MOGAT3-mediated DAG accumulation drives acquired resistance to anti-BRAF/anti-EGFR therapy in BRAFV600E-mutant metastatic colorectal cancer
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
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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Research Article Gastroenterology

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 7

Reducing intratumoral DAG with fenofibrate overcomes the resistance of BRAFV600E-mutant mCRC tumors upon dual therapy.

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Reducing intratumoral DAG with fenofibrate overcomes the resistance of B...
(A–C) Xenograft tumor size in nude mice inoculated with encorafenib- and cetuximab-resistant BRAFV600E-mutant mCRC tumor tissues treated with vehicle (PBS), encorafenib (20 mg/kg), cetuximab (20 mg/kg), or fenofibrate (100 mg/kg), alone or all 3 together (n = 6). (A) Representative tumor images. (B) Quantification of DAG levels in tumor tissues. (C) Quantification of tumor growth (n = 6). (D) Representative images of H&E, Ki67, Oil Red O, and TUNEL staining. (E) The quantitation of Ki67 and TUNEL (n = 4). (F) Immunoblot analysis of PKCα/CRAF and MEK/ERK signaling in tumor tissues related to A. (G and H) Xenograft tumor size in nude mice inoculated with encorafenib- and cetuximab-resistant BRAFV600E-mutant mCRC tumor tissues orally treated with vehicle (PBS), encorafenib/cetuximab (20 mg/kg, 20 mg/kg), encorafenib/cetuximab/fenofibrate (20 mg/kg, 20 mg/kg, 100 mg/kg), encorafenib/cetuximab/fenofibrate/PMA (20 mg/kg, 20 mg/kg, 100 mg/kg, 20 mg/kg), encorafenib/cetuximab/PKC-IN-1 (20 mg/kg, 20 mg/kg, 30 mg/kg), or encorafenib/cetuximab/RAF-IN-1 (20 mg/kg, 20 mg/kg, 30 mg/kg) (n = 6). (G) Representative images of xenograft tumor growth in nude mice. (H) Quantification of tumor growth. (I) Western bolt assessing the protein expression of PKCα/CRAF/MEK/ERK signaling in encorafenib/cetuximab-resistant PDXs from G. The tumor tissues were harvested for Western blotting to detect the indicated signaling proteins. A representative blot is shown from 3 independent experiments. The data are presented as mean ± SEM of 3 independent experiments. NS, no significance. ***P < 0.001 by 1-way ANOVA with Tukey’s multiple-comparison test (B and E) or 2-way ANOVA with Tukey’s multiple-comparison test (C and H).