Compounds that have the potential to prevent breast cancer, by limiting the growth of stem cells, exist in spices like turmeric and pepper.These are a small number of cells that fuel a tumor's growth, according to researchers at the University of Michigan.
The researchers found that when the dietary compounds curcumin, which is derived from the Indian spice turmeric, and piperine, derived from black peppers, were applied to breast cells in culture, they decreased the number of stem cells without affecting normal differentiated cells.
"If we can limit the number of stem cells, we can limit the number of cells with potential to form tumors," said lead author Dr. Madhuri Kakarala.
Cancer stem cells are the small number of cells within a tumor that fuel the tumor's growth.
Current chemotherapies do not work against these cells, which is why cancer recurs and spreads.
According to researchers, eliminating the cancer stem cells is key to controlling cancer.
In addition, decreasing the number of normal stem cells - unspecialised cells that can give rise to any type of cell in that organ - can decrease the risk of cancer.
In the current study, a solution of curcumin and piperine was applied to the cell cultures at the equivalent of about 20 times the potency of what could be consumed through diet.
The compounds are available at this potency in a capsule form that could be taken by mouth.
The researchers applied a series of tests to the cells, looking at markers for breast stem cells and the effects of curcumin and piperine, both alone and combined, on the stem cell levels.
They found that piperine enhanced the effects of curcumin, and that the compounds interrupted the self-renewal process that is the hallmark of cancer-initiating stem cells.
Besides, the compounds had no affect on cell differentiation, which is the normal process of cell development.
"This shows that these compounds are not toxic to normal breast tissue. Women at high risk of breast cancer right now can choose to take the drugs tamoxifen or raloxifene for prevention, but most women won't take these drugs because there is too much toxicity. The concept that dietary compounds can help is attractive, and curcumin and piperine appear to have very low toxicity," said Kakarala.
The study is the first to suggest these dietary compounds could prevent cancer by targeting stem cells.
It has been published online in the journal Breast Cancer Research and Treatment.