The cannabinoid δ9-tetrahydrocannabinol inhibits RAS-MAPK and PI3K-AKT survival signalling and induces BAD-mediated apoptosis in colorectal cancer cells
Deregulation of cell survival pathways and resistance to apoptosis are widely accepted to be fundamental aspects of tumorigenesis.
As in many tumours, the aberrant growth and survival of colorectal tumour cells is dependent upon a small number of highly activated signalling pathways, the inhibition of which elicits potent growth inhibitory or apoptotic responses in tumour cells.
Accordingly, there is considerable interest in therapeutics that can modulate survival signalling pathways and target cancer cells for death.
There is emerging evidence that cannabinoids, especially Δ9-tetrahydrocannabinol (THC), may represent novel anticancer agents, due to their ability to regulate signalling pathways critical for cell growth and survival.
Here, we report that CB1 and CB2 cannabinoid receptors are expressed in human colorectal adenoma and carcinoma cells, and show for the first time that THC induces apoptosis in colorectal cancer cells. ...
These data suggest an important role for CB1 receptors and BAD in the regulation of apoptosis in colorectal cancer cells.
The use of THC, or selective targeting of the CB1 receptor, may represent a novel strategy for colorectal cancer therapy.
Cannabinoid Receptor Activation Induces Apoptosis through Tumor Necrosis Factor α–Mediated Ceramide De novo Synthesis in Colon Cancer Cells
Cannabinoids have been recently proposed as a new family of potential antitumor agents.
The present study was undertaken to investigate the expression of the two cannabinoid receptors, CB1 and CB2, in colorectal cancer and to provide new insight into the molecular pathways underlying the apoptotic activity induced by their activation.
Cannabinoid receptor expression was investigated in both human cancer specimens and in the ... colon cancer cell lines.
The effects of the CB1 agonist ... on tumor cell apoptosis and ceramide and tumor necrosis factor (TNF)-α production were evaluated.
We show that the CB1 receptor was mainly expressed in human normal colonic epithelium whereas tumor tissue was strongly positive for the CB2 receptor.
The activation of the CB1 and, more efficiently, of the CB2 receptors induced apoptosis and increased ceramide levels in the ... cells.
The CB2 agonist ... also reduced the growth of ... cells in a mouse model of colon cancer.
Cannabinoids in intestinal inflammation and cancer
Emerging evidence suggests that cannabinoids may exert beneficial effects in intestinal inflammation and cancer. Adaptive changes of the endocannabinoid system have been observed in intestinal biopsies from patients with inflammatory bowel disease and colon cancer.
Studies on epithelial cells have shown that cannabinoids exert antiproliferative, antimetastatic and apoptotic effects as well as reducing cytokine release and promoting wound healing.
In vivo, cannabinoids – via direct or indirect activation of CB1 and/or CB2 receptors – exert protective effects in well-established models of intestinal inflammation and colon cancer.
Pharmacological elevation of endocannabinoid levels may be a promising strategy to counteract intestinal inflammation and colon cancer.
Chemopreventive effect of the non-psychotropic phytocannabinoid cannabidiol on experimental colon cancer
Colon cancer affects millions of individuals in Western countries.
Cannabidiol, a safe and non-psychotropic ingredient of Cannabis sativa, exerts pharmacological actions (antioxidant and intestinal antinflammatory) and mechanisms (inhibition of endocannabinoid enzymatic degradation) potentially beneficial for colon carcinogenesis.
Thus, we investigated its possible chemopreventive effect in the model of colon cancer ...
Cannabidiol-reduced ACF, polyps and tumours ...
In colorectal carcinoma cell lines, cannabidiol protected DNA from oxidative damage, increased endocannabinoid levels and reduced cell proliferation ...
It is concluded that cannabidiol exerts chemopreventive effect in vivo and reduces cell proliferation through multiple mechanisms.
Phytomedicine: International Journal of Phytotherapy and Phytopharmacology
December 27, 2013
Inhibition of colon carcinogenesis by a standardized Cannabis sativa extract with high content of cannabidiol
Colon cancer is a major public health problem.
Cannabis-based medicines are useful adjunctive treatments in cancer patients.
Here, we have investigated the effect of a standardized Cannabis sativa extract with high content of cannabidiol (CBD), here named CBD BDS, i.e. CBD botanical drug substance, on colorectal cancer cell proliferation and in experimental models of colon cancer in vivo.
Proliferation was evaluated in colorectal carcinoma ... as well as in healthy colonic cells ...
CBD BDS binding was evaluated by its ability to displace [3H]CP55940 from human cannabinoid CB1 and CB2 receptors.
In vivo, the effect of CBD BDS was examined on the preneoplastic lesions (aberrant crypt foci), polyps and tumours induced by the carcinogenic agent azoxymethane (AOM) as well as in a xenograft model of colon cancer in mice.
CBD BDS and CBD reduced cell proliferation in tumoral, but not in healthy, cells.
The effect of CBD BDS was counteracted by selective CB1 and CB2 receptor antagonists.
Pure CBD reduced cell proliferation in a CB1-sensitive antagonist manner only.
In binding assays, CBD BDS showed greater affinity than pure CBD for both CB1 and CB2 receptors, with pure CBD having very little affinity.
In vivo, CBD BDS reduced AOM-induced preneoplastic lesions and polyps as well as tumour growth in the xenograft model of colon cancer.
CBD BDS [Cannabidiol Botanical Drug Substance] attenuates colon carcinogenesis and inhibits colorectal cancer cell proliferation via CB1 and CB2 receptor activation.
The results may have some clinical relevance for the use of Cannabis-based medicines in cancer patients.
In Vitro Cellular and Developmental Biology - Animal
Physiological intestinal oxygen modulates the Caco-2 cell model and increases sensitivity to the phytocannabinoid cannabidiol
The Caco-2 cell model is widely used as a model of colon cancer and small intestinal epithelium but, like most cell models, is cultured in atmospheric oxygen conditions (∼21%).
This does not reflect the physiological oxygen range found in the colon.
In this study, we investigated the effect of adapting the Caco-2 cell line to routine culturing in a physiological oxygen (5%) environment.
Under these conditions, cells maintain a number of key characteristics of the Caco-2 model, such as increased formation of tight junctions and alkaline phosphatase expression over the differentiation period and maintenance of barrier function.
However, these cells exhibit differential oxidative metabolism, proliferate less and become larger during differentiation.
In addition, these cells were more sensitive to cannabidiol-induced antiproliferative actions through changes in cellular energetics: from a drop of oxygen consumption rate and loss of mitochondrial membrane integrity in cells treated under atmospheric conditions to an increase in reactive oxygen species in intact mitochondria in cells treated under low-oxygen conditions.
Inclusion of an additional physiological parameter, sodium butyrate, into the medium revealed a cannabidiol-induced proliferative response at low doses.
These effects could impact on its development as an anticancer therapeutic, but overall, the data supports the principle that culturing cells in microenvironments that more closely mimic the in vivo conditions is important for drug screening and mechanism of action studies.
Turned-Off Cannabinoid Receptor Turns on Colorectal Tumor Growth
Researchers find CB1 suppresses tumors, a new potential path for treatment, prevention
M. D. Anderson News Release 08/01/08
New preclinical research shows that cannabinoid cell surface receptor CB1 plays a tumor-suppressing role in human colorectal cancer, scientists report in the Aug. 1 edition of the journal Cancer Research.
CB1 is well-established for relieving pain and nausea, elevating mood and stimulating appetite by serving as a docking station for the cannabinoid group of signaling molecules. It now may serve as a new path for cancer prevention or treatment.
"We've found that CB1 expression is lost in most colorectal cancers, and when that happens a cancer-promoting protein is free to inhibit cell death," said senior author Raymond DuBois, M.D., Ph.D., provost and executive vice president of The University of Texas M. D. Anderson Cancer Center.
DuBois and collaborators from Vanderbilt-Ingram Cancer Center also show that CB1 expression can be restored with an existing drug, decitabine. They found that mice prone to developing intestinal tumors that also have functioning CB1 receptors develop fewer and smaller tumors when treated with a drug that mimics a cannabinoid receptor ligand. Ligands are molecules that function by binding to specific receptors. Agonists are synthetic molecules that mimic the action of a natural molecule.
"Potential application of cannabinoids as anti-tumor drugs is an exciting prospect, because cannabinoid agonists are being evaluated now to treat the side-effects of chemotherapy and radiation therapy," DuBois said. "Turning CB1 back on and then treating with a cannabinoid agonist could provide a new approach to colorectal cancer treatment or prevention."
Cannabinoids are a group of ligands that serve a variety of cell-signaling roles. Some are produced by the body internally (endocannabinoids). External cannabinoids include manmade versions and those present in plants, most famously the active ingredient in marijuana (THC).
Receptor shutdown by methylation
Endocannabinoid signaling is important to the normal functioning of the digestive system and has been shown to protect the colon against inflammation. Since chronic inflammation is a known risk factor for colorectal cancer, the researchers decided to look into the role of cannabinoid receptors in a mouse model of colon cancer.
"People have looked at cannabinoids in cancer earlier, mainly in cell culture experiments," DuBois said. "The molecular mechanisms for loss of the receptor and its effect on cancer have not been previously shown."
First, the team found that CB1 was largely absent in 18 of 19 human tumor specimens and in 9 of 10 colorectal cancer cell lines. Further experimentation showed that the gene that encodes the CB1 protein was not damaged, but shut down chemically by the attachment of methyl groups - a carbon atom surrounded by three hydrogen atoms - to the gene encoding CB1.
Treating cell lines with decitabine, a demethylating agent approved for some types of leukemia, removed the methyl groups, restoring gene expression in 7 of 8 cell lines and full expression of CB1 protein in three lines.
Next, the group found that deletion of the CB1 gene in a strain of mice that spontaneously develops precancerous polyps resulted in a 2.5-to-3.8-fold increase in the number of polyps and a 10-fold increase in the number of large growths, those most likely to develop into cancer.
Treating mice that had the CB1 receptor with an endocannabinoid agonist resulted in a decline in polyps ranging from 16.7 percent to 50 percent. The reduction was greater for larger polyps.
CB1 thwarts survivin, a protein that protects cancer
Cannabinoids previously had been shown to kill cancer cells in lab experiments by inducing apoptosis - programmed cell death. The team confirmed the role of CB1 in apoptosis, showing that tumor cells with high CB1 expression were sensitive to apoptosis when treated by a cannabinoid agonist. Cell lines with silenced CB1 resisted cell death.
A series of experiments showed that CB1 increases cancer cell death by stifling a protein called survivin. Survivin is overexpressed in nearly every human tumor but is barely detectable in normal tissue, DuBois noted. Overexpression of survivin is associated with poor outcome and reduced apoptosis in colorectal cancer patients. The researchers pinpointed a cell signaling pathway by which activated CB1 cuts down survivin.
"Just increasing the levels of cannabinoids to treat colorectal cancer won't work if the CB1 receptor is not present," DuBois said. This suggests that treating first with a demethylating agent, such as decitabine, to reactivate CB1 in the tumor and following up with a cannabinoid might be an effective attack on colorectal cancer.
Scarcity of CB1 also is associated with Huntington's disease, Alzheimer's disease and multiple sclerosis. Further investigation, the researchers note, is needed to define its role in those diseases and other types of cancer. The team also analyzed the other main cannabinoid receptor, CB2, and found no role for it in colorectal cancer.
They also treated the mice with a CB1 antagonist, a compound that binds to the receptor but does not activate it. Mice with CB1 blocked in this manner also showed an increase in the number and size of polyps. A CB1 antagonist called rimonabant is currently marketed overseas for weight loss. The researchers note that a patient's risk for colorectal cancer should be assessed when use of such drugs is being considered.
The study was funded by grants from the National Cancer Institute and the National Colorectal Cancer Research Alliance.
Co-authors with DuBois are first author Dingzhi Wang, Ph.D., Haibin Wang, Ph.D., Wei Ning, Michael Backlund, Ph.D., and Dushansu K. Dey, Ph.D., all of the Vanderbilt-Ingram Cancer Center. 08/01/08