A new method for detecting polymorphisms in the TPMT gene based on Real Time PCR

摘要

Methods of molecular biology have been more and more frequently implemented for the diagnosticpurposes and optimization of pharmacotherapy. Pharmacogenomics is a scientific discipline dealing with therelationship between genotype and pharmacotherapy. An example of implementing research results into clinicalpractice is the testing of variant alleles of the gene for thiopurin S-methyltransferase (TPMT) in connection withthe azathioprine (AZA) therapy. Even though the AZA therapy in IBD patients is very effective, 10-28% ofpatients experience adverse side effects. The most serious, occurring in 2-5% of patients is leukopenia, which isconnected with the insufficient ability of an organism to biotransform active AZA derivatives [1, 2, 3]. Themajor metabolic pathway of this drug is methylation catalysed by the TPMT enzyme. Gene coding for thisenzyme occurs in several allele variants, some of which strongly correlate with the occurrence of leukopenia.Catalytic activity of TPMT is lower in carriers of these alleles, which results in accumulation of activemetabolites [4]. From the perspective of clinical impact, the most important variant alleles in the Caucasianpopulation are TPMT*3A (characterised by nucleotide substitution 460G>A and 719A>G), TPMT*3B(460G>A), TPMT*3C (719A>G), and TPMT*2 (238G>C) –see Figure 1.