TY - JOUR
T1 - A Citrate Synthase Splice Variant Rewires the TCA Cycle to Promote Colorectal Cancer Progression
AU - Cheung, Justin Chak Ting
AU - Ng, Lok Wan
AU - Zhu, Zhongxu
AU - Chen, Bonan
AU - Li, Stephen
AU - Xu, Mingjing
AU - Ding, Xiaofan
AU - Pu, Dandan
AU - Hu, Yi
AU - Ren, Yuqing
AU - Kang, Wei
AU - Li, Ming
AU - Wong, Jason Wing Hon
AU - Wang, Xin
AU - Cheng, Yuen Kit
AU - Aik, Wei Shen
AU - Wong, Ka-Leung
AU - Ng, Simon Siu Man
AU - Wong, Nathalie
AU - Dong, Yujuan
N1 - We thank the Center for PanorOmic Sciences–Proteomics and Metabolomics Core (PM Core), HKUMed, University of Hong Kong, for performing GC-MS/MS runs. We also thank Professor Masahiro Sugimoto from the Institute for Advanced Biosciences, Keio University, for providing valuable metabolomic data. We also thank the lab members of Dr. Christine Chio Iok In from Columbia University
Irving Medical Center for the insightful discussions. This work was supported by the Hong Kong Research Grants Council Area of Excellence Scheme (ref. AoE/M-401/20), Research, Academic and Industry Sectors One-plus Scheme (ref. RAI/24/ 1/077A), the Hong Kong Research Grants Council General Research Fund (ref. 14115123), Chinese University of Hong Kong Direct Grant (ref. 4054798), and Collaborative Research Fund (ref. C4024-22GF).
Publisher Copyright:
©2025 The Authors; Published by the American Association for Cancer Research.
PY - 2025/11/14
Y1 - 2025/11/14
N2 - Metabolic reprogramming, notably alterations in the tricarboxylic acid (TCA) cycle, has emerged as a hallmark of cancer that supports tumor growth and metastasis. Despite the TCA cycle being a classical central metabolic pathway, further exploration is needed to fully elucidate the intricate manifestations and contributory mechanisms of TCA cycle rewiring in colorectal carcinogenesis. In this study, we identified a splicing isoform of citrate synthase (CS), CS-ΔEx4, and unveiled its role in TCA cycle dysregulation in colorectal cancer. CS-ΔEx4 was distinctly upregulated in colorectal cancer tumors compared with the canonical CS full-length (CS-FL) isoform. Clinical analyses established a strong correlation between elevated CS-ΔEx4 expression and cancer recurrence as well as inferior survival outcomes in patients with colorectal cancer. Functional experiments revealed the active contribution of CS-ΔEx4 to the aggressive phenotype of colorectal cancer cells both in vitro and in vivo. Mechanistically, CS-ΔEx4 formed a heterocomplex with CS-FL within the mitochondria that influenced the enzymatic function of canonical CS and accelerated TCA cycle flux, thereby promoting the accumulation of the oncometabolite 2-hydroxyglutarate. The CS-ΔEx4-mediated metabolic alterations engendered epigenomic modulations that drove the upregulation of oncogenic gene signatures. In silico screening identified a small molecule with potent antiproliferative effects in colorectal cancer cell line and organoid models that selectively antagonized the CS-ΔEx4 and CS-FL heterocomplex activity while sparing the CS-FL homodimers. Together, this study discovered the presence of a spliced CS isoform that promotes colorectal cancer progression and identified a molecule that holds potential for targeting the CS-ΔEx4 and CS-FL heterocomplex. SIGNIFICANCE: The citrate synthase variant CS-ΔEx4 augments TCA metabolic flux to facilitate epigenetic reprogramming and colorectal carcinogenesis and can be targeted with a small molecule, providing a promising treatment strategy for colorectal cancer. See related commentary by Schatton and Frezza, p. 4293.
AB - Metabolic reprogramming, notably alterations in the tricarboxylic acid (TCA) cycle, has emerged as a hallmark of cancer that supports tumor growth and metastasis. Despite the TCA cycle being a classical central metabolic pathway, further exploration is needed to fully elucidate the intricate manifestations and contributory mechanisms of TCA cycle rewiring in colorectal carcinogenesis. In this study, we identified a splicing isoform of citrate synthase (CS), CS-ΔEx4, and unveiled its role in TCA cycle dysregulation in colorectal cancer. CS-ΔEx4 was distinctly upregulated in colorectal cancer tumors compared with the canonical CS full-length (CS-FL) isoform. Clinical analyses established a strong correlation between elevated CS-ΔEx4 expression and cancer recurrence as well as inferior survival outcomes in patients with colorectal cancer. Functional experiments revealed the active contribution of CS-ΔEx4 to the aggressive phenotype of colorectal cancer cells both in vitro and in vivo. Mechanistically, CS-ΔEx4 formed a heterocomplex with CS-FL within the mitochondria that influenced the enzymatic function of canonical CS and accelerated TCA cycle flux, thereby promoting the accumulation of the oncometabolite 2-hydroxyglutarate. The CS-ΔEx4-mediated metabolic alterations engendered epigenomic modulations that drove the upregulation of oncogenic gene signatures. In silico screening identified a small molecule with potent antiproliferative effects in colorectal cancer cell line and organoid models that selectively antagonized the CS-ΔEx4 and CS-FL heterocomplex activity while sparing the CS-FL homodimers. Together, this study discovered the presence of a spliced CS isoform that promotes colorectal cancer progression and identified a molecule that holds potential for targeting the CS-ΔEx4 and CS-FL heterocomplex. SIGNIFICANCE: The citrate synthase variant CS-ΔEx4 augments TCA metabolic flux to facilitate epigenetic reprogramming and colorectal carcinogenesis and can be targeted with a small molecule, providing a promising treatment strategy for colorectal cancer. See related commentary by Schatton and Frezza, p. 4293.
UR - https://www.scopus.com/pages/publications/105021878032
U2 - 10.1158/0008-5472.CAN-24-2355
DO - 10.1158/0008-5472.CAN-24-2355
M3 - Journal article
C2 - 40900036
SN - 1538-7445
VL - 85
SP - 4450
EP - 4468
JO - Cancer Research
JF - Cancer Research
IS - 22
ER -
