HPGDS and lung cancer: For example, glutathione S-transferase (GST) null genotypes seem to be related to a higher incidence of polycyclic aromatic hydrocarbon DNA adducts and a higher risk of lung cancer,42-45 yet some studies have found no such associations.46 One study showed an increased risk of lung cancer among individuals combining GST null genotype and a smoking consumption of at least 35 pack-years.47 Certainly, many tobacco carcinogens are metabolized by enzymes of the P450 cytochrome family and GST family.