such as K-ras (15). The strong parallels that exist in mechanisms of NNK carcinogenesis between rodents and humans led the International Agency for Research on Cancer to classify NNK as “carcinogenic to humans” (18). Thus, our data indicate that smokers who carry the CHRNA3 or A5 variant are expected to be at increased risk of lung cancer, compared to smokers who do not carry these alleles -- even if they smoke the same number of cigarettes -- because they smoke more intensely and are, therefore, exposed to greater levels of carcinogens.
