(A) and (B) Protein lysates were prepared under the same treatment conditions as in Figure 1 (for monolayer, Figure 4A) and Figure 2 (for spheres, Figure 4B) before being subjected to immunoblot. (C) MTS or ATP assays of stable melanoma cells, 1205Lu, SK-MEL-28, and WM852c, carrying a control shRNA (shcontrol) or a shRNA against NOXA (sh NOXA). The viability of the DMSO control for each cell line was set to 100%. The data of 1205Lu and SKMEL-28 cell lines are from MTS assay while WM852c cell line is from ATP assay. (D) Primary sphere assays of stable melanoma cells, A375, SK-MEL-28, and WM852c, carrying a control shRNA (shcontrol) or a shRNA against NOXA (sh NOXA). For all the experiments above, cells were treated for 48 hours in monolayer condition or sphere conditions with the following treatments: vehicle (DMSO), 3.3μM ABT-737, 0.83μM GSI-I, or combination of the both drugs. (E) Immunoblot confirmed the knockdown of NOXA in the indicated cell lines. * indicates p < 0.05; ** indicates p < 0.01; *** indicates p < 0.001.