ATF 5 polymorphisms influence ATF function and response to treatment in children with childhood acute lymphoblastic leukemia Running title : Polymorphisms of aspraginase pathway and ALL outcome

Asparaginase is a standard and critical component in the therapy of childhood ALL. Asparagine synthetase (ASNS), the basic region leucine zipper transcription factors ATF5 and arginosuccinate synthase 1 (ASS1) have been shown to mediate antileukemic effect of asparaginase and to display variable expression between leukemia cells that are resistant and sensitive to treatment. Fourteen polymorphisms in regulatory and coding regions of these genes were investigated for an association with ALL outcome. Lower event free survival (EFS) was associated with ATF5 T1562C, tandem repeat ASNS polymorphism and derived haplotype, as well as with ASS1 G1343T and G34T substitutions (p≤0.03). Associations were limited to patients who received E.coli asparaginase. Variations that sustained correction for multiple testing (ATF5 T1562C, p=0.005, ASNS tandem repeat and related haplotype, p≤0.01) were subsequently analyzed in the replication cohort. The E.coli dependent association of ATF5 T1562 allele with reduced EFS was confirmed (p=0.01). Gene reporter assay showed that the haplotype tagged by the T1562 had higher promoter activity (p≤0.01). Remaining regulatory polymorphisms appeared also to affect ATF5 function; two additional high-activity haplotypes were identified (p≤0.02) and further corroborated by quantitative mRNA analysis in lymphoblastoid cell lines. ATF5regulated increase in ASNS expression in a response to more efficacious E.coli induced asparagine depletion might explain observed results. For personal use only. on November 12, 2017. by guest www.bloodjournal.org From