Primary tumor-derived systemic nANGPTL4 inhibits metastasis.

Primary tumors and distant site metastases form a bidirectionally communicating system. Yet, the molecular mechanisms of this crosstalk are poorly understood. Here, we identified the proteolytically cleaved fragments of angiopoietin-like 4 (ANGPTL4) as contextually active protumorigenic and antitumorigenic contributors in this communication ecosystem. Preclinical studies in multiple tumor models revealed that the C-terminal fragment (cANGPTL4) promoted tumor growth and metastasis. In contrast, the N-terminal fragment of ANGPTL4 (nANGPTL4) inhibited metastasis and enhanced overall survival in a postsurgical metastasis model by inhibiting WNT signaling and reducing vascularity at the metastatic site. Tracing ANGPTL4 and its fragments in tumor patients detected full-length ANGPTL4 primarily in tumor tissues, whereas nANGPTL4 predominated in systemic circulation and correlated inversely with disease progression. The study highlights the spatial context of the proteolytic cleavage-dependent pro- and antitumorigenic functions of ANGPTL4 and identifies and validates nANGPTL4 as a novel biomarker of tumor progression and antimetastatic therapeutic agent.

Calorimetric approach for comparison of Angiopoietin-like protein 4 with other pancreatic lipase inhibitors.

Pancreatic lipase (PNLIP) is a digestive enzyme that is a potential drug target for the treatment of obesity. A better understanding of its regulation mechanisms would facilitate the development of new therapeutics. Recent studies indicate that intestinal lipolysis by PNLIP is reduced by Angiopoietin-like protein 4 (ANGPTL4), whose N-terminal domain (nANGPTL4) is a known inactivator of lipoprotein lipase (LPL) in blood circulation and adipocytes. To elucidate the mechanism of PNLIP inhibition by ANGPTL4, we developed a novel approach, using isothermal titration calorimetry (ITC). The obtained results were compared with those of well-described inhibitors of PNLIP - ε-polylysine (EPL), (-)-epigallocatechin-3-gallate (EGCG) and tetrahydrolipstatin. We demonstrate that ITC allows to investigate PNLIP inhibition mechanisms in complex substrate emulsions and that the ITC-based assay is highly sensitive - the lowest concentration for quantification of PNLIP is 1.5 pM. Combining ITC with surface plasmon resonance and fluorescence measurements, we present evidence that ANGPTL4 is a lipid-binding protein that influences PNLIP activity through interactions with components of substrate emulsions (bile salts, phospholipids and triglycerides), and this promotes the aggregation of triglyceride emulsions similarly to the PNLIP inhibitors EPL and EGCG. In the absence of substrate emulsion, unlike in the case of LPL, ANGPTL4 did not induce the inactivation of PNLIP. Our data also prove that due to various interactions with components of substrate systems, the effect of a PNLIP inhibitor depends on whether its effect is measured in a complex substrate emulsion or in a simple substrate system.

Angiopoietin-Like 4 Attenuates Brain Edema and Neurological Deficits in a Mouse Model of Experimental Intracerebral Hemorrhage.

BACKGROUND Angiopoietin-like 4 (ANGPTL4) is neuroprotective when administered acutely for the treatment of cerebral ischemia. The aim of the present study was to evaluate the preventive effects of ANGPTL4 on the formation of brain edema and to determine whether it promotes the recovery of neurological function following intracerebral hemorrhage (ICH). MATERIAL AND METHODS Recombinant human ANGPTL4 (rhANGPTL4; 40 µg/kg) or a vehicle was administered intraperitoneally 5 min prior to bacterial collagenase-induced ICH in male C57/B6J mice. Behavioral tests were performed prior to ICH and at days 1, 3, 7, 14, 21, and 28 after ICH. Brain edema and hematoma volume were examined separately using the wet weight/dry weight method and hematoxylin-eosin staining. The integrity of the tight and adherens junctions was quantified via immunofluorescence. The ultrastructure of the blood-brain barrier (BBB) was examined using transmission electron microscopy. Vascular endothelial (VE)-cadherin, claudin-5, Src, and phospho-Src in the ipsilateral and contralateral striatum were detected by Western blot analysis. RESULTS RhANGPTL4 reduced brain edema and hematoma volume and improved neurological functional recovery over the subsequent 4 weeks when compared with the control group. rhANGPTL4 significantly increased VE-cadherin and claudin-5-positive areas and relative amounts in the peri­hematoma region compared with the control group. In addition, ANGPTL4 significantly reduced the ratio of phospho-Src to Src. The significant reduction of Src kinase activity in the peri­hematoma region of ANGPTL-treated mice was paralleled by a decrease in vascular permeability and edema formation. CONCLUSIONS These results suggest that ANGPTL4 is a relevant target for vasculoprotection and cerebral protection during stroke.