We previously showed that the
proteasome inhibitor carfilzomib and the
histone deacetylase inhibitor (HDACI)
vorinostat cooperated to induce cell apoptosis in one
T-cell leukemia cell line in vitro, implying the possibility of the combination treatment of
carfilzomib and
vorinostat as a potential therapeutic strategy in
human T-cell leukemia/lymphoma. Here we report that combination treatment of
carfilzomib and
vorinostat enhanced cell apoptosis and induced a marked increase in G2-M arrest,
reactive oxygen species (ROS) generation, and activated the members of
mitogen-activated protein kinases (MAPK) family, including the stress-activated
kinases JNK, p38MAPK, and ERK1/2.
Carfilzomib/
vorinostat-mediated apoptosis was blocked by the ROS scavenger
N-acetylcysteine (NAC). The JNK inhibitor
SP600125 and the p38MAPK inhibitor
SB203580 but not the MEK1/2 inhibitor
U0126 significantly attenuated
carfilzomib/
vorinostat-induced apoptosis, suggesting that p38MAPK and JNK activation contribute to
carfilzomib and
vorinostat-induced apoptosis. This was further confirmed via short hairpin (
shRNA)
RNA knockdown of p38MAPK and JNK. Interestingly, the ROS scavenger NAC attenuated
carfilzomib/
vorinostat-mediated activation of p38MAPK and JNK. However, p38MAPK
shRNA but not JNK
shRNA diminished
carfilzomib/
vorinostat-mediated ROS generation. In contrast, overexpression of p38MAPK significantly increased
carfilzomib/
vorinostat-mediated ROS generation, suggesting that an amplification loop exists between ROS and p38MAPK pathway. Combination treatment of
carfilzomib and
vorinostat enhanced their individual antitumor activity in both a human xenograft model as well as human primary
T-cell leukemia/
lymphoma cells. These data suggest the potential clinical benefit and underlying molecular mechanism of combining
carfilzomib with
vorinostat in the treatment of
human T-cell leukemia/lymphoma.