Breast Cancer and Tamoxifen

Estrogen receptor comprises several structural domains with specific and overlapping functions. A number of monoclonal and polyclonal antibodies are available, some of which show affinity for specific domains of the ER molecule. The antibodies discussed below are efficient tools for ER immunohistochemistry on sections of formalin-fixed, paraffin-embedded tissues and facilitate the cellular site expression of ERa and ER 3 receptors in human and rat tissues. Most of these antibodies are used for labeling ERs in breast tissue in conjunction with pretreatment with antigen retrieval methods. 

FIGURE 11.4. Immunostained estrogen receptor a in invasive ductal carcinoma of the breast, using microwave heat pretreatment and monoclonal antibody ERID5 specific for ERa (diluted 1 100). This antibody is superior to monoclonal antibody H222. Courtesy of King-Chung Lee. 

Saunders et al. (1997) have raised a polyclonal antiserum using a peptide specific for ER 3. The peptide (CLSKAKRNGGHAPRVLEL) corresponding to amino acids 196-213 of rat ER(3 was conjugated to keyhole limpet hemocyanin and used to immunize rabbits according to standard procedures. Polyclonal IgGs were purified from serum on a Hitrap protein A Sepharose column based on the manufacturer s instruction (Pharmacia). 

The effects of binding these site-directed, monoclonal antibodies to specific regions of the ER molecule on the conformation of this molecule have been determined. Such studies indicate that the conformational change within a small stretch of the ER molecule 

A reliable method of measuring the ER content in human breast cancer is important for optimal treatment and a qualified estimate of the recurrence-free survival of the patient. The majority of the studies on the expression of ERs, especially ER 3 in human tissues, have been accomplished using RNA techniques such as reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. Although the RT-PCR method is an effective tool to describe the presence of a particular gene in the tissue, this approach does not indicate the specific cell that expresses the gene. 

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