BACKGROUND: Although the prognostic value of the ATP-binding cassette, subfamily 
C (ABCC) transporters in childhood neuroblastoma is usually attributed to their 
role in cytotoxic drug efflux, certain observations have suggested that these 
multidrug transporters might contribute to the malignant phenotype independent 
of cytotoxic drug efflux.
METHODS: A v-myc myelocytomatosis viral related oncogene, neuroblastoma derived 
(MYCN)-driven transgenic mouse neuroblastoma model was crossed with an 
Abcc1-deficient mouse strain (658 hMYCN(1/-), 205 hMYCN(+/1) mice) or, 
alternatively, treated with the ABCC1 inhibitor, Reversan (n = 20). ABCC genes 
were suppressed using short interfering RNA or overexpressed by stable 
transfection in neuroblastoma cell lines BE(2)-C, SH-EP, and SH-SY5Y, which were 
then assessed for wound closure ability, clonogenic capacity, morphological 
differentiation, and cell growth. Real-time quantitative polymerase chain 
reaction was used to examine the clinical significance of ABCC family gene 
expression in a large prospectively accrued cohort of patients (n = 209) with 
primary neuroblastomas. Kaplan-Meier survival analysis and Cox regression were 
used to test for associations with event-free and overall survival. Except where 
noted, all statistical tests were two-sided.
RESULTS: Inhibition of ABCC1 statistically significantly inhibited neuroblastoma 
development in hMYCN transgenic mice (mean age for palpable tumor: treated mice, 
47.2 days; control mice, 41.9 days; hazard ratio [HR] = 9.3, 95% confidence 
interval [CI] = 2.65 to 32; P < .001). Suppression of ABCC1 in vitro inhibited 
wound closure (P < .001) and clonogenicity (P = .006); suppression of ABCC4 
enhanced morphological differentiation (P < .001) and inhibited cell growth (P < 
.001). Analysis of 209 neuroblastoma patient tumors revealed that, in contrast 
with ABCC1 and ABCC4, low rather than high ABCC3 expression was associated with 
reduced event-free survival (HR of recurrence or death = 2.4, 95% CI = 1.4 to 
4.2; P = .001), with 23 of 53 patients with low ABCC3 expression experiencing 
recurrence or death compared with 31 of 155 patients with high ABCC3. Moreover, 
overexpression of ABCC3 in vitro inhibited neuroblastoma cell migration (P < 
.001) and clonogenicity (P = .03). The combined expression of ABCC1, ABCC3, and 
ABCC4 was associated with patients having an adverse event, such that of the 12 
patients with the "poor prognosis" expression pattern, 10 experienced recurrence 
or death (HR of recurrence or death = 12.3, 95% CI = 6 to 27; P < .001).
CONCLUSION: ABCC transporters can affect neuroblastoma biology independently of 
their role in chemotherapeutic drug efflux, enhancing their potential as targets 
for therapeutic intervention.