Genic-intergenic polymorphisms of CYP1A genes and their clinical impact

The humancytochrome P450 1A (CYP1A) subfamily genes, CYP1A1 and CYP1A2, encoding monooxygenases are critically involved in biotransformation of key endogenous substrates (estradiol, arachidonic acid, cholesterol) and exogenous compounds (smoke constituents, carcinogens, caffeine, therapeutic drugs). This suggests their significant involvement in multiple biological pathways with a primary role of maintaining endogenous homeostasis and xenobiotic detoxification. Large interindividual variability exist in CYP1A gene expression and/or catalytic activity of the enzyme, which is primarily due to the existence of polymorphic alleles which encode them. These polymorphisms (mainly single nucleotide polymorphisms, SNPs) have been extensively studied as susceptibility factors in a spectrum of clinical phenotypes. An in-depth understanding of the effects of polymorphic CYP1A genes on the differential metabolic activity and the resulting biological pathways is needed to explain the clinical implications of CYP1A polymorphisms. The present review is intended to provide an integrated understanding of CYP1A metabolic activity with unique substrate specificity and their involvement in physiological and pathophysiological roles. The article further emphasizes on the impact of widely studied CYP1A1 and CYP1A2 SNPs and their complex interaction with non-genetic factors like smoking and caffeine intake on multiple clinical phenotypes. Finally, we attempted to discuss the alterations in metabolism/physiology concerning the polymorphic CYP1A genes, which may underlie the reported clinical associations. This knowledge may provide insights into the disease pathogenesis, risk stratification, response to therapy and potential drug targets for individuals with certain CYP1A genotypes.

Association of CYP1A2 and GST gene variants with asthma in cases presenting with allergic chronic rhinosinusitis

Background

Inter-individual differences in regulation and activity of xenobiotic metabolizing enzymes (XMEs) CYP1A and GST might cause distinct susceptibility to chronic rhinosinusitis (CRS) phenotypes that need to be explored. Therefore, the present study aimed to evaluate the role and risk of CYP1A and GST gene variants in allergic CRS subjects with and without asthma. A total of 224 allergic CRS cases with asthma, 252 allergic CRS cases without asthma, and 350 healthy control subjects were subjected to genetic analysis. Gene variants of cytochrome P450 (CYP1A1 T3801 rs4646903, A2455G rs1048943, C2453A rs1799814 and CYP1A2 G3858A rs2069514, T739G rs2069526, C163A rs762551) and glutathione S-transferase P (GSTP1 A313G rs1605 & C341T rs1799811) were investigated by polymerase chain reaction-restriction fragment length polymorphism and GSTM1null, and GSTT1null by multiplex PCR methods.

Results

TG genotype of CYP1A2 rs2069526 (OR 1.73, 95% CI 1.20–2.50, p < 0.002), TC genotype of CYP1A1 rs4646903 (OR 1.43, 95% CI 1.03–1.98, p < 0.031) and GSTM1del (OR 1.87, 95% CI 1.24–2.81, p < 0.003) and were found to be significantly associated with only allergic CRS cases. CYP1A2 rs2069526 (OR 2.33, 95% CI 1.61–3.37, p < 0.001), GG genotype of GSTP1 rs1605 (OR 4.75, 95% CI 2.62–8.63, p < 0.001), GSTM1del (OR 1.82, 95% CI 1.19–2.78, p < 0.006), GSTM1/GSTT1 double null (OR 2.58, 95% CI 1.36–4.87, p < 0.004) and were found to be significantly associated with asthma in allergic CRS cases. Further, G-G-C haplotype of CYP1A2 rs2069514, rs2069526 and rs762551 gene variants was found to increase the risk for asthma by 5 folds in allergic CRS subjects (OR 5.53, 95% CI 1.76–17.31, p < 0.003) while T-G-C haplotype of CYP1A1 rs4646903, rs1048943, rs1799814 (OR 0.11, 95% CI (0.01–0.95, p < 0.045) and A-T haplotype of GSTP1 rs1605, rs1799811 (OR 0.27, 95% CI (0.08–0.89, p < 0.032) showed protective effect in allergic CRS group.

Conclusion

The present study reports the significantly increased association of CYP1A2, GSTM, and GSTP gene variants with asthma in allergic CRS.

Application of CRS-PCR-RFLP to identify CYP1A1 gene polymorphism

BACKGROUND

Cytochrome P4501A1 (CYP1A1) is a member of the cytochrome P450 gene family and plays an important role in the metabolism of exogenous and endogenous material. In recent research, it has been shown that its genetic polymorphisms are associated with many diseases. But the isoschizomers such as the BsrDI enzyme required for the detection of this polymorphism are expensive.

METHODS

The study used an improved PCR-RFLP method with mismatched base for detection of the single-nucleotide polymorphism rs1048943. A new restriction enzyme cutting site was created by created restriction site PCR (CRS-PCR), and the restriction enzyme StyI for RFLP was cheaper than other enzymes. A total of 320 samples from Han Chinese were tested to evaluate this novel method. The PCR results were confirmed by DNA sequencing.

RESULTS

After detecting 320 Chinese Han individuals, the genotype frequencies were 63.74% for AA, 31.54% for AG, and 4.72% for GG. The allelic frequencies were 75.48% for A and 24.52% for G. The x² test showed the genotype and allele frequencies of CYP1A1 do not deviate from Hardy-Weinberg equilibrium, and the sequences of amplified products were consistent with the one published in GenBank with the exception of mismatched base.

CONCLUSIONS

Based on PCR with mismatched primers we designed, the CYP1A1 polymorphism could be identified effectively with low cost.

Genetic polymorphisms in promoter and intronic regions of CYP1A2 gene in Roma and Hungarian population samples

The purpose of this study was to determine the interethnic differences of four CYP1A2 drug metabolizing enzyme variants. A total of 404 Roma and 396 Hungarian healthy subjects were genotyped for -163C>A, -729C>T, -2467delT and -3860G>A variants of CYP1A2 by RT-PCR and PCR-RFLP technique. The -3860A and -729T allele were not detectable in Roma samples, while in Hungarian samples were present with 2.02% and 0.25% prevalence, respectively. There was a 1.5-fold difference in presence of homozygous -163AA genotype between Hungarian and Roma samples (49.5% vs. 31.9%, p<0.001). The -163A allele frequency was 68.6% in Hungarians and 56.9% in Romas (p=0.025). The -2467delT allele frequency was 6.81% in Roma group and 5.81% in Hungarians. The most frequent allelic constellation was -3860G/-2467T/-729C/-163A in both populations. In conclusion, Hungarians have markedly elevated chance for rapid metabolism of CYP1A2 substrates, intensified procarcinogen activation and increased risk for cancers.

CYP1A1 gene polymorphisms and smoking status as modifier factors for lung cancer risk

OBJECTIVE

Lung cancer remains the most prevalent malignancy worldwide. Susceptibility to lung cancer has been shown to be modulated by inheritance of polymorphic genes. Several metabolic enzymes are currently under investigation for their possible role in lung cancer susceptibility, including members of the cytochrome P450 (CYP) superfamily. The aim of this work was to identify the correlation between CYP1A1 m1 and m2 polymorphisms and lung cancer risk and figure its interactions with smoking as genetic modifiers in the etiology of lung cancer in the Egyptian population.

MATERIALS AND METHODS

One hundred and ten patients with lung cancer and one hundred and ten controls were enrolled in the study. CYP1A1 m1 and m2 polymorphisms were determined using polymerase chain reaction restriction fragment length polymorphism.

RESULTS

Subjects carrying TC and CC genotypes of CYP1A1 m1 and AG and GG genotypes of CYP1A1 m2 were significantly more likely to develop lung cancer especially squamous cell carcinoma. The proportion of lung cancer attributable to the interaction of smoking and CYP1A1 m1 and CYP1A1 m2 polymorphisms was 32% and 52% respectively.

CONCLUSION

Our results revealed that CYP1A1 m1 and m2 polymorphisms contribute to smoking related lung cancer risk in the Egyptian population.