Metabolic and antiproliferative consequences of activated polyamine catabolism in LNCaP prostate carcinoma cells
Metabolic and antiproliferative consequences of activated polyamine catabolism in LNCaP prostate carcinoma cells
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DOI：
10.1074/jbc.m403323200
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发表时间：
2004-06-25
影响因子：
4.8
通讯作者：
Porter, CW
中科院分区：
文献类型：
--
作者：
Kee, K;Vujcic, S;Porter, CW
细胞内多胺池的耗竭总是抑制细胞生长。虽然这通常是通过抑制多胺生物合成来实现的，但我们认为，在亚精胺/精胺N6(1)-乙酰转移酶（SSAT）水平上激活多胺分解代谢可能更有效地实现这一目标；该策略首先在MCF-7乳腺癌细胞中得到验证。我们现在研究的可能性是，由于前列腺中多胺稳态的独特方面，来源于它的肿瘤细胞可能对激活的多胺分解代谢特别敏感。因此，SSAT通过四环素调节（Tet-off）系统在LNCaP前列腺癌细胞中有条件地过表达。四环素去除导致SSAT mRNA快速增加近10倍，酶活性增加近20倍。SSAT产物N-1-乙酰精胺、N-1-乙酰精胺和N-1、n -12-二乙酰精胺在细胞内和细胞外积累。SSAT诱导也导致生长抑制，但不像在MCF-7细胞中那样伴有多胺池耗竭。相反，细胞内亚精胺和精胺池是通过鸟氨酸脱羧酶和s -腺苷蛋氨酸脱羧酶活性的代偿性增强维持在或高于对照水平的。这反过来又通过多胺代谢的生物合成和分解代谢臂产生了高速率的代谢通量。在四环素去除过程中，使用生物合成抑制剂α -二氟甲基鸟氨酸阻断了通量并防止了生长抑制。因此，通量诱导的生长抑制似乎源于代谢产物的过度积累和/或代谢前体的消耗。代谢影响也不排除是可能的影响因素，包括高水平的腐胺和乙酰化多胺，s -腺苷蛋氨酸减少50%，SSAT辅助因子乙酰辅酶a下降45%。总体而言，该研究表明LNCaP细胞中多胺分解代谢的激活引起多胺生物合成和下游代谢事件的代偿性增加，最终导致生长抑制。
Depletion of intracellular polyamine pools invariably inhibits cell growth. Although this is usually accomplished by inhibiting polyamine biosynthesis, we reasoned that this might be more effectively achieved by activation of polyamine catabolism at the level of spermidine/ spermine N6(1)-acetyltransferase (SSAT); a strategy first validated in MCF-7 breast carcinoma cells. We now examine the possibility that, due to unique aspects of polyamine homeostasis in the prostate gland, tumor cells derived from it may be particularly sensitive to activated polyamine catabolism. Thus, SSAT was conditionally overexpressed in LNCaP prostate carcinoma cells via a tetracycline-regulatable (Tet-off) system. Tetracycline removal resulted in a rapid similar to10-fold increase in SSAT mRNA and an increase of similar to20-fold in enzyme activity. SSAT products N-1-acetylspermidine, N-1-acetylspermine, and N-1, N-12-diacetylspermine accumulated intracellularly and extracellularly. SSAT induction also led to a growth inhibition that was not accompanied by polyamine pool depletion as it was in MCF-7 cells. Rather, intracellular spermidine and spermine pools were maintained at or above control levels by a robust compensatory increase in ornithine decarboxylase and S-adenosylmethionine decarboxylase activities. This, in turn, gave rise to a high rate of metabolic flux through both the biosynthetic and catabolic arms of polyamine metabolism. Treatment with the biosynthesis inhibitor alpha-difluoromethylornithine during tetracycline removal interrupted flux and prevented growth inhibition. Thus, flux-induced growth inhibition appears to derive from overaccumulation of metabolic products and/or from depletion of metabolic precursors. Metabolic effects that were not excluded as possible contributing factors include high levels of putrescine and acetylated polyamines, a 50% reduction in S-adenosylmethionine, and a 45% decline in the SSAT cofactor acetyl-CoA. Overall, the study demonstrates that activation of polyamine catabolism in LNCaP cells elicits a compensatory increase in polyamine biosynthesis and downstream metabolic events that culminate in growth inhibition.