TPMT gene expression is increased during maintenance therapy in childhood acute lymphoblastic leukemia patients in a TPMT gene promoter variable number of tandem repeat-dependent manner

Abstract

Aims: 6-mercaptopurine influences in vitro TPMT gene expression in a TPMT promoter variable number of tandem repeats (VNTR)-dependent manner. We studied TPMT expression following 6-mercaptopurine and methotrexate administration in childhood acute lymphoblastic leukemia (ALL) patients and the pharmacogenomic potential of the VNTR architecture.

Materials & methods: TPMT gene expression was determined in childhood ALL patients at diagnosis (n = 57) and during the maintenance therapy (n = 27).

Results: A threefold increase of TPMT gene expression was obtained during maintenance therapy, modulated by the architecture of the VNTR region.

Conclusion: The TPMT promoter genetic variants need to be considered at the very beginning of the maintenance therapy for childhood ALL patients. The TPMT promoter VNTR region may serve as a pharmacogenomic biomarker when introducing thiopurine therapy.

Keywords: 6-mercaptopurine; TPMT expression; TPMT genetic variations; VNTR; childhood acute lymphoblastic leukemia; maintenance therapy; pharmacogenomics; variable number of tandem repeats.