Cigarette smoke causes lung cancer because it suppresses production of a "caretaker" protein that normally fixes DNA and compels faulty cells to self-destruct, according to researchers at the Oregon Health & Science University Cancer Institute.

Science Daily reported May 14 that researcher Laura Hays, Ph.D., and colleagues found that smoking slows production of the FANCD2 protein, which leads to DNA damage and cancer.

"These findings show the important role FANCD2 plays in protecting lung cells against cigarette smoke, and may explain why cigarette smoke is so toxic to these cells," said Hays.

The study was published in the May 2008 issue of the British Journal of Cancer.