What is the HER-2 receptor?

In 25% of breast cancer cases, the gene that codes for the HER-2 receptor proteins does not work properly and makes many copies of itself.

HER-2, or human epidermal growth factor receptor 2, is a gene that can influence the development of breast cancer. When a patient makes a pathological report, it must include information on the status of the HER-2 receptor, since this information informs whether this gene influences the formation of cancer.

Genes contain the formulas for the various proteins that a cell needs to stay healthy and function normally. Some genes, and the proteins they produce, can influence the behavior of breast cancer.

In this way, cancer cells in a tissue sample are analyzed using a biopsy or other techniques to see which genes are normal and which genes are altered. The proteins produced by cells can also be analyzed.

Breast cancer overview

Breast cancer is a type of cancer that forms in the cells of the breast. It can develop in both men and women. However, male cases only represent 1% of diagnosed cases of breast cancer.

1 in 8 women suffers from breast cancer in Spain, being the cancer with the highest incidence in women in this country. It represents 25% of all cancer cases. The incidence has increased after the introduction of mammography in early diagnosis programs and continues to increase with the aging of the population.

This cancer develops from the uncontrolled growth of cells in the breast. The tumor can appear in different structures of this organ, for example in the ducts. When proliferation occurs, certain proteins and molecules are more numerous, such as HER-2 or the proliferation marker Ki67.

In addition, there are certain risk factors that greatly increase the probability of suffering from this disease. Among them, we can mention:

  • Genetic predisposition.
  • History of atypical hyperplasia.
  • Not having children or having them at an older age.
  • Exposure to estrogens.
  • Radiation.
  • Sedentary lifestyle.
  • Diet: the Mediterranean diet reduces the risk of breast cancer by 30%, however, the Western diet increases it.

HER-2 receiver

HER-2 proteins are receptors on breast cells, produced by the HER-2 gene. In normal situations, these receptors are necessary for the breast to grow healthy, for breast cells to divide, and to repair themselves.

But in 25% of cases of this cancer, the gene that codes for the HER-2 receptor proteins does not work as it should and makes many copies of itself. This phenomenon is known as HER-2 gene amplification.

In this way, all the extra copies of this gene send the information so that more HER-2 receptors are synthesized, overexpressing themselves. As a result, cells in the breast grow and divide in an uncontrolled way, causing cancer.

HER-2 + or HER-2-breast cancer

Depending on whether or not this gene is amplified, breast cancer can be classified into:

  • HER-2 positive: these  are cases of breast cancer with amplification of the HER-2 gene or overexpression of this protein.
  • HER-2 negative: it occurs when the cancer does not present or overexpression of the HER-2 gene or protein.

In general, HER-2 positive cancer has a poor prognosis because it tends to grow faster and is more likely to spread and re-form. However, new advances in research have made it possible to develop new antiHER-2 drugs that have provided great results. An example of these drugs is trastuzumab.

Determination of the HER-2 receptor in patients with breast cancer

Today there are 4 clinical tests that allow us to analyze the presence of this receptor:

  • Immunohistochemistry or IHC: This test indicates if there is too much HER-2 protein in cancer cells. Results are expressed as follows:0 (negative),1+ (negative),2+ (ambiguous),or3+ (positive).
  • FISH or fluorescent in situ hybridization analysis: the results of this test allow us to know if there are too many copies of the HER-2 gene in the affected cells.
  • CISH or HER-2 analysis by chromogenic in situ hybridization with subtraction probe technology: as above, shows if there are too many copies of the HER-2 gene.
  • ISH or HER-2 analysis by in situ hybridization: shows the same data as the previous two.

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