Carfilzomib Triggers Cell Death in Chronic Lymphocytic Leukemia by Inducing Proapoptotic and Endoplasmic Reticulum Stress Responses.

Abstract

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-1's 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. ©2016 AACR.

• Authors: Betty Lamothe, William G Wierda, Michael J Keating, Varsha Gandhi
• Journal: Clinical cancer research : an official journal of the American Association for Cancer Research (Clin Cancer Res) Vol. 22 Issue 18 Pg. 4712-26 (Sep 15 2016) ISSN: 1557-3265 [Electronic] United States
• PMID: 27026200 (Publication Type: Journal Article)
• Copyright: ©2016 American Association for Cancer Research.

Chemical References

• Antineoplastic Agents
• Biomarkers
• DDIT3 protein, human
• Oligopeptides
• Ubiquitinated Proteins
• Transcription Factor CHOP
• carfilzomib
• ATR protein, human
• Ataxia Telangiectasia Mutated Proteins
• Proteasome Endopeptidase Complex

Topics

• Adult
• Aged
• Antineoplastic Agents (pharmacology)
• Apoptosis (drug effects)
• Ataxia Telangiectasia Mutated Proteins (metabolism)
• Biomarkers
• Cell Line, Tumor
• Endoplasmic Reticulum Stress (drug effects)
• Female
• Humans
• Leukemia, Lymphocytic, Chronic, B-Cell (diagnosis, metabolism, therapy)
• Male
• Middle Aged
• Mutation
• Oligopeptides (pharmacology)
• Proteasome Endopeptidase Complex (metabolism)
• Protein Binding
• Transcription Factor CHOP (metabolism)
• Ubiquitinated Proteins (metabolism)