Submitted October 5, 2007
Accepted March 11, 2008
BH3-only proteins Noxa, Bmf and Bim are necessary for arsenic trioxide induced cell death in myeloma
Alejo A Morales, Delia Gutman, Kelvin P Lee, and Lawrence H Boise*
Microbiology and Immunology and The Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, FL, United States
Department of Immunology and Medicine, Roswell Park Cancer Institute, Buffalo, NY, United States
* Corresponding author; email: lboise{at}med.miami.edu.
The use of Arsenic Trioxide (ATO) to treat Multiple Myeloma (MM) is supported by preclinical studies as well as several Phase II studies, but the precise mechanism(s) of action of ATO have not been completely elucidated. We utilized gene expression profiling to determine the regulation of apoptosis-related genes by ATO in four MM cell lines and then focused on Bcl-2 family genes. ATO induced up-regulation of three pro-apoptotic BH3-only proteins (Noxa, Bmf and Puma) and down-regulation of two anti-apoptotic proteins Mcl-1 and Bcl-XL. Co-immunoprecipitation demonstrated that Noxa and Puma bind Mcl-1 to release Bak and Bim within 6 h of ATO addition. Bak and Bim are also released from Bcl-XL. Silencing of Bmf, Noxa and Bim significantly protected cells from ATO-induced apoptosis, while Puma silencing had no effect. Consistent with a role for Noxa inhibition of Mcl-1, the Bad-mimetic ABT-737 synergized with ATO in the killing of two MM lines. Finally Noxa expression was enhanced by GSH depletion and inhibited by increasing GSH levels in the cells. Understanding the pattern of BH3-only protein response should aid in the rational design of arsenic containing regimens.
