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Steroid hormones (from vitamin D to suprarenal hormones) act by their fixation to a specific receptor situated inside the cell nucleus. The complex is a DNA transcription factor which induces various protein syntheses. Steroid receptors are proteins from 427 to 984 amino acids with many analogical zones from one species to another and from one receptor type to another.

General diagram of the action of steroid hormones on hormone sensitive cancer cells The steroids, linked to more or less specific serum proteins, freely penetrate into the cancer cells and are then transported towards the nucleus by a specific cytosol receptor. The receptor itself is bound to the heat shock protein. When in the nucleus, the receptor activates the transcription of the synthesis necessary for good cell trophicity. .

Receptors are active in several domains:

• Specific hormone recognition domain,
  
• DNA Binding domain

Assay methods for receptors

Two techniques are used:

• Either isotope techniques, using a tracing dose of radioactive hormone, which tests the nuclear extracts
  
• Or immunochemical techniques which can be applied on tissue extracts or directly on histological preparations.

In clinical practice, oestrogen and progesterone receptors are tested in breast cancer specimens. There is an excellent correlation between the presence of oestrogen receptors in tumour tissue and the response to hormonal therapy.

Relationship between the presence of receptors and survival in breast cancer.

Progesterone receptors are synthesised after the action of oestrogens and thus reflect the actions of both oestrogens and progesterone on tumour cells.

The presence of receptors is a good prognostic factor: breast cancer patients with positive receptors have a longer survival without relapse than patients without detectable receptors.

There has been less study on receptors for prostate cancer. The conversion of testosterone by the prostate cell via a 5- α reductase, enables the reduced hormonal molecule to penetrate into the nucleus.

Hormonal therapy is based on the possibilities of breaking the interaction between testosterone or its derivative with its receptors, thus reducing the transcription factors induced by the combination of the hormone and its receptor.