sensitivity in pediatric acute lymphoblastic leukemia Effect of polymorphisms in folate-related genes on in-vitro methotrexate

We studied whether common polymorphisms in genes involved in folate metabolism affect MTX sensitivity. Ex-vivo MTX sensitivity of lymphoblasts obtained from pediatric ALL patients (n=157) was determined by the in-situ thymidylate synthase inhibition assay after either continuous (21-h; TSI50,cont) or short-term (3-h; TSI50,short) MTX exposure. DNA was isolated from lymphoblasts obtained from cytospin slides. Polymorphisms in methylenetetrahydrofolate reductase (MTHFR 677C>T, MTHFR 1298A>C), methionine synthase (MTR 2756A>G), methionine synthase reductase (MTRR 66A>G), methylenetetrahydrofolate dehydrogenase (MTHFD1 1958G>A), serine hydroxymethyl transferase (SHMT1 1420C>T), thymidylate synthase (TS 2R3R), and the reduced folate carrier (RFC 80G>A) were detected by PCR-RFLP or real-time PCR. Patients with the MTHFR 1298AC variant or the MTRR 66 G-allele showed decreased in-vitro MTX sensitivity measured under both test conditions. SHMT1 1420TT homozygotes only showed decreased MTX sensitivity in the TSI50,cont. In conclusion, polymorphisms in the folate-related genes MTHFR, MTRR, and SHMT1 are related to MTX resistance in pediatric ALL patients. only. For personal use at PENN STATE UNIVERSITY on February 23, 2013. bloodjournal.hematologylibrary.org From