PRS PSRC Podium Proofs 2016
Gayle M. Gordillo, MD, Ayan Biswas, PhD, Savita Khanna, PhD, Xueliang Pan, PhD, Chandan K. Sen, PhD
From the Ohio State University, Columbus, Ohio.
PURPOSE: Highly elevated levels of Nox-4, a protein that generates H2O2, is seen in both human hemangiomas and a murine model of hemangioendothelioma. Tumor-forming endothelial (EOMA) cells are able to escape cell death despite excessive Nox-4-derived nuclear oxidant burden. The objective of this study was to characterize the mechanisms by which EOMA cells evade oxidant toxicity and thrive.
METHODS: Multidrug resistance-associated protein-1 (MRP-1) is a transport protein that eliminates toxic molecules from cells including chemotherapy agents such as vinca alkaloids and oxidized glutathione (GSSG). MRP-1 activity was measured by calcein exclusion and glutathione measurements were taken using high-performance liquid chromatography.
RESULTS: In EOMA, nuclear GSSG/GSH ratio was 5-fold higher compared with cytosol. Compared with those in healthy murine arterial endothelial cells (MAEs), cellular GSSG/GSH was over twice in EOMA. MRP-1 activity was twice as high in EOMA compared with MAE. Hyperactive YB-1 and Ape/Ref-1 were responsible for high MRP-1 inhibition, and knockdown resulted in elevation of nuclear GSSG causing death of EOMA cells. Disulfide loading of cells by inhibition of GSSG reductase was effective in causing EOMA death as well. In summary, EOMA cells survive a heavy oxidant burden by rapid efflux of GSSG, which is lethal if trapped within the cell.
CONCLUSIONS: A hyperactive MRP-1 system for GSSG efflux acts as a critical survival factor for these cells, but it also promotes chemotherapy resistance. MRP-1 may be a productive target for endothelial cell tumor therapeutics.