Expression of multidrug resistance-related markers in primary neuroblastoma.

Background: Multidrug resistance is associated with a poor prognosis in various human cancers. However, the clinical significance of the expression of multidrug resistance-related markers in neuroblastoma is still on debate. In this study, the effect of the expression of p-glycoprotein (P-gp), multidrug resistance-associated protein (MRP), and lung resistance protein (LRP) in neuroblastoma was evaluated.

Methods: The streptavidin-biotin immunoperoxidase (SP) technique was used to evaluate the expression of P-gp, MRP, and LRP in 70 cases of untreated primary neuroblastoma.

Results: The frequencies of the expression of P-gp, MRP, and LRP were 61.4%, 38.6%, and 24.3%, respectively. A significant positive correlation was observed between P-gp and MRP expression (P=0.001), as well as between LRP and MRP expression (P=0.01). The rates of expression of P-gp and MRP were higher in tumors from patients aged greater than one year old than in tumors from patients aged less than 1 year old at time of diagnosis (P=0.01 and 0.018, respectively). MRP expression in tumors that had metastasized was significantly more frequent than in tumors that had not metastasized (P=0.015). The expression of all tested proteins showed a significant relationship with whether or not the tumor had differentiated (P=0.006, 0.000 or 0.001, respectively). MRP expression was significantly associated with a reduction in both median survival time and 2-year cumulative survival (P=0.02). By contrast, P-gp and MRP expression did not correlate with survival. According to Cox regression analysis, only the co-expression of P-gp and MRP had significant prognostic value (relative hazard, 3.513, P=0.033).

Conclusions: The intrinsic, multidrug resistance of neuroblastoma involves the combined effects of P-gp, MRP, and LRP. MRP expression may be an important factor determining prognosis in neuroblastoma.