Abstract 897 Hematology-Oncology I Platform, Saturday, 5/1

Neuroblastoma, a tumor of peripheral neural crest origin, is the third most common tumor of childhood. We have developed a model for neuroblastoma by targeting expression of the human MYCN gene to the peripheral neural crest of transgenic mice. These mice develop tumors with many features of childhood neuroblastoma.

To further probe the role of MYCN in transcriptional activation and in transformation, we have constructed a fusion protein between the entire MYCN structural gene and the ligand binding domain of the murine estradiol receptor. The protein product of this fusion gene is expressed constitutively, but its activity is dependent on the presence of estrogen in the cellular growth medium. We have verified that MYCN-ER can conditionally transform Rat1A cells, and can upregulate the expression of ornithine decarboxylase. In addition, we demonstrate that MYCN-ER promotes entry of quiescent rodent cells into the cell cycle, causes apoptosis in rodent cells starved for serum, and induces aneuploidy. We have introduced MYCN-ER into human neuroblastoma cells and grown the resulting cells in the presence or absence of estrogen. RNA isolated from these cells was used to probe an array of human cDNA clones to identify transcriptional targets of MYCN. The results of these studies will be discussed.

To identify genes that cooperate with MYCN in the pathogenesis of neuroblastoma, we have generated transgenic mice in a polymorphic genetic background. Tumors from these animals were collected and a genome wide mitotic screen was performed using allelic imbalance analysis. We have identified a number of genetic regions which show allelic imbalance using two or more polymorphic PCR based markers per chromosome. A comparison of these data with prior data generated by comparative genomic hybridization will be presented.