How Do Cigarettes Cause Cancer?

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It is now well established that cancer is caused by mutations (usually multiple) in the genes that control the way in which cells mature and divide. Cigarette smoke consists of a mixture containing thousands of different organic chemicals. Many of these compounds are carcinogenic (cancer- producing). They act on the DNA of the cell and change the genetic code within genes. When changes in this code occur in certain genes (oncogenes=cancer genes, and tumor suppressor genes) the behavior of the cell changes. A normal cell does not multiply unless there is a good reason for it to do so. When it does multiply, it stops when it receives an order from the body to do so. The normal cell matures; it stays in contact with other cells of the same kind to form a tissue. It does not harm it's local environment, and it does not stray into other parts of the body. This is because the normal cell has genes that represent a sort of computer program or blueprint specifying the proper behavior of the cell. When the normal genes are damaged, the cell can take on abnormal behaviors.

Usually one mutation will not cause a cancer. Over the years, as exposure to carcinogens continues, the number of mutations builds up, and the behavior of the damaged cells becomes increasingly bizzare and dangerous. First the cells become atypical, then dysplastic, before becoming frankly cancerous. These changes were clearly documented in dogs exposed to tobacco smoke by Dr. Oscar Auerbach in New Jersey in the 1950s and have since been repeatedly documented by other scientists.

In the past few years, there has been an explosive growth of precise information concerning the genes that are involved with cancer. This knowledge offers hope that we will soon have more effective treatment of lung cancer on a molecular level. For more information on genetic changes in cancer try this site. Cancer Genome Project