CYP2E1 polymorphism, cigarette smoking, p53 expression, and survival in non-small cell lung cancer: A long term follow-up study

The expression of selected gene products involved in cell differentiation and cell growth and genetic polymorphism of detoxifying genes was examined in 105 surgically resected nonsmall cell lung cancer (NSCLC) patients, and the relationship of these factors was correlated with cigarette smoking and patient survival. Genotyping of peripheral blood lymphocytes from 87 patients was performed for CYP2E1, GSTM1, GSTT1, mEH, and MPO detoxifying genes using polymerase chain reaction. Formalin-fixed, paraffin-embedded tissue was immunostained with antibodies to p53, p27, phospho-AKT, and bcl-2 using the avidin-biotin-peroxidase method and tissue microarray technique. Tumors were assigned a positive or negative score based on more than 10% of tumor cells staining positive with the antibody. The subtypes of NSCLC included 48 adenocarcinomas, 47 squamous cell carcinomas, and 10 large cell undifferentiated carcinomas. A total of 54 tumors were pathologic stage I, 23 were stage II, and 26 were stage III. All subjects smoked (range, 10-175 pack-years; mean, 60 pack-years). The mean overall survival was 112 weeks (median, 129 weeks). Patients with p53-positive tumors had significantly fewer pack-years of smoking (52 pack-years vs 72 pack-years; P = 0.021), smoked fewer years (34 years vs 40 years; P = 0.018), and had significantly better survival compared with those with p53-negative tumors (P = 0.045). When smoking history was further analyzed, the authors found that p53 expression was associated with the number of years smoked and not the number of packs smoked per day. Patients with squamous cell carcinoma had smoked longer compared with those with adenocarcinoma (P = 0.011). Significant association was seen between the CYP2E1 wild-type allele and better survival (P = 0.016). Patients with stage I tumors had better survival compared with stages II and III (P = 0.032). No association was found between survival and tumor type; tumor differentiation; expression of phospho-AKT, p27, and bcl-2; and polymorphic metabolizing genes other than CYP2E1. The significant association of long duration of smoking (>40 years) with loss of p53 expression and poor survival suggests inactivation of the protective p53 pathway in those who had a history of more than 40 years of smoking.