TY - JOUR
T1 - Carfilzomib triggers cell death in chronic lymphocytic leukemia by inducing proapoptotic and endoplasmic reticulum stress responses
AU - Lamothe, Betty
AU - Wierda, William G.
AU - Keating, Michael J.
AU - Gandhi, Varsha
N1 - Publisher Copyright:
©2016 American Association for Cancer Research.
PY - 2016/9/15
Y1 - 2016/9/15
N2 - Purpose: Carfilzomib, while active in B-cell neoplasms, displayed heterogeneous response in chronic lymphocytic leukemia (CLL) samples from patients and showed interpatient variability to carfilzomib-induced cell death. To understand this variability and predict patients who would respond to carfilzomib, we investigated the mechanism by which carfilzomib induces CLL cell death. Experimental Design: Using CLL patient samples and cell lines, complementary knockdown and knockout cells, and carfilzomib-resistant cell lines, we evaluated changes in intracellular networks to identify molecules responsible for carfilzomib's cytotoxic activity. Lysates from carfilzomib-treated cells were immunoblotted for molecules involved in ubiquitin, apoptotic, and endoplasmic reticulum (ER) stress response pathways and results correlated with carfilzomib cytotoxic activity. Coimmunoprecipitation and pull-down assays were performed to identify complex interactions among MCL-1, Noxa, and Bak. Results: Carfilzomib triggered ER stress and activation of both the intrinsic and extrinsic apoptotic pathways through alteration of the ubiquitin proteasome pathway. Consequently, the transcription factor CCAAT/enhancer-binding protein homology protein (CHOP) accumulated in response to carfilzomib, and CHOP depletion conferred protection against cytotoxicity. Carfilzomib also induced accumulation of MCL-1 and Noxa, whereby MCL-1 preferentially formed a complex with Noxa and consequently relieved MCL-10s protective effect on sequestering Bak. Accordingly, depletion of Noxa or both Bak and Bax conferred protection against carfilzomib-induced cell death. Conclusions: Collectively, carfilzomib induced ER stress culminating in activation of intrinsic and extrinsic caspase pathways, and we identified the CHOP protein level as a biomarker that could predict sensitivity to carfilzomib in CLL. Clin Cancer Res; 22(18); 4712-26.
AB - Purpose: Carfilzomib, while active in B-cell neoplasms, displayed heterogeneous response in chronic lymphocytic leukemia (CLL) samples from patients and showed interpatient variability to carfilzomib-induced cell death. To understand this variability and predict patients who would respond to carfilzomib, we investigated the mechanism by which carfilzomib induces CLL cell death. Experimental Design: Using CLL patient samples and cell lines, complementary knockdown and knockout cells, and carfilzomib-resistant cell lines, we evaluated changes in intracellular networks to identify molecules responsible for carfilzomib's cytotoxic activity. Lysates from carfilzomib-treated cells were immunoblotted for molecules involved in ubiquitin, apoptotic, and endoplasmic reticulum (ER) stress response pathways and results correlated with carfilzomib cytotoxic activity. Coimmunoprecipitation and pull-down assays were performed to identify complex interactions among MCL-1, Noxa, and Bak. Results: Carfilzomib triggered ER stress and activation of both the intrinsic and extrinsic apoptotic pathways through alteration of the ubiquitin proteasome pathway. Consequently, the transcription factor CCAAT/enhancer-binding protein homology protein (CHOP) accumulated in response to carfilzomib, and CHOP depletion conferred protection against cytotoxicity. Carfilzomib also induced accumulation of MCL-1 and Noxa, whereby MCL-1 preferentially formed a complex with Noxa and consequently relieved MCL-10s protective effect on sequestering Bak. Accordingly, depletion of Noxa or both Bak and Bax conferred protection against carfilzomib-induced cell death. Conclusions: Collectively, carfilzomib induced ER stress culminating in activation of intrinsic and extrinsic caspase pathways, and we identified the CHOP protein level as a biomarker that could predict sensitivity to carfilzomib in CLL. Clin Cancer Res; 22(18); 4712-26.
UR - http://www.scopus.com/inward/record.url?scp=84990985895&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84990985895&partnerID=8YFLogxK
U2 - 10.1158/1078-0432.CCR-15-2522
DO - 10.1158/1078-0432.CCR-15-2522
M3 - Article
C2 - 27026200
AN - SCOPUS:84990985895
SN - 1078-0432
VL - 22
SP - 4712
EP - 4726
JO - Clinical Cancer Research
JF - Clinical Cancer Research
IS - 18
ER -