Sabizabulin induces apoptosis in BT474 and SKBR3 cells in a concentration-dependent manner. (A) A panel of apoptotic markers was profiled by western blotting after 24 h of treatment with colchicine or paclitaxel (100 nM) or sabizabulin (10, 20, 50, or 100 nM) in BT474 and SKBR3 cells. Signal from cleaved-PARP (anti-cleaved-PARP, CST 5625, 1:1000), phosphorylated BCL2 (pBCL2; anti-pBCL2, 2827 CST 1:1000) and cleaved caspase-3 (CST 9661, 1:500) was first normalized to β-actin (CST 3700, 1:20,000) by ImageJ densitometry, with the 100 nM sabizabulin-treated lane set to 1.0. (B) Cleaved-PARP and cleaved-caspase-3 levels in both HER2+ cell lines were determined by western blotting after treatment with 100 nM of sabizabulin for 12, 24, 48, and 72 h after normalization to β-actin. Data are representative of three independent biological replicate assays.