brain tissue, leading to tumor recurrence, which is ultimately incurable. It is, therefore, essential to discover master regulators that control GBM invasiveness and target them therapeutically. We demonstrate here that the transcriptional regulator Id-1 plays a critical role in modulating the invasiveness of GBM cell lines and primary GBM cells. Id-1 expression levels positively correlate with glioma cell invasiveness in culture and with histopathological grades in patient biopsies. Id-1 knockdown dramatically reduces GBM cell invasion that is accompanied by profound morphological changes and robust reduction in expression levels of “mesenchymal” markers, as well as inhibition of self-renewal potential and down-regulation of glioma stem cell markers. Importantly, genetic knockdown of Id-1 leads to a significant increase in survival in an orthotopic model of human GBM. Furthermore, we show that a non-toxic compound, cannabidiol, significantly down-regulates Id-1 gene expression and associated glioma cell invasiveness and self-renewal. Additionally, cannabidiol significantly inhibits the invasion of GBM cells through an organotypic brain slice and glioma progression in vivo. Our results suggest that Id-1 regulates multiple tumor-promoting pathways in GBM, and that drugs targeting Id-1 represent a novel and promising strategy for improving the therapy and outcome of GBM patients.

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