Taxol induces caspase-independent cytoplasmic vacuolization and cell death through endoplasmic reticulum (ER) swelling in ASTC-a-1 cells

High concentration of taxol was found to induce programmed cell death (PCD) and cytoplasm vacuolization in human lung adenocarcinoma (ASTC-a-1) cells. To elucidate the relationship between the PCD and cytoplasm vacuolization, confocal fluorescence microscopy was performed on the cytoplasm vacuolization, endoplasmic reticulum (ER) and mitochondria swelling after taxol treatment in living cells. erRFP plasmid was used to probe the ER distribution, and SCAT3 plasmid was used to monitor the caspase-3 activation in living cells. Our results showed that taxol induced concentration-dependent and caspases-independent cytoplasm vacuolization and cell death through ER and mitochondria swelling. Live confocal imaging of ASTC-a-1 cells stably expressing SCAT3 further verified that taxol-induced cytoplasm vacuolization and cell death was caspase-3-independent. In conclusion, we found for the first time that taxol induces a paraptosis-like PCD in the ASTC-a-1 cells by cytoplasm vacuolization due to the swelling of both ER and mitochondria without activating the caspase enzymes.