In this study, the anti-cancer effects of the chemotherapy drug 5-fluorouracil (also known as Fluorouracil, 5-FU or Adrucil) in MDA-MB-453 human breast cancer cells (which overexpress ErbB2) was found to be enhanced by the addition of apigenin to the treatment. Apigenin is a flavone found most abundantly in parsley, celery, bell peppers and Chinese cabbage. Cellular proliferation was observed to be significantly inhibited in cells exposed to 5-fluorouracil plus apigenin, compared with the proliferation in cells exposed only to 5-fluorouracil. Similarly, the level of ErbB2 was found to be unaffected by 5-fluorouracil alone, but was markedly reduced in cells treated with both 5-fluorouracil and apigenin. The authors conclude that 5-fluorouracil acts synergistically with apigenin in inhibiting cell growth and inducing apoptosis through the down-regulation of ErbB2 expression and Akt signaling.