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 3

MOGAT3-mediated DAG elevation determines anti-BRAF/EGFR treatment failure in BRAFV600E-mutant mCRC tumors.

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MOGAT3-mediated DAG elevation determines anti-BRAF/EGFR treatment failur...
(A) Representative IHC images of MOGAT3 in baseline, sensitive, and resistant tumor tissues. Scale bar: 100 μm. (B) Top: Western blots showing protein expression of MOGAT3 in RKO, RKO EC-R, HT29, and HT29 EC-R cells. Representative blots are shown. MOGAT3KO RKO EC-R and HT29 EC-R, along with RKO EC-R-CTRL and HT29 EC-R-CTRL cell lines, were exposed to 2 μM encorafenib/4 μM cetuximab for 96 hours. Bottom: Relative OD value was assessed to determine cell viability by the CCK-8 assay (n = 3). (C–E) Xenograft tumor size in nude mice inoculated with RKO EC-R cells (CTRL) or MOGAT3KO RKO EC-R cells, and treated with just encorafenib-cetuximab or encorafenib-cetuximab in combination with i.p. injection of DAG. (C) Tumor weight, (D) tumor DAG level, and (E) tumor growth in nude mice (n = 6). (F–H) Xenograft tumor size in nude mice inoculated with RKO cells (Nc) or RKO Oe-MOGAT3 cells and treated with encorafenib-cetuximab. (F) Xenograft tumor weight, (G) DAG level in tumor tissues, and (H) tumor growth (n = 6). (I–K) Xenograft tumor size in nude mice inoculated with encorafenib-cetuximab–resistant BRAFV600E-mutant mCRC tumor tissues. PDXs were treated with vehicle (PBS), 20 mg/kg encorafenib/20 mg/kg cetuximab, or MOGAT3 inhibitor PF-06471553 (Pf; 50 mg/kg) alone or in combination with encorafenib-cetuximab. (I) Xenograft tumor weight, (J) DAG level in tumor tissues, and (K) growth in nude mice (n = 6). The data are presented as mean ± SEM of 3 independent experiments. NS, no significance. ***P < 0.001 by 2-way ANOVA with Tukey’s multiple-comparison test (B, E, H, and K), 1-way ANOVA with Tukey’s multiple-comparison test (C, D, I, and J), or 2-tailed, unpaired t test (F and G).