PTX induces the apoptosis of HCC1806 parental cells, and not HCC1806-TxR cells. Western blot analysis of (A) HCC1806 and (B) HCC1806-TxR cells for cleaved forms of PARP and caspase-3, markers of apoptotic cell death, following the treatment with dimethyl sulfoxide or PTX for 48 h. β-actin was used as a loading control. PTX, paclitaxel; TxR, taxol resistant; PARP, poly(ADP-ribose) polymerase; cl., cleaved.