Sunday, 27 May 2012

Breast Cancer and Soy Isoflavones

Cancer is caused by a series of mutations in a cell, which will enable it to evade the checkpoints of the normal cell cycle. Once it is able to do so, it can multiply quickly to form a tumor. The tumor will then be able to metastasize, or invade, other organs of the body. This disrupts their normal functions, eventually leading to death.
In this case, there are 2 genes that are important in cancer research. The first is MDM2, or Murine Double Minute, which is an oncogene. The second is p53, which is a tumor suppressor gene. p53 is one of the cells’ normal defenses against abnormal cell development.

In a normal human, when there are abnormalities in the DNA, p53 functions to stimulate repair mechanisms, arrest cell cycle or initiate apoptosis if all else fails. MDM2, represses this function by binding to p53. This results in to p53 activity. Malignant mutations in DNA are not able to be corrected, and so the cancer cells are more likely to survive and spread.

Breast cancer is the most frequent cancer type in women, regardless of the country they are from. A study by a group of scientists from the NUS showed that certain MDM2 and p53 gene polymorphisms increase the risk of breast cancer, especially after menopause.

The same study also proved that soy isoflavones can down-regulate MDM2, and hence reducing the chances of getting breast cancer. This is because soy isoflavones have a structure similar to oestrogen, a naturally-occurring hormone in the human body, and thus can bind to the same receptors. At certain levels of oestrogen, there is less risk of breast cancer. During menopause, when a woman’s oestrogen levels decline, consumption of soy isoflavones can help to maintain this oestrogen profile.

Now that we know soy isoflavones can reduce the likelihood of breast cancer, we can promote soy products as part of women’s diets. Also, since both MDM2 and p53 genes have a part to play in the development of breast cancer, further research could be undertaken to discover other compounds that affect these two genes. These compounds may down-regulate the genes (just like the soy isoflavones), or could even up-regulate the genes. In the case of p53, up-regulation will be beneficial because it will limit the survival of abnormal cells in the body.

Lastly, because breast cancer is the leading cause of death in women worldwide, it is imperative to understand its cause and risk factors. Hopefully, with all the research currently being done, there will be a decline in the number of women affected by breast cancer in the future.

Reference paper:
Koh, W., Van Den Berg, D., Jin, A., Wang, R., Yuan, J. & Yu, M.C. (2011). ‘Combined effects of MDM2 SNP309 and TP53 R72P polymorphisms, and soy isoflavones on breast cancer risk among Chinese women in Singapore’. Breast Cancer Res Treat. 130:1011–1019. DOI: 10.1007. [Accessed: 16 March 2012].

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