Functional single nucleotide polymorphism haplotypes in the human equilibrative nucleoside transporter 1.

Area of Science:

• Pharmacogenomics
• Molecular Biology
• Cancer Therapeutics

Background:

• The human equilibrative nucleoside transporter 1 (hENT1) is crucial for delivering cytosine arabinoside (AraC), a key chemotherapy drug for acute leukemias and lymphomas.
• Understanding genetic variations in the hENT1 gene promoter is essential for predicting treatment response.

Purpose of the Study:

• To identify single nucleotide polymorphisms (SNPs) and haplotypes in the hENT1 gene promoter that influence gene expression.
• To investigate the functional impact of these genetic variations on hENT1 expression and potential implications for AraC chemosensitivity.

Main Methods:

• Screening of approximately 1.6 kb upstream of the hENT1 transcription start site for SNPs.
• Reporter gene assays (luciferase) using transfected Cos-1 cells to measure promoter activity of different haplotypes.
• Real-time quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) to assess hENT1 transcript levels in relation to specific haplotypes.

Main Results:

• Identified SNPs at positions -706G>C, -1345C>G, and -1050G>A with varying frequencies across ethnic groups.
• Four hENT1 promoter haplotypes (CGG, CAG, CGC, GAG) were analyzed; CAG, CGC, and GAG showed significantly higher reporter activity compared to CGG.
• In vitro and in vivo analyses suggested that hENT1 promoter haplotypes, rather than single SNPs, significantly influence hENT1 gene expression levels.

Conclusions:

• hENT1 promoter haplotypes can modulate hENT1 gene expression.
• These variations may play a role in determining individual sensitivity to AraC chemotherapy in acute leukemias and lymphomas.
• Further research is warranted to confirm the clinical impact of hENT1 promoter haplotypes on AraC treatment outcomes.