Cell lines from MYCN transgenic murine tumours reflect the molecular and biological characteristics of human neuroblastoma.

Overexpression of the human MYCN oncogene driven by a tyrosine hydroxylase promoter causes tumours in transgenic mice that recapitulate the childhood cancer neuroblastoma. To establish an in vitro model to study this process, a series of isogenic cell lines were developed from these MYCN-driven murine tumours. Lines were established from tumours arising in homozygous and hemizygous MYCN transgenic mice. Hemizygous tumours gave rise to cell lines growing only in suspension. Homozygous tumours gave rise to similar suspension lines as well as morphologically distinct substrate-adherent lines characteristic of human S-type neuroblastoma cells. FISH analysis demonstrated selective MYCN transgene amplification in cell lines derived from hemizygous mice. Comparative genomic hybridisation (CGH) and fluorescence in situ hybridisation (FISH) analysis confirmed a range of neuroblastoma-associated genetic changes in the various lines, in particular, gain of regions syntenic with human 17q. These isogenic lines together with the transgenic mice thus represent valuable models for investigating the biological characteristics of aggressive neuroblastoma.

Effects of MYCN antisense oligonucleotide administration on tumorigenesis in a murine model of neuroblastoma.

BACKGROUND: Human MYCN (hMYCN) oncogene amplification is a powerful predictor of treatment failure in childhood neuroblastoma, and dysregulation of hMYCN protein expression appears to be critically involved in the pathogenesis of this disease. We used hMYCN antisense (AS) oligonucleotides to investigate, both in vitro and in vivo, the therapeutic potential of inhibiting hMYCN expression. METHODS: We transiently transfected human neuroblastoma IMR-32 cells, which have an amplified hMYCN gene, with fluorescently labeled hMYCN AS or scrambled (SCR) control oligonucleotides and used fluorescence-activated cell sorting to enrich for cell populations containing different levels of the oligonucleotides. We used fluorescence immunocytochemistry or reverse transcription polymerase chain reaction to assay gene expression levels and trypan blue exclusion to assay growth inhibition in the cell populations. We examined the effects of continuous treatment for 6 weeks with AS or SCR oligonucleotides via subcutaneously implanted microosmotic pumps on tumor growth in a transgenic mouse model of hMYCN-induced neuroblastoma (n = 20 mice per group). All statistical tests were two-sided. RESULTS: IMR-32 cells treated with AS oligonucleotides had approximately half as much hMYCN protein and cell proliferation as either SCR oligonucleotide-transfected or mock-transfected controls; the differences were statistically significant. Transgenic mice treated with AS oligonucleotides had lower tumor incidence and statistically significantly lower tumor mass than SCR-treated or untreated control mice. Compared with control treatments, AS oligonucleotide treatment in vitro and in vivo was associated with decreased expression of hMYCN and putative hMYCN target genes but not with that of closely related genes. Several AS oligonucleotide-treated mice developed tumors contralateral to the site of oligonucleotide administration, whereas SCR oligonucleotide-treated or untreated mice displayed bilateral tumor growth. CONCLUSIONS: Decreased expression of hMYCN protein is achievable with the use of AS oligonucleotide treatment, even in the presence of hMYCN oncogene amplification. Antisense strategies targeting the hMYCN oncogene in vivo decrease mouse neuroblastoma tumorigenesis. Investigation of their clinical effect in children with neuroblastoma is warranted.