MOGAT3-mediated DAG accumulation drives acquired resistance to anti-BRAF/anti-EGFR therapy in BRAFV600E-mutant metastatic colorectal cancer
Jiawei Wang, … , Zhenyu Ju, Zhangfa Song
Jiawei Wang, … , Zhenyu Ju, Zhangfa Song
Published October 22, 2024
Citation Information: J Clin Invest. 2024;134(24):e182217. https://doi.org/10.1172/JCI182217.
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MOGAT3-mediated DAG accumulation drives acquired resistance to anti-BRAF/anti-EGFR therapy in BRAFV600E-mutant metastatic colorectal cancer

Abstract

BRAFV600E-mutant metastatic colorectal cancer (mCRC) is associated with poor prognosis. The combination of anti-BRAF/anti-EGFR (encorafenib/cetuximab) treatment for patients with BRAFV600E-mutant mCRC improves clinical benefits; unfortunately, inevitable acquired resistance limits the treatment outcome, and the mechanism has not been validated. Here, we discovered that monoacylglycerol O-acyltransferase 3–mediated (MOGAT3-mediated) diacylglycerol (DAG) accumulation contributed to acquired resistance to encorafenib/cetuximab by dissecting a BRAFV600E-mutant mCRC patient–derived xenograft (PDX) model exposed to encorafenib/cetuximab administration. Mechanistically, the upregulated MOGAT3 promoted DAG synthesis and reduced fatty acid oxidation–promoting DAG accumulation and activated PKCα/CRAF/MEK/ERK signaling, driving acquired resistance. Resistance-induced hypoxia promoted MOGAT3 transcriptional elevation; simultaneously, MOGAT3-mediated DAG accumulation increased HIF1A expression at the translation level through PKCα/CRAF/eIF4E activation, strengthening the resistance status. Intriguingly, reducing intratumoral DAG with fenofibrate or PF-06471553 restored the antitumor efficacy of encorafenib/cetuximab in resistant BRAFV600E-mutant mCRC, which interrupted PKCα/CRAF/MEK/ERK signaling. These findings reveal the critical role of the metabolite DAG as a modulator of encorafenib/cetuximab efficacy in BRAFV600E-mutant mCRC, suggesting that fenofibrate might prove beneficial for resistant BRAFV600E-mutant mCRC patients.

Authors

Jiawei Wang, Huogang Wang, Wei Zhou, Xin Luo, Huijuan Wang, Qing Meng, Jiaxin Chen, Xiaoyu Chen, Yingqiang Liu, David W. Chan, Zhenyu Ju, Zhangfa Song

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Figure 5

MOGAT3 reactivates MAPK through DAG-mediated PKCα/CRAF axis.

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MOGAT3 reactivates MAPK through DAG-mediated PKCα/CRAF axis. (A) RKO EC-...
(A) RKO EC-R cells transfected with siRNA-NC, siRNA-MOGAT3-1, or siRNA-MOGAT3-2 were treated with 2 μM encorafenib/4 μM cetuximab for 72 hours. Western blot assessing MOGAT3 and MEK/ERK signaling. Representative blots are shown. (B) Immunoblot analysis of MEK/ERK signaling in RKO EC-R cells treated with 2 μM encorafenib/4 μM cetuximab, 10 μM PF-06471553 (Pf), alone or in combination for 48 hours. (C) RKO EC-R cells transfected with siRNA-NC, siRNA-MOGAT3-1, or siRNA-MOGAT3-2 treated with 2 μM encorafenib/4 μM cetuximab for 72 hours. Western blot detecting MOGAT3 and PKCα/CRAF signaling. (D) Immunofluorescence of p-PKCα signaling in HT29 and HT29 EC-R cells. Representative images are shown. Scale bar: 10 μm. The images on the far right were further magnified ×4. (E) Immunoblot analysis of PKCα/CRAF signaling in RKO EC-R cells treated with 2 μM encorafenib/4 μM cetuximab, Pf (10 μM), alone or a combination of both for 48 hours. (F) Western blot detecting PKCα/CRAF and MEK/ERK signaling in RKO EC-R cells treated with siRNA-PKCα, siRNA-CRAF, or a combination of both for 48 hours. (G) Immunoblot analysis of PKCα/CRAF and MEK/ERK signaling in RKO cells treated with 0.25 μM encorafenib/0.5 μM cetuximab, 10 μM DAG, or a combination of both for 48 hours. (H) Western bolts detecting the intracellular signal change in encorafenib/cetuximab-resistant PDXs from Figure 3I. The tumor tissues were harvested for Western blotting to detect the indicated signaling proteins. A representative blot is shown from 3 independent experiments.