SLEEPING BEAUTY FINDS PARTNERS OF ONCOGENIC MYC - A TRANSPOSON-BASED INSERTIONAL MUTAGENESIS SCREEN IN THE EMU-MYC MOUSE

Myc triggers a transcriptional program inducing hyper-replication and proliferation but also tumor suppressive mechanisms like apoptosis. Therefore, Myc dependent tumors display high selective pressure to accumulate secondary mutations blocking these tumor-suppressive pathways. In the Eµ-myc mouse model, Myc is constitutively expressed in the B-cell linage under the control of the immunoglobulin heavy chain enhancer. The most prominent failsafe program known to be disrupted in Eµ-myc lymphomas is the p53-ARF pathway. In order to find novel cooperating partners of Myc leading to transformation we applied a conditional Sleeping Beauty transposon-based mutagenesis screen in vivo. By adoptive transplantation of Eµ-myc hematopoietic progenitors we generated 312 experimental animals, prone for lymphoma onset. Data show a strong genetic cooperation between the Eµ-myc transgene and SB transposon mobilization with accelerated tumor onset. Arising lymphomas were of the pre/pro- and immature B-cell stage and infiltration included extra-lymphatic tissue like the liver. The genomic sequences immediately adjacent to integrated transposons of 184 lymphomas were enriched by ligation-mediated PCR and were sequenced with a multiplexed approach. Based on published (Brett et al., 2011) and new bioinformatic methods, we identify 338 common integration sites (CIS) of which 188 were found mutated in human B-cell lymphoma. Pathway and GO term analysis reveal modulation of the Ras-MAP-kinase signaling pathway. Next to well-known modulators of Myc-induced lymphomagenesis including Bcl-XL, p53, ARF and Mdm2, we find CIS that were not yet reported in Eµ-myc lymphoma like Map3K5.