Tumor metastasis is the final, fatal stage of cancer, but studies show THC and CBD can shut this down.
Metastasis is the process by which cancer cells escape the main part of the tumor and invade neighboring tissues and organs and/or travel to other parts of the body. Certain types of cancers are more aggressive than others, and are therefore more likely to metastasize. These cancers are very difficult to treat and are fatal to patients. In order for cancer cells to migrate and invade other tissues, they must first escape the main tumor and move into the extracellular matrix (ECM) surrounding the tumor. They can then continue to grow into neighboring tissues, or they can enter the blood stream or the lymphatic system to spread to other parts of the body.
Cell to cell adhesion, ECM degradation, and chemotaxis (or other types of cell movement) are all essential processes for cancer cells to successfully metastasize. Angiogenesis is another important process for sustaining the growth of a new or existing tumor. Studies have found that these metastatic processes can be inhibited by phytocannabinoids isolated from the cannabis plant (THC and CBD) as well as endocannabinoids produced by our bodies and synthetic cannabinoids.
In multiple studies, cannabinoids were found to block angiogenesis by reducing expression of the ligand and its associated receptors in the vascular endothelial growth factor (VEGF) pathway. With the VEGF system down, tumors will be unable to grow new blood vessels to help feed its out-of-control growth. New tumors resulting from metastasis to peripheral tissues, like the lungs, also require angiogenesis to sustain their development and growth.
CBD has been found to inhibit the production of metalloproteinases (MMPs). These proteins play a role in angiogenesis by breaking down components of the ECM to allow new blood vessels to form. They also aid in the migration of cancer cells away from the main tumor. In order for a cancer cell to escape the tumor, it must use MMPs to break down the ECM that surrounds the tumor. This has been shown to be particularly critical for treating glioma tumors, which grow and spread so quickly that they are nearly impossible to remove surgically. CBD was able to reduce the aggressiveness of gliomas by inhibiting their invasion capability in part by inhibiting MMPs.
In addition to MMPs, cell invasiveness is also governed by cell-cell adhesion. Certain kinds of adhesive proteins, like focal adhesion kinases (FAKs), promote metastasis when they are increased in number. These proteins allow the cell to migrate away from the tumor more easily. Cannabinoids have been found to inhibit FAKs in cancer cells, reducing their ability to migrate.
In breast cancer, CBD turned off the Id-1 gene, a pro-metastatic gene that is an aggressiveness marker in breast cancer. As a result, breast cancer cells treated with CBD were less invasive. Inhibiting Id-1 has a chain-reaction effect, in which other genes that promote metastasis are also down-regulated, resulting in an overall reduction in cancer aggressiveness.
Tumor metastasis is the final stage of cancer advancement, and the one that is most often fatal to cancer patients. Laboratory studies have found that cannabinoids like THC and CBD are effective at shutting down the essential processes that allow cancer cells to metastasize. On their own, or in concert with traditional cancer therapies, cannabinoids could be a new frontier in cancer treatment.