Genetics and breast cancer

Within the world of oncology, breast cancer is perhaps one of the best-known cancers, possibly because it is the most diagnosed cancer in the world (1). Population ageing, one of the main consequences of the welfare society, or the greater prevalence of risk factors such as for overweight or physical inactivity, and changes in reproductive patterns (2) are some of the factors that have increased the incidence of cancer in recent decades. Among women in developing countries, breast cancer continues to be the leading cause of death (2). Moreover, the incidence varies significantly by ethnicity (3).

Classification and Oncogenes

An oncogene is an abnormal or activated gene that results from the mutation of an allele of a normal gene called a proto-oncogene. Oncogenes are responsible for transforming a normal cell into a malignant cell that will develop a specific type of cancer.

In breast cancer, there are several types, depending on the absence or presence of estrogen/progesterone receptors (4):

  • Hormone receptor-positive/ERBB2 negative.
  • ERBB2 positive
  • Triple-negative (tumours lack the three standard molecular markers).

Regarding oncogenes, one of the most important associated with breast cancer is HER2. Precisely for this reason, its progression is studied and analyzed in terms of survival and potential recurrence (5), that is, the possibility that the tumour may recur.

Evolution and approach to the disease

In retrospect, a positive fact is that the mortality rate has been steadily decreasing for the last thirty years (6). There is proof also that many breast cancers are non-metastatic at diagnosis (4). In turn, some research suggests that not all cells within breast cancer can develop tumours (7).

If we return to the classification and take, for example, the triple-negative type, we can affirm that it is the most likely to recur. On the other hand, it has a high survival rate concerning other types. In either case, it is essential to identify and know in depth the patterns that manifest each of these typologies. In this way, clinical strategies will have a more personalized approach to establish increasingly effective treatments.

Treatments

In addition to cyclophosphamides, recent research has shown that trastuzumab, an adjunct to chemotherapy, offers good survival results (8). However, gene expression analysis in breast cancer has not made it possible to establish therapeutic strategies adapted to each individual (9).

Breast cancer in men

Breast cancer is not a disease exclusive to the female sex. It can also occur in men of any age, although it is more common in older men. In any case, the incidence is much lower than in women. Its prevalence is less than 5%.

Detection, diagnosis and prevention

In genetics, we cannot understand breast cancer without speaking of genomic instability, an essential concept in understanding its development (10). Genomic instability is the increased tendency to present DNA mutations or other genetic changes that appear during cell division and is usually associated with many types of cancer.

Among the most critical genetic tools we have found, two are particularly noteworthy:

– MicroRNAs, which are diagnostic biomarkers. For example, miR-99a-5p (11) has recently been discovered in breast cancer and identified as a good tool for the early detection of breast cancer.

Genetic tests can be preventive when they analyze part of the genes involved in pathology or diagnostic when they examine all the DNA that affects the pathology.

24Genetics tests, as preventive tests, allow people to make more informed decisions that help them improve their well-being. Specifically, our Health test includes the CHEK2, CDH1 and ATM genes directly related to breast cancer (12).

Bibliography:

  1. World Health Organization. 2021. https://www.who.int/es/news-room/fact-sheets/detail/cancer
  2. Torre, L.A., et al. (2015). Global cancer statistics, 2012. CA: A Cancer Journal for Clinicians, 65.
  3. Momenimovahed, Z., & Salehiniya, H. (2019). Epidemiological characteristics of and risk factors for breast cancer in the world. Breast Cancer: Targets and Therapy, 11, 151 – 164.
  4. Waks, A.G., & Winer, E. (2019). Breast Cancer Treatment: A Review. JAMA, 321, 288–300.
  5. Slamon, D., et al. (1989). Studies of the HER-2/neu proto-oncogene in human breast and ovarian cancer. Science, 244 4905, 707-12 .
  6. DeSantis, C., et al. (2019). Breast cancer statistics, 2019. CA: A Cancer Journal for Clinicians, 69.
  7. Veer, L.J., et al. (2002). Gene expression profiling predicts clinical outcome of breast cancer. Nature, 415, 530-536.
  8. Al-Hajj, M., et al.(2003). Prospective identification of tumorigenic breast cancer cells. Proceedings of the National Academy of Sciences of the United States of America, 100, 3983 – 3988.
  9. Slamon, D., et al. (2001). Use of chemotherapy plus a monoclonal antibody against HER2 for metastatic breast cancer that overexpresses HER2. The New England journal of medicine, 344 11, 783-92
  10. Yeow, Z.Y., et al. Targeting TRIM37-driven centrosome dysfunction in 17q23-amplified breast cancer. Nature 585, 447–452 (2020). https://doi.org/10.1038/s41586-020-2690-1
  11. ACS Sens. 2021, 6, 3, 1022–1029. February 18, 2021. https://doi.org/10.1021/acssensors.0c02222
  12. Health report. (2021). 24Genetics
 

Written by Debora Pino García

Geneticist

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