ABCB1 and neuroblastoma: We had selected the neuroblastoma cell line SHEP as additional model for our study because it differs in two crucial parameters from UKF-NB-3: 1) SHEP cells do not harbor a MYCN amplification, a major marker of high-risk neuroblastoma [1,2], and 2) SHEP cells are characterized by intrinsic ABCB1 expression.