Brief report Polymorphism G80A in the reduced folate carrier gene and its relationship to methotrexate plasma levels and outcome of childhood acute lymphoblastic leukemia

Methotrexate (MTX) is a key compound of chemotherapeutic regimens used in the treatment of childhood acute lymphoblastic leukemia (ALL). Resistance to this drug may arise by, among other factors, altered cellular uptake that may hamper the efficacy of the treatment. Recently, a G80A polymorphism has been described in the reduced folate carrier gene (RFC1), which encodes the major MTX transporter. Here, we assessed the association between the genetic polymorphisms G80A and both MTX plasma levels and childhood ALL outcome. Children with the A80 variant had worse prognoses than patients with the GG genotype (P .04), as shown by event-free survival estimates. Patients homozygous for A80 had higher levels of MTX (P .004) than the other genotype groups. Possible explanations for observed associations are discussed; however, additional experiments are required to achieve understanding of the underlying mechanism. (Blood. 2002;100: 3832-3834)