Functional characterization of common protein variants in the efflux transporter ABCC11 and identification of T546M...

Area of Science:

• Pharmacogenomics
• Molecular Biology
• Cellular Transport Mechanisms

Background:

• Multidrug resistance protein 8 (ABCC11) is an efflux transporter crucial for drug resistance, particularly against antiviral and anticancer agents like 5-fluorouracil (5-FU).
• While ABCC11 missense variants are implicated in variable drug responses, their functional consequences remain largely uncharacterized, with the exception of the 'earwax variant' (c.538G>A).

Purpose of the Study:

• To investigate the functional consequences of frequently occurring ABCC11 missense variants on drug transport.
• To identify novel variants impacting 5-fluorouracil (5-FU) metabolism and toxicity.

Main Methods:

• Generation of human embryonic kidney 293 cells stably expressing various ABCC11 missense variants using 'Screen and Insert' technology.
• In silico prediction analyses, in vitro plasma membrane vesicle uptake assays, immunoblotting, and immunolocalization experiments were performed.
• Analysis of allele frequencies across 14 diverse subpopulations.

Main Results:

• The c.1637C>T (T546M) variant was identified as a novel, functionally damaging ABCC11 variant.
• This variant demonstrated markedly reduced transport function for 5-FdUMP, the active cytotoxic metabolite of 5-FU.
• The c.1637C>T variant showed the highest allele frequencies in European and American populations (up to 11%) compared to African and Asian populations (up to 3%).

Conclusions:

• The c.1637C>T ABCC11 variant significantly impairs the transport of 5-FU's active metabolite, contributing to 5-FU-related toxicity.
• This finding highlights the importance of ABCC11 genetic variations in personalized medicine, particularly for 5-FU chemotherapy.
• Ethnic-specific allele frequencies of the c.1637C>T variant suggest differential susceptibility to 5-FU toxicity across populations.