# Cannabinoid research in breast cancer treatment > Live situation record from CLSTR: https://clstr.news/situations/cannabinoid-research-in-breast-cancer-treatment > Updated: 2026-09-02T20:30:00.000Z. Sources: 2. Developments: 2. Research into cannabinoid compounds has identified potential therapeutic applications for treating breast cancer. Initial studies focused on cannabidiol (CBD), demonstrating its ability to reduce the proliferation of HER2-positive breast cancer cells and lower HER2 gene expression. Researchers found that combining CBD with trastuzumab enhanced antiproliferative effects, and further investigations explored how CBD interacts with Tamoxifen to address drug resistance and tumor recurrence by affecting the tumor microenvironment. Subsequent research shifted focus to the effects of ultra-low doses of THC. Findings published in Communications Biology suggest that low-dose THC may prevent breast cancer cells from reverting to an aggressive, stem-cell-like state. Using human organoids and mouse models, researchers observed that this treatment resulted in cells that were less invasive and showed reduced self-renewal. This effect, which appeared to persist for up to 100 days after treatment cessation, is primarily driven by the CB2R receptor rather than the psychoactive CB1R receptor. ## Timeline ### 2026-09-02: Low-dose THC may reduce breast cancer cell aggressiveness, study finds A study published in Communications Biology suggests low-dose THC can keep breast cancer cells in a less aggressive, more mature state for months, potentially reducing tumor invasiveness. 2 sources. https://clstr.news/cluster/low-dose-thc-may-reduce-breast-cancer-cell-aggressiveness-study-finds ### 2026-08-16: Cannabidiol shows potential in breast cancer research Studies suggest cannabidiol (CBD) may enhance breast cancer treatments by reducing HER2 receptor expression and potentially mitigating drug resistance when combined with drugs like trastuzumab and Tamoxifen. 3 sources. https://clstr.news/cluster/cannabidiol-shows-potential-in-breast-cancer-research --- Cite as: Cannabinoid research in breast cancer treatment. CLSTR, https://clstr.news/situations/cannabinoid-research-in-breast-cancer-treatment