In most types of solid tumors, the metastasis of invasive tumor cells from their origin to different organs throughout the body is often lethal to patients. Recent research has uncovered the crucial role of cancer stem cells (CSC) in tumor metastasis and drug resistance. CSCs account for a tiny subpopulation of tumor cells – only 0.1-1% – but have self-protecting, apoptosis (cell death) evading, long living properties as well as the deadly capability to give rise to multiple lineages of tumorous cells. Meanwhile, conventional cancer therapies like chemotherapy and radiotherapy often only inhibit tumor growth temporarily while lacking efficacy in eradicating CSCs. Hence, CSCs are a critical target in oncology.
Because the anti-neoplastic activity of cannabinoids has been documented in breast cancer cells robustly, scientists at the University of Tehran, Tehran, Iran recently investigated this effect against breast cancer stem cells. They evaluated 2 synthetic cannabinoids, one that activates the CB1 receptor and one that blocks this receptor. CB1 receptor is a major biological target bound to and activated by many cannabinoids, including THC and CBD from cannabis. These compounds were tested on a breast cancer cell line known to be aggressive and a population of breast cancer stem cells.
The researchers found that although neither compounds reduce cancer cell proliferation, the activator of CB1 significantly inhibits the invasiveness of both cancer cells and cancer stem cells. In contrast, the blocker of CB1 significantly accelerates their ability to migrate and invade. This finding is encouraging, as it indicates that cannabinoids may interfere with not only aggressive cancer cells, but also invasive breast cancer stem cells and therefore can aid cancer eradication.