Do Toxic Chemicals Cause Cancers?

How do the chemicals in cigarettes increase the rate of growth in your cells and cause cancers?

• Answer:

  Without going into the biochemistry of it (though, if that's what you are looking for, do add that to the question), a giant plethora of chemicals in cigarettes act on cellular DNA, DNA repair mechanisms, or metabolic pathways to cause cancer. Generally speaking, they increase rate of mutation in the DNA or alter gene expression which act in one or more ways. They can "turn on" proto-oncogenes (genes that, when expressed, promote cell division) during times that they shouldn't be on, causing the cell division. Alternatively, mutations of tumor suppressor genes or change in expression of their regulators can "turn off" or "break" (mutate into a non-functional gene) a tumor-suppressor gene, which is one that, when active, inhibits cell division.