Lestaurtinib Inhibits Histone Phosphorylation and Androgen-Dependent Gene Expression in Prostate Cancer Cells

BackgroundEpigenetics is defined as heritable changes in gene expression that are not based on changes in the DNA sequence. Posttranslational modification of histone proteins is a major mechanism of epigenetic regulation. The kinase PRK1 (protein kinase C related kinase 1, also known as PKN1) phosphorylates histone H3 at threonine 11 and is involved in the regulation of androgen receptor signalling. Thus, it has been identified as a novel drug target but little is known about PRK1 inhibitors and consequences of its inhibition.
Methodology/Principal FindingUsing a focused library screening approach, we identified the clinical candidate lestaurtinib (also known as CEP-701) as a new inhibitor of PRK1. Based on a generated 3D model of the PRK1 kinase using the homolog PKC-theta (protein kinase c theta) protein as a template, the key interaction of lestaurtinib with PRK1 was analyzed by means of molecular docking studies. Furthermore, the effects on histone H3 threonine phosphorylation and androgen-dependent gene expression was evaluated in prostate cancer cells.
Conclusions/SignificanceLestaurtinib inhibits PRK1 very potently in vitro and in vivo. Applied to cell culture it inhibits histone H3 threonine phosphorylation and androgen-dependent gene expression, a feature that has not been known yet. Thus our findings have implication both for understanding of the clinical activity of lestaurtinib as well as for future PRK1 inhibitors.

背景 表观遗传学（Epigenetics）被定义为不依赖DNA序列改变的基因表达可遗传变化。组蛋白的翻译后修饰是表观遗传调控的主要机制。激酶PRK1（蛋白激酶C相关激酶1，又称PKN1）可在苏氨酸11位点磷酸化组蛋白H3，并参与雄激素受体信号通路的调控。因此，PRK1被鉴定为新型药物靶点，但目前关于PRK1抑制剂及其抑制后的生物学效应的研究仍较为匮乏。
方法与主要发现 本研究通过聚焦化合物库筛选策略，将临床候选药物莱司他汀（lestaurtinib，又称CEP-701）鉴定为一种新型PRK1抑制剂。本研究以同源蛋白PKC-theta（蛋白激酶Cθ）为模板，构建了PRK1激酶的三维结构模型，并通过分子对接分析阐明了莱司他汀与PRK1的关键相互作用模式。此外，本研究在前列腺癌细胞中评估了该化合物对组蛋白H3苏氨酸磷酸化以及雄激素依赖型基因表达的影响。
结论与意义 莱司他汀在体外与体内均展现出强效的PRK1抑制活性。在细胞培养实验中，该药物可抑制组蛋白H3苏氨酸磷酸化与雄激素依赖型基因表达，这一作用此前尚未被报道。因此，本研究结果既有助于阐明莱司他汀的临床活性机制，也可为未来PRK1抑制剂的开发提供理论依据。