Carcinogens: Cancer Causing Substances
Since the 1940s, scientists have isolated compounds and tested their ability to induce cancer. Substances which can cause cancer are known as carcinogens. The process of cancer development is called carcinogenesis. There had been a suspicion that carcinogens functioned by causing DNA mutations. One observation supporting this was that x-rays, which damage DNA, lead to an increased incidence of cancer.
Bacteria have proven to be good models for determining the mutagenic potential of compounds. Bruce Ames, a biochemist, developed an assay to identify potential mutagens. The Ames test works 'backwards' from what one might expect. The test starts with mutant bacteria and looks for chemicals that can change them back into normal (wild type) bacteria. In the Ames test, a potential mutagen is placed on a paper disc in the center of a petri dish on which only bacterial cells that mutate are able to grow. The mutagenic potential of the compound in question is determined by the amount of bacterial growth seen. Information obtained in this way was shown to be comparable to results from tests in rodents. Researchers have also manipulated mouse cells to make them potential targets for carcinogens and have transferred genes from cancerous cells into healthy mice--all of which have led to the conclusion that mutations in key genes can lead to the changes that result in cancer.
Reference:
Pitot, H.C., Goldsworthy, T., Moran, S. The natural history of carcinogenesis: Implications of experimental carcinogenesis in the genesis of human cancer. Journal of Supramolecular Structure and Cellular Biochemistry; Volume 17, Issue 2 , Pages 133 146. Published Online: 19 Feb 2004.




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