Scientists from the University of Kansas, Missouri, Colombia, claim that maundiflavones, found naturally in herbs and vegetables, may mitigate the increased risk of breast cancer associated with the combination of natural estrogen and synthetic progesterone used in hormone replacement therapy (HRT). Worldwide, millions of women are receiving hormone replacement therapy that includes estrogen and progestin to combat the symptoms of menopause. However, studies are increasingly showing that the use of such treatments may increase the risk of breast cancer. Salman Hayder, who led the study, explains that while most older women typically have breast tissue lesions, “these lesions don’t usually form tumors until they are “triggered” in some way – such as in this case by progestin intake, which causes blood vessels around the cells to proliferate, essentially supplying the lesions with a lot of nutrients that allow them to keep expanding.” Hayder’s group found that “once human breast cancer cells start to develop, they exhibit stem cell-like properties, which make them harder to kill.” In the study, breast cancer cells were exposed to varying concentrations of maundiflavone in vitro for 24 or 48 hours. It was found that maundiflavones showed an effect of reducing the activity of cancer cells, both in terms of time and dose. The blood vessels that provide nutrients to cancer cells were reduced, thus leading to the death of cancer cells. Also, the stem cell properties that normally promote cancer cell development were reduced. Overall, the study found that mullein flavonoids have antitumor effects. Based on these results, Hayder tested the effects of maundiflavone in laboratory mice with breast cancer and again found a reduction in both angiogenesis and hematopoietic stem cell properties.