Enhanced tumor growth elicited by L-type amino acid transporter 1 in human malignant glioma cells
Enhanced tumor growth elicited by L-type amino acid transporter 1 in human malignant glioma cells
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DOI：
10.1227/01.neu.0000316018.51292.19
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发表时间：
2008-02-01
期刊：
影响因子：
4.8
通讯作者：
Nagane, Motoo
中科院分区：
文献类型：
--
作者：
Kobayashi, Keiichi;Ohnishi, Akiko;Nagane, Motoo
目的：研究L型氨基酸转运蛋白1（LAT 1）的表达和功能，LAT 1是L系统的主要催化亚基，负责与共价结合的4F 2重链协同转运大的中性氨基酸，包括大多数必需氨基酸，并与肿瘤发生有关。使用Western印迹和逆转录聚合酶链反应分析人胶质瘤细胞系和肿瘤标本的LAT 1表达。使用L-[C-14]亮氨酸测量中性氨基酸摄取速率。分别用3-（4，5-二甲基噻唑-2-基）-2，5-二苯基溴化四氮唑和末端脱氧核苷酸转移酶介导的缺口末端标记法检测2-氨基双环-（2，2，1）-庚烷-2-羧酸对L系统的抑制作用。结果：LAT 1在大多数人高级别胶质瘤和胶质瘤细胞系中均有不同水平的表达，其中4F 2重链的表达更为普遍。LAT 1高表达的胶质瘤细胞对L-[C-14]亮氨酸的摄取率显着增加。2-氨基双环-（2，2，1）-庚烷-2-羧酸处理不仅抑制了与细胞周期蛋白依赖性激酶抑制剂p21（WAF 1）的上调相关的脱氧核糖核酸合成，而且还增强了与半胱天冬酶激活相关的凋亡，从而在具有高LAT 1表达水平的胶质瘤细胞中发挥细胞抑制和杀细胞作用。结论：LAT 1是系统L的主要转运蛋白，在高级别胶质瘤中的表达水平高于低级别胶质瘤和脑组织，可能在体内肿瘤细胞增殖和生长中起重要作用。
OBJECTIVE: To study the expression and function of L-type amino acid transporter 1 (LAT1), a major catalytic subunit of system L that is responsible for the transport of large neutral amino acids, including most essential amino acids, in concert with the covalently bound 4F2 heavy chain, and is implicated in tumorigenesis.METHODS: Human glioma cell lines and tumor specimens were analyzed for LAT1 expression using Western blotting and reverse transcription polymerase chain reaction analysis. The rate of neutral amino acid uptake was measured using L-[C-14] leucine. The proliferation and apoptosis rates were analyzed by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide and terminal deoxynucleotidyl transferase-mediated nick end-labeling assays, respectively, on inhibition of system L by 2-aminobicyclo-(2, 2, 1)-heptane-2-carboxylic acid. The effects on proliferation and tumor growth caused by exogenously overexpressed LAT1 were similarly analyzed.RESULTS: LAT1 was expressed in most human high-grade gliomas and glioma cell lines at various levels, with more ubiquitous expression of 4F2 heavy chain. Glioma cells with high LAT1 expression exhibited a marked increase in the uptake rate of L-[C-14]leucine. 2-Aminobicyclo-(2, 2, 1)-heptane-2-carboxylic acid treatment not only suppressed deoxyribonucleic acid synthesis in association with the up-regulation of the cyclin-dependent kinase inhibitor p21(WAF1) but also enhanced apoptosis with caspase activation, thereby exerting both cytostatic and cytocidal effects in glioma cells with high LAT1 expression levels. Furthermore, overexpression of LAT1 in glioma cells with low endogenous LAT1 expression significantly enhanced the rates of tumor cell growth in athymic mice.CONCLUSION: LAT1, the major transporter of system L, is frequently expressed at higher levels in high-grade gliomas than in low-grade gliomas and brain tissues, and it may play an important role in enhancing the rates of tumor cell proliferation and growth in vivo.