delta9-tetrahydrocannabinol (THC), a mixed CB1 and CB2 receptor agonist, is the primary active constituent of Cannabis sativa and is currently being used in a clinical trial for the treatment of aggressive recurrent glioblastoma multiforme (GBM). Cannabinoids are also being used in clinical trials for purposes unrelated to their direct anticancer activity. The compounds have been reported to be well tolerated during chronic oral and systemic administration. In addition to delta9-THC, cannabidiol (CBD), cannabinol (CBN) and cannabigerol (CBG) are also present in reasonable quantities in Cannabis. CBN has low affinity for CB1 and CB2 receptors, whereas the non-psychotropic cannabinoids, CBD and CBG, have negligible affinity for the cloned receptors. We have determined that these additional cannabinoids are also effective and inhibiting aggressive cancers. Importantly, we have discovered in vitro that a synergistic increase in the antiproliferative and apoptotic activity of cannabinoids can be produced by combining specific ratios of CB1 and CB2 receptors agonists with non-psychotropic cannabinoids.
We are currently determining the molecular mechanism that may explain the synergistic increase in anticancer activity that is observed with the combination treatments. We are also studying whether this combination strategy will lead to greater antitumor activity in vivo.
In addition to the combination therapy project, we are working in collaboration with Dr. Pierre Desprez to develop novel inhibitors of Id-1 using cannabinoid compounds. Id-1 is a helix-loop-helix protein that acts as an inhibitor of basic helix-loop-helix transcription factors that control cell differentiation, development and carcinogenesis. Past research of Id-1 expression in normal and cancerous breast cells, as well as in mouse mammary glands and in human breast cancer biopsies, demonstrated that increased Id-1 expression was associated with a proliferative and invasive phenotype. Specifically, it was found that Id-1 was constitutively expressed at a high level in aggressive breast cancer cells and human biopsies, and that aggressiveness was reverted in vitro and in vivo when Id-1 expression was targeted using antisense technology. Importantly, we have recently discovered that CBD, a nontoxic cannabinoid that lacks psychoactivity, can inhibit Id-1 gene expression in metastatic breast cancer cells and consequently their aggressive phenotype. The down-regulation of expression was the result of the inhibition of the endogenous Id-1 promoter and corresponding mRNA and protein levels. CBD and compounds based off of its structure can therefore potentially be used as therapeutic agents. CBD also inhibits breast cancer metastasis in vivo.
H/T High on Health: CBD in the Food Supply