Antisecretory Factor–Mediated Inhibition of Cell Volume Dynamics Produces Antitumor Activity in Glioblastoma

Abstract

Interstitial fluid pressure (IFP) presents a barrier to drug uptake in solid tumors, including the aggressive primary brain tumor glioblastoma (GBM). It remains unclear how fluid dynamics impacts tumor progression and can be targeted therapeutically. To address this issue, a novel telemetry-based approach was developed to measure changes in IFP during progression of GBM xenografts. Antisecretory factor (AF) is an endogenous protein that displays antisecretory effects in animals and patients. Here, endogenous induction of AF protein or exogenous administration of AF peptide reduced IFP and increased drug uptake in GBM xenografts. AF inhibited cell volume regulation of GBM cells, an effect that was phenocopied by the sodium-potassium-chloride cotransporter 1 (SLC12A2/NKCC1) inhibitor bumetanide. As a result, AF induced apoptosis and increased survival in GBM models., the ability of AF to reduce GBM cell proliferation was phenocopied by bumetanide and NKCC1 knockdown. Next, AF's ability to sensitize GBM cells to the alkylating agent temozolomide, standard of care in GBM patients, was evaluated. Importantly, combination of AF induction and temozolomide treatment blocked regrowth in GBM xenografts. Thus, AF-mediated inhibition of cell volume regulation represents a novel strategy to increase drug uptake and improve outcome in GBM. .

Antisecretory Factor May Reduce ICP in Severe TBI—A Case Series

“…The exact mechanism of AF is unknown, but it has been proposed to act by modulation of proteasomes, complement, and myeloid cells (8)(9)(10). A recent report shows that AF inhibits the NKCC1 ion pump; the latter also has been implicated in the evolution of edema in TBI (11,12).…”

Matrix protease production, epithelial-to-mesenchymal transition marker expression and invasion of glioblastoma cells in response to osmotic or hydrostatic pressure

“…Hyperosmolarity increases GBM matrix protease production. To test the effect of hyper or hypo-osmotic stress on matrix protease production in cell-conditioned medium, cell viability in response to increased (by addition of NaCl) or decreased (by addition of water) osmolality over 6,12,24 and 48 h was assessed in preliminary experiments ( Supplementary Fig. S1).…”

“…Using magnetic resonance spectroscopy, the concentration of myoinositol, an organic osmolyte indicative of cell metabolic reaction to osmotic changes into the brain, was shown to be lower in GBM compared to control tissue, to increase after bevacizumab treatment (which normalizes the vasculature and reduces the oedema), and to correlate with better overall survival of the patients 27 . Interstitial fluid pressure reduction (via strategies such as induction of endogenous antisecretory factor (AF) or administration of exogenous AF peptide) improved the outcome of GBM in patient-derived xenograpft mouse experimental models 24 and blocked compression-induced proliferation of GBM oncospheres 24 . Hyper and hypo-osmolar stress can affect cell processes including signal transduction, ion homeostasis, volume regulatory processes, cytoskeletal organisation, cell cycle and energy metabolism, with a significant proportion of regulatory processes common to both types of stress 28 .…”

“…Hydrostatic pressure increases matrix protease production and eMt marker expression by GBM cells. GBM cells are subjected to increasing interstitial fluid pressure as the tumour grows 24 . We tested the effect of increased hydrostatic pressure on matrix protease production.…”

Unlocking the Dangers of a Stiffening Brain

“…Transcriptional profiling has enabled subgrouping of gliomas along a proneural-mesenchymal spectrum. Encapsulated within the skull, gliomas develop in a mechanically challenged environment in which fluid accumulation and high interstitial fluid pressure compresses the tumor and the surrounding normal tissue, driving GBM aggression (Ilkhanizadeh et al, 2018). The significance of mechanical irregularities was recently highlighted in gliomas in which progression from low-grade to high-grade gliomas, and less aggressive proneural to more aggressive mesenchymal GBMs, was accompanied by enhanced deposition of ECM components such as tenascin C, as well as an overall increase in tissue stiffness (Barnes et al, 2018;Miroshnikova et al, 2016).…”