Fig. 6.

Efflux and survival of mitoxantrone from neuroblastoma SP cells. (A) Efflux of mitoxantrone in primary neuroblastoma samples from five patients (nos. 1–5) with relapsed disease after incubation with Hoechst 33342 dye and mitoxantrone. Fluorescence was plotted for three gated cell populations: SP (solid line), non-SP (dashed line), and control (dotted line) (P < 0.05). (B) JF and SK-N-SH lines were cultured in the presence of 0, 1, or 10 ng/ml mitoxantrone for 3 days, then analyzed for the SP cells. (C) Fifty SP or non-SP cells were sorted in six replicates into 96-well plates and cultured with 1 ng/ml mitoxantrone. After 14 days of culture, the number of colonies formed in each well was counted (*, P < 0.05).