Development of resistance to vincristine and doxorubicin in neuroblastoma alters malignant properties and induces additional karyotype changes: a preclinical model.

Cytotoxic drug treatment of neuroblastoma often leads to the development of drug resistance and may be associated with increased malignancy. To study the effects of long-term cytotoxic treatment on malignant properties of tumor cells, we established 2 neuroblastoma cell sublines resistant to vincristine (VCR) and doxorubicin (DOX). Both established cell lines (UKF-NB-2(r)VCR(20) and UKF-NB-2(r)DOX(100)) were highly resistant to VCR, DOX and vice-versa but retained their sensitivity to cisplatin. UKF-NB-2(r)VCR(20) and UKF-NB-2(r)DOX(100) expressed significant amounts of P-glycoprotein, while parental cells were P-glycoprotein negative. GD2 expression was upregulated, whereas NCAM expression was decreased in both resistant cells. Spectral karyotype (SKY) analysis revealed complex aberrant karyotypes in all cell lines and additional acquired karyotype changes in both resistant cells. All cell lines harbored high levels of N-myc amplification. Compared to parental cells, UKF-NB-2(r)VCR(20) and UKF-NB-2(r)DOX(100) exhibited more than 2-fold increase in clonal growth in vitro, accelerated adhesion and transendothelial penetration and higher tumorigenicity in vivo. We conclude that development of drug resistance and acquisition of certain karyotypic alterations is associated with an increase of additional malignant properties that may contribute to the poor prognosis in advanced forms of NB. The 2 novel neuroblastoma cell sublines also provide useful models for the study of drug resistance in aggressive forms of neuroblastoma.