Mediating Passive Tumor Accumulation through Particle Size, Tumor Type, and Location

Area of Science:

• Nanomedicine
• Biomedical Engineering
• Cancer Research

Background:

• The enhanced permeation and retention (EPR) effect is crucial for passive tumor targeting in nanomedicine.
• However, the clinical translation of EPR-based strategies is hindered by its controversial and variable nature.
• Factors influencing EPR, including nanoparticle characteristics and tumor microenvironment, require further investigation.

Purpose of the Study:

• To investigate the influence of nanoparticle size, tumor model, and location on the EPR effect.
• To evaluate the correlation between tumor microvessel density, vascular permeability, and particle accumulation.
• To assess nanoparticle penetration and accumulation in both subcutaneous and orthotopic tumor models.

Main Methods:

• Evaluation of PRINT nanoparticle accumulation (55×60 nm, 80×180 nm, 80×320 nm) in four subcutaneous tumor models (SKOV3, 344SQ, A549, A431).
• Assessment of tumor microenvironment factors including microvessel density, vascular permeability, lymphatics, stromal content, and immune cells via immunohistochemistry and immunofluorescence.
• Comparison of nanoparticle accumulation in subcutaneous versus orthotopic/metastatic tumor models.

Main Results:

• Significant particle size dependence and model-specific accumulation trends were observed.
• Tumor microvessel density correlated with overall nanoparticle accumulation.
• Smaller nanoparticles showed deeper tissue penetration, while larger ones localized near vasculature.
• Stromal content influenced penetration of smaller nanoparticles.
• Preferential accumulation in primary and metastatic tumors was noted for smaller particles.
• Orthotopic lung tumors showed higher accumulation than flank models; ovarian tumors showed consistent accumulation across locations.

Conclusions:

• The EPR effect is highly variable and significantly influenced by nanoparticle size, tumor type, and anatomical location.
• Tumor microenvironment characteristics play a critical role in mediating nanoparticle accumulation and penetration.
• These findings highlight the need for tailored nanomedicine design and preclinical models to optimize tumor targeting efficacy.