Objective: Polyethylene glycol-modified gold nanostar particles (GNS-PEG) were constructed to investigate whether the degradation of extracellular matrix in triple-negative breast cancer could improve the tumor delivery of GNS-PEG and enhance the efficacy of photothermal therapy. Methods: GNS-PEG were constructed and characterized for physicochemical properties as well as photothermal properties. At the cellular level, the cytotoxicity of halofuginone (HF) and the effect of photothermal therapy were detected. Mouse model of triple negative breast cancer was established by subcutaneous inoculation of 4T1 cells in BALB/c nude mice. Five injections of HF were given via tail vein (HF group), and tumor sections were stained with Masson stain and immunohistochemical staining for transforming growth factor β1 (TGFβ1), α-smooth muscle actin (α-SMA) and CD31 to observe the effect of tumor stromal degradation. Five injections of HF via tail vein followed by GNS-PEG (HF+ GNS-PEG group) were applied to determine the content of gold in tumor tissues by inductively coupled plasma mass spectrometry. The tumor sites of the mice in the GNS-PEG and HF+ GNS-PEG groups were irradiated with NIR laser and the temperature changes were recorded with an IR camera. The tumour growth and weight changes of mice in each group were observed. Ki-67 immunohistochemical staining, TdT-mediated dUTP nick-end labeling and HE staining were performed on tumor tissue sections from each group to observe tumor proliferation, apoptosis and necrosis. HE staining was performed on heart, liver, spleen, lung and kidney tissues from each group to observe the morphological changes of cells. Results: GNS-PEG nanoparticles showed a multi-branched structure with a particle size of 73.5±1.4 nm. The absorption peak of GNS was 810 nm, which is in the near infrared region. The photothermal conversion rate of GNS-PEG was up to 79.3%, and the photothermal effect could be controlled by the laser energy. HF has a concentration-dependent cytotoxicity, with a cell survival rate being as low as (22.8±2.6)% at HF concentration of up to 1 000 nmol/L. The photothermal effect of GNS-PEG was significant in killing tumor cells, with a cell survival rate of (32.7±5.2)% at the concentration of 25 pmol/L. The collagen area fraction, TGFβ1 integrated optical density and α-SMA integrated optical density in the tumor tissues of mice in the HF group were (2.1±0.2)%, 3.1±0.4 and 5.2±1.9, respectively, which were lower than those of the control group (all P<0.01), and the vessel diameter was 8.6±2.9 μm, which was higher than that of the control group (P<0.05). In the HF+ GNS-PEG group, the concentration of gold in tissues was 52.4 μg/g, higher than that in the GNS-PEG group (15.9 μg/g, P<0.05). After laser irradiation, the temperature of the tumor site in the HF+ GNS-PEG group was significantly higher than that in the GNS-PEG group. At the 4th minute, the temperatures of the tumor site in the GNS-PEG and HF+ GNS-PEG groups were 51.5 ℃ and 57.7 ℃ respectively; the tumor volume in the HF+ GNS-PEG group was effectively suppressed. The body weights of the mice in each group did not change significantly during the monitoring period. No significant abnormalities were observed in the main organs of the mice in the GNS-PEG group, but some hepatocytes in the HF and HF+ GNS-PEG groups showed edema and degeneration. Conclusion: The remodeling of extracellular matrix in triple-negative breast cancer could significantly improve the intratumoral delivery of GNS-PEG and thus achieve better photothermal therapy effect.
目的： 探讨降解肿瘤细胞周围基质对聚乙二醇修饰的金纳米星(GNS－PEG)肿瘤递送及三阴性乳腺癌光热治疗疗效的影响。 方法： 构建GNS－PEG颗粒，观察其理化特征并检测其光热性能。在细胞水平检测常山酮(HF)和光热治疗的细胞毒性。于BALB/c裸鼠皮下接种4T1细胞建立三阴性乳腺癌小鼠模型。经尾静脉注射5次HF(HF组)，对肿瘤组织切片行马松染色及转化生长因子β1(TGFβ1)、α－平滑肌肌动蛋白(α－SMA)、CD31免疫组化染色，观察肿瘤基质降解效果。经尾静脉注射5次HF后再注射GNS－PEG(HF+GNS－PEG组)，采用电感耦合等离子体质谱法测定肿瘤组织中GNS－PEG的含量。以近红外激光照射GNS－PEG组和HF+GNS－PEG组小鼠的肿瘤部位，用红外摄像机记录温度变化。观察各组小鼠的肿瘤生长和体重变化情况。对各组小鼠的肿瘤组织切片行Ki－67免疫组化染色、原位末端转移酶标记染色和HE染色，观察肿瘤增殖、凋亡及坏死情况。对各组小鼠的心、肝、脾、肺及肾组织切片行HE染色，观察细胞形态变化。 结果： 成功构建了具有多枝结构的GNS－PEG颗粒，粒径为73.5 nm。GNS的吸收峰为810 nm，处于近红外区。GNS－PEG的光热转换率高达79.3%，并且可以通过激光能量控制光热效果。HF具有浓度依赖的细胞毒性，当HF浓度达1 000 nmol/L时，4T1细胞存活率低至(22.8±2.6)%。GNS－PEG的光热作用对4T1细胞杀伤效果显著，当浓度达25 pmol/L时，细胞存活率为(32.7±5.2)%。HF组小鼠肿瘤组织中胶原蛋白容积分数、TGFβ1积分光密度和α－SMA积分光密度分别为(2.1±0.2)%、3.1±0.4、5.2±1.9，均低于对照组(均P<0.01)，血管直径为(8.6±2.9)μm，高于对照组(P<0.05)。HF+GNS－PEG组小鼠肿瘤组织中金元素浓度为52.4 μg/g，高于GNS－PEG组(15.9 μg/g，P<0.05)。激光照射后，HF+GNS－PEG组小鼠肿瘤部位的温度明显高于GNS－PEG组，第4 min时，GNS－PEG组和HF+GNS－PEG组小鼠肿瘤部位温度分别为51.5 ℃和57.7 ℃；HF+GNS－PEG组小鼠的肿瘤体积得到有效抑制。各组小鼠的体重在监测期间未发生显著变化。GNS－PEG组小鼠的主要脏器未见明显异常，但HF组和HF+GNS－PEG组可见部分肝细胞水肿、变性。 结论： 降解三阴性乳腺癌的肿瘤细胞周围基质能明显改善GNS－PEG的肿瘤递送，提高光热治疗疗效。.
Keywords: Drug delivery; Extracellular matrix; Gold nanostar; Halofuginone; Thermotherapy; Triple-negative breast neoplasms.