Researchers have found that hormones produced during pregnancy induce a protein that directly inhibits the growth of breast cancer. This protein, alpha-fetoprotein (AFP), may serve as a viable, well-tolerated agent for the treatment and prevention of breast cancer, according to findings published in Cancer Prevention Research

Recent studies have shown that hormones released during pregnancy, such as oestrogen, progesterone and human chorionic gonadotropin, reduce womens risk for breast cancer. AFP is a protein normally produced by the liver and yolk sac of a fetus. A study was done administering pregnancy hormones to carcinogen-exposed rats led them to produce AFP, which in turn produces the protective effect of pregnancy in the absence of pregnancy.

Results from this study showed that treatment with oestrogen plus progesterone, oestrogen alone or human chorionic gonadotropin reduced the incidence of mammary cancers in rats. Furthermore, the researchers noted that each of these treatments elevated the serum level of AFP and that AFP directly inhibited the growth of breast cancer cells growing in culture, suggesting that these hormones of pregnancy are preventing breast cancer through their induction of AFP.

These preclinical findings are important and suggest a role of AFP in breast cancer prevention, they are not yet ready to be used in the clinic. The researchers have not directly demonstrated the cancer preventive activity of AFP, instead they found an association of these hormones preventing mammary tumours. None of these treatments prevented mammary tumors in 100 percent of the rats, it appears to delay mammary tumor formation and prevent breast cancer development in approximately 30 to 50 percent of the rats. This study is promising and suggests that additional animal studies need to be done before translation to humans.

Cancer Prevention