Tackling Brain Tumors

“Taking Aim at Brain Tumors” reports that nanoparticles carrying small interfering RNA were able to cross the blood-brain barrier (BBB) and were trapped in glioblastoma cells in animal models “because they are trapped in the tumors’ unusually distorted blood vessels” (C&EN, Nov. 4, page 9).

However, the blood-tumor barrier (BTB) is quite unlike the BBB. In normal brain vasculature, capillaries form tight junctions that prevent passive ingress of molecules and proteins into the brain. Crossing the BBB is a significant challenge owing to both the structural barrier and drug efflux transporters that express in capillaries. Brain tumor vasculature is different and considered to be fenestrated, or leaky. This leakiness results, for example, in contrast enhancement in tumors by gadolinium-based contrast agents that do not enter normal brain regions. This is also true for nanoparticles of varying sizes.

Matthew D. Hall
Bethesda, Md.