MYCN amplification confers enhanced folate dependence and methotrexate sensitivity in neuroblastoma

// Diana T. Lau 1 , Claudia L. Flemming 1 , Samuele Gherardi 2 , Giovanni Perini 2 , Andre Oberthuer 3 , Matthias Fischer 3 , Dilafruz Juraeva 4 , Benedikt Brors 4 , Chengyuan Xue 1 , Murray D. Norris 1 , Glenn M. Marshall 1,5 , Michelle Haber 1 , Jamie I. Fletcher 1,* and Lesley J. Ashton 6,* 1 Children’s Cancer Institute Australia, Lowy Cancer Research Centre, Randwick, NSW, Australia 2 Department of Biology, University of Bologna, Bologna, Italy 3 Children’s Hospital, Department of Pediatric Oncology and Hematology, University of Cologne and Centre for Molecular Medicine Cologne, Cologne, Germany 4 Division of Theoretical Bioinformatics, German Cancer Research Center, Heidelberg, Germany 5 Kids Cancer Centre, Sydney Children’s Hospital, Randwick, NSW, Australia 6 Faculty of Medicine, School of Women’s and Children’s Health, University of New South Wales, Sydney, NSW, Australia and Research Portfolio, University of Sydney, Sydney, NSW, Australia * These authors have contributed equally to this work Correspondence to: Jamie I. Fletcher, email: // Lesley J. Ashton, email: // Keywords : MYCN, MYC, SLC19A1, methotrexate, neuroblastoma Received : February 10, 2015 Accepted : March 10, 2015 Published : March 30, 2015 Abstract MYCN amplification occurs in 20% of neuroblastomas and is strongly related to poor clinical outcome. We have identified folate-mediated one-carbon metabolism as highly upregulated in neuroblastoma tumors with MYCN amplification and have validated this finding experimentally by showing that MYCN amplified neuroblastoma cell lines have a higher requirement for folate and are significantly more sensitive to the antifolate methotrexate than cell lines without MYCN amplification. We have demonstrated that methotrexate uptake in neuroblastoma cells is mediated principally by the reduced folate carrier (RFC; SLC19A1 ), that SLC19A1 and MYCN expression are highly correlated in both patient tumors and cell lines, and that SLC19A1 is a direct transcriptional target of N-Myc. Finally, we assessed the relationship between SLC19A1 expression and patient survival in two independent primary tumor cohorts and found that SLC19A1 expression was associated with increased risk of relapse or death, and that SLC19A1 expression retained prognostic significance independent of age, disease stage and MYCN amplification. This study adds upregulation of folate-mediated one-carbon metabolism to the known consequences of MYCN amplification, and suggests that this pathway might be targeted in poor outcome tumors with MYCN amplification and high SLC19A1 expression.