Abstract 2156: Childhood exposure to secondhand smoke, nicotine dependence, and DRD1 are associated with lung cancer risk

Children who are exposed to secondhand smoke (SHS) are faced with an increased risk of nicotine dependence later in life. We have previously shown that children exposed to SHS have an increased risk of lung cancer as adults. Furthermore, genetic variation plays a role in the susceptibility of individuals to lung cancer. The gene DRD1 mediates dopamine signaling following nicotine exposure, thus we reasoned that DRD1 may be related to lung cancer via modulation of the nicotine reward pathway. Our previous studies identified 4 SNPs (rs4809294, rs2292975, rs4861327, rs686) that were predicted to modulate a microRNA binding site and we assessed the association of these SNPs with lung cancer risk. Our current study investigated whether these SNPs were associated with nicotine dependence and whether this had a subsequent effect on lung cancer risk. We used the National Cancer Institute-Maryland lung cancer case-control study. Cases and controls were recruited from the greater Baltimore metropolitan area. We used ordinal logistic regression to examine the association between SNPs and nicotine dependence. Logistic regression adjusted for age, gender and smoking was used to assess the association between SNPs and lung cancer risk. No significant associations were found between genotypes in the 4 SNPs and nicotine dependence levels (n=1,450). Individuals with the heterozygous allele (AG) exposed to SHS during childhood had increased odds of lung cancer compared to those with the homozygous wild type allele (AA) for rs686 (OR=1.52, CI= 1.12, 2.07). Individuals with the homozygous variant allele (GG) exposed to childhood SHS had increased odds of lung cancer compared to individuals with the homozygous wild type allele (AA) (OR=2.11, CI= 1.45, 3.10). Individuals with the heterozygous allele (GA) and the highest levels of nicotine dependence who were also exposed to childhood SHS, had higher odds of lung cancer than those with the homozygous recessive allele (AA) (OR=3.50, CI=1.37, 8.96). Consistent with earlier findings, heterozygotes (AG) had increased odds of lung cancer but this was not statistically significant (OR=1.90, CI= 0.82, 4.40). To further explore this association, we examined the effect of race on this relationship. Caucasians with the heterozygous allele (AG), the highest levels of nicotine dependence and childhood SHS, had increased odds of lung cancer compared to those with the homozygous recessive allele (AA) for rs686 (OR=1.47, CI=1.06, 2.05). Caucas