siRNAs that specifically silence the expression of cancer-related genes offer a therapeutic approach in oncology. However, it remains critical to determine the true mechanism of their therapeutic effects. Here, we describe the preclinical development of chemically modified siRNA targeting the essential cell-cycle proteins polo-like kinase 1 (PLK1) and kinesin spindle protein (KSP) in mice. siRNA formulated in stable nucleic acid lipid particles (SNALP) displayed potent antitumor efficacy in both hepatic and subcutaneous tumor models. This was correlated with target gene silencing following a single intravenous administration that was sufficient to cause extensive mitotic disruption and tumor cell apoptosis. Our siRNA formulations induced no measurable immune response, minimizing the potential for nonspecific effects. Additionally, RNAi-specific mRNA cleavage products were found in tumor cells, and their presence correlated with the duration of target mRNA silencing. Histological biomarkers confirmed that RNAi-mediated gene silencing effectively inhibited the target's biological activity. This report supports an RNAi-mediated mechanism of action for siRNA antitumor effects, suggesting a new methodology for targeting other key genes in cancer development with siRNA-based therapeutics.

中文翻译：

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确认基于 siRNA 的癌症疗法在小鼠中的 RNAi 介导的作用机制。

特异性沉默癌症相关基因表达的 siRNA 为肿瘤学提供了一种治疗方法。然而，确定其治疗效果的真正机制仍然至关重要。在这里，我们描述了针对小鼠必需细胞周期蛋白 polo 样激酶 1 (PLK1) 和驱动蛋白纺锤体蛋白 (KSP) 的化学修饰 siRNA 的临床前开发。在稳定核酸脂质颗粒 (SNALP) 中配制的 siRNA 在肝脏和皮下肿瘤模型中均显示出强大的抗肿瘤功效。这与单次静脉内给药后的靶基因沉默有关，后者足以引起广泛的有丝分裂破坏和肿瘤细胞凋亡。我们的 siRNA 配方不会引起可测量的免疫反应，最大限度地减少了非特异性效应的可能性。此外，在肿瘤细胞中发现了 RNAi 特异性 mRNA 切割产物，它们的存在与目标 mRNA 沉默的持续时间相关。组织学生物标志物证实，RNAi 介导的基因沉默有效地抑制了靶标的生物活性。该报告支持 siRNA 抗肿瘤作用的 RNAi 介导的作用机制，提出了一种新的方法，用于使用基于 siRNA 的疗法靶向癌症发展中的其他关键基因。