Introduction to Cancer
What is cancer?
Cancer is a term for a disease, which there is a continous growing of cells without stopping and spread into surrounding tissues. The normal cells, molecules, and blood vessels could be influenced by the cancer cells. Cancer cells can induce nearby normal cells to form blood vessels that supply tumors with oxygen and nutrients, which they need to grow. These blood vessels also remove waste products from tumors. Cancer cells are also often able to evade the immune system, a network of organs, tissues, and specialised cells that protects the body from infections and other conditions. Normally, the immune system removes damaged or abnormal cells from the body. However, cancer cells are able to “hide” from the immune system[1,2].
What causes cancer?
There are four main groups that can causes cancer[1]:
biological or internal factors, such as age, gender, inherited genetic defects and skin type
environmental exposure, for instance to radon and UV radiation, and fine particulate matter
occupational risk factors, including carcinogens such as many chemicals, radioactive materials and asbestos
lifestyle-related factors, such as tobacco, alcohol, UV radiation in sunlight, and some food-related factors, such as nitrites and poly aromatic hydrocarbons generated by barbecuing food).
Modifiable cancer risk factors
1. Dietary consumption that has been more strongly associated with the development of cancer
Dietary consumption of processed meat. This meat includes ham, bacon, hot dogs, sausage, and some deli meats. The word "processed" that mentioned before refers to meat that has been treated to preserve or flavor it, includes curing, salting, fermenting, and smoking. According to International Journal of Epidemiology, eating this meat can increase the risk of developing colorectal cancer about 19% for 25 gram serving every day, which is equivalent to a slice of ham. Also, risk of colorectal cancer rose by 18% for 50 gram serving red meat every daily, equal to a thick piece of roast beef[3]. Coloretal cancer caused by activation of Toll-like receptors at the intestinal epithelial surface and triggers the NF-Κb inflammatory pathway[4]. Furthermore, when meat is cooked at high temperatures, it produces carcinogenic compound such as heterocyclic aromatic amines, N-nitroso-compounds, and polycyclic aromatic hydrocarbons[5].
2. Obesity has been identified as a risk factor for a lot of cancers
Did you have obese history from your ancestry or you got obese because you are notget used to do healthy lifestyle? How did I know if I have obesity? Well, you can measure your Body Mass Index (BMI) and classify whether your body weight is normal, overweight, or obese by this formula: BMI = (body weight (kg))/(body height (m^2 ) ) If you get result 30-39.9, you should control your eating schedule[6]:
Mechanism have been suggested to explain how obesity might increase the risks of some cancers :
Abdominal obesity is associated with changes in the circulating concentrations of adipokines (produced by fat) and increased adipose tissue inflammation with the production of cytokines. These changes can result to increase in production of insulin from the pancreatic beta cell to maintain normal glucose levels and leading to hyperinsulinemia (high insulin in circulating blood). Endogenous insulin acting on the liver increases insulin-like growth factor I (IGF-I) synthesis causing changes in circulating concentration of IGF-binding protein (IGFBPs). These changes leading to lipid abnormalities, characterised by increased very low density lipoprotein (VLDL) and triglycerides, decreased high density lipoprotein (HDL), also lower hepatic production which may lead to increased the level of estrogen and testosterone. In addition, excess adiposity resulted local aromatisation of androgens to estrogens and may affect tumor growth[7].
Fig 1. Molecular mechanism of action of obesity-cancer link[8]
3. Cancer types are attributable to cigarette smoking
Nicotine is a common substance in tobaco smoke and is highly addictive. Nicotine is not a carcinogen. Drug metabolising enzymes such as the cytochromes P450, glutathione S-transferases, and UDP-glucuronosyl transferases are substrates for most carcinogen substances in cigarette smoke which catalyze their conversion to more water soluble forms that are detoxified and can be readily excreted. Although during this process, reactive intermediates such as carbocations or epoxides are produced and these electrophilic compounds can react with nucleophilic sites in DNA such as the nitrogen or oxygen atoms of deoxyguanosine and other DNA bases. These reactions leading to the formation of DNA adducts which are critical in the carcinogenic process. Providing the DNA adducts persist unrepaired, they can cause miscoding during DNA replication as bypass polymerases catalyse the insertion of the wrong base opposite the adduct. The result is a permanent mutation. As long as this mutation occurs in a critical region of an oncogene such as KRAS or a tumor suppressor gene such as TP53, resulted in loss of normal cellular growth control mechanisms and development of cancer.
4. Physical activity can affect your risks of cancer
Physical activity at high intensity are linked to lower risks for several cancers such as colon, breast, and endometrial cancers. According to the US Department of Health and Human Services, recommended physical activity for adults is at least 150-300 minutes per week of moderate intensity aerobic, or 75-150 minutes per week of vigorous intensity aerobic activity, or an equivalent combination of moderate and vigorous intensity aerobic activity[9]. Moderate intensity activities including brisk walking, dancing, water aerobics, gardening, and biking slower than 10 miles per hour. While vigorous intensity activities such as running, swimming, hiking, cycling 10 miles per hour, and heavy yard work[10].
Further Read:
Do animals get cancer?
REFERENCE
[1]Cancer Society of Finland, 2013, What causes cancer, https://www.allaboutcancer.fi/facts-about-cancer/what-causes-cancer/
[2]National Cancer Institute, What Is Cancer?, 2015, https://www.cancer.gov/about-cancer/understanding/what-is-cancer
[3]Harvard Women’s Health Watch, 2019, Red and processed meats raise colorectal cancer risk, https://www.health.harvard.edu/staying-healthy/red-and-processed-meats-raise-colorectal-cancer-risk
[4] Kopp, T.I., Vogel, U., Tjonneland, A., and Andersen, V., 2018, Meat and fiber intake and interaction with pattern recognition receptors (TLR1, TLR2, TLR4, and TLR10) in relation to colorectal cancer in a Danish prospective, case-cohort study, The American journal of clinical nutrition, 107(3), 465-479.
[5] Gu, M.J., Huang, Q.C., Bao, C.Z., Li, Y.J., Li, X.Q., Ye, D., Ye, Z.H., Chen,K., and Wang, J.B., 2018, Attributable causes of colorectal cancer in China, BMC cancer, 18(1), 38.
[6] Wells, B.G., Dipiro, J.T., Schwinghammer, T.L., dan Dipiro, C.V., 2015, Pharmacotherapy Handbook Ninth Edition, US: McGraw-Hill Education.
[7] Gallagher, E.J., & LeRoith, D., 2015, Obesity and diabetes: the increased risk of cancer and cancer-related mortality, Physiological reviews, 95(3), 727-748.
[8] O’Flanagan, C.H., Bowers, L.W., Allott, E.H., dan Hursting, S.D., 2017, Molecular and metabolic mechanisms underlying the obesity–cancer link, Energy Balancer and Obesity (IARC Working Group Reports 10). Lyon, France: International Agency for Research on Cancer, 95-104.
[9] Medscape, 2018, Physical Activity Guidelines Advisory Comittee of the US Dept. Of Health and Human Services, https://reference.medscape.com/viewarticle/905775
[10] American Heart Association (AHA), 2018, American Heart Association Recommendations for Physical Activity in Adults and Kids, https://www.heart.org/en/healthy-living/fitness/fitness-basics/aha-recs-for-physical-activity-in-adults