Smoking is the most potent known cause of lung cancer. The question is: Why do some longtime smokers come down with the deadly disease whereas others escape it? New research points to a genetic culprit that also was fingered as upping a person's likelihood of becoming hooked on cigarettes.

Two new studies link a variation in a gene residing on chromosome 15 (of a person's 23 pairs of chromosomes) to a heightened risk of developing lung cancer; a third study suggests that the same mutation  affects a person's tendency to become addicted to smokes and, by extension, develop the dreaded disease. Lung cancer is diagnosed in some 200,000 Americans and kills more than 150,000 each year.