Tamoxifen - The Oestrogen Antagonist.

The mechanism by which Tamoxifen mediates the control of cancerous cells is due to the fact that it exhibits oestrogen antagonist properties (i.e. inhibits the function of oestrogen). This is the property which led to investigation in its contraceptive activity. It was then recognised that the oestrogen antagonist activity could be useful in the treatment of cancer in females.

In breast cancer tissue Tamoxifen acts as a oestrogen antagonist. However in other tissues of the body Tamoxifen also shows partial and in some cases full agonist activity. So in order to determine the mode of action of Tamoxifen the type of tissue to be treated must be considered. In this case study we are only concerned with Tamoxifen's action in breast tissue.

Shown above is an oestrogen receptor alpha ligand.

In the body this protein binds to oestrogen and oestrogendiol to promote the growth of cells. Tamoxifen competitively inhibts the binding of oestrogen and oestrogendiol to this protein and therefore reduces the production of cancerous cells.

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Huw Tanner.Undergraduate Year 2 .Imperial College of Science,Technology and Medicine.

CIT Project

Study of Tamoxifen.