CYP2D6 T188C variant is associated with lung cancer risk in the Chinese population

Genetic susceptibility of lung cancer in Chinese population: An overview of systematic reviews and meta-analyses

BACKGROUND

Genetic susceptibility of lung cancer has been widely studied for Chinese population, and meta-analysis of candidate gene association studies has also been performed for those genes. However, the overall evidence has not been well recognized.

OBJECTIVE

To investigate genetic association for the risk of lung cancer in Chinese.

METHOD

An overview of systematic reviews and meta-analyses of candidate gene association studies for lung cancer in Chinese was performed up to August 10^th , 2016. The AMSTAR tool was used to assess the quality of the included systematic reviews and meta-analyses. Bibliometric analysis was performed to analyze the characteristics of reviews.

RESULTS

A total of 21 variants in 17 genes from 20 meta-analyses were included in this study. All 20 meta-analyses were published from 2011 to 2016. The quality scores of AMSTAR ranged from 3 to 7. All included genes were in the pathogenesis of lung cancer, such as the CYPs genes, GSTs genes, and base excision repair genes. Three polymorphisms were found to be associated with decreased risk of lung cancer for Chinese, 15 polymorphisms were found to be associated with increased risk of lung cancer for Chinese, but three polymorphisms were found to be not associated with lung cancer risk for Chinese.

CONCLUSION

The current study supports the genetic risk factors of lung cancer for Chinese are more likely to be variants from genes that contribute to the etiology of lung cancer.

Impact of physiological, pathological and environmental factors on the expression and activity of human cytochrome P450 2D6 and implications in precision medicine

With only 1.3-4.3% in total hepatic CYP content, human CYP2D6 can metabolize more than 160 drugs. It is a highly polymorphic enzyme and subject to marked inhibition by a number of drugs, causing a large interindividual variability in drug clearance and drug response and drug-drug interactions. The expression and activity of CYP2D6 are regulated by a number of physiological, pathological and environmental factors at transcriptional, post-transcriptional, translational and epigenetic levels. DNA hypermethylation and histone modifications can repress the expression of CYP2D6. Hepatocyte nuclear factor-4α binds to a directly repeated element in the promoter of CYP2D6 and thus regulates the expression of CYP2D6. Small heterodimer partner represses hepatocyte nuclear factor-4α-mediated transactivation of CYP2D6. GW4064, a farnesoid X receptor agonist, decreases hepatic CYP2D6 expression and activity while increasing small heterodimer partner expression and its recruitment to the CYP2D6 promoter. The genotypes are key determinants of interindividual variability in CYP2D6 expression and activity. Recent genome-wide association studies have identified a large number of genes that can regulate CYP2D6. Pregnancy induces CYP2D6 via unknown mechanisms. Renal or liver diseases, smoking and alcohol use have minor to moderate effects only on CYP2D6 activity. Unlike CYP1 and 3 and other CYP2 members, CYP2D6 is resistant to typical inducers such as rifampin, phenobarbital and dexamethasone. Post-translational modifications such as phosphorylation of CYP2D6 Ser135 have been observed, but the functional impact is unknown. Further functional and validation studies are needed to clarify the role of nuclear receptors, epigenetic factors and other factors in the regulation of CYP2D6.