Faculty of Pharmaceutical Sciences, Hokkaido University, Japan.
Faculty of Pharmaceutical Sciences, Hokkaido University, Japan.
J Control Release. 2017 Apr 10;251:1-10. doi: 10.1016/j.jconrel.2017.02.010. Epub 2017 Feb 10.
The vascular endothelial growth factor (VEGF)-mediated enhancement in vascular permeability is considered to be a major factor in tumor-targeting delivery via the enhanced permeability and retention (EPR) effect. We previously reported that the silencing of the endothelial VEGF receptor (VEGFR2) by a liposomal siRNA system (RGD-MEND) resulted in an enhanced intratumoral distribution of polyethylene glycol (PEG)-modified liposomes (LPs) in a renal cell carcinoma, a type of hypervascularized cancer, although the inhibition of VEGF signaling would be expected to decrease the permeability of the tumor vasculature. We herein report that the enhancement in the intratumoral distribution of LPs by VEGFR2 inhibition was dependent on the vascular type of the tumor (stroma vessel type; SV and tumor vessel type; TV). In the case of TV-type tumors (renal cell carcinoma and hepatocellular carcinoma), inhibiting VEGFR2 improved intratumoral distribution, while no effect was found in the case of SV-type tumors (colorectal cancer). Moreover, through a comparison of the intratumoral distribution of LPs with a variety of physical properties (100nm vs 400nm, neutral vs negative vs positive), VEGFR2 inhibition was found to alter the tumor microenvironment, including heparan sulfate proteoglycans (HSPGs). In addition, the results regarding the effect of the size of nanoparticles indicated that VEGFR2 inhibition improved the penetration of nanoparticles through the vessel wall, but not via permeability, suggesting the involvement of an unknown mechanism. Our findings suggest that a combination of anti-angiogenic therapy and delivery via the EPR effect would be useful in certain cases, and that altering the tumor microenvironment by VEGFR2 blockade has a drastic effect on the intratumoral distribution of nanoparticles.
血管内皮生长因子(VEGF)介导的血管通透性增加被认为是通过增强通透性和保留(EPR)效应实现肿瘤靶向递药的主要因素。我们之前报道过,通过脂质体 siRNA 系统(RGD-MEND)沉默内皮 VEGF 受体(VEGFR2)会导致聚乙二醇(PEG)修饰的脂质体(LPs)在肾细胞癌(一种富血管化的癌症)中的肿瘤内分布增强,尽管 VEGF 信号的抑制预计会降低肿瘤血管的通透性。我们在此报告称,VEGFR2 抑制增强了 LP 在肿瘤内的分布,这取决于肿瘤的血管类型(基质血管类型;SV 和肿瘤血管类型;TV)。在 TV 型肿瘤(肾细胞癌和肝细胞癌)的情况下,抑制 VEGFR2 可改善肿瘤内分布,而在 SV 型肿瘤(结直肠癌)中则没有发现这种效果。此外,通过比较具有各种物理性质(100nm 与 400nm、中性与负与正)的 LP 在肿瘤内的分布,发现 VEGFR2 抑制会改变肿瘤微环境,包括硫酸乙酰肝素蛋白聚糖(HSPGs)。此外,关于纳米粒子大小影响的结果表明,VEGFR2 抑制可改善纳米粒子通过血管壁的穿透性,而不是通过通透性,这表明存在未知的机制。我们的研究结果表明,抗血管生成治疗与 EPR 效应相结合在某些情况下可能是有用的,并且 VEGFR2 阻断对肿瘤微环境的改变对纳米粒子在肿瘤内的分布有重大影响。