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Lung Cancer - when your normal cells turn against you

By Vicki Mozo



Lung cancer is a disease affecting many men and women from around the world. It continues to become an important source of medical concern due to the high mortality rate associated with lung cancer.1

From normal to becoming cancerous

Lung cancer, similar to other cancers, is a result of the abnormal growth of neoplastic cells, which used to be normal somatic cells. Under normal conditions, the somatic cells of our body divide mitotically. Mitosis is a strictly regulated cellular process. However, there are instances when the regulators of mitosis are disrupted leading to an awry, unrestrained cell division. Eventually, a mass of cells known as tumor is formed. If the tumor is benign, it means it is not recurrent and not generally harmful to health, especially when it is removed surgically. When a tumor recurs even after removal and if it affects the health of the individual, it may be regarded as malignant. And if any of the neoplastic cells eventually becomes capable of metastasis, it can spread to other parts of the body and set out a new mass of neoplastic cells. At this stage, the malignant cells have become cancerous and grown aggressively, invading other body tissues not just lungs. 2 What makes lung cells cancerous and develop lung cancer is the exposure of the individual to the cancer-predisposing substances called carcinogens found typically in the air.

The culprit

Does smoking lead to lung cancer?  This is truly a heated debate you've probably watched from documentaries (even read in fictional stories such as in John Grisham's The Runaway Jury).  Amidst the high number of people smoking, many of them refute this notion since not all smokers eventually develop lung cancer.  Nevertheless, an epidemiological study by NIH has found that a pattern depicting the growing number of smokers accord to that of the mounting number of lung cancers (see figure).   Other independent research groups have also found a strong correlation between lung cancer and cigarette smoking, with about 90% lung cancer mortality is linked to smoking.3  Thus, an assumption that smoking is one of the major causes of lung cancer persists since several cases of lung cancer involve individuals who are smokers.  If they are correct, how come not all smokers develop lung cancer?  Presumably, the reason lies on the various factors that predispose the individual to develop cancer, as well as the extent and history of cigarette smoking comes to play.




NIH graph showing the correlation and time-lag between tobacco smoking and lung cancer rate in the U.S. male population.
[Source: Wikipedia]


A typical cigarette or tobacco contains an overwhelming number of carcinogens; the two most important chemical compounds in a tobacco smoke include the nitrosamines and benzopyrene.4  A person exposed to these compounds is at risk to forming lung cancer but the likelihood depends on the extent of exposure over time. The longer is the exposure to cigarette carcinogens the higher is the probability a lung cancer will develop.

Cigarette or tobacco smoking is not only the major factor leading to lung cancer.  Another major factor is the quality of air we breathe.  Inhaling air pollutants, such as radon, can lead to mutations and subsequently to lung cancer.  Radon, a radioactive gas, is in fact, the second leading factor associated with lung cancer.5

Certain respiratory diseases such as asbestos-related lung disease and viral infections can also lead to lung cancer.  Asbestos are toxic and dangerous to health when inhaled by damaging lung tissues.  Human papillomavirus, simian virus 40, and cytomegalovirus, are some of the viruses associated with lung cancer by disrupting the cell cycle process or by inhibiting apoptosis.

Recent findings on smoking and lung cancer

A recent study has shown that people who smoke immediately after waking up have greater risk for lung cancer.  The research team has found that people who take their first cigarette for the day within an hour after waking up were about 1.3 times more likely to have lung cancer and those who smoked within 30 minutes after waking up were 1.79 times more at risk.6


1 National Cancer Institute. (2009). Lung cancer. http://www.nlm.nih.gov/medlineplus/lungcancer.html
2 Stöppler MC. (2011). Lung cancer. http://www.medicinenet.com/script/main/art.asp?articlekey=406&page=1
3 Peto R, Lopez AD, Boreham J, Thun M. (2006). Mortality from smoking in developed countries 1950–2000: Indirect estimates from National Vital Statistics. Clinical Trial Service Unit & Epidemiological Studies Unit.
4 Hecht S. (2003). Tobacco carcinogens, their biomarkers and tobacco-induced cancer. Nature Reviews Cancer, 3(10), 733–744. doi:10.1038/nrc1190
5 Catelinois O, Rogel A, Laurier D, Billon S, Hemon D, Verger P, Tirmarche M. (2006). Lung cancer attributable to indoor radon exposure in france: impact of the risk models and uncertainty analysis. Environ. Health Perspect., 114(9), 1361–1366. doi:0.1289/ehp.9070.
6 Dallas ME. (2011). Morning smokers may be at higher cancer risk. http://yourlife.usatoday.com/health/story/2011/08/Morning-smokers-may-be-at-higher-cancer-risk/49883834/1


To cite (CSE-style):

Mozo V. 2011 May 20. Lung Cancer - when your normal cells turn against you [Internet]. Biology-Online.org; [cited yyyy mmm dd]. Available from http://www.biology-online.org


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