1. The Unfolded Protein Response: A Novel Therapeutic Target for Poor Prognostic BRAF Mutant Colorectal Cancer.
- Author
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Forsythe N, Refaat A, Javadi A, Khawaja H, Weir JA, Emam H, Allen WL, Burkamp F, Popovici V, Jithesh PV, Isella C, Labonte MJ, Mills IG, Johnston PG, and Van Schaeybroeck S
- Subjects
- Antineoplastic Agents pharmacology, Apoptosis drug effects, Apoptosis genetics, Biomarkers, Tumor, Cell Line, Tumor, Cell Survival drug effects, Cell Survival genetics, Colorectal Neoplasms drug therapy, Colorectal Neoplasms mortality, Endoplasmic Reticulum Chaperone BiP, Endoplasmic Reticulum Stress drug effects, Endoplasmic Reticulum Stress genetics, Heat-Shock Proteins genetics, Heat-Shock Proteins metabolism, Humans, Hydroxamic Acids pharmacology, MAP Kinase Signaling System, Models, Biological, Oligopeptides pharmacology, Prognosis, Protein Biosynthesis, Proto-Oncogene Proteins B-raf metabolism, Pyrimidines pharmacology, Signal Transduction drug effects, Transcription Factor CHOP genetics, Transcription Factor CHOP metabolism, Colorectal Neoplasms genetics, Colorectal Neoplasms metabolism, Mutation, Protein Kinase Inhibitors pharmacology, Proto-Oncogene Proteins B-raf antagonists & inhibitors, Proto-Oncogene Proteins B-raf genetics, Unfolded Protein Response drug effects
- Abstract
BRAF
V600E mutations occur in ∼10% of colorectal cancer cases, are associated with poor survival, and have limited responses to BRAF/MEK inhibition with or without EGFR inhibition. There is an unmet need to understand the biology of poor prognostic BRAF MT colorectal cancer. We have used differential gene expression and pathway analyses of untreated stage II and stage III BRAF MT (discovery set: n = 31; validation set: n = 26) colorectal cancer, and an siRNA screen to characterize the biology underpinning the BRAF MT subgroup with poorest outcome. These analyses identified the unfolded protein response (UPR) as a novel and druggable pathway associated with the BRAF MT colorectal cancer subgroup with poorest outcome. We also found that oncogenic BRAF drives endoplasmic reticulum (ER) stress and UPR pathway activation through MEK/ERK. Furthermore, inhibition of GRP78, the master regulator of the UPR, using siRNA or small molecule inhibition, resulted in acute ER stress and apoptosis, in particular in BRAF MT colorectal cancer cells. In addition, dual targeting of protein degradation using combined Carfilzomib (proteasome inhibitor) and ACY-1215 (HDAC6-selective inhibitor) treatment resulted in marked accumulation of protein aggregates, acute ER stress, apoptosis, and therapeutic efficacy in BRAF MT in vitro and xenograft models. Mechanistically, we found that the apoptosis following combined Carfilzomib/ACY-1215 treatment is mediated through increased CHOP expression. Taken together, our findings indicate that oncogenic BRAF induces chronic ER stress and that inducers of acute ER stress could be a novel treatment strategy for poor prognostic BRAF MT colorectal cancer. Mol Cancer Ther; 17(6); 1280-90. ©2018 AACR ., (©2018 American Association for Cancer Research.)- Published
- 2018
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