MYCN oncogene amplification is frequently observed in aggressive childhood neuroblastoma. Using an unbiased large-scale mutagenesis screen in neuroblastoma-prone transgenic mice, we identify a single germline point mutation in the transcriptional corepressor Runx1t1, which abolishes MYCN-driven tumorigenesis. This loss-of-function mutation disrupts a highly conserved zinc finger domain within Runx1t1. Deletion of one Runx1t1 allele in an independent Runx1t1 knockout mouse model is also sufficient to prevent MYCN-driven neuroblastoma development, and reverse ganglia hyperplasia, a known pre-requisite for tumorigenesis. Silencing RUNX1T1 in human neuroblastoma cells decreases colony formation in vitro, and inhibits tumor growth in vivo. Moreover, RUNX1T1 knockdown inhibits the viability of PAX3-FOXO1 fusion-driven rhabdomyosarcoma and MYC-driven small cell lung cancer cells. Despite the role of Runx1t1 in MYCN-driven tumorigenesis neither gene directly regulates the other. We show RUNX1T1 forms part of a transcriptional LSD1-CoREST3-HDAC repressive complex recruited by HAND2 to enhancer regions to regulate chromatin accessibility and cell-fate pathway genes.

Supplementary Figure Legends 1-3 from ODC1 Is a Critical Determinant of MYCN Oncogenesis and a Therapeutic Target in Neuroblastoma

Supplementary Figure 1 from ODC1 Is a Critical Determinant of MYCN Oncogenesis and a Therapeutic Target in Neuroblastoma

Supplementary Figure 3 from ODC1 Is a Critical Determinant of MYCN Oncogenesis and a Therapeutic Target in Neuroblastoma

PDF file - 65K, Treatment with cisplatin and radiation therapy increases IAP gene expression in additional medulloblastoma cell lines

PDF file - 257K, Treatment with irradiation and LBW242 leads to apoptosis in medulloblastoma cell lines

PDF file - 47K, Supplementary Table 1 The combinatorial index of medulloblastoma cell lines treated with a combination of 1uM LBW-242 and 2 Gy (Daoy, D283) or 4Gy (UW228) irradiation in a colony formation assay. A CI of < 1 denotes a synergistic interaction, a CI of 1 +/-0.2 denotes an additive interaction, and a CI of > 1 indicates an antagonistic interaction. Supplementary Table 2: Clinical characteristics of patients from which short term primary tumor cultures were derived.Supplementary Table 3: The ID50 of medulloblastoma cell lines and primary cultures treated with LBW-242 and Cisplatin, calculated from synergy assay curves using interpolated x values (Graph Pad Prism 5). (IA = Inactive as single agent; N/A = not applicable.)

Supplementary Figure 2 from ODC1 Is a Critical Determinant of MYCN Oncogenesis and a Therapeutic Target in Neuroblastoma

Abstract Medulloblastoma is the most common malignant brain tumor of childhood. Novel therapeutic strategies are urgently needed to overcome cytotoxic resistance. We hypothesized that antiapoptotic signals contribute to resistance and that treatment with proapoptotic agents could increase the efficacy of conventional therapies. A PCR array was used to assess the status of the apoptotic signaling pathway in medulloblastoma cells after treatment with cytotoxic chemotherapy. Treatment with cisplatin led to the upregulation of antiapoptotic signals, including inhibitor of apoptosis proteins (IAP), in medulloblastoma cells. We subsequently investigated the synergistic effect of a small-molecule IAP inhibitor, LBW242, in combination with cisplatin and/or radiotherapy in three human medulloblastoma cell lines and 5 short term primary patient medulloblastoma cultures. The addition of LBW242 to chemotherapy resulted in significantly increased antitumor activity with a similar effect observed in combination with radiotherapy. Measurement of caspase-8 and -9 activity indicated that the synergy resulted from induction of both the intrinsic and extrinsic apoptotic pathways. Apoptosis was confirmed by Annexin V staining and activation of caspases 3/7. Xenograft models were used to evaluate the mechanism of action and efficacy in vivo. The combination therapy significantly reduced the tumor burden in a medulloblastoma xenograft model and TUNEL analysis in a medulloblastoma orthograft confirmed in vivo induction of apoptosis. These findings support the strategy of targeting IAPs in combination with cytotoxic therapy as a novel treatment strategy for patients with medulloblastoma. Mol Cancer Ther; 11(12); 2654–63. ©2012 AACR.

Abstract 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 α-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. [Cancer Res 2008;68(23):9735–45]

516 The majority of child cancer arises in embryonal cells which have persisted beyond birth, having failed to undergo cell death following normal organogenesis in utero. The mechanism of embryonal cell persistence, and thus, tumour initiation are unknown. Resistance to spontaneous regression by neuroblasts is an important early step in human neuroblastoma tumorigenesis. We have previously shown that perinatal expression of a MYCN transgene in paravertebral murine neuroblasts mediates transient neuroblast proliferation and resistance to apoptotic cell death, as the first step in neuroblastoma tumorigenesis (Hansford et al., PNAS 2004). Here we analysed the mechanism of resistance to apoptotic cell death in primary ganglion cells from MYCN transgenic, compared with normal mice. MYCN-mediated resistance to cell death was seen in ganglion cells following a variety of different death stimuli: nerve growth factor (NGF) withdrawal, hypoxia, nutrient deprivation and doxorubicin. The mRNA expression levels of known MycN transcriptional target genes in 2-week old primary ganglion tissue from normal and MYCN transgenic mice was then assessed. We found only induction of telomerase, α-prothymosin, multidrug resistance protein-1, MCM7 minichromosome maintenance deficient-7 and ornithine decarboxylase in MYCN mouse tissues. We next used an adenoviral gene transfer system to express deletion mutant MycN proteins in normal primary ganglion cells, and showed that only the Myc Box II domain of the full-length MycN protein was necessary for MycN-mediated resistance to NGF withdrawal. Following NGF withdrawal, ganglion cells from MYCN mice demonstrated markedly reduced nuclear translocation of both apoptosis-inducing factor and caspase-activated DNAse. The response of regulatory and effector proteins in the known apoptosis pathway activated by NGF withdrawal was then studied. Following NGF withdrawal, MYCN transgenic and normal ganglion cells did not differ for the phosphorylation responses of Jun kinase, ATF2, or c-Jun, or nuclear translocation of FOXO3a and consequent Bim transcription. In contrast, translocation of Bax to mitochondria was significantly reduced in MYCN, compared with normal, ganglion cells. Taken together our data indicate a MycN-driven mechanism for death resistance in neuroblasts involving the Myc Box II domain of the MycN protein and Bax translocation, which may represent a general mechanism for embryonal cancer initiation.

The mechanisms causing persistence of embryonal cells that later give rise to tumors is unknown. One tumorigenic factor in the embryonal childhood tumor neuroblastoma is the MYCN protooncogene. Here we show that normal mice developed neuroblast hyperplasia in paravertebral ganglia at birth that completely regressed by 2 weeks of age. In contrast, ganglia from MYCN transgenic (TH-MYCN) mice demonstrated a marked increase in neuroblast hyperplasia and MycN expression during week 1. Regression of neuroblast hyperplasia was then delayed and incomplete before neuroblastoma tumor formation at 6 and 13 weeks in homo- and hemizygote mice, respectively. Paravertebral neuronal cells cultured from perinatal TH-MYCN mice exhibited 3- to 10-fold resistance to nerve growth factor (NGF) withdrawal, compared with normal mice. Both low- and high-affinity NGF receptors were expressed in perinatal neuroblast hyperplasia but not in neuroblastoma tumor tissue. MYCN transgene amplification was present at low levels in perinatal neuroblast hyperplasia from both homo-and hemizygote TH-MYCN mice. However, only in hemizygous mice did tumor formation correlate with a stepwise increase in the frequency of MYCN amplification. These data suggest that inappropriate perinatal MycN expression in paravertebral ganglia cells from TH-MYCN mice initiated tumorigenesis by altering the physiologic process of neural crest cell deletion. Persisting embryonal neural crest cells underwent further changes, such as MYCN amplification and repression of NGF receptor expression, during tumor progression. Our studies provide a model for studying perinatal factors influencing embryonal tumor initiation.