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14 cannabis patient care | vol. 2 no. 3 cannapatientcare.com research focus Promotes Breast Cancer Growth Despite a wealth of studies supporting the breast cancer-fight- ing effects of cannabis, there are two studies that have shown that cannabis may actually promote tumor growth in breast cancer cells. Noteworthy is the fact that in both of those cas- es, the researchers indicated that the breast cancer cells that were examined expressed "low to undetectable levels of can- nabinoid receptors" (20,29). The lack of cannabinoid receptors could thus be used as a marker for cases in which cannabis should not be used for cancer therapy. Breast Cancer Markers for Cannabinoid Treatment So, what we have is that breast cancer is diverse and may be classified based on the types of receptors the breast cancer cells express. In particular, a large portion of breast cancer cells have cannabinoid receptors and should thus react to cannabis. Indeed, surveys of breast cancer patients indicate that a significant portion of patients uses cannabis to relive symptoms, and clinical studies establish the efficacy of canna- bis to treat the symptoms of cancer in general as well the side effects of cancer treatments. While clinical evidence assessing the benefits of cannabis for treating breast cancer have not yet been conducted, there is a large body of preclinical re- search establishing a theoretical basis for using cannabis, not only to treat the symptoms of breast cancer, but also to attack the cancer itself. Yet, there is reason for caution, as a few studies have shown that cannabinoids may, in fact, promote the growth of breast cancer cells. So, then, what we need is a good marker not only for deter- mining when cannabinoids should be considered as a treat- ment for breast cancer, given cannabis's anti-cancer potential, but also for determining when cannabinoids should not be considered for treatment, due to its pro-cancer potential. Researchers have shown that: 1. Cannabinoid receptors (CBRs) are not expressed in non-tumor breast tissue (12,32). 2. Cancer cells that have higher CBR expression tend to be more aggressive (11,12,15,31,32), as well as more respon- sive to cannabis (29,31,32). 3. Cancer cells that have lower CBR expression tend to be either less responsive to cannabis (12) or even stimulat- ed by cannabis (11,29,30). 4. Cannabinoids may suppress immune system functioning (31). Taken together, researchers have concluded that when CBR ex- pression is low, then the negative effects of cannabinoids on in- hibiting other immune responses to cancer growth outweighs any tumor-suppressing effects cannabinoids might have (30,31). Clear- ly, then, when CBR expression on breast cancer tumors is low, can- nabinoids should not be considered as an anti-cancer therapeutic. If, on the other hand, CBR expression on breast cancer tu- mors is high, then the beneficial effects of cannabinoids on suppressing tumor activity outweigh their negative effects on suppressing immune system activity (30,31). So, then when CBR expression on breast cancer tumors is high, cannabinoids should be considered as an anti-cancer therapeutic. References (1) L. Harris, A. Munson, M. Friedman,. et al, "Retardation of tumor growth by D9-tetrahydrocannabinol," The Pharmacologist (1974). (2) A. Munson, L. Harris, M. Friedman, W. Dewey, and R. Carchman, "Antineoplastic Activity of Cannabinoid," J. Natl. Cancer Inst. DOI: 10.1093/ jnci/55.3.597. Retrieved from pubmed.ncbi.nlm.nih.gov/1159836/ (1975). (3) S. Rahman, et al, "The onus of cannabinoids in interrupting the molecular odyssey of breast cancer: A critical perspective on UPRER and beyond," (2019). Saudi Pharmaceutical Journal. DOI: 10.1016/j.jsps.2019.01.005 Retrieved from www.sciencedirect.com/science/article/pii/S1319016419300064 (2019). (4) Breast Cancer Treatment (Adult) (PDQ®)–Patient Version. (2021, Apr 8) National Cancer Institute. Retrieved from www.cancer.gov/types/breast/patient/breast-treatment-pdq. (5) L. Baram, E. Peled, P. Berman, B. Yellin, E. Besser, M. Benami, I. Louria-Hayon, G. Lewitus, and D. Meiri, "The heterogeneity and complexity of Cannabis extracts So, then, what we need is a good marker not only for determining when cannabinoids should be considered as a treatment for breast cancer, given cannabis's anti-cancer potential, but also for determining when cannabinoids should not be considered for treatment, due to its pro-cancer potential.