Neuroblastoma is a frequently lethal childhood
tumor in which MYC gene deregulation, commonly as MYCN amplification, portends poor outcome. Identifying the requisite biopathways downstream of MYC may provide therapeutic opportunities. We used transcriptome analyses to show that MYCN-amplified
neuroblastomas have coordinately deregulated myriad
polyamine enzymes (including ODC1, SRM, SMS, AMD1, OAZ2, and SMOX) to enhance
polyamine biosynthesis. High-risk
tumors without MYCN amplification also overexpress ODC1, the rate-limiting
enzyme in
polyamine biosynthesis, when compared with lower-risk
tumors, suggesting that this pathway may be pivotal. Indeed, elevated ODC1 (independent of MYCN amplification) was associated with reduced survival in a large independent
neuroblastoma cohort. As
polyamines are essential for cell survival and linked to
cancer progression, we studied
polyamine antagonism to test for metabolic dependence on this pathway in
neuroblastoma. The Odc inhibitor
alpha-difluoromethylornithine (DFMO) inhibited neuroblast proliferation in vitro and suppressed
oncogenesis in vivo. DFMO treatment of
neuroblastoma-prone genetically engineered mice (TH-MYCN) extended
tumor latency and survival in homozygous mice and prevented
oncogenesis in hemizygous mice. In the latter, transient Odc ablation permanently prevented
tumor onset consistent with a time-limited window for embryonal
tumor initiation. Importantly, we show that DFMO augments antitumor efficacy of conventional cytotoxics in vivo. This work implicates
polyamine biosynthesis as an arbiter of MYCN
oncogenesis and shows initial efficacy for
polyamine depletion strategies in
neuroblastoma, a strategy that may have utility for this and other MYC-driven embryonal
tumors.