Marverti Gaetano, Giuseppina Monti Maria, Pegg Anthony E, McCloskey Diane E, Bettuzzi Saverio, Ligabue Alessio, Caporali Andrea, D'Arca Domenico, Moruzzi Maria Stella
Dipartimento di Scienze Biomediche, Sezione di Chimica Biologica, Università di Modena e Reggio Emilia, Via Campi 287, I-41100 Modena, Italy.
Carcinogenesis. 2005 Oct;26(10):1677-86. doi: 10.1093/carcin/bgi129. Epub 2005 May 19.
The limited induction of spermidine/spermine N1-acetyltransferase (SSAT) activity has been implicated as an important determinant of the reduced response to the spermine analogue N1,N12-bis(ethyl)spermine (BESpm) by the cisplatin or cis-diamminedichloroplatinum(II) (cDDP)-resistant human ovarian carcinoma cell line (C13*). We checked whether or not under conditions of SSAT overexpression, enzyme induction and cell sensitivity to both, BESpm and cDDP, were restored to levels comparable with those of more responsive cDDP-sensitive 2008 cells. We transiently transfected the SSAT repressed C13* cells with two expression vectors driving human SSAT overexpression by diverse promoters. We then analysed their responses in the absence and in the presence of BESpm. SSAT activity was promptly, but briefly, expressed by transfection with both pOP/SSAT and pCMV-SSAT plasmids. However, only in the presence of BESpm, did SSAT activity reach the highest levels of induction for longer duration, with different time-courses for the two vectors, that paralleled the effect on cell growth. Under these conditions, growth sensitivity to BESpm of the less-responsive C13* cells was 25% reverted to cell growth inhibition displayed by 2008 cells. More interestingly, the sensitivity to cDDP cytotoxicity also increased in parallel to SSAT overexpression. BESpm induction of pCMV-SSAT-transfected cells caused a further 20-30% reduction of cell survival induced by cDDP, almost recovering the sensitivity of 2008 cells. The enhanced effectiveness of cDDP was also confirmed by the comet assay, showing an increase in the number and length of tails of damaged DNA. These findings confirm that SSAT overexpression inhibits cell growth and enhances growth sensitivity to BESpm in C13* cells, showing for the first time that restoring high inducibility of SSAT activity subverts the reduced sensitivity to cDDP of SSAT-deficient cells, making them almost indistinguishable from the responsive parental 2008 cells.
亚精胺/精胺N1 - 乙酰基转移酶（SSAT）活性的有限诱导被认为是顺铂或顺 - 二氨二氯铂（II）（cDDP）耐药的人卵巢癌细胞系（C13*）对精胺类似物N1，N12 - 双（乙基）精胺（BESpm）反应降低的一个重要决定因素。我们检查了在SSAT过表达的条件下，酶诱导以及细胞对BESpm和cDDP的敏感性是否恢复到与更敏感的cDDP敏感的2008细胞相当的水平。我们用两种由不同启动子驱动人SSAT过表达的表达载体瞬时转染了SSAT受抑制的C13细胞。然后我们分析了它们在不存在和存在BESpm的情况下的反应。用pOP/SSAT和pCMV - SSAT质粒转染均能迅速但短暂地表达SSAT活性。然而，只有在存在BESpm的情况下，SSAT活性才能在更长时间内达到最高诱导水平，两种载体的时间进程不同，这与对细胞生长的影响平行。在这些条件下，反应较弱的C13细胞对BESpm的生长敏感性有25%恢复到2008细胞所表现出的细胞生长抑制。更有趣的是，对cDDP细胞毒性的敏感性也与SSAT过表达平行增加。BESpm对pCMV - SSAT转染细胞的诱导导致cDDP诱导的细胞存活率进一步降低20 - 30%，几乎恢复到2008细胞的敏感性。彗星试验也证实了cDDP有效性的增强，显示受损DNA尾巴的数量和长度增加。这些发现证实，SSAT过表达抑制C13*细胞的生长并增强其对BESpm的生长敏感性，首次表明恢复SSAT活性的高诱导性可颠覆SSAT缺陷细胞对cDDP的降低敏感性，使其几乎与反应性亲本2008细胞无异。
