Sahu Divya, Gupta Sounak, Hau Andrew M, Nakashima Kazufumi, Leivo Mariah Z, Searles Stephen C, Elson Paul, Bomalaski John S, Casteel Darren E, Boss Gerry R, Hansel Donna E
Department of Pathology, University of California at San Diego, La Jolla, California.
Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio.
Am J Pathol. 2017 Jan;187(1):200-213. doi: 10.1016/j.ajpath.2016.09.004. Epub 2016 Dec 9.
Loss of argininosuccinate synthetase 1 (ASS1), a key enzyme for arginine synthesis, occurs in many cancers, making cells dependent on extracellular arginine and targetable by the arginine-degrading enzyme pegylated arginine deiminase (ADI-PEG 20). We evaluated ASS1 expression and effects of ASS1 loss in bladder cancer which, despite affecting >70,000 people in the United States annually, has limited therapies. ASS1 loss was identified in conventional and micropapillary urothelial carcinoma, small cell, and squamous cell carcinoma subtypes of invasive bladder cancer, as well as in T24, J82, and UM-UC-3 but not in 5637, RT112, and RT4 cell lines. ASS1-deficient cells showed preferential sensitivity to ADI-PEG 20, evidenced by decreased colony formation, reduced cell viability, and increased sub-G1 fractions. ADI-PEG 20 induced general control nonderepressible 2-dependent eukaryotic initiation factor 2α phosphorylation and activating transcription factor 4 and C/EBP homologous protein up-regulation, associated with caspase-independent apoptosis and autophagy. These effects were ablated with selective siRNA silencing of these proteins. ASS1 overexpression in UM-UC-3 or ASS1 silencing in RT112 cells reversed these effects. ADI-PEG 20 treatment of mice bearing contralateral flank UM-UC-3 and RT112 xenografts selectively arrested tumor growth in UM-UC-3 xenografts, which had reduced tumor size, reduced Ki-67, and increased terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining. This suggests that ASS1 loss occurs in invasive bladder cancer and is targetable by ADI-PEG 20.
精氨酸琥珀酸合成酶1（ASS1）是精氨酸合成的关键酶，其缺失存在于多种癌症中，导致细胞依赖细胞外精氨酸，并且可被精氨酸降解酶聚乙二醇化精氨酸脱亚氨酶（ADI-PEG 20）靶向作用。我们评估了ASS1在膀胱癌中的表达及ASS1缺失的影响，膀胱癌在美国每年影响超过7万人，但治疗方法有限。在浸润性膀胱癌的传统型和微乳头型尿路上皮癌、小细胞癌和鳞状细胞癌亚型中以及在T24、J82和UM-UC-3细胞系中发现了ASS1缺失，但在5637、RT112和RT4细胞系中未发现。ASS1缺陷型细胞对ADI-PEG 20表现出优先敏感性，集落形成减少、细胞活力降低和亚G1期细胞比例增加证明了这一点。ADI-PEG 20诱导一般控制非抑制性2依赖性真核起始因子2α磷酸化以及激活转录因子4和C/EBP同源蛋白上调，这与不依赖半胱天冬酶的凋亡和自噬相关联。这些效应通过这些蛋白的选择性siRNA沉默而消除。在UM-UC-3细胞中过表达ASS1或在RT112细胞中沉默ASS1可逆转这些效应。用ADI-PEG 20处理携带对侧胁腹UM-UC-3和RT112异种移植物的小鼠，可选择性地阻止UM-UC-3异种移植物中的肿瘤生长，该异种移植物的肿瘤大小减小、Ki-67降低并且末端脱氧核苷酸转移酶介导的dUTP缺口末端标记染色增加。这表明ASS1缺失发生在浸润性膀胱癌中并且可被ADI-PEG 20靶向作用。
