Collins C L, Wasa M, Souba W W, Abcouwer S F
Department of Surgery, Harvard Medical School, Massachusetts General Hospital, Boston 02114, USA.
J Cell Physiol. 1998 Jul;176(1):166-78. doi: 10.1002/(SICI)1097-4652(199807)176:1<166::AID-JCP18>3.0.CO;2-5.
A continual supply of the amino acid glutamine (GLN) may be necessary for cancerous cell growth. GLN plays a central role in multiple metabolic pathways and has long been considered an essential component of tissue culture media. However, the GLN requirements of tumor cell lines and the factors that determine a cell's need for GLN have not been comprehensively studied. Also, it remains unclear how various metabolic pathways contribute to GLN consumption. In the present study, possible determinants of GLN metabolism were examined in seven breast cell lines, two derived from immortalized normal tissue and five of tumor origin. These cells exhibited different dependencies on media GLN concentration for growth and a wide range of GLN utilization rates. GLN uptake was facilitated by a single, common transporter functionally defined as System ASC. However, the affinities for GLN exhibited by this transporter differed appreciably between cell lines. Furthermore, the concentration at which media GLN became a limiting factor for cellular proliferation correlated with transporter affinity. The origin of the cell lines was not a determinant of GLN metabolism because immortalized cells of nontumor origin exhibited GLN dependence and utilization rates comparable to those of tumor-derived cells. The rates of CO2 production from GLN were similar for each cell lines. Rates of GLN disappearance and glutamate appearance in media were strongly correlated, with 32-80% of media GLN converted to glutamate. Both rates were directly affected by media cystine concentration, suggesting that a large portion of glutamate efflux was coupled with cystine import through the amino acid transport system x(c)-. These results demonstrated that cell growth is a function of GLN influx and suggest that GLN is used to supply glutamate and cystine, perhaps for glutathione synthesis.
持续供应氨基酸谷氨酰胺（GLN）可能是癌细胞生长所必需的。GLN在多种代谢途径中起核心作用，长期以来一直被认为是组织培养基的重要成分。然而，肿瘤细胞系对GLN的需求以及决定细胞对GLN需求的因素尚未得到全面研究。此外，尚不清楚各种代谢途径如何促进GLN的消耗。在本研究中，在七种乳腺癌细胞系中检测了GLN代谢的可能决定因素，其中两种源自永生化正常组织，五种源自肿瘤组织。这些细胞在生长对培养基GLN浓度的依赖性以及GLN利用率方面表现出不同。一种功能上定义为系统ASC的单一通用转运蛋白促进了GLN的摄取。然而，该转运蛋白对GLN的亲和力在不同细胞系之间存在明显差异。此外，培养基GLN成为细胞增殖限制因素的浓度与转运蛋白亲和力相关。细胞系的来源不是GLN代谢的决定因素，因为非肿瘤来源的永生化细胞表现出与肿瘤来源细胞相当的GLN依赖性和利用率。每个细胞系从GLN产生CO2的速率相似。培养基中GLN消失的速率和谷氨酸出现的速率密切相关，32%至80%的培养基GLN转化为谷氨酸。这两个速率都直接受培养基胱氨酸浓度的影响，表明大部分谷氨酸外流与通过氨基酸转运系统x(c)-的胱氨酸内流相关。这些结果表明细胞生长是GLN流入的函数，并表明GLN用于供应谷氨酸和胱氨酸，可能用于谷胱甘肽合成。
