Inter-individual differences in quantitative expression could underlie a propensity for lung cancer. To determine precise individual gene expression signatures on a lung compartment-specific basis, we investigated the expression of carcinogen metabolism genes encoding cytochromes P450 (CYP) 1B1, 2A13, glutathione S-transferase (GST) P1, and a tumor suppressor gene p16 in laser capture microdissected samples of human alveolar compartment (AC) and bronchial epithelial compartment (BEC) lung tissue from 62 smokers and non-smokers.
Tobacco exposure was determined by plasma nicotine, cotinine, and smoking history. Precise mRNA expression was determined using our RNA-specific qRT-PCR strategy, and correlated with detailed demographic and clinical characteristics.
Several correlations of mRNA expression included: (a) CYP1B1 in AC (positively with plasma nicotine level, P = 0.008; plasma cotinine level, P = 0.001); (b) GSTP1 in AC (positively with plasma cotinine level, P = 0.003); (c) GSTP1 in BEC (negatively with smoke dose, P = 0.043; occupational risk, P = 0.019). CYP2A13 was rarely expressed in AC, and not expressed in BEC. p16 expression was not correlated with any measured factor. For each gene, subjects showed expression that was individually concordant between these compartments. No clear association of mRNA expression with lung cancer risk was observed in this pilot analysis.
The association between lung mRNA expression and tobacco exposure implies that gene-tobacco interaction is a measurable quantitative trait, albeit with wide inter-individual variation. Gene expression tends to be concordant for alveolar and bronchial compartments for these genes in an individual, controlling for proximate tobacco exposure.