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.
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.
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
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.
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
To cite (CSE-style):
Mozo V. 2011 May 20. Lung Cancer – when your normal cells turn against
you [Internet]. biologyonline.com; [cited yyyy mmm dd]. Available from
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