Transport of molecules in the tumor interstitium: a review.

The transport of fluid and solute molecules in the interstitium is governed by the biological and physicochemical properties of the interstitial compartment as well as the physicochemical properties of the test molecule. The composition of the interstitial compartment of neoplastic tissues is significantly different from that of most normal tissues. In general the tumor interstitial compartment is characterized by large interstitial space, high collagen concentration, low proteoglycan and hyaluronate concentrations, high interstitial fluid pressure and flow, absence of anatomically well-defined functioning lymphatic network, high effective interstitial diffusion coefficient of macromolecules, as well as large hydraulic conductivity and interstitial convection compared to most normal tissues. While these factors favor movement of macromolecules in the tumor interstitium, high interstitial pressure and low microvascular pressure may retard extravasation of molecules and cells, especially in large tumors. These differences in transport parameters have major implications in tumor growth and metastases, as well as in tumor detection and treatment.