Abstract:
GSTP 1 and NQO 1 gene polymorphisms were considered to be risk indicators
of tobacco induced lung cancer. GSTP 1 gene expresses a detoxifying enzyme
and its polymorphism leads to a change in the amino acid IIe to Val at position
105 in the amino acid sequence of the enzyme. Thus changing its specificity
and activity towards potent carcinogens, like the active benzo(a) pyrene-diolepoxide
(BPDE) present in tobacco. NQO1 gene expresses a detoxifying
enzyme, it protect cells and DNA from both natural and chemical quinones.
NQO 1 gene polymorphism at position 609 in DNA sequence is a C-T
transition which leads to a change in enzymatic activity to almost null activity.
Both polymorphisms have been characterized by restriction fragment length
polymorphism (RFLP). The sampled population comprised 195 individuals
from a controlled population at both LAU Beirut and Byblos campuses. All individuals voluntarily gave sputum sample and answered a respiratory health
questionnaire. DNA was extracted from each sputum sample and polymerase
chain reaction (PCR) and RFLP were performed for each of the genes
respectively. Sampled individuals were of two age groups: 107 were under 25
and 88 were over 40. They were equally divided between smokers and nonsmokers.
For GSTP 1 the genotypic frequency distribution in the total
population was: (IT) 26.15%, (IV) 60.51% and (VV) 13.33%. While for NQO1
the genotypic frequency was (CC) 31.28%, (CT) 55.38%, (TT) 14.87%. In the
overall population a higher GSTP 1 (II) genotype frequency was determined in
smokers while (IV) and (VV) were more frequent in non-smokers. The higher
(II) frequency would suggest a lower risk of lung cancer in smokers. The
NQO 1 (CC) genotype frequency was highest in smokers while that of (CT)
and (TT) was highest in non-smokers, thus indicating a lower risk in smokers.
The stratified analysis according to age and smoking showed unreliable and
controversial spectrum of susceptibility between age groups which could be
due to decrease of sample size with subgrouping.
