Ming Zhengnan, Luo Tiao, Zou Zizheng, Luo Wensong, Hu Xiyuan, Chen Ling, Zhou Jiang, Liu Xiaohe, Liu Mingquan, Li Jijia, Luo Junli, Ma Dayou, Liu Suyou, Luo Zhiyong
Department of Biochemistry and Molecular Biology, School of Life Sciences, Central South University, Changsha, China.
Xiangya Stomatological Hospital, Central South University, Changsha, China.
Hepatol Commun. 2025 Aug 15;9(9). doi: 10.1097/HC9.0000000000000769. eCollection 2025 Sep 1.
The urea cycle and pyrimidine synthesis occur mainly in the liver and undergo opposite changes during hepatocarcinogenesis. Argininosuccinate synthase 1 (ASS1) and carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase (CAD) are key enzymes in the urea cycle and pyrimidine synthesis, respectively, and compete for the common substrate, aspartate. Moreover, ASS1 is lowly expressed in certain cancers, while CAD is highly expressed. However, the role of ASS1 and CAD in liver cancer still remains unclear.
ASS1 and CAD expression in liver cancer were detected by tissue microarrays. Overexpression of ASS1 and CAD was achieved via lentivirus methods. All in vitro experiments were conducted in cells. The interactions of ASS1 and CAD were detected by co-immunoprecipitation (Co-IP) and GST-pull down. The in vivo study was conducted in a BALB/c nude mouse model. Intracellular metabolites were detected by LC-MS/MS.
ASS1 was lowly expressed in liver cancer, while CAD was highly expressed. In patients with recurrent liver cancer, ASS1 and CAD were significantly negatively correlated. Moreover, liver cancer patients with low ASS1 expression and high CAD expression had a poor prognosis. ASS1 and CAD interacted directly and promoted CAD ubiquitination through STUB1. In addition, Overexpression of CAD attenuated the tumor-suppressive effect of ASS1 in liver cancer cells. Pyrimidine supplementation enhanced the growth of liver cancer cells with ASS1 overexpression.
ASS1 deficiency causes an imbalance in the urea cycle and pyrimidine synthesis in liver cancer. ASS1 directly controls the ubiquitination of CAD via STUB1, rather than just competing with aspartate, thereby suppressing liver cancer. Thus, ASS1 has potential as a druggable target in liver cancer.
尿素循环和嘧啶合成主要发生在肝脏中，并且在肝癌发生过程中呈现相反的变化。精氨琥珀酸合酶1（ASS1）和氨甲酰磷酸合成酶2、天冬氨酸转氨甲酰酶和二氢乳清酸酶（CAD）分别是尿素循环和嘧啶合成中的关键酶，它们竞争共同底物天冬氨酸。此外，ASS1在某些癌症中低表达，而CAD高表达。然而，ASS1和CAD在肝癌中的作用仍不清楚。
通过组织芯片检测肝癌中ASS1和CAD的表达。通过慢病毒方法实现ASS1和CAD的过表达。所有体外实验均在细胞中进行。通过免疫共沉淀（Co-IP）和GST下拉检测ASS1和CAD的相互作用。体内研究在BALB/c裸鼠模型中进行。通过液相色谱-串联质谱（LC-MS/MS）检测细胞内代谢物。
ASS1在肝癌中低表达，而CAD高表达。在复发性肝癌患者中，ASS1和CAD显著负相关。此外，ASS1低表达和CAD高表达的肝癌患者预后较差。ASS1和CAD直接相互作用，并通过STUB1促进CAD泛素化。此外，CAD的过表达减弱了ASS1在肝癌细胞中的肿瘤抑制作用。补充嘧啶增强了ASS1过表达的肝癌细胞的生长。
ASS1缺乏导致肝癌中尿素循环和嘧啶合成失衡。ASS1通过STUB1直接控制CAD的泛素化，而不仅仅是与天冬氨酸竞争，从而抑制肝癌。因此，ASS1有潜力成为肝癌的可药物靶向。
