Role of tumor-host interactions in interstitial diffusion of macromolecules: cranial vs. subcutaneous tumors

Area of Science:

• Biomedical Engineering
• Oncology
• Drug Delivery

Background:

• Large novel therapeutics face challenges in penetrating the tumor extracellular matrix (ECM).
• ECM characteristics, influenced by tumor-host interactions, dictate macromolecule transport and therapeutic efficacy.
• Understanding ECM's role is crucial for improving drug delivery to solid tumors.

Purpose of the Study:

• To investigate how ECM composition, structure, and distribution influence macromolecule and liposome diffusion in tumors.
• To determine if diffusion properties vary with tumor type and anatomical location.
• To correlate ECM features with observed diffusion rates.

Main Methods:

• Measured diffusion coefficients of macromolecules and liposomes using fluorescence recovery after photobleaching.
• Utilized cranial windows (CWs) and dorsal chambers (DCs) to model tumor growth.
• Quantified collagen type I levels and organization within the ECM.

Main Results:

• Macromolecule diffusion was significantly slower in dorsal chamber (DC) tumors compared to cranial window (CW) tumors.
• Slower diffusion in DC tumors correlated with higher collagen type I levels and fibril organization.
• Diffusion hindrance was pronounced for molecules with diameters similar to interfibrillar spaces, being 5- to 10-fold slower in DC tumors.
• Increased host stromal cell density in DC tumors was associated with enhanced collagen synthesis and organization.

Conclusions:

• Tumor extracellular matrix properties critically regulate macromolecule transport.
• Anatomical location and tumor-host interactions significantly alter ECM structure and diffusion hindrance.
• Development of site-specific drug carriers is necessary to overcome ECM barriers and enhance molecular medicine delivery to solid tumors.