[3H]-paclitaxel and [3H]-mitoxantrone accumulation assay

For the [³H]-paclitaxel accumulation assay, KB-3-1 and its drug resistant subline KB-C2 were used. Briefly, 5 × 10⁵ cells were cultured in 24-well plates overnight before the assay, and VS-4718 was added 2 h prior to the addition of [³H]-paclitaxel. After incubating with [³H]-paclitaxel with or without VS-4718 for 2 h at 37°C, cells were washed twice with iced PBS, and lysed with 0.25% trypsin before being placed in 5 mL scintillation fluid. Radioactivity of cells was measured in the Packard TRI-CARB 1900CA liquid scintillation analyzer (Packard Instrument, Downers Grove, IL). NCI-H460, NCI-H46/MX20, were used for [³H]-mitoxantrone accumulation assay as previously described (Sun et al., 2012).