Expression of the gene for multidrug-resistance-associated protein and outcome in patients with neuroblastoma.
BACKGROUND
Overexpression of the gene for the multidrug-resistance-associated protein (MRP) has been linked with resistance to chemotherapeutic agents (multidrug resistance) in vitro. The expression of MRP by neuroblastoma cells correlates with N-myc oncogene amplification, a well-established prognostic indicator in patients with neuroblastoma.


METHODS
To relate MRP gene expression to established prognostic markers and the clinical outcome of neuroblastoma, we analyzed MRP expression in specimens of primary tumors from 60 patients with neuroblastoma.


RESULTS
Levels of MRP gene expression were significantly higher in tumors with N-myc amplification than in tumors without such amplification (P < 0.001). High levels of MRP expression were strongly associated with reductions in both survival and event-free survival (P < 0.001) in the overall study population and in subgroups of patients without N-myc amplification and patients with localized disease. For the overall study population, the five-year cumulative survival rates in the groups with high and low levels of MRP expression were 57 percent (95 percent confidence interval, 37 to 78 percent) and 94 percent (95 percent confidence interval, 86 to 100 percent), respectively. In contrast, expression of the MDR1 multi-drug-resistance gene was not predictive of survival or event-free survival. After adjustment by multivariate analysis for the effects of N-myc amplification and other prognostic indicators, high levels of MRP expression retained significant prognostic value for poor survival (relative hazard, 14.9; P = 0.01) and poor event-free survival (relative hazard, 9.7; P = 0.004), whereas N-myc amplification had no prognostic value.


CONCLUSIONS
High levels of MRP gene expression in patients with neuroblastoma correlate strongly with poor outcome. The findings suggest that expression of this multidrug-resistance gene accounts for the association between N-myc amplification and reduced survival.
Norris
M D
MD
Children's Leukaemia and Cancer Research Centre, University of New South Wales, Sydney, Australia.
Bordow
S B
SB
Marshall
G M
GM
Haber
P S
PS
Cohn
S L
SL
Haber
M
M
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics; D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D002675:Child, Preschool; D018572:Disease-Free Survival; D018432:Drug Resistance, Multiple / Q000235:genetics*; D005784:Gene Amplification; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D016259:Genes, myc; D006801:Humans; D007223:Infant; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins / Q000235:genetics*; D009447:Neuroblastoma / Q000235:genetics* / Q000401:mortality; D011379:Prognosis; D016016:Proportional Hazards Models; D015996:Survival Rate
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins