FIGURE 5.

KS18 is effective against MM-resistant cells and re-sensitizes bortezomib resistant cells to bortezomib. (A), A panel of human MM U266-resistant cell lines (U266-VTX-R, U266-ABT-R, U266-LEN-R, and U266-BTZ-R) were treated for 72 h with increasing dosages of KS18 (0–25 µM), and cytotoxicity was assessed using the MTT assay. (B), KS18 (5 µM) was applied to several resistant cells for 24 h. (C, D), Immunoprecipitation followed by western blotting was performed in U266 bortezomib resistant cells treated with KS18 (5 µM) for 24 h (E), the colony forming ability of U266 bortezomib resistant (U266-BTZ-R) cells was assessed as described under Materials and Methods section. (F), U266-BTZ-R cells were subjected to a 24-h treatment with BTZ (20 nM) or KS18 (5 µM), either individually or in combination, followed by staining with Annexin V dye and analysis using FACS. The total count of apoptotic cells was quantified (n = 3), and a one-way ANOVA was conducted utilizing GraphPad Prism software. In all experiments vehicle treated cells served as control. Wherever applicable GraphPad prism was used for graphical representation and IC₅₀ calculation. *P ≤ 0.05, ***P ≤ 0.001, ****P ≤ 0.000, ns, not significant.