Cannabis And Cancer

Cannabinoids are a very exciting prospect in oncology. We have shown for the first time that the order in which cannabinoids and chemotherapy are used is crucial in determining the overall effectiveness of this treatment.
Dr. Wai Liu
University of London

Phytocannabinoids are the most notable type of cannabinoid, and they occur naturally in the cannabis plant. Thousands of pre-clinical studies done in laboratories and on animals have shown that cannabinoids may stop cancer cells from dividing and invading normal tissue, and they may block the blood supply to tumors. Some of studies also indicate that cannabinoids may enhance the body's immune response against the growth and spread of tumors.

Palliative effect of cannabinoids on many cancer associated symptoms is probably a fact most established by the scientific community.

One such study, published recently in the International Journal of Oncology looked at the potential use of cannabinoids in conjunction with existing chemotherapy drugs. The researchers found that cannabidiols and THC, when used alone, killed leukemia cells. However, when used in conjunction, their potency was significantly improved; the whole was more than the sum of the parts.

Their research data also showed that an initial dose of chemotherapy followed by cannabinoids improved overall outcomes against the leukemia cells. Combining chemotherapy with cannabinoids provided better results than giving chemotherapy alone, or just the combination of cannabidiols and THC. However, this increased potency was only seen if the cannabinoids were given after the chemotherapy, and not the other way around.

"Accumulating data from preclinical models suggest that cannabinoids elicit anti-cancer effects on several levels of cancer progression. Clinical studies are now urgently needed to investigate the impact of cannabinoids on cancer growth and progression in patients."
Prof. Burkhard Hinz
Rostock University Medical Center, Germany

These research studies have paved the path for new clinical trials to explore strategies to develop cannabinoid-based combinational therapies by combining the administration of cannabinoids with other anticancer agents to act synergistically to inhibit tumor growth.

Data from ClinicalTrials.gov indicates exactly that. Even though less than 25 cannabis related human clinical trials have taken place on cancer in the last decade, a bulk of those clinical trials have been focused on pain relief in patients with advanced malignancy or preventing nausea and vomiting in patients receiving chemotherapy.

Antitumor effects are probably the second most important action of cannabinoids on cancer patients. A large body of scientific evidence strongly supports that THC and other cannabinoid agonists exert anticancer actions in preclinical models of cancer (in immunocompetent mice) through a well-established mechanism of action which primarily relies on the ability of the cannabinoids (THC/CBD) to bind and activate the cannabinoid receptors and stimulate autophagy-mediated apoptotic cancer cell death through a cell signaling mechanism.

Here are examples of few studies that showed how the endocannabinoid system plays a tumor suppressor role in different cancer types and cannabinoids (endogenous, phytocannabinoids or synthetic) act as efficient anti tumoral agents in a wide range of cancer cells.

This study explored the anti‐cancer effects with a synthetic cannabinoid in treating prostate cancer. In vivo (laboratory settings), administration of the synthetic cannabinoid significantly reduced prostate cancer cell proliferation, migration, and invasion, induced apoptosis, and arrested cell growth in a dose‐dependent manner.

Malignant melanoma is a complex malignancy with significant morbidity and mortality. The incidence continues to rise, and despite advances in treatment, the prognosis is poor. A unique study was developed focusing on the effects of treatment with a cannabinoid (CBD) derivative on malignant melanoma tumors in an in vivo (animal) setting. A significant decrease in tumor size was detected in mice treated with CBD when compared with the control group resulting in increased survival and less tumorgenicity (ability of cells to give rise to either benign or malignant progressively growing tumor).

Breast cancer represents approximately 30% of newly diagnosed cancers each year. In approximately one third of them, receptors (See Science section to learn about receptors) called ErbB2 are found in abundance. These receptors, binding themselves to certain ligands, activate cell signaling that promote proliferation and survival of the tumor. Even though advances in the treatment of these tumors have led to antibodies (Trastuzumab) that neutralizes ErbB2 receptors, around 75% of patients with ErbB2-overexpressing tumors do not respond to the antibodies. This particular study discovered that Human ErbB2-positive breast tumors expresses CB2 receptors and that THC (Δ9-tetrahydrocannabinol) and a synthetic CBD (JWH-133) significantly reduce tumor progression in a clinically relevant model of ErbB2-positive metastatic breast cancer. More interestingly, cannabinoids not only impaired tumor growth, but also blocked further tumor generation.

Several such studies on the anti tumoral nature of cannabis on cancer can be found in our Related Research Section.

However, Daner’s Hope believes that further studies and human clinical trial are imperative to analyze the efficacy of the combinational therapy of cannabinoids and other anticancer agents in treating various types and stages of cancer. Likewise, further research is required to identify the precise molecular cross-talk mechanisms that become activated upon exposure of cancer cells to cannabinoids in combination with different chemotherapeutic agents.