PRIMA-1Met induces myeloma cell death independent of p53 by impairing the GSH/ROS balance

Abstract

The aim of this study was to assess the efficiency of p53 reactivation and induction of massive apoptosis (PRIMA-1Met) in inducingmyeloma cell death, using 27 human myeloma cell lines (HMCLs) and 23 primary samples. Measuring the lethal dose (LD50) of HMCLs revealed thatHMCLs displayed heterogeneous sensitivity,with an LD50 ranging from4 μM to more than 200 μM. The sensitivity of HMCLs did not correlate with myeloma genomic heterogeneity or TP53 status, and PRIMA-1Met did not induce or increase expression of the p53 target genes CDKN1A or TNFRSF10B/DR5. However, PRIMA-1Met increased expression of NOXA in a p53-independent manner, and NOXA silencing decreased PRIMA1Met-induced cell death. PRIMA-1Met depleted glutathione (GSH) content and induced reactive oxygen species production.The expression of GSH synthetase correlated with PRIMA-1Met LD50 values, and we showed that a GSH decrease mediated by GSH synthetase silencing or by and L-buthionine sulphoximine, an irreversible inhibitor of γ-glutamylcysteine synthetase, increased PRIMA-1Met-induced cell death and overcame PRIMA-1Met resistance. PRIMA-1Met (10 μM) induced cell death in 65% of primary cells independent of the presence of del17p; did not increase DR5 expression, arguing against an activation of p53 pathway; and synergized with L-buthionine sulphoximine in all samples. Finally, we showed in mouse TP53neg JJN3-xenograft model that PRIMA-1Met inhibited myeloma growth and synergized with L-buthionine sulphoximine in vivo.