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Cannabis with breast cancer treatment: propitious or pernicious?


Cannabis has been used for various medicinal applications including, but not limited to, cancer: most commonly to treat chemotherapy-associated side effects. Cannabis is often used for its palliative effects in the form of purified cannabinoids, or as extracts. This study was conducted using two breast cancer cell lines and aimed to evaluate potential anti-proliferative “intra-entourage effects” between purified phytocannabinoids resembling the THC and CBD ratios of medicinal and recreational cannabis strains, as well as to investigate potential “inter-entourage effects” between the different ratios and the phytochemicals found in a Cannabis sativa extract. This study also aimed to evaluate the potential interaction between cannabinoids and chemotherapeutic agents. The data identified an intra-entourage effect present in the MCF-7 cells when treated with a recreational, but not a medicinal, cannabis formulation. This effect may be due to THC partially exerting its anti-proliferative effects through the estrogen receptor (ER), present in the MCF-7 cell line. Little to no intra-entourage effects were observed in the MDA-MB-231 cell line and no inter-entourage effects were observed in either cell line. The simultaneous treatment of the MCF-7 cell line with various cannabinoid formulations and the common breast cancer treatment, tamoxifen, resulted in the diminished anti-proliferative activity of tamoxifen, an effect that was more evident when combined with recreational cannabis formulations. Since cannabis is commonly used in palliative care to treat chemotherapy-associated side effects, further research is required to investigate the potential interference of various cannabis formulations to ensure that the efficacy of chemotherapeutic agents is not compromised.

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We would like to thank the South African community for contacting our research group and inspiring this investigation when they discovered our research interests. We hope our limited findings will assist them in making informed health decisions. R. Schoeman and A. de la Harpe would like to acknowledge Nelson Mandela University and the National Research Foundation (NRF) for the provision of research scholarships. Running costs for this study were covered by the Nelson Mandela University (NMU).


The funding has been received from National Research Foundation.

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RS: conceptualization; methodology; formal analysis; investigation. ADLH: writing—original draft, visualization. NB: methodology; supervision; writing—review and editing. CLF: conceptualization; methodology; supervision; writing—review and editing; resources; project administration; funding acquisition.

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Correspondence to Carminita L. Frost.

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All co-authors declare that they have no conflict of interest.

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Schoeman, R., de la Harpe, A., Beukes, N. et al. Cannabis with breast cancer treatment: propitious or pernicious?. 3 Biotech 12, 54 (2022).

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  • Cannabinoids
  • Cannabis extract
  • Combination therapy
  • Breast cancer