Genetic changes leading to uncontrolled cell growth and tumor formation
For the cellular mechanisms of cancer development, see Carcinogenesis and Oncogenomics.
Cancer is caused by genetic changes leading to uncontrolled cell growth and tumor formation. The basic cause of sporadic (non-familial) cancers is DNA damage and genomic instability.[1][2] A minority of cancers are due to inherited genetic mutations.[3] Most cancers are related to environmental, lifestyle, or behavioral exposures.[4] Cancer is generally not contagious in humans, though it can be caused by oncoviruses and cancer bacteria. The term "environmental", as used by cancer researchers, refers to everything outside the body that interacts with humans.[5] The environment is not limited to the biophysical environment (e.g. exposure to factors such as air pollution or sunlight), but also includes lifestyle and behavioral factors.[6]
Over one third of cancer deaths worldwide (and about 75–80% in the United States) are potentially avoidable by reducing exposure to known factors.[7][8] Common environmental factors that contribute to cancer death include exposure to different chemical and physical agents (tobacco use accounts for 25–30% of cancer deaths), environmental pollutants, diet and obesity (30–35%), infections (15–20%), and radiation (both ionizing and non-ionizing, up to 10%).[9] These factors act, at least partly, by altering the function of genes within cells.[10] Typically many such genetic changes are required before cancer develops.[10] Aging has been repeatedly and consistently regarded as an important aspect to consider when evaluating the risk factors for the development of particular cancers. Many molecular and cellular changes involved in the development of cancer accumulate during the aging process and eventually manifest as cancer.[11]
^Basu, Ashis K (23 March 2018). "DNA Damage, Mutagenesis and Cancer". Int. J. Mol. Sci. (Review). 19 (4): 970. doi:10.3390/ijms19040970. PMC 5979367. PMID 29570697.
^Ferguson LR, Chen H, Collins AR, Connell M, Damia G, Dasgupta S, et al. (December 2015). "Genomic instability in human cancer: Molecular insights and opportunities for therapeutic attack and prevention through diet and nutrition". Seminars in Cancer Biology (Review). 35 Suppl (Suppl). Elsevier: S5–S24. doi:10.1016/j.semcancer.2015.03.005. PMC 4600419. PMID 25869442.
^Roukos DH (April 2009). "Genome-wide association studies: how predictable is a person's cancer risk?". Expert Review of Anticancer Therapy (Editorial). 9 (4): 389–92. doi:10.1586/era.09.12. PMID 19374592. S2CID 24746283.
^Stewart BW, Wild CP, eds. (2014). "Cancer etiology". World Cancer Report 2014. World Health Organization. pp. 16–54. ISBN 978-9283204299.
^Cancer and the Environment: What you Need to Know, What You Can Do. NIH Publication No. 03-2039: National Institutes of Health. 2003. Cancer develops over several years and has many causes. Several factors both inside and outside the body contribute to the development of cancer. In this context, scientists refer to everything outside the body that interacts with humans as 'environmental'.{{cite book}}: CS1 maint: location (link)
^Manton KG, Akushevich I, Kravchenko J (2009). "3 Cancer Risk Factors (3.2 Environmental Cancer Risk Factors)". Cancer mortality and morbidity patterns from the U. S. population: an interdisciplinary approach. Berlin: Springer. p. 118. ISBN 978-0-387-78192-1 – via Open Library. The term environment refers not only to air, water, and soil but also to substances and conditions at home and at the workplace, including diet, smoking, alcohol, drugs, exposure to chemicals, sunlight, ionizing radiation, electromagnetic fields, infectious agents, etc. Lifestyle, economic and behavioral factors are all aspects of our environment.
^Doll R, Peto R (June 1981). "The causes of cancer: quantitative estimates of avoidable risks of cancer in the United States today". Journal of the National Cancer Institute. 66 (6): 1191–308. doi:10.1093/jnci/66.6.1192. PMID 7017215.
^Whiteman DC, Wilson LF (October 2016). "The fractions of cancer attributable to modifiable factors: A global review". Cancer Epidemiology (Review). 44. Elsevier: 203–221. doi:10.1016/j.canep.2016.06.013. ISSN 1877-783X. PMID 27460784 – via ScienceDirect.
^Anand P, Kunnumakkara AB, Kunnumakara AB, Sundaram C, Harikumar KB, Tharakan ST, Lai OS, Sung B, Aggarwal BB (September 2008). "Cancer is a preventable disease that requires major lifestyle changes". Pharmaceutical Research (Expert review). 25 (9): 2097–116. doi:10.1007/s11095-008-9661-9. PMC 2515569. PMID 18626751.
^ abWorld Cancer Report 2014. World Health Organization. 2014. pp. Chapter 1.1. ISBN 978-9283204299.
^"Cancer Fact sheet N°297". World Health Organization. February 2014. Retrieved 10 June 2014.
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