INTERSTITIAL FLUID FLOW MAGNITUDES DRIVE CHANGES TO THE GLIOMA MICROENVIRONMENT

Interstitial fluid flow around brain tumors is increased above normal levels. This force has been shown to drive tumor cell invasion in brain tumors and alter the extracellular matrix, vasculature, immune and cellular niches in non-nervous tissues in ways that promote tumor progression [1]. Here, by applying our dynamic contrast enhanced MRI method and analysis [2], we measured interstitial fluid flow in multiple patient cell line-derived xenograft models of glioma in mice (n=6–8 per group, four different lines). The range of interstitial velocity magnitudes is similar across these models (range from 0.1–2.6 micron/s), though intratumoral variability is high. We examined tumors by immunohistochemistry including tumor cells (proliferating cells, ki67; stem-like cells, Nestin and Sox2; apoptotic cells, Caspase 3/7), the cellular microenvironment (astrocytes, GFAP and GLAST; microglia/macrophages, Iba-1 and CX3CR1; blood vessels, CD31; neurons, NeuN and Neurofilament; oligodendrocytes, OSP1), and of the extracellular space (hyaluronan, HABP; tenascin C; white matter tracts, fluoromyelin; cytokines). Fluid flow pathways and rates are dictated by anatomical features of the brain in these models (i.e. blood vessels and white matter tracts). Blood vessel density did not significantly correlate with regions of higher velocities. Based on our observations we performed in vitro experiments in a 3D tissue engineered model of the glioma microenvironment [3] to assess invasion within the range of measured flow rates. Velocities were controlled using either microfluidic pump driven flow or pressure driven flow and cellular outcomes were assessed using flow cytometry and immunocytochemistry of the 3D gel system. The results of these studies will be discussed. 1) Munson, Shieh, Cancer Management Research (2014) 6: 317; 2) Kingsmore, Vaccari, Abler, et al. APL Bioengineering (In press); 3) Harris, Yuan, Munson, Methods (2018) 134:20–31.