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Pre-Clinical Study Shows Marijuana Compound Inhibits Tumor Size, Growth and Metastasis of Human Cancer

Last week there was some pretty hot pre-clinical science news pre-published on-line in the journal, Breast Cancer Research and Treatment. Cannabidiol (CBD; note the benzene ring contained within the molecular structure), is one biochemical constituent in the cannabis ("marijuana") plant of which "only THC [?9-tetrahydrocannabinol] is psychoactive." "At least 66 other cannabinoids are also present in cannabis, including cannabidiol (CBD), cannabinol (CBN) and tetrahydrocannabivarin (THCV) among many others, which are believed to result in different effects from those of THC alone.[7]" ("Marijuana," accessed Sept. 28, 2010).

In the pre-clinical study conducted under lead researcher, Sean McAllister, PhD at The California Pacific Medical Center Research Institute, cannabidiol (CBD) was delivered directly to cells and found to inhibit tumor mass size, proliferation and invasion of human cancer cells. Also, it was demonstrated that treatment with CBD significantly reduces primary tumor mass as well as the size and number. For more than ten years, McAllister and his scientific team have been investigating the genes responsible for the spread of cancer. Cannibadiol was found in 2007 to inhibit the gene that controls the spread of cancer:

According to cancer researcher Yvez Desprez, Ph.D., "The problem is not the cancer itself, the problem is the spread of the cancer. When this type of gene [Id-1] is expressed, the cells basically go crazy and they’re very aggressive and they metastasize everywhere in the body." Dr. McAllister says, "We could expect that if we create really effective inhibitors against it, we could potentially treat many types of aggressive cancers." (from "Marijuana compound could help fight breast cancer," Nov. 19, 2007, ABC’s KGO-TV San Francisco).

One of the most exciting aspects of this announcement is that CBD may provide one of the only low- or non-toxic therapeutic alternatives to conventional chemotherapy and its associated adverse effects:

Invasion and metastasis of aggressive breast cancer cells are the final and fatal steps during cancer progression. Clinically, there are still limited therapeutic interventions for aggressive and metastatic breast cancers available. Therefore, effective, targeted, and non-toxic therapies are urgently required. Id-1 [..] has recently been shown to be a key regulator of the metastatic potential of breast and additional cancers. We previously reported that cannabidiol (CBD), a cannabinoid with a low toxicity profile, down-regulated Id-1 gene expression in aggressive human breast cancer cells in culture. [.. W]e determined pathways leading to the down-regulation of Id-1 expression by CBD and consequently to the inhibition of the proliferative and invasive phenotype of human breast cancer cells. [.. T]wo different syngeneic models of tumor metastasis to the lungs were chosen to determine whether treatment with CBD would reduce metastasis in vivo. We show that CBD inhibits human breast cancer cell proliferation and invasion [..]. Moreover, [..] we then show that treatment with CBD significantly reduces primary tumor mass as well as the size and number of lung metastatic foci in two models of metastasis. Our data demonstrate the efficacy of CBD in pre-clinical models of breast cancer. The results have the potential to lead to the development of novel non-toxic compounds for the treatment of breast cancer metastasis, and the information gained from these experiments broaden our knowledge of both Id-1 and cannabinoid biology as it pertains to cancer progression. (from "Pathways mediating the effects of cannabidiol on the reduction of breast cancer cell proliferation, invasion, and metastasis," Sept. 22, 2010)

Although this is the very careful, conditional language of the bench scientist, this is a pretty big deal– even for research considered at an early stage.

Cancer Research UK investigator, Dr. Joanna Owens, says:

[.. t]he findings will need to be followed up with clinical trials in humans to see if the CBD is safe, and whether the beneficial effects can be replicated. Several cancer drugs based on plant chemicals are already used widely, such as vincristine – which is derived from a type of flower called Madagascar Periwinkle and is used to treat breast and lung cancer. It will be interesting to see whether CBD will join them. (from "Cannabis compound ‘halts cancer’" Nov. 19, 2007, BBC News)

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