Figure 4.

Anti-OAcGD2 mAb causes an increase in the plasma membrane topotecan permeability followed by a gain of topotecan-induced caspase-3 activation. (A) NXS2, IMR5, LAN1, and LAN5 neuroblastoma cells were incubated with topotecan in the presence of either mAb 8B6 or control IgG for 30 minutes. After incubation, intracellular fluorescence of topotecan was analyzed by flow cytometry. The geometric mean fluorescence intensities (MFIs) of the different experimental conditions were normalized to the MFIs of tumor cells incubated with topotecan alone. A gain of topotecan uptake was seen in all neuroblastoma cell incubated with mAb 8B6 + topotecan, as indicated. (B) The cells in (A) were also assessed by Western blot analysis for caspase-3 activation detection. The right panels show representative images of immunoblots of cleaved caspase-3. Elevated level of cleaved caspase-3 was seen in all neuroblastoma cells treated with mAb 8B6 + topotecan, as indicated. Similar results were observed in three independent experiments. Data presented are mean ± SEM of triplicate experiments. * p < 0.05, ** p < 0.01, *** p < 0.001.