Cancer-causing chemicals oncogenes

In the study of the patients with kidney cancer associated with the use of aristolochia, samples of kidney tissue were taken from patients. When analysed these were found to contain aristolochic acid, a known constituent of the herb. Molecules related to aristolochic acid were found bound to DNA from aU the kidney samples analysed. When molecules of a chemical become bound to DNA, dysfunction of the molecule can result in various ways. The binding to DNA can lead to mutations or other disturbances in DNA function which underlie cancer, such as switching on cancer genes or oncogenes. Many carcinogens (or their active metabolites) have been found to bind to DNA and this is believed to be part of the process by which chemicals cause cancer. 

Following identihcation of the Rous sarcoma virus, a substantial number of additional tumor-causing (oncogenic) viruses have been identified. We are left with the key question of how to reconcile two observations on the one hand, chemicals or chemical substances cause cancer, on the other hand, viruses cause cancer. These observations split the oncology community into two camps. As frequently happens in science, neither camp had the full story and the two opposing viewpoints proved to be entirely compatible. 

If the chemical is absorbed and bypasses our defenses, the chemical must then get into a cell or activate a receptor (a chemical switch) to have an effect. The binding to a receptor, which requires some specific chemical attribute, can then alter the cell s function or even activate a so-called oncogene that can result in cancer. Binding to a receptor itself is a dose-response phenomenon, and there is a threshold below which no effect is caused. 

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