ing Cancer is a disease in which abnormal cells divide rapidly, uncontrollably and invade other cells or tissues of the body. However, the development of cancer (called carcinogenesis) is a very slow process that happens over time. Therefore, cancer can appear when you least expect it and because carcinogenesis is a slow process, cancer might not meet you in your life time if preventive measures are taken. 

What Causes cancer?

Cancer is caused by carcinogens. A carcinogen is a substance, microorganism or agent which  induce the development of cancer. This may due to their ability to interact with DNA and cause gene mutation or  due to their ability to disrupt cellular metabolic processes.  A carcinogen can be naturally occurring or man made. Examples of commonly known carcinogens include ultraviolet rays from sunlight, viruses such as Hepatitis B and C, asbestos, automobile exhaust fumes, red or processed meat, cigarette smoke etc. However, exposure to a carcinogen does not guarantee you will get cancer. Many other factors are usually at play such as genetic makeup, amount and duration of exposure, age, environmental factors etc. Because cancer results from a combination of several factors, continuous preventive measures are necessary to avoid cancer. 

The following substances, factors, microorganism or agents cause cancer:

    Infectious Agent

    Infectious agents such as parasites, viruses or bacteria have been identified to cause cancer or increase the risk of developing cancer. These agents cause cancer through chronic inflammation, weakening of the immune system (or immunosuppression), promoting high rate of proliferation, inducing resistance to apoptosis, altering genetic stability, triggering abnormal DNA repair, disruption of signaling pathways, interference with telomerase shortening and changes in cell polarity. 

    Seven viruses including human papillomavirus (HPV), Epstein–Barr virus (EBV), hepatitis  B and C  virus (HBV and HCV), human T-cell lymphoma virus 1 (HTLV-1), Merkel cell polyomavirus (MCPyV), and Kaposi’s sarcoma virus (KSVH or HHV8) are known to cause cancer. One bacterium (Helicobacter pylori) is known to cause cancer. Finally, 3 parasites have also been identified to cause cancer and include Schistosoma haematobiumOpithorchis viverrini, and Clonorchis sinensis.

    The following table shows the type of microorganism, name of microorganism and the type of cancer tthey are associated with. 

    Table 1: Microorganisms and Associated Cancers
    Type of Microorganism Name of Microorganism Associated Cancer
    Virus Human papillomavirus (HPV) Cervical, head and neck and anogenital tract carcinomas
    Epstein–Barr virus (EBV) Burkitt’s lymphoma, Hodgkin’s lymphoma, immune-suppression-related lymphoma;
    nasopharyngeal and stomach carcinoma
    Hepatitis B Virus (HBV) Hepatocellular carcinoma
    Hepatitis C Virus (HCV) Hepatocellular carcinoma
    Human T-cell lymphoma virus 1 (HTLV-1) Adult T-cell leukaemia/lymphoma
    Merkel cell polyomavirus (MCPyV) Merkel cell carcinoma
    Kaposi’s sarcoma virus (KSVH) Primary effusion lymphoma and Kaposi sarcoma
    Bacterium Helicobacter pylori Gastric cancer and gastric mucosa-associated lymphoid tissue (MALT) lymphoma
    Parasite Schistosoma haematobium Bladder cancer
    Opithorchis viverrini cholangiocarcinoma (CAA, bile duct cancer)
    Clonorchis sinensis Bile duct cancer

    Sources: (1) Morales-Sánchez, Abigail, and Ezequiel M Fuentes-Pananá. 2014. “Human Viruses and Cancer.” Viruses 6 (10). Multidisciplinary Digital Publishing Institute (MDPI): 4047–79. (2) Morales-Sánchez, A. & Fuentes-Pananá, E. Human Viruses and Cancer. Viruses. (6): 4047-4079. (2014) (3) White, JR., Winter, JA. & Robinson, K. Differential inflammatory response to Helicobacter pylori infection: etiology and clinical outcomes. Journal of Inflammation Research. (8): 137—14. (2015) (4) Vandeven, Natalie, and Paul Nghiem. 2014. “Pathogen-Driven Cancers and Emerging Immune Therapeutic Strategies.” Cancer Immunology Research 2 (1). NIH Public Access: 9–14.

    Exposure to Chemicals

    Exposure to a chemical could be internal based on what you eat, drink, inhale, or smoke. Also, it could be external based on what you physically come into contact with. Examples include genetically modified food, processed food, junk food, smoking, drinking alcohol, automobile exhaust fumes, asbestos and chemicals such as benzene, arsenic, industrial tar, coal, paraffin and certain types of oil. The golden rule is that, anything which is not natural or necessary to your body is a potential candidate for sponsoring cancer.

    Exposure to Radiation

    Exposure to radiation also leads to cancer. Cancer can be caused by both ionizing and non-ionizing radiations. Ionizing radiation include X-rays, gamma rays, alpha particles, beta particles, and neutrons. Non-ionizing radiation on the other hand include ultraviolet (UV) rays from sunlight. Too much exposure to UV radiation will cause sunburn and this will increase your risk of developing cancer. Radiation causes cancer by damaging tissues or DNA. 

    Physical Inactivity, Overweight or Obese

    Being physically inactive can lead to overweight and obesity. Overweight and obesity are linked to increase risk for 13 different types of cancer. These include cancer of the breast (in women who have gone through menopause), colon and rectum, uterus, gallbladder, upper stomach, kidneys, liver, ovaries, pancreas, thyroid, adenocarcinoma of the esophagus, meningioma (a type of brain cancer), and multiple myeloma (a type of blood cancer).

    Overweight and obesity cause cancer because of the presence of excess fat. Excess fat continuously send signals to the body. Such signals trigger inflammatory response and increase the levels of growth hormones and sex hormones. Consequently, cells start to divide more often and more quickly. Such will increase the risk of developing cancer over time. 

    Although overweight and obesity are linked to cancer in adults, no such link is found in children. 

    Autoimmune and Chronic Disease

    An autoimmune disease is one in which your immune system mistakenly attack healthy cells of your body. Examples include type I diabetes, vasculitis, rheumatoid arthritis, and Sjögren’s Syndrome. A chronic disease on the other hand is one in which develops slowly overtime, exerts a long term effect and require continuous medical attention. Examples include gastritis, heart diseases, asthma, Alzheimer’s disease and kidney diseases. 

    Endogenous or Internal Factors

    Your genetic composition or makeup plays a critical role on whether you will develop cancer or not.  Therefore, factors such as family history, age, gender, skin type, or genetically inherited diseases will determine if you will develop cancer or not. In fact, cancer has been shown to be more prevalent in older people.
    Sometimes, your body also makes mistakes during replication. Such  errors in replication will cause gene mutation and may lead to cancer. 

    How to prevent cancer

    Cancer can be prevented in the following ways:

    1. Get vaccinated against cancer causing viruses. There are currently vaccines available against the human papillomavirus (HPV) and Hepatitis B virus (HBV).
    2. Practice safe sex, effective hygiene practices and regular check-ups to avoid infections from cancer causing microorganisms.
    3. Eat healthy and natural. Eat more fruits, vegetables, and whole grains and cook your own food. Avoid buying junk or processed food.
    4. Drink alcohol only in moderation.
    5. Stop smoking.
    6. Wear breathing mask, safety goggles and wash hands when dealing with chemicals.
    7. Minimize prolong and long-term exposure to chemicals.
    8. Minimize exposure to radiation. Protect your skin with proper clothing, stay in shades to avoid skin burns and use sunscreen whenever possible. 
    9. Certain medications cause cancer. Therefore, whenever possible avoid medications and try to heal naturally except it’s necessary or beyond your control.
    10. Exercise regularly and stay physically fit.
    11. Avoid unhealthy weight gain.
    12. Go for regular checkups, including cancer screening tests. This will allow for cancer to be detected early enough and hence results to better treatment outcome.
    13. Go for genetic counselling. Your genetic makeup or family history can put you at risk of developing cancer. Genetic counseling helps you determine your genetic risk of having cancer and advice you on what to do.