Dataset Information

Segmental chromosomal alterations lead to a higher risk of relapse in infants with MYCN-non-amplified localised unresectable/disseminated neuroblastoma (a SIOPEN collaborative study).

ABSTRACT:

Background

In neuroblastoma (NB), the presence of segmental chromosome alterations (SCAs) is associated with a higher risk of relapse.

Methods

In order to analyse the role of SCAs in infants with localised unresectable/disseminated NB without MYCN amplification, we have performed an array CGH analysis of tumours from infants enrolled in the prospective European INES trials.

Results

Tumour samples from 218 out of 300 enroled patients could be analysed. Segmental chromosome alterations were observed in 11%, 20% and 59% of infants enroled in trials INES99.1 (localised unresectable NB), INES99.2 (stage 4s) and INES99.3 (stage 4) (P<0.0001). Progression-free survival was poorer in patients whose tumours harboured SCA, in the whole population and in trials INES99.1 and INES99.2, in the absence of clinical symptoms (log-rank test, P=0.0001, P=0.04 and P=0.0003, respectively). In multivariate analysis, a SCA genomic profile was the strongest predictor of poorer progression-free survival.

Conclusion

In infants with stage 4s MYCN-non-amplified NB, a SCA genomic profile identifies patients who will require upfront treatment even in the absence of other clinical indication for therapy, whereas in infants with localised unresectable NB, a genomic profile characterised by the absence of SCA identifies patients in whom treatment reduction might be possible. These findings will be implemented in a future international trial.

SUBMITTER: Schleiermacher G

PROVIDER: S-EPMC3251887 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Neuroblastoma derived from primitive sympathetic neural precursors is a common type of solid tumor in infants. MYCN proto?oncogene bHLH transcription factor (MYCN) amplification and 1p36 deletion are important factors associated with the poor prognosis of neuroblastoma. Expression levels of MYCN and c?MYB proto?oncogene transcription factor (c?myb) decline during the differentiation of neuroblastoma cells; E2F transcription factor 1 (E2F1) activates the MYCN promoter. However, the underlying mechanism of MYCN overexpression and amplification requires further investigation. In the present study, potential c?Myb target genes, and the effect of c?myb RNA interference (RNAi) on MYCN expression and amplification were investigated in MYCN?amplified neuroblastoma cell lines. The mRNA expression levels and MYCN gene copy number in five neuroblastoma cell lines were determined by quantitative polymerase chain reaction. In addition, variations in potential target gene expression and MYCN gene copy number between pre? and post?c?myb RNAi treatment groups in MYCN?amplified Kelly, IMR32, SIMA and MHH?NB?11 cell lines, normalized to those of non?MYCN?amplified SH?SY5Y, were examined. To determine the associations between gene expression levels and chromosomal aberrations, MYCN amplification and 1p36 alterations in interphases/metaphases were analyzed using fluorescence in situ hybridization. Statistical analyses revealed correlations between 1p36 alterations and the expression of c?myb, MYB proto?oncogene like 2 (B?myb) and cyclin dependent kinase inhibitor 1A (p21). Additionally, the results of the present study also demonstrated that c?myb may be associated with E2F1 and L3MBTL1 histone methyl?lysine binding protein (L3MBTL1) expression, and that E2F1 may contribute to MYCN, B?myb, p21 and chromatin licensing and DNA replication factor 1 (hCdt1) expression, but to the repression of geminin (GMNN). On c?myb RNAi treatment, L3MBTL1 expression was silenced, while GMNN was upregulated, indicating G2/M arrest. In addition, MYCN gene copy number increased following treatment with c?myb RNAi. Notably, the present study also reported a 43.545% sequence identity between upstream of MYCN and Drosophila melanogaster amplification control element 3, suggesting that expression and/or amplification mechanisms of developmentally?regulated genes may be evolutionarily conserved. In conclusion, c?myb may be associated with regulating MYCN expression and amplification. c?myb, B?myb and p21 may also serve a role against chromosome 1p aberrations. Together, it was concluded that MYCN gene is amplified during S phase, potentially via a replication?based mechanism.