During the past several years, new molecular biomarkers have been discovered that are important targets for the diagnosis and therapy of breast cancer. Three important biomarkers and therapeutic targets that aid in the prognosis of breast cancer are Estrogen Receptor (ER), Progesterone Receptor (PR), and Human Epidermal growth factor receptor 2 (HER2/neu or HER-2). Receptors are proteins on the outside surfaces of cells that can attach to certain substances, such as hormones, that circulate in the blood.
ER and PR
Normal breast cells and some breast cancer cells have receptors that attach to estrogen and progesterone which often fuels the growth of breast cancer cells. Breast cancer is evaluated after the biopsy/surgery to see if it has estrogen or progesterone receptors. Some cancer cells do not contain either while others contain both. ER and PR negative tumors appear to be more malignant and result in a worse prognosis than with ER and PR positive tumors.
ER or PR positive breast cancer patients are more likely to benefit from hormone suppression therapy such as Tamoxifen or aromatase inhibitors (i.e. Arimidex, Aromasin, Femara, Faslodex, or Evista) which work by blocking the hormone receptors so they cannot signal cancer cells to grow. Hormone suppression medication can help prevent recurrences of breast cancer.
ER and PR negative breast cancer do not respond to hormone treatment, but do respond to other treatments such as Herceptin which is discussed below for treatment of HER2/neu positive breast cancer.
HER2 is another important prognosis marker for breast cancer. This gene sends control signals to your cells to grow, divide, and make pairs. A healthy breast has 2 copies of HER2 gene. Certain types of breast cancer are initiated when a breast cell has more than 2 copies of this gene, which leads the affected cells to grow and divide much too quickly. This genetic error is not inherited but is most likely caused by age and wear and tear on the body. If the cancer is HER2 positive then the cells are growing rapidly and creating the cancer. HER2 negative means that the protein is not causing the cancer. HER2 has been found in 15 to 25 % of invasive breast carcinomas, and is related to metastiatic potential and poor survival.
There are 2 tests that are used to diagnose HER2/neu type breast cancer. The first is the ImmunoHistoChemisty (IHC), which measures the production of the HER2 protein by the tumor. The test results are raked as 0, 1+, 2+, or 3+. If the results are 3+ then the cancer is positive for HER2. The second test is called the Fluorescence In Situ Hybridization (FISH), which uses fluorescent probes to look at the number of HER2 gene copies in a tumor cell. The test is HER2 positive if there are more than 2 copies of the gene.
Herceptin is a drug which is currently being used in conjunction with other chemotherapy drugs to treat HER2 positive breast cancer. This drug works by targeting the HER2 protein production which helps to stop the growth of the HER2 positive cancer cells. Herceptin also shrinks the HER2 positive tumors before surgery, rids the body of the positive tumors that have spread beyond the original tumor, and helps prevent recurrence of the HER2 positive cancer if it was a tumor ≥ 2cm or if the cancer had spread to the lymph nodes.
It is important to start treatment right away in cases of HER2/neu positive breast cancer in order to help improve survival as well as to help prevent recurrences.
Medscape. “Estrogen Receptor and HER2/neu Status Affect Primary Breast Tumors”. ©2008 BioMed Central, Ltd. www.medscape.com.

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