INHIBITION OF TUMOR-CELL GROWTH BY INTERFERON-GAMMA IS MEDIATED BY 2 DISTINCT MECHANISMS DEPENDENT UPON OXYGEN-TENSION - INDUCTION OF TRYPTOPHAN DEGRADATION AND DEPLETION OF INTRACELLULAR NICOTINAMIDE ADENINE-DINUCLEOTIDE
INHIBITION OF TUMOR-CELL GROWTH BY INTERFERON-GAMMA IS MEDIATED BY 2 DISTINCT MECHANISMS DEPENDENT UPON OXYGEN-TENSION - INDUCTION OF TRYPTOPHAN DEGRADATION AND DEPLETION OF INTRACELLULAR NICOTINAMIDE ADENINE-DINUCLEOTIDE
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DOI：
10.1172/jci114247
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发表时间：
1989-09-01
影响因子：
15.9
通讯作者：
POGUE, SL
中科院分区：
文献类型：
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作者：
AUNE, TM;POGUE, SL
干扰素-γ可抑制多种人类肿瘤细胞系的生长。(干扰素-γ)在试管中。这一机制还没有得到很好的理解。目前的实验确定了两种不同的机制来解释干扰素-γ的生长抑制活性。对干扰素-γ最敏感的细胞系。(10-30U/ml干扰素-γ抑制。3d内)用干扰素-γ刺激。将培养上清液中的色氨酸氧化为犬尿氨酸，48-72 h后完全消除培养上清液中的色氨酸，加入L色氨酸，但不加入其他芳香族氨基酸、其他必需氨基酸或D-色氨酸，可阻止干扰素-γ对细胞生长的抑制。干扰素-γ的量。产生50%细胞生长抑制所需的浓度与培养液中L-色氨酸的浓度直接相关，并从apprx开始增加。当培养液中色氨酸浓度从25微米增加到1000微米时，BT20和HT29细胞的生长抑制不受色氨酸的影响。干扰素-γ的抑制作用。5~6d后100~300U/ml，加入二磷酸腺苷-核糖基转移酶(ADP-RT)、3-氨基苯甲酰胺或烟酰胺两种抑制剂可完全阻止。加入干扰素-γ后，ADP-RT活性增强。ADP-RT催化烟酰胺腺嘌呤二核苷酸(NAD)的ADP部分进入蛋白质，导致细胞内NAD的耗竭。所有被测试的肿瘤细胞系在干扰素-γ处理后细胞内NAD水平都降低了。而NAD的丧失先于细胞生长抑制12-24小时。干扰素-γ介导的细胞生长抑制抑制阻止细胞内NAD水平的丧失。活性氧的产生导致DNA链断裂，从而激活ADP-RT。经干扰素-γ处理后，BT20和HT29细胞DNA链断裂增加，而ME180和A549细胞未见明显的DNA断裂。已知的催化色氨酸脱环为犬尿氨酸的两种酶需要超氧阴离子才能起作用。ME180和A549细胞经干扰素-γ培养后，释放出大量的超氧阴离子。降低氧浓度可降低干扰素-γ的产生能力。抑制肿瘤细胞体外生长。细胞内谷胱甘肽已被证明可以保护细胞免受各种因素的氧化损伤。细胞内谷胱甘肽浓度的升高或降低分别降低或提高了细胞系对干扰素-γ的敏感性。这些数据表明，至少有两种不同的机制可以解释干扰素-γ。介导性抑制肿瘤细胞生长。这两种机制似乎对氧分压和细胞内谷胱甘肽浓度的变化都很敏感，这两种机制都会导致细胞内NAD的丢失。
Growth of a variety of human tumor cell lines is inhibited by interferon-.gamma. (IFN-.gamma.) in vitro. This mechanism is not well understood. The present experiments identify two separate mechanisms which account for the growth inhibitory activity of IFN-.gamma.. Cell lines most sensitive to IFN-.gamma. (inhibited by 10-30 U/ml IFN-.gamma. in 3 d) were stimulated by IFN-.gamma. to oxidize tryptophan in media to kynurenine and completely eliminated tryptophan from the culture media after 48-72 h. Addition of L-tryptophan, but not other aromatic amino acids, other essential amino acids, or D-tryptophan, prevented inhibition of cell growth by IFN-.gamma.. The amount of IFN-.gamma. required to yield 50% inhibition of cell growth was directly related to the concentration of L-tryptophan in culture media and increased from .apprx. 3 to 600 U/ml as the concentration of tryptophan in the media was increased from 25 to 1,000 .mu.M. By contrast, inhibition of growth of the cell lines, BT20 and HT29, was not prevented by addition of tryptophan. Inhibition by IFN-.gamma. (100-300 U/ml after 5-6 d) was, however, completely prevented by addition of two inhibitors of adenosine diphosphate-ribosyl transferase (ADP-RT), 3-aminobenzamide or nicotinamide. Activity of ADP-RT was increased in these cell lines after addition of IFN-.gamma.. ADP-RT catalyzes the incorporation of the ADP moiety of nicotinamide adenine dinucleotide (NAD) into proteins and causes depletion of intracellular NAD. All tumor cell lines tested had reduced levels of intracellular NAD after treatment with IFN-.gamma. and loss of NAD preceded inhibition of cell growth by 12-24 h. Inhibitors of IFN-.gamma.-mediated inhibition of cell growth prevented loss of levels of intracellular NAD. Generation of reactive oxygen species lead to DNA strand breaks which result in activation of ADP-RT. Increased DNA strand breaks were induced in BT20 and HT29 cells but not ME180 and A549 cells after culture with IFN-.gamma.. The two enzymes known to catalyze the decyclization of tryptophan to kynurenine require superoxide anion for act ivity. Increased amounts of superoxide anion were released from ME180 and A549 cells after culture with IFN-.gamma.. Reduced oxygen concentration decreased the ability of IFN-.gamma. to inhibit tumor cell growth in vitro. Intracellular glutathione has been shown to protect cells against oxidative damage by various agents. Elevation or reduction of intracellular glutathione concentrations lowered or raised sensitivity of cell lines to IFN-.gamma., respectively. These data indicate that at least two distinct mechanisms can account for IFN-.gamma. mediated inhibition of tumor cell growth. Both mechanisms appear to be sensitive to oxygen tension and to changes in intracellular glutathione concentrations, and both mechanisms lead to loss of intracellular NAD.