Luteolin confers yellow coloring to a number of vegetables and fruits. Luteolin has been shown induce cell death in several breast cancer cell lines in a time- and dose-dependent manner. Luteolin has also been shown to inhibit angiogenesis (new blood vessel formation) and aromatase activity (in which androgens are converted into estrogens). Diets high in luteolin have been linked to reduced risk of breast cancer.
In addition, luteolin has been shown to induce apoptosis (programmed cell death) and reduce proliferation in multidrug resistant hormone receptor positive (ER+/PR+) breast cancer cells. In fact, luteolin has been shown increase the anti-cancer effects of the chemotherapy drugs Adriamycin (doxorubicin) and Taxol (paclitaxel). In addition, luteolin has been demonstrated to sensitize tamoxifen-resistant breast cancer cells to tamoxifen, thereby improving its treatment effects. Now a new study has reported that luteolin reduces proliferation in ER+/PR+ and triple negative (ER-/PR-/HER2-) breast cancer cells by reducing the effects of epidermal growth factor (EGF).
Sources of luteolin
Like apigenin, luteolin is a flavone, a subclass of flavonoids, which are plant pigments found primarily in fruits and vegetables. Apigenin and luteolin are often found together in the same foods. Parsley and celery are the most abundant food sources of luteolin; it is also found in bell peppers and hot peppers, carrots, artichokes, olives and olive oil. Luteolin is also found in culinary herbs such as mint, rosemary, sage and thyme. However, note that we recommend against consuming sage for breast cancer survivors.
There is some evidence that the impact of flavonoids on breast cancer cells depends on the dosage, with low and high doses both potentially stimulating breast cancer cell growth in some cases. When flavonoids are consumed as part of food, they are combined with other micronutrients that have been shown to act synergistically against breast cancer. Consuming flavonoid-rich foods is safe. However, since safe and effective dosages of luteolin, a phytoestrogen, have not been established, luteolin supplements are not recommended, especially during chemotherapy.
Latest research finds luteolin inhibits proliferation by counteracting EGFR
The study referenced at the beginning of this news story was designed to determine how luteolin inhibits the proliferation of breast cancer cells induced by EGF, which binds to epidermal growth factor receptor (EGFR). Breast cancer patients with tumors having positive EGFR expression have a less favorable prognosis than those with EGFR-negative tumors. Activation of EGFR with EGF promotes proliferation and migration of tumor cells, thus facilitating the spread of cancer.
The authors first assessed the increase in proliferation of ER+/PR+ (MCF-7) cells induced by EGF, as well as the inhibitory effect of luteolin on the proliferation of both ER+/PR+ and triple negative (MDA-MB-231) breast cancer cells. The authors then investigated the effects of luteolin on the expression of EGFR and other pathways influenced by EGF in MCF-7 cells. The results demonstrated that luteolin could significantly inhibit the proliferation of MCF-7 and MDA-MB-231 cells. However, the effect was more pronounced in MCF-7 cells. In addition, luteolin was shown to inhibit proliferation induced by EGF in MCF-7 cells. The authors conclude that luteolin may inhibit EGF-induced activities of the EGFR signaling pathway in human breast cancer cell lines. The study results could provide a theoretical foundation for the development of luteolin as an anti-cancer drug.