Inhibition of the de novo pyrimidine biosynthesis pathway limits ribosomal RNA transcription causing nucleolar stress in glioblastoma cells.
Inhibition of the de novo pyrimidine biosynthesis pathway limits ribosomal RNA transcription causing nucleolar stress in glioblastoma cells.
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DOI：
10.1371/journal.pgen.1009117
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发表时间：
2020-11
期刊：
影响因子：
4.5
通讯作者：
Conacci-Sorrell M
中科院分区：
文献类型：
--
作者：
Lafita-Navarro MC;Venkateswaran N;Kilgore JA;Kanji S;Han J;Barnes S;Williams NS;Buszczak M;Burma S;Conacci-Sorrell M
胶质母细胞瘤是脑部最常见、最具侵袭性的癌症；由于对化疗药物替莫唑胺（temozolomide）的耐药，其预后不良的特点往往是复发，耐药是由MGMT等DNA修复酶的表达增加引起的。不良的预后和有限的治疗选择导致研究针对了解胶质母细胞瘤细胞的特定脆弱性。通过新生生物合成途径导致核苷酸合成增加的代谢适应正在成为驱动胶质母细胞瘤生长的关键改变。在这项研究中，我们发现在高级别胶质瘤和胶质母细胞瘤细胞系中，嘧啶重新生物合成所必需的酶DHODH和UMPS升高。我们证明DHODH的活性是维持核糖体DNA转录（rDNA）所必需的。用特异性抑制剂brequinar或ML390对DHODH进行药理抑制，可有效地消耗体外和体内生长的胶质母细胞瘤细胞中的嘧啶库，并破坏rDNA转录，导致核核应激。核仁胁迫表现为转录因子UBF和核仁组织者核磷蛋白1 （NPM1）的异常重新分布，以及转录因子p53的稳定。此外，DHODH抑制降低了胶质母细胞瘤细胞的增殖，包括替莫唑胺耐药细胞。重要的是，在培养基中加入外源性尿苷，通过挽救途径重建嘧啶的细胞池，恢复了由DHODH抑制剂引起的受损的rDNA转录、核仁形态、p53水平和胶质母细胞瘤细胞的增殖。我们的体内数据表明，虽然抑制DHODH导致肿瘤细胞中嘧啶的急剧减少，但它并不影响正常脑和肝组织中嘧啶的总体水平，这表明通过挽救途径产生的嘧啶可能在维持正常细胞中这些核苷酸方面发挥重要作用。我们的研究表明，胶质母细胞瘤细胞严重依赖于新生嘧啶生物合成途径来产生核糖体RNA (rRNA)，因此，我们确定了一种通过特异性抑制新生嘧啶生物合成途径来抑制核糖体产生并从而抑制胶质母细胞瘤细胞增殖的方法。胶质母细胞瘤是最恶性的脑肿瘤，目前的标准治疗方法是在十多年前建立的，它依赖于手术、放疗和DNA甲基化剂替莫唑胺的结合。在这里，我们报告了一种新的方法，通过抑制嘧啶的新生生物合成来靶向胶质母细胞瘤的生长，这优先限制了核糖体RNA （rRNA）的产生。癌细胞具有较高的rRNA合成速率，因此它们可以产生足够的核糖体来满足与细胞生长和分裂有关的蛋白质合成的需求。因此，通过减少核苷酸的可用性来靶向异常rRNA的产生可能为治疗胶质母细胞瘤和其他类型的肿瘤提供有效的策略。
Glioblastoma is the most common and aggressive type of cancer in the brain; its poor prognosis is often marked by reoccurrence due to resistance to the chemotherapeutic agent temozolomide, which is triggered by an increase in the expression of DNA repair enzymes such as MGMT. The poor prognosis and limited therapeutic options led to studies targeted at understanding specific vulnerabilities of glioblastoma cells. Metabolic adaptations leading to increased synthesis of nucleotides by de novo biosynthesis pathways are emerging as key alterations driving glioblastoma growth. In this study, we show that enzymes necessary for the de novo biosynthesis of pyrimidines, DHODH and UMPS, are elevated in high grade gliomas and in glioblastoma cell lines. We demonstrate that DHODH’s activity is necessary to maintain ribosomal DNA transcription (rDNA). Pharmacological inhibition of DHODH with the specific inhibitors brequinar or ML390 effectively depleted the pool of pyrimidines in glioblastoma cells grown in vitro and in vivo and impaired rDNA transcription, leading to nucleolar stress. Nucleolar stress was visualized by the aberrant redistribution of the transcription factor UBF and the nucleolar organizer nucleophosmin 1 (NPM1), as well as the stabilization of the transcription factor p53. Moreover, DHODH inhibition decreased the proliferation of glioblastoma cells, including temozolomide-resistant cells. Importantly, the addition of exogenous uridine, which reconstitutes the cellular pool of pyrimidine by the salvage pathway, to the culture media recovered the impaired rDNA transcription, nucleolar morphology, p53 levels, and proliferation of glioblastoma cells caused by the DHODH inhibitors. Our in vivo data indicate that while inhibition of DHODH caused a dramatic reduction in pyrimidines in tumor cells, it did not affect the overall pyrimidine levels in normal brain and liver tissues, suggesting that pyrimidine production by the salvage pathway may play an important role in maintaining these nucleotides in normal cells. Our study demonstrates that glioblastoma cells heavily rely on the de novo pyrimidine biosynthesis pathway to generate ribosomal RNA (rRNA) and thus, we identified an approach to inhibit ribosome production and consequently the proliferation of glioblastoma cells through the specific inhibition of the de novo pyrimidine biosynthesis pathway. The current standard therapy for glioblastoma, the most malignant brain tumor, was established more than a decade ago and relies on a combination of surgery, radiation, and the DNA methylating agent temozolomide. Here, we report a new approach to target glioblastoma growth through the inhibition of the de novo biosynthesis of pyrimidines, which preferentially limits ribosomal RNA (rRNA) production. Cancer cells have elevated rates of rRNA synthesis so that they can produce enough ribosomes to meet the demands for protein synthesis that are linked to increase cell growth and division. Therefore, targeting aberrant rRNA production by reducing nucleotide availability could provide an effective strategy to treat glioblastoma and, potentially, other tumor types.
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影响因子：
5.7
作者：
Baumann, Philipp;Mandl-Weber, Sonja;Schmidmaier, Ralf
通讯作者：
Schmidmaier, Ralf
影响因子：
64.5
作者：
ELDEIRY, WS;TOKINO, T;VOGELSTEIN, B
通讯作者：
VOGELSTEIN, B
影响因子：
15.9
作者：
Echizenya, Smile;Ishii, Yukiko;Kondo, Toru
通讯作者：
Kondo, Toru
影响因子：
--
作者：
Chen L;Rousseau RF;Middleton SA;Nichols GL;Newell DR;Lunec J;Tweddle DA
通讯作者：
Tweddle DA
影响因子：
1.1
作者：
Davis ME
通讯作者：
Davis ME