Impact of a single nucleotide polymorphism in the MDM2 gene on neuroblastoma development and aggressiveness: results of a pilot study on 239 patients.
OBJECTIVE
MDM2 is a key negative regulator of p53 activity, and a single nucleotide polymorphism (SNP309, T>G change; rs 2279744) in its promoter increases the affinity for the transcription factor SP1, enhancing MDM2 expression. We carried out a pilot study to investigate the effect of this polymorphism on development and behavior of neuroblastoma, an extracranial pediatric tumor with unfrequent genetic inactivation of p53.


METHODS
We genotyped the MDM2-SNP309 alleles of tumor DNA from 239 neuroblastoma patients and peripheral blood DNA from 237 controls. In 40 of 239 neuroblastomas, the MDM2-SNP309 alleles were also genotyped in peripheral blood DNA. Data were analyzed by two-sided Fisher's exact test, log-rank test, and Kaplan-Meier statistics. Where appropriate, data are reported with 95% confidence intervals (CI).


RESULTS
The frequency of both the T/G and G/G genotypes or the G/G or T/G genotype only was higher in neuroblastoma DNA samples than in controls: 60.3% (95% CI, 54.1-66.5) versus 47.3% (95% CI, 40.9-53.6), 30.4% (95% CI, 22.4-37.8) versus 15.0% (95% CI, 9.2-20.7), and 52.0% (95% CI, 45.0-59.9) versus 41.9% (95% CI, 35.3-48.5), respectively; Two-Sided Fisher's Exact Test P values were 0.006, 0.003, and 0.048, respectively; Odds ratios were 1.69 (95% CI, 1.18-2.43), 2.45 (95% CI, 1.37-4.39) and 1.51 (95% CI, 1.02-2.22), respectively. A significant association (P = 0.016) between heterozygous (T/G)/homozygous (G/G) genotypes at SNP309 and advanced clinical stages was also shown. Homozygous/heterozygous SNP309 variant carriers had a shorter 5-year overall survival than patients with the wild-type allele (P = 0.046; log-rank test). A shorter overall survival in patients with heterozygous/homozygous SNP309 was also observed in the subgroups with age at diagnosis >1 year and adrenal primary tumor (P = 0.024 and P = 0.014, respectively).


CONCLUSIONS
Data from this pilot study suggest that the MDM2 G/G and T/G-SNP309 alleles are markers of increased predisposition to tumor development and disease aggressiveness in neuroblastoma. However, additional studies with larger patient cohorts are required for a definitive assessment of the clinical relevance of these data.
Cattelani
Sara
S
Department of Biomedical Sciences and Oncology, Modena and Reggio Emilia University, Modena, Italy.
Defferrari
Raffaella
R
Marsilio
Sonia
S
Bussolari
Rita
R
Candini
Olivia
O
Corradini
Francesca
F
Ferrari-Amorotti
Giovanna
G
Guerzoni
Clara
C
Pecorari
Luisa
L
Menin
Chiara
C
Bertorelle
Roberta
R
Altavista
Pierluigi
P
McDowell
Heather P
HP
Boldrini
Renata
R
Dominici
Carlo
C
Tonini
Gian Paolo
GP
Raschellà
Giuseppe
G
Calabretta
Bruno
B
D002648:Child; D002675:Child, Preschool; D020022:Genetic Predisposition to Disease; D006801:Humans; D007223:Infant; D053208:Kaplan-Meier Estimate; D009447:Neuroblastoma / Q000235:genetics* / Q000401:mortality / Q000473:pathology*; D010865:Pilot Projects; D016133:Polymerase Chain Reaction; D020641:Polymorphism, Single Nucleotide; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics*
C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2