Shear-induced unfolding triggers adhesion of von Willebrand factor fibers

von Willebrand factor (VWF), a protein present in our circulatory system, is necessary to stop bleeding under high shear-stress conditions as found in small blood vessels. The results presented here help unravel how an increase in hydrodynamic shear stress activates VWF's adhesion potential, leading to the counterintuitive phenomena of enhanced adsorption rate under strong shear conditions. Using a microfluidic device, we were able to mimic a wide range of bloodflow conditions and directly visualize the conformational dynamics of this protein under shear flow. In particular, we find that VWF displays a reversible globule-stretch transition at a critical shear rate gamma(crit) in the absence of any adsorbing surface. Computer simulations reproduce this sharp transition and identify the large size of VWF's repeating units as one of the keys for this unique hydrodynamic activation. In the presence of an adsorbing collagen substrate, we find a large increase in the protein adsorption at the same critical shear rate, suggesting that the globule unfolding in bulk triggers the surface adsorption in the case of a collagen substrate, which provides a sufficient density of binding sites. Monitoring the adsorption process of multiple VWF fibers, we were able to follow the formation of an immobilized network that constitutes a "sticky" grid necessary for blood platelet adhesion under high shear flow. Because areas of high shear stress coincide with a higher chance for vessel wall damage by mechanical forces, we identified the shear-induced increase in the binding probability of VWF as an effective self-regulating repair mechanism of our microvascular system.

Nuclear heparanase-1 activity suppresses melanoma progression via its DNA-binding affinity

Heparanase-1 (HPSE) plays a pivotal role in structural remodeling of the ECM and the glycocalyx, thus conferring protumorigenic, proangiogenic and prometastatic properties to many cancer entities. In addition to its extracellular function, recent studies suggest an intracellular activity of HPSE with a largely unknown significance during tumor progression. Therefore, we investigated the relevance of the dual functions of HPSE to malignant melanoma in vitro, as well as in different mouse melanoma models based on the intradermal or intravenous injection of melanoma cells. Consistent with its extracellular action, an HPSE deficiency led to a reduced shedding of the glycocalyx accompanied by a reduced availability of vascular endothelial growth factor, affecting tumor growth and vascularization. In contrast, we measured an elevated expression of the protumorigenic factors pentraxin-3, tissue factor, TNF-α and most prominently, MMP-9, upon HPSE knockdown. In vivo, an HPSE deficiency was related to increased lymph node metastasis. Since the inhibition of its extracellular function with heparin was unable to block the gene regulatory impact of HPSE, we proposed an intracellular mechanism. Immunostaining revealed a counter-staining of HPSE and NF-κB in the nucleus, suggesting a close relationship between both proteins. This finding was further supported by the discovery of a direct charge-driven molecular interaction between HPSE and DNA by using atomic force microscopy and a co-precipitation approach. Our findings are novel and point towards a dual function for HPSE in malignant melanoma with a protumorigenic extracellular activity and a tumor-suppressive nuclear action. The identification of molecular strategies to shuttle extracellular HPSE into the nuclei of cancer cells could provide new therapeutic options.

Bladder cancer-derived interleukin-1 converts the vascular endothelium into a pro-inflammatory and pro-coagulatory surface

Background

Bladder cancer cells orchestrate tumour progression by pro-inflammatory cytokines. Cytokines modulate the local tumour microenvironment and increase the susceptibility of tumour distant tissues for metastasis. Here, we investigated the impact of human bladder cancer cell derived factors on the ability to modulate and activate human vascular endothelial cells.

Methods

The pro-inflammatory and pro-coagulatory potential of four different bladder cancer cell lines was accessed by qRT-PCR arrays and ELISA. Modulation and activation of endothelial cells was studied in microfluidic devices. Clinical relevance of our findings was confirmed by immune histology in tissue samples of bladder cancer patients and public transcriptome data.

Results

The unbalanced ratio between interleukin (IL)-1 and IL-1 receptor antagonist (IL-1ra) in the secretome of bladder cancer cells converted the quiescent vascular endothelium into a pro-adhesive, pro-inflammatory, and pro-coagulatory surface. Microfluidic experiments showed that tumour cell induced endothelial cell activation promoted leukocyte recruitment and platelet adhesion. Human bladder cancer tissue analysis confirmed that loss of IL-1ra and elevated IL-1 expression was associated with enhanced cancer progression.

Conclusions

Our data indicate that IL-1 and IL-1ra were dysregulated in bladder cancer and could facilitate tumour dissemination through endothelial cell activation. Targeting the IL-1/IL-1ra axis might attenuate tumour-mediated inflammation and metastasis formation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-020-07548-z.