Metastasis is the final and lethal stage of cancer, but studies have shown that it can be stopped by THC and CBD.
Metastasis is the process by which cancer cells move from the main part of the tumor and invade nearby tissues and organs and/or move to other parts of the body. Some types of cancers are more aggressive than others, and are therefore more likely to metastasize. These cancers are very difficult to treat and are often fatal to patients. For cancer cells to migrate and invade other tissues, they must first leave the main tumor and move into the extracellular matrix (ECM) surrounding the tumor. They can then continue to grow in surrounding tissues, or they can enter the bloodstream or lymphatic system and spread to other parts of the body.
Cellular junction, ECM degradation, and chemotaxis (or other types of cellular movement) are essential processes for tumor cells to successfully metastasize. Angiogenesis is another important process in order to sustain 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 several studies, cannabinoids have been observed to stop angiogenesis by reducing the expression of the ligand and its associated receptors in the vascular endothelial growth factor (VEGF) pathway. With the VEGF system out of commission, tumors will not be able to grow new blood vessels to help feed its uncontrolled growth. New tumors arising from metastasis to peripheral tissues, such as the lungs, also require angiogenesis to support their development and growth.
CBD has been found to inhibit the production of metalloproteinases (MMPs). These proteins play a key role in angiogenesis by breaking down components of the ECM, allowing new blood vessels to form. They also aid in the migration of tumor cells away from the primary tumor. For a tumor cell to escape from the tumor, it must use MMPs to break down the ECM surrounding the tumor. This has been shown to be particularly critical for treating gliomas, which grow and spread so quickly that they are nearly impossible to remove surgically. CBD has been able to reduce the aggressiveness of gliomas by inhibiting their ability to invade, in part by inhibiting MMPs.
In addition to MMPs, cell invasiveness is also governed by cell junctions. Certain types of adhesion molecules, such as focal adhesion kinase (FAK), promote metastasis when they increase in number. These proteins allow the cell to migrate away from the tumor more easily. Cannabinoids have been found to inhibit FAK in tumor cells , reducing their ability to migrate.
In breast cancer , CBD turned off the Id-1 gene, a metastatic gene that is a marker of aggressiveness in breast cancer. As a result, CBD-treated breast cancer cells were less invasive. Inhibiting Id-1 produces a knock-on effect, whereby other genes that promote metastasis also decrease activity, causing an overall reduction in cancer aggressiveness.
Metastasis of tumors is the final stage of disease progression, and usually the most fatal for cancer patients. Some laboratory studies have found that cannabinoids such as THC and CBD are effective in blocking the essential processes that allow tumor cells to metastasize. Alone, or in combination with traditional therapies, cannabinoids could constitute a new frontier in cancer treatment.