Received for publication September 17, 2004.
Revised February 28, 2005.
Accepted for publication February 28, 2005.

Farnesyltransferase inhibitor BMS-214662 induces apoptosis in myeloma cells through PUMA upregulation, Bax and Bak activation and Mcl-1 elimination

Abstract

We have studied the mechanism of apoptosis elicited by the farnesyltransferase inhibitor BMS-214662 in human myeloma cell lines. Low concentrations of BMS-214662 efficiently inhibited protein farnesylation but did not affect to the activation of Akt. BMS-214662 treatment increased levels of the BH3-only protein PUMA, induced proapoptotic conformational changes of Bax and Bak, reduction of Mcl-1 levels, _m loss, cytochrome c release, caspase activation, AIF nuclear translocation, phosphatidylserine exposure and development of apoptotic morphology. Western blot analysis of cell extracts revealed the activation of caspases 2, 3, 8 and 9 upon treatment with BMS-214662. The general caspase inhibitor Z-VAD-fmk significantly prevented BMS-214662-induced death in U266 and RPMI 8226 cells but not in NCI-H929 cells. A mixture of selective caspase inhibitors for caspases 9 (Z-LEHD-fmk), 3 (Z- DEVD-fmk) and 6 (Z-VEID-fmk) approached the protective effect of Z-VAD on cell death. However, Z-VAD-fmk did not prevent BMS-214662-induced Bax and Bak activation and decrease of Mcl-1 levels. According to its effect on cell death, Z-VAD-fmk inhibited nuclear translocation of AIF in RPMI 8226 and U266 but not in NCI-H929 cells. These results suggest that apoptosis triggered by BMS- 214662 is initiated by a PUMA/Bax/Bak/Mcl-1-dependent mechanism. In some cell lines, Bax/Bak activation is not sufficient per se to induce mitochondrial failure and release of apoptogenic proteins and so caspases need to be activated to facilitate apoptosis. After _m loss, execution of apoptosis was performed in all cases by a cytochrome c-enabled, caspase-9 triggered, caspase cascade and the nuclear action of AIF.

Key words: Apoptosis, Mechanisms of cell killing/apoptosis, Oncogenes