BRAFV600E 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 BRAFMT colorectal cancer. We have used differential gene expression and pathway analyses of untreated stage II and stage III BRAFMT (discovery set: n = 31; validation set: n = 26) colorectal cancer, and an siRNA screen to characterize the biology underpinning the BRAFMT subgroup with poorest outcome. These analyses identified the unfolded protein response (UPR) as a novel and druggable pathway associated with the BRAFMT 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 BRAFMT 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 BRAFMT 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 BRAFMT colorectal cancer. Mol Cancer Ther; 17(6); 1280-90. ©2018 AACR.

• MeSH
• antitumorózní látky farmakologie   MeSH
• apoptóza účinky léků   genetika   MeSH
• biologické modely MeSH
• inhibitory proteinkinas farmakologie   MeSH
• kolorektální nádory farmakoterapie   genetika   metabolismus   mortalita   MeSH
• kyseliny hydroxamové farmakologie   MeSH
• lidé MeSH
• MAP kinasový signální systém MeSH
• mutace * MeSH
• nádorové biomarkery MeSH
• nádorové buněčné linie MeSH
• oligopeptidy farmakologie   MeSH
• prognóza MeSH
• proteiny tepelného šoku genetika   metabolismus   MeSH
• proteosyntéza MeSH
• protoonkogenní proteiny B-raf antagonisté a inhibitory   genetika   metabolismus   MeSH
• pyrimidiny farmakologie   MeSH
• signální dráha UPR účinky léků   MeSH
• signální transdukce účinky léků   MeSH
• stres endoplazmatického retikula účinky léků   genetika   MeSH
• transkripční faktor CHOP genetika   metabolismus   MeSH
• viabilita buněk účinky léků   genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH