Introduction

Proapoptotic peptide, (KLAKLAK)₂, exhibits strong anti-tumor effect with the help of cell-penetrating peptides such as Pep2, targeting TLR2 with high expression in acute myeloid leukemia (AML). However, the applications are limited due to the peptide’s instability and high cost of synthesis. Recombinant PP7 bacteriophage-like particles (VLPs) can protect the peptides from degradation by proteases, based on their ability to display foreign peptides.

Methods

Here, we evaluated the feasibility of PP7 VLPs carrying Pep2 and (KLAKLAK)₂ (2PP7-Pep2-KLAK VLPs) expressed in E. coli. We further investigated the characteristics including size, toxicity, thermal stability, penetrating ability, anti-tumor activity, and potential anti-tumor mechanism of 2PP7-Pep2-KLAK VLPs.

Results

2PP7-Pep2-KLAK VLPs was expressed in E. coli BL21(DE3) successfully with high yield and thermal stability. They penetrated the AML cells THP-1 rapidly after 30 min of incubation. Moreover, 2PP7-Pep2-KLAK VLPs were non-replicative, non-infectious, and non-toxic against normal cells, but inhibited the proliferation of THP-1 cells by inducing cell apoptosis after 24 h of exposure. This effect extends through 120 h of exposure, indicating their anti-proliferation effect was superior to that of synthetic peptides. In addition to the mitochondrial apoptotic pathway, the anti-tumor activity of 2PP7-Pep2-KLAK VLPs was also correlated with down-regulation of expression of enhancer of zeste homolog 2 (EZH2) and trimethylation of histone H3K27.

Conclusions

We identified the feasibility to prepare the stable, active Pep2-KLAK peptide by using PP7 bacteriophage as the vehicle. We revealed this peptide was an inhibitor of EZH2. 2PP7-Pep2-KLAK VLPs may have significant clinical implications in the treatment of MLL-AF9 AML as an epigenetic modulator.

中文翻译：

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一种通过下调 EZH2 诱导急性髓系白血病细胞凋亡的稳定 Pep2 促凋亡肽。

介绍

促凋亡肽 (KLAKLAK) ₂在细胞穿透肽（如 Pep2）的帮助下表现出强大的抗肿瘤作用，靶向在急性髓性白血病 (AML) 中高表达的 TLR2。然而，由于肽的不稳定性和高合成成本，应用受到限制。重组 PP7 噬菌体样颗粒 (VLP) 基于其展示外源肽的能力，可以保护肽免于被蛋白酶降解。

方法

在这里，我们评估了携带 Pep2 和 (KLAKLAK) ₂ (2PP7-Pep2-KLAK VLP) 在大肠杆菌中表达的 PP7 VLP 的可行性。我们进一步研究了2PP7-Pep2-KLAK VLPs的大小、毒性、热稳定性、穿透能力、抗肿瘤活性和潜在的抗肿瘤机制等特征。

结果

2PP7-Pep2-KLAK VLPs 在大肠杆菌BL21(DE3) 中成功表达，具有高产率和热稳定性。孵育 30 分钟后，它们迅速穿透了 AML 细胞 THP-1。此外，2PP7-Pep2-KLAK VLPs 对正常细胞具有非复制性、非感染性和无毒作用，但在暴露 24 小时后通过诱导细胞凋亡抑制 THP-1 细胞的增殖。这种效果持续暴露 120 小时，表明它们的抗增殖效果优于合成肽。除了线粒体凋亡途径外，2PP7-Pep2-KLAK VLPs 的抗肿瘤活性还与 zeste 同源物 2 (EZH2) 增强子的表达下调和组蛋白 H3K27 的三甲基化有关。

结论

我们确定了使用 PP7 噬菌体作为载体制备稳定、有活性的 Pep2-KLAK 肽的可行性。我们发现这种肽是 EZH2 的抑制剂。2PP7-Pep2-KLAK VLPs 作为表观遗传调节剂在治疗 MLL-AF9 AML 中可能具有重要的临床意义。