Citations

Abstract Glutathione S-transferase P1 (GSTP1) is of importance for cancer research because of its role in detoxifying carcinogens, activating antineoplastic prodrugs, metabolizing chemotherapeutic agents, and its involvement in cell cycle and apoptosis regulation. Two common GSTP1 genetic polymorphisms have been studied extensively. However, the full range of GSTP1 genetic variation has not been systematically characterized in the absence of disease pathology. We set out to identify common GSTP1 polymorphisms in four ethnic groups, followed by functional genomic studies. All exons, splice junctions, and the 5′-flanking region of GSTP1 were resequenced using 60 DNA samples each from four ethnic groups. The 35 single-nucleotide polymorphisms (SNP) identified included six nonsynonymous SNPs and 17 previously unreported polymorphisms. GSTP1 variant allozymes were then expressed in COS-1 cells, and five displayed significantly altered levels of enzyme activity. One decreased to 22% of the wild-type (WT) activity. Four variant allozymes had Km values that differed significantly from that of the WT, and five showed altered levels of immunoreactive protein compared with WT, with a significant correlation (r = 0.79, P < 0.007) between levels of immunoreactive protein and enzyme activity in these samples. In the Mexican American population, five linked SNPs were significantly associated with GSTP1 mRNA expression, one of which was found by electrophoretic mobility shift assay to alter protein binding. These studies have identified functionally significant genetic variation, in addition to the two frequently studied GSTP1 nonsynonymous SNPs, that may influence GSTP1's contribution to carcinogen and drug metabolism, and possibly disease pathogenesis and/or drug response. [Cancer Res 2008;68(12):4791–801]

Thromboangiitis obliterans (TAO) is often cited as an extreme phenotype of vasculopathy and tobacco dependence. Although tobacco exposure is essential to progression of arterial ischemia in TAO, expert opinion differs regarding the degree of tobacco dependence in this population. The authors designed a prospective, case-control study to test the hypothesis that subjects with TAO have a greater degree of tobacco dependence than control subjects with coronary atherosclerosis (coronary artery disease [CAD]) do. Subjects with TAO (n=218, confirmed by angiography, biopsy, or noninvasive arterial testing) or CAD (n=343, diagnosed by coronary angiography) were mailed a standardized questionnaire regarding tobacco use, to which 103 and 273 responded, respectively. The degree of tobacco dependence in each group was ascertained by several methods, including the Fagerström Test for Nicotine Dependence Questionnaire. The TAO group was younger at index date (year of first diagnosis for TAO patients, year of percutaneous transluminal coronary angioplasty [PTCA] for CAD patients) (TAO 37.6 ±9.0 vs CAD 43.3 ±4.9 yr, p<0.0001), but the groups did not differ in age at first tobacco exposure (TAO 16.7 ±3.1 vs CAD 17.3 ±4.2 yr, p=0.67), current tobacco use at time of survey (TAO 54% vs CAD 46%, p=0.17), or Fagerström score (TAO 4.7 ±2.3 vs CAD 5.1 ±2.3, p=0.24). Kaplan-Meier curves showed no significant difference in time to stopping tobacco use after first diagnosis (p=0.076). TAO subjects smoked fewer cigarettes per day than CAD subjects (TAO 22.3 ±10.7 vs CAD 27.7 ±15.3 cigarettes/day, p=0.003). Among current smokers (n=170), TAO subjects also smoked fewer cigarettes/day (20.2 ±8.2 vs 24.6 ±12.7, p=0.03), and were more likely to have made a serious attempt to stop (97% vs 90%, p=0.03). In contrast to case reports of extreme tobacco dependence in the TAO population, the degree of tobacco dependence in subjects with TAO is similar to that in subjects with CAD.