05/09/2026
According to a study published in the Journal of Cellular Biochemistry, low doses of quercetin — a flavonoid naturally found in foods like onions, apples, berries, and tea — were able to slow the growth of aggressive HER2-positive breast cancer cells (SK-Br3 and MDA-MB-453). Researchers used physiologically relevant doses around 5–10 μM, levels considered achievable in the bloodstream through regular intake rather than extremely high laboratory-only doses. Instead of directly killing the cancer cells, quercetin pushed them into a cellular “stop mode” known as G1 cell cycle arrest, preventing the cells from continuing to replicate and spread.
The study found that quercetin increased the protective protein p21, reduced phosphorylation of the retinoblastoma protein (pRb), and suppressed key division-driving proteins like cyclin B1 and CDK1 — all of which are heavily involved in uncontrolled tumor growth. Interestingly, the low-dose quercetin had little effect on normal breast cells (MCF-10A), suggesting a more selective effect toward rapidly dividing cancer cells. Researchers also observed mild DNA stress and activation of the Chk2 pathway, which further contributed to shutting down the cancer cells’ ability to progress through the cell cycle.
