Review
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Oncol. Feb 10, 2016; 7(1): 54-86
Published online Feb 10, 2016. doi: 10.5306/wjco.v7.i1.54
Historical review of the causes of cancer
Clarke Brian Blackadar
Clarke Brian Blackadar, Department of Food Science, Ontario Agricultural College, University of Guelph, Guelph, ON N1G 2W1, Canada
Author contributions: Blackadar CB solely contributed to this review.
Conflict-of-interest statement: I declare that I have no conflicts of interest.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Clarke Brian Blackadar, Visting Researcher, Department of Food Science, Ontario Agricultural College, Universtity of Guelph, 50 Stone Rd E, Guelph, ON N1G 2W1, Canada. c.brianblackadar@hotmail.com
Telephone: +1-519-7807420 Fax: +1-519-8246631
Received: August 20, 2015
Peer-review started: August 22, 2015
First decision: September 22, 2015
Revised: October 31, 2015
Accepted: November 24, 2015
Article in press: November 25, 2015
Published online: February 10, 2016
Abstract

In the early 1900s, numerous seminal publications reported that high rates of cancer occurred in certain occupations. During this period, work with infectious agents produced only meager results which seemed irrelevant to humans. Then in the 1980s ground breaking evidence began to emerge that a variety of viruses also cause cancer in humans. There is now sufficient evidence of carcinogenicity in humans for human T-cell lymphotrophic virus, human immunodeficiency virus, hepatitis B virus, hepatitis C virus, human papillomavirus, Epstein-Barr virus, and human herpes virus 8 according to the International Agency for Research on Cancer (IARC). Many other causes of cancer have also been identified by the IARC, which include: Sunlight, tobacco, pharmaceuticals, hormones, alcohol, parasites, fungi, bacteria, salted fish, wood dust, and herbs. The World Cancer Research Fund and the American Institute for Cancer Research have determined additional causes of cancer, which include beta carotene, red meat, processed meats, low fibre diets, not breast feeding, obesity, increased adult height and sedentary lifestyles. In brief, a historical review of the discoveries of the causes of human cancer is presented with extended discussions of the difficulties encountered in identifying viral causes of cancer.

Keywords: Infections, Causes, Cancer, Carcinogens, Historical, Etiology, International agency for research on cancer

Core tip: The International Agency for Research on Cancer has worked for around 45 years evaluating the scientific literature, concerning the potential of around 1000 different agents to cause cancer. Those agents which were determined to definitively cause cancer in humans are reviewed from a historical perspective. It is reviewed how there were many complexities in identifying infectious agents as causes of cancer. The author incidentally discovered while writing this review that natural factors are an additional and relatively underappreciated cause of cancer.