Regulation of Bax Activation and Apoptotic Response to Microtubule-damaging Agents by p53 Transcription-dependent and -independent Pathways

Abstract

Microtubule-damaging agents (MDA) are potent antineoplastic drugs that are widely used in clinical treatment for a variety of cancers. However, the precise mechanisms underlying MDA-induced cell death are largely unknown. Here, we report that both p53 and Bax are central participants in the MDA-mediated cell death machinery in HCT116 human colon cancer cells. MDA, including epothilone B analogue (BMS-247550) and vinblastine, induced apoptosis of Bax-positive HCT116 cells in a p53-dependent manner; p53 was required for MDAinduced Bax conformational change. In response to MDA treatment, the BH3-only proapoptotic protein PUMA was up-regulated in p53-positive but not in p53 knockout HCT116 cells. Moreover, PUMA knockout HCT116 cells were resistant to MDA-induced Bax conformational change and apoptosis. In addition, introducing p53 plasmid DNA into p53-deficient HCT116 cells restored PUMA expression and apoptotic response to MDA treatment. However, ectopic expression of the p53 point mutation L22Q/W23S, but not the proline-rich domain deletion mutants 83-393 and ⌬ProAE, could also sensitize p53 knockout HCT116 cells to MDA-induced Bax activation and apoptosis, although all mutants failed to restore PUMA expression. Together, these findings suggest that p53 acts upstream of Bax to promote MDA-mediated cell death in a proline-rich domain-dependent manner through both transcription-dependent (by up-regulating PUMA expression) and -independent mechanisms in human colon cancer HCT116 cells.

Microtubule inhibitors: Differentiating tubulin-inhibiting agents based on mechanisms of action, clinical activity, and resistance

“…Moreover, ixabepilone-induced apoptosis was associated with activation of caspase-2 whereas taxanes were associated with caspase-9 activation (51). Consistent with these results, ixabepiloneinduced apoptosis in breast cancer cells was also shown to occur through p53-dependent activation of Bax (52). However, in breast cancer cells, p53-dependent activation of Bax was shown to occur via transcription-dependent (elevated expression of PUMA) and transcription-independent (direct translocation of p53 to the mitochondria) mechanisms (Table 3; ref.…”

Mitochondria-mediated apoptosis by diallyl trisulfide in human prostate cancer cells is associated with generation of reactive oxygen species and regulated by Bax/Bak

“…Although the precise mechanism by which Bax and Bak regulate DATS-induced cell death remains elusive, it is possible that DATS treatment causes conformation change and oligomerization of Bax/Bak leading to their translocation to the mitochondria. This possibility is likely based on following considerations: (a) Bax activation by certain apoptotic stimuli is dependent on ROS generation (38), which is observed in DATS-treated prostate cancer cells (present study), and (b) microtubuledamaging agents have been shown to cause Bax activation (48), and DATS treatment is known to disrupt tubulin network (18). However, further studies are needed to systematically explore this possibility.…”

Resveratrol Induces p53-independent, X-linked Inhibitor of Apoptosis Protein (XIAP)-mediated Bax Protein Oligomerization on Mitochondria to Initiate Cytochrome c Release and Caspase Activation

“…These findings support that p53 does not interact with Bax/Bak and that p53-Bax or p53-Bak interaction may not be critical for resveratrolinduced cytochrome c release in cancer cells. It has been reported that wild type p53 as well as mutant p53 can promote Bax activation on mitochondria (80,81), whereas other studies suggest that p53 translocation to mitochondria does not induce Bax activation and apoptosis (82,83). Expression of mutant p53 in cancer cells confers selective advantage and resistance to apoptosis (84 -86).…”