A new study has reported that apigenin may inhibit the development of progestin-induced mammary tumors in a rat model of breast cancer. Apigenin is a flavonoid found in a variety of foods, chief among them celery and parsley. Progestin in combination hormone replacement therapy (HRT) has been linked to increased risk of breast cancer. Vascular endothelial growth factor (VEGF) is vital for tumor blood vessel formation. The authors previously demonstrated that medroxyprogesterone acetate, a synthetic progestin used in HRT and birth control pills, increases production of VEGF by tumor cells, resulting in the development of new blood vessels and tumor growth.

In the current study, apigenin was found to significantly delay the development of progestin-accelerated mammary tumors in the rats. Apigenin also reduced the number of mammary tumors. While apigenin delayed the appearance of tumors, it did not block the initial stages of cancer development within the mammary pads. Apigenin was found to reduce progestin-dependent increases in VEGF. On the other hand, estrogen and progesterone receptor levels were not different in the mammary glands of progestin-treated animals, progestin-treated animals administered apigenin, and placebo-treated animals. Nor were there any differences in the number of estrogen receptor positive (ER+) cells. However, the number of progesterone receptor positive (PR+) cells was lower in rats treated with progestin or progestin plus apigenin compared with those treated with a placebo. The authors conclude that apigenin might have important chemopreventive properties for those breast cancers that develop in response to progestins.

Better to consume apigenin in foods rather than supplements

It is unclear what dosage of apigenin would be required to counteract the cancer-promoting effects of combination HRT or birth control pills in women. Apigenin can act both as an estrogen and as an anti-estrogen depending on the dosage, and can actually stimulate the growth of estrogen receptor positive breast cancer cells under some circumstances. While apigenin may increase the effectiveness of radiation treatment, it has varying interactions with different types of chemotherapy. For example, one study found that apigenin reduced the cytotoxicity of doxorubicin (Adriamycin). Based on the available evidence, compared to consuming it as part of foods in the diet, supplementation with apigenin appears to be unwise.