PO.ET08.02 · 实验与分子治疗
用于增强放疗的pH靶向钆基纳米颗粒
pH-targeted gadolinium-based nanoparticles for enhanced radiotherapy
作者与单位 Authors & Affiliations
摘要 Abstract
中文摘要
钆基纳米颗粒（GdNP）是设计用于放射增敏和MRI对比增强的小于5 nm的颗粒。Gd（Z = 64）的高原子序数能够实现高效的X射线吸收和在肿瘤内的剂量沉积，而肿瘤蓄积则通过增强渗透和滞留效应促成。既往临床试验为静脉注射GdNP在宫颈癌和脑转移患者中的安全性和潜在治疗获益提供了初步证据。为提高肿瘤特异性，我们将GdNP与pH低插入肽（pHLIP）偶联，后者通过pH依赖性膜插入靶向酸性肿瘤微环境。既往工作证明，与GdNP偶联的pHLIP在体外增强了钆摄取和放射增敏。在pH 6.2（类肿瘤）和pH 7.4（生理）条件下，用培养的A549人肺腺癌细胞进行了体外实验。克隆形成实验和ICP-MS分析显示，虽然pHLIP-GdNP（0.17 mM剂量）未显著改变细胞存活，但与未偶联的GdNP相比，它在酸性条件下将细胞内钆水平提高了约18倍。在体内，荷皮下植入A549肿瘤的小鼠接受了10 Gy X射线照射，伴有或不伴有未偶联GdNP或pHLIP-GdNP预处理（300 mg/kg；n = 7只小鼠/组）。与对照相比，所有受照射组均表现出显著的肿瘤生长延迟（P < 0.013），但尽管Gd在肿瘤中蓄积，纳米颗粒治疗队列中未观察到额外的放射增敏。MRI T1成像显示，在给予GdNP后T1弛豫时间缩短，在注射pHLIP-GdNP后缩短更为明显，表明对比剂递送增强。这些发现表明，pHLIP偶联改善了钆摄取和MRI可见性，但在当前条件下并未增强放疗疗效。与既往工作不同，本研究使用了更简单的共价键而非二硫键将pHLIP与GdNP偶联，这可能解释了疗效的下降。重新引入二硫键连接可能至关重要，因为它使偶联物在循环中保持稳定，同时在插入酸性肿瘤细胞后释放纳米颗粒载荷，从而可能提高治疗疗效。
查看英文原文 English abstract
Gadolinium-based nanoparticles (GdNP) are sub-5 nm particles designed for radiosensitization and MRI contrast enhancement. The high atomic number of Gd (Z = 64) enables efficient X-ray absorption and dose deposition within tumors, with tumor accumulation facilitated by the enhanced permeability and retention effect. Previous clinical trials have provided preliminary evidence for the safety and potential therapeutic benefit of intravenous GdNP in patients with cervical cancer and brain metastases. To improve tumor specificity, we conjugated GdNP with pH-low insertion peptide (pHLIP), which targets the acidic tumor microenvironment through pH-dependent membrane insertion. Previous work demonstrated that pHLIP conjugated to GdNP enhanced gadolinium uptake and radiosensitization in vitro. In vitro experiments were performed with cultured A549 human lung adenocarcinoma cells at pH 6.2 (tumor-like) and pH 7.4 (physiologic) conditions. Clonogenic assays and ICP-MS analysis revealed that while pHLIP-GdNP (0.17 mM dose) did not significantly alter cell survival, it increased intracellular gadolinium levels by approximately 18-fold under acidic conditions compared to unconjugated GdNP. In vivo, mice bearing subcutaneously implanted A549 tumors received 10 Gy X-ray irradiation with or without unconjugated GdNP or pHLIP-GdNP pretreatment (300 mg/kg; n = 7 mice/group). All irradiated groups exhibited significant tumor growth delay compared to controls (P < 0.013), but no additional radiosensitization was observed in the nanoparticle-treated cohorts, despite Gd accumulation in the tumor. MRI T1 mapping demonstrated shortened T1 relaxation times following GdNP administration, with greater reduction following pHLIP-GdNP injection, indicating enhanced contrast agent delivery. These findings suggest that pHLIP conjugation improves gadolinium uptake and MRI visibility but does not enhance radiotherapeutic efficacy under current conditions. Departing from previous work, this study used a simpler covalent bond to conjugate pHLIP to GdNP rather than a disulfide bridge, which may explain the decreased efficacy. Reintroducing the disulfide linkage might be critical, as it allows the conjugate to remain stable in circulation while releasing nanoparticle cargo upon insertion into acidic tumor cells, potentially increasing therapeutic efficacy.
利益披露 Disclosure
J. Wen, None..
Y. Xue, None..
W. Liu, None..
G. Pratx, None.