Role of polyamines on cell proliferation and differentiation

1. 利用亚精胺乙酰转移酶（speG）基因缺陷突变体CAG2242和克隆的speG基因，研究了大肠杆菌亚精胺乙酰转移酶的生理功能。有无0.5 mM亚精胺的情况下，大肠杆菌CAG2242的生长均正常。然而，添加0.5 mM亚精胺后，大肠杆菌CAG2242在开始生长后48 h的细胞活力明显下降。细胞中积累的亚精胺量约为无亚精胺细胞的3倍。将克隆的speG基因转化到大肠杆菌CAG2242中，恢复了细胞活力。在生长后28 h，亚精胺的积累导致蛋白质合成减少，但DNA和RNA合成没有减少。几种蛋白质的合成特别受到抑制。它们包括核糖体调节因子和OmpC蛋白。由于核糖体调节因子在细胞生长的固定阶段对细胞活力至关重要，因此蛋白质的减少被认为是细胞活力下降的原因之一。核糖体调节因子的降低主要发生在翻译水平。研究了1,15-双（乙胺）-4,8,12-三氮杂戊烷（BE3333）对肿瘤细胞生长的影响。BE3333抑制鸟氨酸脱羧酶和s -腺苷蛋氨酸脱羧酶，诱导亚精胺/精胺N^1-乙酰转移酶，从而减少多胺的数量。BE3333在细胞中积累的浓度是对照细胞中精胺的3-5倍。累积的BE3333抑制蛋白质合成，尤其是线粒体蛋白质合成，并降低ATP的量。蛋白质合成的抑制与随后的细胞生长抑制相关。BE3333在体外系统中对小鼠FM3A乳腺癌细胞、人SW480和SW620结肠肿瘤细胞、Lu-65A和A549肺肿瘤细胞、MCF-7乳腺肿瘤细胞、MALME-3M和A375黑色素瘤细胞的生长均有抑制作用，抑制范围为0.5 ~ 10 μ m。BE3333每日静脉注射（30 mg/kg）或腹腔注射（50 mg/kg），连续5天显著抑制人肿瘤SW620异种移植到裸鼠体内的生长。BE3333对肺肿瘤（Lu-65、Lx-1、Lc-1和Lu-61）、胃肿瘤（Sc-6和St-15）和黑色素瘤（SEKI）的生长也有抑制作用。结果表明，BE3333对快速和缓慢生长的肿瘤均有效，具有合理的短期宿主毒性。少

1. Physiological functions of spermidine acetyltransferase in Escherichia coli have been studied using the spermidine acetyltransferase (speG) gene-deficient mutant CAG2242 and the cloned speG gene. The growth of E.coli CAG2242 was normal in the presence and absence of 0.5 mM spermidine. However, cell viability of E.coli CAG2242 at 48 h after the onset of growth decreased greatly by the addition of 0.5 mM spermidine. The amount of spermidine accumulated in the cells was approximately 3-fold that in the cells grown in the absence of spermidine. Transformation of the cloned speG gene to E.coli CAG2242 recovered the cell viability. The accumulation of spermidine caused a decrease in protein synthesis but not in DNA and RNA synthesis at 28 h after the onset of growth. The synthesis of several kinds of proteins was particularly inhibited. They included ribosome mudulation factor and OmpC protein. Since the ribosome modulation factor is essential for cell viability at the stationary phase of … More growth, the decrease in the protein was thought to be one of the reasons for the decrease in cell viability. The decrease in the ribosome modulation factor mainly occured at the translational level.2. Effects of 1,15-bis (ethylamino) -4,8,12-triazapentadecane (BE3333) on the growth of tumor cells were studied in in vitro systems and with tumor xenografts in mice. BE3333 suppressed ornithine decarboxylase and S-adenosylmethionine decarboxylase, induced spermidine/spermine N^1-acetyltransferase, and thus decreased the amount of polyamines. BE3333 accumulated in cells at a concentration 3-5-fold that of spermine in control cells. The accumulated BE3333 inhibited protein synthesis, especially mitochondrial protein synthesis, and decreased the amount of ATP.The inhibition of protein synthesis was correlated with the subsequent inhibition of cell growth. BE3333 showed inhibitory effects in in vitro systems against the growth of mouse FM3A mammary carcinoma cells, human SW480 and SW620 colon tumor cells, Lu-65A and A549 lung tumor cells, MCF-7 breast tumor cells, and MALME-3M and A375 melanoma cells at a range of 0.5-10 muM.Intravenous (30 mg/kg) or i. p. (50 mg/kg) daily injections of BE3333 for 5 days greatly suppressed the growth of human tumor SW620 xenotrasplanted into nude mice. BE3333 also showed inhibitory effects against the growth of lung tumors (Lu-65, Lx-1, Lc-1, and Lu-61), stomach tumors (Sc-6 and St-15), and melanoma (SEKI) xenotransplanted into nude mice. The results indicate that BE3333 is effective against both rapid-and slow-growting tumors, with reasonable short-term host toxicity. Less