Studies on the mutation and polymorphism of the TPMT gene in Chinese children with acute leukemia

Objective To investigate the allelic frequencies and distribution of single-nucleotide polymorphisms within the coding region (cSNPs) of thiopurine S-methyhransferase gene (TPMT) in Chinese children with acute leukemia (AL) and healthy controls, in order to provide genetic references for individual chemotherapy for AL patients by studying the relationship between the cSNP in human TPMT and chemotherapeutic effect of thiopurine drugs. Methods The bone marrow samples from 53 children with AL and peripheral blood samples from 115 healthy children were obtained to prepare complementary DNAs (cDNAs). The cDNAs were analyzed for the polymorphisms in the TPMT gene by reverse transcriptase-polymerase chain reaction (RT-PCR)-denaturing gradient gel electrophoresis (DGGE) and DNA sequencing. The distribution of each genotype was evaluated. Results Two novel heterozygote mutations, 210C>T (CTOC,silent) and 622T>C (F208L), were identified in the coding region of the TPMT in a single sample, respectively. The mother of the child with mutation 622T>C was confirmed as the same genotype by DGGE and sequencing (NCBI_ss accession numbers 107796292 and 107795933). Two known polymorphisms, 474T>C (silent) and 719A>G (T240C), were identified. The alletic frequencies were 14.2%, 2.83% and 17.0%, 3. 04% in the AL children and control children respectively, with the total allelic frequencies of 16.2% (first reported in the Chinese Han population) and 2.99% respectively. No association with susceptibility to disease was observed. Conclusion Two novel mutations and two known polymorphisms were identified in Chinese children by RT-PCR-DGGE combined with DNA sequencing,which provides the first step to identify genetic markers for predicting variability in response to and toxicity of thiopurine drugs. Key words: thiopurine S-methyhransferase gene;  mutation;  coding single-nucleotide polymorphisms;  denaturing gradient gel electrophoresis;  acute leukemia