Proof That Cannabis Needs To Be Part of Treatment For Breast Cancer
These studies tell us that cannabinoids are effective in reducing tumor growth, size, and stopping metastasis in breast cancer cells.
Breast cancer is the most common, and is now the second leading cause of cancer death in American women (lung cancer is number one). Metastasis is the big killer, responsible for approximately 90% of breast cancer-related deaths. This disease requires treatment using additional alternative therapies that have increased efficacy and low toxicity.
Studies suggest that regulation issues within the endocannabinoid system may trigger cancer by fostering the body conditions that allow mutated cells to proliferate and migrate. Cannabinoid receptors CB1 (central) and CB2 (peripheral) have been shown to be over-expressed in tumor cells (compared with normal cells) for various types of cancers, especially breast and liver cancers.
Synthetic Cannabinoids and Breast Cancer Cells
Given that breast cancer tumors have more CB2 receptors than healthy tissue does, a team of researchers set out to find out if cannabinioids could be used to stop the tumor growth. The study used a synthetic CB2 agonist (a chemical that binds to the receptor and activates it). THC, found in the cannabis plant, is natural agonist of the CB2 (and CB1) receptors.
Mice treated with the synthetic CB2 agonist saw 40-50% reduction in tumor growth and 65-80% reduction in metastasis. Additionally, when scientists treated the cancerous mice with a CB2 antagonist (a chemical that prevents receptor activation), these benefits reversed. This tells us that endocannabinoid receptors modulate tumor growth and metastasis.
Patients (91%) with the HER-2 mutation (ErbB2-positive tumors) over express CB2 receptors. HER-2 is a very aggressive form of breast cancer, compared to other forms. Fortunately, both THC (phytocannabinoid) and the synthetic CB2 agonist reduced tumor growth, tumor number, and the amount/severity of metastases in animal models of HER-2.
Cannabinoids also have a modulatory effect on triple negative breast cancer cells (cancer cells that lack HER-2/ErbB2, estrogen and/or progesterone receptors).
Interestingly, COX-2 is an inflammatory enzyme that expresses in 40% of human cases for invasive breast cancer. This enzyme promotes metastasis. Studies have shown that a cannabinoid called cannabidiolic acid (CBDa) is a selective COX-2 inhibitor. This means that CBDa inhibits COX-2 by down-regulating and also through the suppression of genes that are positively involved in the metastasis of cancer cells.
Cannabinoids exert their anti-cancer effects by binding to CB1 and CB2 receptors. Since these anti-tumorigenic effects are dependent on the cell line or tumor type, the endocannabinoid system provides a targeted treatment of cancer by demonstrating selective action on tumor cells while not affecting normal cells.
Stathmin and Tau Protein Regulation
Microtubule Associated Proteins (MAPs) stathmin and tau are the key proteins in cancer metastasis. Both interact with microtubules (responsible for forming cytoplasm, the living matter of all cells) to regulate their function.
People use stathmin, a phosphoprotein, to measure and predict the aggressiveness of many cancers. These include endometrial and breast cancers. High stathmin levels in a primary tumor is an identifier of high risk for recurrent disease in patients. Unfortunately, it also predicts a poor overall survival rate; and it predicts a less robust response to chemotherapy. When doctors measured stathmin and tau expression levels in breast cancer cells, the analysis showed that the ratio of a high tau to stathmin ratio is prognostic for improved survival in breast cancer patients.
A Cannabis sativa extract effectively reduced tau and stathmin gene expression in cancer cells. It also significantly decreased the migration of cancer cell lines. Growing evidence indicates that tau can provide a selective advantage during metastasis in cancer patients. Since this protein contributes to the metastatic efficiency of breast tumor cells, anti-tau drugs may potentially inhibit tumor metastasis.
This indicates that cannabis-based medicines are effective supplemental treatment in cancer patients.