Variants in the CYP2B6 3'UTR Alter In Vitro and In Vivo CYP2B6 Activity: Potential Role of MicroRNAs

Area of Science:

• Pharmacogenomics
• Molecular Biology
• Drug Metabolism

Background:

• CYP2B6 genetic variants, particularly CYP2B6*6 and CYP2B6*18, are known to reduce enzyme activity.
• However, these known variants do not fully explain the observed inter-individual variability in CYP2B6 activity.
• Genetic variations in the 3' untranslated region (3'UTR) are increasingly recognized for their role in regulating gene expression and influencing drug response.

Purpose of the Study:

• To investigate the impact of 3'UTR genetic variants on CYP2B6 activity and its contribution to drug metabolism variability.
• To identify specific 3'UTR variants associated with altered efavirenz pharmacokinetics.
• To elucidate the mechanism by which 3'UTR variants affect CYP2B6 activity, focusing on microRNA regulation.

Main Methods:

• Analysis of five 3'UTR variants in relation to efavirenz AUC0-48 (8-OH-EFV/EFV) ratios in healthy volunteers.
• In silico prediction of microRNA binding site creation by the rs70950385 variant.
• In vitro luciferase reporter assays to confirm the functional impact of the rs70950385 variant on microRNA-mediated regulation.

Main Results:

• Five 3'UTR variants were significantly associated with altered efavirenz AUC0-48 ratios.
• The rs70950385 (AG>CA) variant was linked to a 33% decrease in CYP2B6 activity in normal metabolizers.
• Luciferase assays confirmed that the variant allele (CA) created a miR-1275 binding site, reducing CYP2B6 activity by 11.3% compared to the wild-type allele (AG).

Conclusions:

• A CYP2B6 3'UTR variant (rs70950385) contributes significantly to inter-individual variability in CYP2B6 activity.
• This variant exerts its effect by creating a microRNA binding site, leading to reduced enzyme expression or activity.
• Understanding these genetic factors is crucial for predicting drug response and optimizing pharmacotherapy.