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Cancer and Genetics

What is cancer?

Cells are the basic units that make up the human body, and they grow and divide to create new cells as the body needs them, forming our organs and tissues. Usually, they die when they grow old or become too damaged, and new cells take their place [1]. Cancer originates when some cells grow uncontrollably, go beyond their limits and spread to other parts of the body. It can start in almost any organ or tissue, which comprises about 30 trillion cells [2], [3].

 

– Tumors and cancer

Occasionally, the genetic material of the cell changes and the control of its growth is affected so that the cells begin to divide too rapidly and do not die naturally [4], [5]. This can result in an irregular accumulation of cells, known as a tumor or neoplasm [6]. However, unlike commonly believed, they are not all synonymous with cancer [7], [8]. Instead, we can differentiate two types of tumors:

  • Benign or non-cancerous.
  • Malignant or cancerous.

The difference lies in the fact that the former is located in a specific tissue or organ. In the latter, their cells can be released into the circulatory system and spread throughout the body, giving rise to new tumors, other organs and tissues. This process is called metastasis [1]. However, not all cancers originate from solid tumors. In the case of some cancers related to the circulatory system, such as leucemia, immature cells become cancerous and, released into the bloodstream, displace healthy cells.

 

– Types of cancer

The word cancer is a broad term that encompasses more than 200 types. Each one has particular characteristics that may even be completely different from the rest. Thus, we can consider them independent diseases with specific causes, evolution and treatment [9]. Nevertheless, six major categories can be distinguished [10]:

  • Carcinoma: of epithelial origin or cancer of the internal or external lining of the body.
  • Sarcoma: originates in supportive and connective tissues, such as bone, tendons, cartilage, muscle and fat.
  • Myeloma: originates in the plasma cells of the bone marrow. These are responsible for producing some of the blood proteins.
  • Leukaemia: they originate in the bone marrow, which produces either white or red blood cells.
  • Lymphoma: they develop in the glands or lymph nodes of the lymphatic system.
  • Mixed types: include those cancers that involve different categories or different varieties within the same category.

 

Health and incidence

In recent decades, the number of cancers diagnosed has increased. This is due to increased population, improved early detection techniques, and increased life expectancy. However, the risk of mortality from this cause has decreased considerably (Figure 1) [11], [12]. It is estimated that 2.7 million people in the European Union were diagnosed with cancer during 2020, and another 1.3 million people died from it. The overall economic impact of cancer in Europe is estimated at more than €100 billion annually [13]. For example, in 2018, the total cost was about €199 billion (€378 per capita) [14].

Cancer mortality rate in Europe per 100,000 population between 1943 and 2018. Source: International Agency for Research on Cancer – World Health Organization.

Risk factors and prevention

There are multiple risk factors in cancer development, and they may differ for each type of cancer. Many of them can be modifiable, especially those related to lifestyles, such as alcohol and tobacco consumption, intense and prolonged exposure to sunlight, unbalanced diet and unprotected sex. However, others are not avoidable, such as inherited genetic predisposition, age, certain infections that increase the risk, or chemicals in the environment, especially atmospheric pollution [15].

Between 30% and 50% of cancer deaths could be avoided by making changes in the principal risk factors and carrying out prevention strategies, in addition to early detection and treatment [3]. Some of the preventive measures are the following:

  • Avoiding tobacco and alcohol consumption.
  • Maintain a healthy weight and diet.
  • Exercise frequently.
  • Practice safe sex and get vaccinated against hepatitis B and human papillomavirus (HPV).
  • Reduce exposure to ultraviolet radiation and use sunscreen.
  • Avoid air pollution and smoke in the home resulting from the use of solid fuels.
  • Receive regular medical care.

Presenting one or several risk factors does not imply the development of the disease, but it dramatically increases the probabilities. Similarly, cancer can develop without showing any risk factor [15].

 

Treatment 

There is a multitude of treatments for cancer. Treatment will depend on the type of cancer and how advanced it is. In most cases, a combination of treatments will be used to remission the pathology. Among the different kinds of treatment, we can find the following [16]:

  • Surgery: generally performed to remove the malignant tumor generating cancer.

  • Radiotherapy: performed by subjecting the patient to high doses of radiation to destroy cancerous cells and thus reduce the size of the tumors.

  • Chemotherapy: involves the administration of drugs to eliminate malignant cells.

  • Immunotherapy: involves boosting the immune system to help it fight cancer.

  • Targeted therapy: the treatment focuses on slowing down or paralyzing abnormal changes in cancer cells by preventing them from growing and dividing uncontrollably, thus reducing their spread to other parts of the body.

  • Hormone therapy: used mainly for prostate and breast cancers, it slows down and stops the growth of cancerous tumors through the use of various hormones.

  • Stem cell transplants: generally used after treatment with chemotherapy or radiotherapy, they are used to restore blood stem cells destroyed after treatment.

  • Biomarker tests: allow the detection of genes and proteins that provide information about cancer, such as its location and stage.

The side effects are very diverse and, many of them, specific to each of the treatments.

 

How does cancer originate from a genetic point of view?

Part of the factors that cause cancer is genetic, generating changes in the genes that control the functioning of our cells, especially their growth and division. [4]. Genes contain the information necessary for synthesizing proteins that allow the correct functioning of cells and the organism. Mutations are changes in this genetic information that occur frequently. Most of them have no repercussions and, for those that are harmful, the organism has a genetic repair mechanism that attempts to correct them. Sometimes, however, deleterious mutations occur that cause damage to this genetic information that the repair mechanisms are unable to fix. If these mutations affect the division and growth mechanisms, they could lead to the onset of cancer [17]. These mutations can be:

  • Acquired is the most frequent and occurs throughout a person’s life in specific cells, generally due to exposure to carcinogenic substances. They are not transmitted from parents to children.
  • Germline: these occur in the sperm or egg cells and are transmitted to the offspring. As they affect the reproductive cells, these mutations are hereditary.

The presence of such mutations does not ensure cancer development but indicates a certain predisposition to develop cancer during a person’s lifetime [11], [18]. Generally, the process of cancer development (carcinogenesis) involves the accumulation of multiple mutations in a long process that can last many years. A few mutations cause cell growth and division higher than the standard rate in the first phase but not enough to develop cancer. However, suppose new mutations continue to originate in these affected cells. In that case, cell multiplication increases uncontrollably. They become increasingly involved in their shape, size and function until they acquire the capacity to invade other tissues and organs, thus giving rise to cancer (Figure 2) [18].

Figure 2. Phases in the development of a tumor. Source: Spanish Association Against Cancer.

Cancer and 24Genetics

At 24Genetics, we offer you our Health and Pharmacogenetics tests that include certain specific markers related to the genetic predisposition to suffer from different types of cancer and the effectiveness of several drugs involved in its treatment.

 

Bibliography

[1] American Society of Clinical Oncology, “What is Cancer? | Cancer.net.” https://www.cancer.net/navigating-cancer-care/cancer-basics/what-c%C3%A1ncer (accessed Jan. 26, 2022).

[2] E. Bianconi et al., “An estimation of the number of cells in the human body,” https://doi.org/10.3109/03014460.2013.807878, vol. 40, no. 6, pp. 463–471, Nov. 2013, doi: 10.3109/03014460.2013.807878.

[3] World Health Organization, “Cancer – WHO.” https://www.who.int/health-topics/cancer#tab=tab_1 (accessed Jan. 25, 2022).

[4] National Cancer Institute at the National Institutes of Health, “What Is Cancer? – NCI.” https://www.cancer.gov/about-cancer/understanding/what-is-cancer (accessed Jan. 25, 2022).

[5] National Health Service, “Cancer – NHS.” https://www.nhs.uk/conditions/cancer/ (accessed Jan. 25, 2022).

[6] National Cancer Institute at the National Institutes of Health, “Definition of neoplasm – NCI Dictionary of Cancer Terms – National Cancer Institute.” https://www.cancer.gov/publications/dictionaries/cancer-terms/def/neoplasm (accessed Jan. 26, 2022).

[7] MedlinePlus, “Cáncer: MedlinePlus enciclopedia médica.” https://medlineplus.gov/spanish/ency/article/001289.htm (accessed Jan. 25, 2022).

[8] MedlinePlus, “Tumor: MedlinePlus enciclopedia médica.” https://medlineplus.gov/spanish/ency/article/001310.htm (accessed Jan. 26, 2022).

[9] Asociación Española Contra el Cáncer, “¿Cuántos Tipos de Cáncer Existen? | AECC.” https://www.contraelcancer.es/es/todo-sobre-cancer/tipos-cancer (accessed Jan. 26, 2022).

[10] National Cancer Institute at the National Institutes of Health, “Cancer Classification | SEER Training.” https://training.seer.cancer.gov/disease/categories/classification.html (accessed Jan. 26, 2022).

[11] Sociedad Española de Oncología Médica, “¿Qué es el cáncer y cómo se desarrolla?” https://seom.org/informacion-sobre-el-cancer/que-es-el-cancer-y-como-se-desarrolla (accessed Jan. 26, 2022).

[12] International Agency for Research on Cancer – World Health Organization, “Global Cancer Observatory.” https://gco.iarc.fr/ (accessed Jan. 26, 2022).

[13] European Commission, “Europe’s Beating Cancer Plan,” COMMUNICATION FROM THE COMMISSION TO THE EUROPEAN PARLIAMENT AND THE COUNCIL. Brussels, 2021.

[14] T. Hofmarcher, P. Lindgren, N. Wilking, and B. Jönsson, “The cost of cancer in Europe 2018,” European Journal of Cancer, vol. 129, pp. 41–49, Apr. 2020, doi: 10.1016/J.EJCA.2020.01.011.

[15] Hospital Clínic de Barcelona, “Causas del Cáncer | PortalCLÍNIC.” https://www.clinicbarcelona.org/asistencia/enfermedades/cancer/causas-y-factores-de-riesgo (accessed Jan. 26, 2022).

[16] National Cancer Institute at the National Institutes of Health, “Types of Cancer Treatment – National Cancer Institute.” https://www.cancer.gov/about-cancer/treatment/types (accessed Jan. 26, 2022).

[17] American Society of Clinical Oncology, “The Genetics of Cancer | Cancer.net.” https://www.cancer.net/navigating-cancer-care/cancer-basics/genetics/genetics-cancer (accessed Jan. 26, 2022).

[18] Asociación Española Contra el Cáncer, “Origen del Cáncer. ¿Cómo se produce el Cáncer? | AECC.” https://www.contraelcancer.es/es/todo-sobre-cancer/que-es-cancer/origen (accessed Jan. 26, 2022).

 

 

Written by Manuel de la Mata

Geneticist

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