ATPS-63: OSMOTIC SWELLING REGULATES TUMOR GROWTH AND DRUG UPTAKE IN HUMAN GLIOBLASTOMA

BACKGROUND: High interstitial fluid pressure (IFP) represents a barrier for drug uptake in human GBM, the most common primary brain tumor. Fluid accumulation and high cell density compress tumors and promote osmotic swelling of tumor cells. Although studies have clarified the role of tumor vasculature, it remains unclear whether osmotic swelling of cancer cells regulates tumor growth and drug uptake. METHODS: To address this, we used human GBM tumorspheres and xenografts. We developed methodology to measure IFP in GBM xenografts and mechanical compression in 3D-cultures. Fluorescent-based sensors were used to measure cell volume and chloride levels. To reduce IFP and osmotic swelling in GBM cells, we established exogenous or endogenous induction of antisecretory factor (AF), known to be safe in patients, reduces elevated intracranial pressure in rodents, and lowers IFP in subcutaneous solid tumors. RESULTS: Intriguingly, our data demonstrate that elevated pressure drives proliferation of GBM tumorspheres. Transcriptional profiling showed that increased compression regulates genes involved in translation and ion transport. AF peptide completely blocked compression-induced proliferation and transcriptional changes. We found that AF targeted the sodium-potassium-chloride channel (NKCC1), more potently than the NKCC1 inhibitor bumetanide, and prevented restoration of cell volume and chloride permeability under hyperosmotic conditions. AF therapy effectively reduced tumor growth, increased drug uptake, and extended survival in GBM xenografts, effects that were mediated through lowering of IFP, reduced cell volume, and inhibition of NKCC1 activity. CONCLUSIONS: We find that elevated IFP in human GBMs maintains osmotic swelling in tumor cells as a second barrier for drug uptake. Our results further show that elevated pressure is a driver of proliferation, survival, and translational control. AF therapy represents a novel approach to inhibit NKCC1 activity and osmotic swelling in human GBMs, leading to reduced tumor growth and increased drug uptake, ultimately improving the outcome for this disease.