AI-02 * HYPOXIA AS A MEASURE OF FUNCTIONAL STATUS OF GLIOBLASTOMA VASCULATURE

Abstract

INTRODUCTION: Glioblastoma (GBMs) exhibit distinct histopathological features including microvascular hyperplasia and heterogenous hypoxia within the tumor microenvironment. Newly formed vessels are often leaky/dysfunctional with intravascular thrombosis and potentially contribute to the hypoxic/necrotic foci seen throughout GBMs. By analyzing orthotopic xenograft models of GBM, we have established the correlation between tumor blood vessel and oxygen diffusion gradient. Additionally, we have established the effect of anti-angiogenic therapies (AATx) such as VEGF-Trap on this correlation. METHOD: Patient derived GSCs and established GBM cell line (U87) with or without VEGF-Trap were injected orthotopically in forebrains of NOD/SCID mice. Following 3-4 weeks of cell implantation, the mice were sacrificed and brains were harvested and imbedded in paraffin blocks. The sections were then stained for CD31 (endothelial marker) and CAIX (hypoxia marker). Images were scanned and quantified; using ImageJ (http://imagej.nih.gov/ij/), measurements include distance from tumor blood vessels to nearest hypoxic foci, total percent hypoxia, and cell proliferation. RESULTS: In literature it has been shown that any functional micro-vessel in normal tissue allows oxygen diffusion up to 100 µm radius. Using this as a guideline, we have defined the functional state of microvessels in our orthoptic tumor. We found that approximately 13% of the tumor blood vessels were dysfunctional, as their distance from immediate hypoxic cells was less than 20 µm. Upon treatment with AATx, we observed significant decrease in numbers of functional tumor blood vessels and cell prolliferation with concomitant increase in hypoxic areas within the tumor. CONCLUSIONS: AATx results in a significant decrease in the number of functional blood vessels - as measured by their proximity to the nearest hypoxic cells - and cell proliferation. We have provided a quantitative measure - distinct histopathological features including hypoxic and necrotic foci, microvascular hyperplasia and increased cell proliferation - for what was previously describe in qualitive terms in literature.