Cisplatin-induced synthetic lethality to arginine-starvation therapy by transcriptional suppression of ASS1 is regulated by DEC1, HIF-1α, and c-Myc transcription network and is independent of ASS1 promoter DNA methylation.
Cisplatin-induced synthetic lethality to arginine-starvation therapy by transcriptional suppression of ASS1 is regulated by DEC1, HIF-1α, and c-Myc transcription network and is independent of ASS1 promoter DNA methylation.
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DOI：
10.18632/oncotarget.12308
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发表时间：
2016-12-13
期刊：
影响因子：
--
通讯作者：
Kuo MT
中科院分区：
文献类型：
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作者：
Long Y;Tsai WB;Chang JT;Estecio M;Wangpaichitr M;Savaraj N;Feun LG;Chen HH;Kuo MT
许多人类肿瘤需要细胞外精氨酸(Arg)来生长，因为Arg从头合成的关键酶-精氨酸琥珀酸合成酶1(ASS1)被沉默。这些肿瘤对使用聚乙二醇化精氨酸脱亚胺酶(ADI-PEG20)的Arg饥饿疗法很敏感，该酶可以消化细胞外的Arg。以往的许多研究报道ASS1沉默是由于DNA甲基化导致ASS1表达的表观遗传失活，去甲基化试剂5-氮杂脱氧胞苷(aza-DC)可以诱导ASS1的表达。此外，据报道顺铂通过ASS1启动子甲基化抑制ASS1的表达，导致对ADI-PEG20治疗的合成致死性。我们在此报道顺铂抑制ass1的表达是由于HIF-1α的上调和c-myc的下调，这两种基因分别通过与ass1启动子的相互结合而对ass1的表达起到负向和正向调节作用。相反，我们发现Aza-DC通过下调HIF-1α而上调c-Myc来诱导ASS1mRNA的表达。我们进一步证明时钟蛋白DEC1是HIF-1、α和c-Myc的主要调节者，它们调节ASS1.CDDP上调DEC1的表达，而aza-DC抑制其表达。使用两种蛋白酶体抑制剂Bortezomib和carfilzomib诱导HIF-1α积聚，我们进一步证明了HIF-1α参与沉默As1以维持Arg营养缺陷性靶向治疗。
Many human tumors require extracellular arginine (Arg) for growth because the key enzyme for de novo biosynthesis of Arg, argininosuccinate synthetase 1 (ASS1), is silenced. These tumors are sensitive to Arg-starvation therapy using pegylated arginine deiminase (ADI-PEG20) which digests extracellular Arg. Many previous studies reported that ASS1 silencing is due to epigenetic inactivation of ASS1 expression by DNA methylation, and that the demethylation agent 5-aza-deoxycytidine (Aza-dC) can induce ASS1 expression. Moreover, it was reported that cisplatin suppresses ASS1 expression through ASS1 promoter methylation, leading to synthetic lethality to ADI-PEG20 treatment. We report here that cisplatin supppresses ASS1 expression is due to upregulation of HIF-1α and downregulation of c-Myc, which function as negative and positive regulators of ASS1 expression, respectively, by reciprocal bindings to the ASS1 promoter. In contrast, we found that Aza-dC induces ASS1 expression by downregulation of HIF-1α but upregulation of c-Myc. We further demonstrated that the clock protein DEC1 is the master regulator of HIF-1α and c-Myc that regulate ASS1. cDDP upregulates DEC1, whereas Aza-dC suppresses its expression. Using two proteasomal inhibitors bortezomib and carfilzomib which induce HIF-1α accumulation, we further demonstrated that HIF-1α is involved in ASS1 silencing for the maintenance of Arg auxotrophy for targeted Arg-starvation therapy.