No evidence for involvement of SDHD in neuroblastoma pathogenesis.
BACKGROUND
Deletions in the long arm of chromosome 11 are observed in a subgroup of advanced stage neuroblastomas with poor outcome. The deleted region harbours the tumour suppressor gene SDHD that is frequently mutated in paraganglioma and pheochromocytoma, which are, like neuroblastoma, tumours originating from the neural crest. In this study, we sought for evidence for involvement of SDHD in neuroblastoma.


METHODS
SDHD was investigated on the genome, transcriptome and proteome level using mutation screening, methylation specific PCR, real-time quantitative PCR based homozygous deletion screening and mRNA expression profiling, immunoblotting, functional protein analysis and ultrastructural imaging of the mitochondria.


RESULTS
Analysis at the genomic level of 67 tumour samples and 37 cell lines revealed at least 2 bona-fide mutations in cell lines without allelic loss at 11q23: a 4bp-deletion causing skip of exon 3 resulting in a premature stop codon in cell line N206, and a Y93C mutation in cell line NMB located in a region affected by germline SDHD mutations causing hereditary paraganglioma. No evidence for hypermethylation of the SDHD promotor region was observed, nor could we detect homozygous deletions. Interestingly, SDHD mRNA expression was significantly reduced in SDHD mutated cell lines and cell lines with 11q allelic loss as compared to both cell lines without 11q allelic loss and normal foetal neuroblast cells. However, protein analyses and assessment of mitochondrial morphology presently do not provide clues as to the possible effect of reduced SDHD expression on the neuroblastoma tumour phenotype.


CONCLUSIONS
Our study provides no indications for 2-hit involvement of SDHD in the pathogenesis of neuroblastoma. Also, although a haplo-insufficient mechanism for SDHD involvement in advanced stage neuroblastoma could be considered, the present data do not provide consistent evidence for this hypothesis.
De Preter
Katleen
K
Center for Medical Genetics, Ghent University Hospital, K5, De Pintelaan 185, B-9000 Ghent, Belgium. katleen.depreter@ugent.be
Vandesompele
Jo
J
Hoebeeck
Jasmien
J
Vandenbroecke
Caroline
C
Smet
Jöel
J
Nuyts
Annick
A
Laureys
Geneviève
G
Combaret
Valérie
V
Van Roy
Nadine
N
Roels
Frank
F
Van Coster
Rudy
R
Praet
Marleen
M
De Paepe
Anne
A
Speleman
Frank
F
D001483:Base Sequence; D045744:Cell Line, Tumor; D002880:Chromosomes, Human, Pair 11 / Q000235:genetics*; D004273:DNA, Neoplasm / Q000302:isolation & purification; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008745:Methylation; D008928:Mitochondria / Q000648:ultrastructure; D008969:Molecular Sequence Data; D009154:Mutation; D009447:Neuroblastoma / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure*; D012333:RNA, Messenger / Q000302:isolation & purification; D012334:RNA, Neoplasm / Q000302:isolation & purification; D013385:Succinate Dehydrogenase
D004273:DNA, Neoplasm; D008565:Membrane Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; C491545:SDHD protein, human; D013385:Succinate Dehydrogenase