Tumour cells evade immune surveillance by upregulating the surface expression of programmed death-ligand 1 (PD-L1), which interacts with programmed death-1 (PD-1) receptor on T cells to elicit the immune checkpoint response. Anti-PD-1 antibodies have shown remarkable promise in treating tumours, including metastatic melanoma. However, the patient response rate is low. A better understanding of PD-L1-mediated immune evasion is needed to predict patient response and improve treatment efficacy. Here we report that metastatic melanomas release extracellular vesicles, mostly in the form of exosomes, that carry PD-L1 on their surface. Stimulation with interferon-γ (IFN-γ) increases the amount of PD-L1 on these vesicles, which suppresses the function of CD8 T cells and facilitates tumour growth. In patients with metastatic melanoma, the level of circulating exosomal PD-L1 positively correlates with that of IFN-γ, and varies during the course of anti-PD-1 therapy. The magnitudes of the increase in circulating exosomal PD-L1 during early stages of treatment, as an indicator of the adaptive response of the tumour cells to T cell reinvigoration, stratifies clinical responders from non-responders. Our study unveils a mechanism by which tumour cells systemically suppress the immune system, and provides a rationale for the application of exosomal PD-L1 as a predictor for anti-PD-1 therapy.

Cell-derived microvesicles (MVs), which are biogenic nanosized membrane-bound vesicles that convey bioactive molecules between cells, have recently received attention for use as natural therapeutic platforms. However, the medical applications of MV-based delivery platforms are limited by the lack of effective methods for the efficient isolation of MVs and the convenient tuning of their targeting properties. Herein, we report the development of magnetic and folate (FA)-modified MVs based on a donor cell-assisted membrane modification strategy. MVs inherit the membrane properties of their donor cells, which allows them to be modified with the biotin and FA on their own membrane. By conjugating with streptavidin-modified iron oxide nanoparticles (SA-IONPs), the MVs can be conveniently, efficiently, and rapidly isolated from the supernatant of their donor cells using magnetic activated sorting. Moreover, the conjugated magnetic nanoparticles and FA confer magnetic and ligand targeting activities on the MVs. Then, the MVs were transformed into antitumor delivery platforms by directly loading doxorubicin via electroporation. The modified MVs exhibited significantly enhanced antitumor efficacy both in vitro and in vivo. Taken together, this study provides an efficient and convenient strategy for the simultaneous isolation of cell-derived MVs and transformation into targeted drug delivery nanovectors, thus facilitating the development of natural therapeutic nanoplatforms.

We report a hydroelasticity-based microfluidic oscillator that converts otherwise steady laminar flow to oscillatory flow. It incorporates an elastic diaphragm to enhance nonlinearity of the flow. Negative differential flow resistance is observed. High-frequency oscillatory flow is produced passively through interactions among hydrodynamic, elastic and inertial forces, without resorting to external actuators and control equipment. Driven by fluid flow and pressure, this device can operate in either steady laminar flow or oscillatory flow states, or work as a valve. Its applications for flow control and operation, and mixing enhancement are demonstrated.

In micromixer studies, compared with the design, modeling and characterization, the influence of the fluid properties on mixing has been less discussed. This topic is of practical significance as the properties of diverse biological and chemical liquids to be mixed have large variations. Here, we report a microfluidic mixer for mixing fluids with widely different viscosities. It contains an interconnected multi-channel network through which the bulk fluid volumes are divided into smaller ones and chaotically reorganized. Then, the multiple fluid streams are driven into an expansion chamber which triggers viscous flow instabilities. Experiments with the co-flow of glycerol and aqueous solutions show an automatic transition of the flow from a steady state to a 'turbulent' state, significantly enhancing the mixing. This observation is rather interesting considering that it occurs in a passive flow and the average Reynolds number involved is small. Further testing indicates that this mixer works well at viscosity ratio (chi) up to the order of 10(4).

Tumor angiogenesis is critical for tumor progression as the new blood vessels supply nutrients and facilitate metastasis. Previous studies indicate tumor associated lymphocytes, including B cells and T cells, contribute to tumor angiogenesis and tumor progression. The present study aims to identify the function of Lymphotoxin‐α (LT‐α), which is secreted by the activated lymphocytes, in the tumor angiogenesis of head and neck squamous cell carcinoma (HNSCC). The coculture system between HNSCC cell line Cal27 and primary lymphocytes revealed that tumor cells promoted the LT‐α secretion in the cocultured lymphocytes. In vitro data further demonstrated that LT‐α promoted the proliferation, migration and tube formation of human umbilical vein endothelial cells (HUVECs) by enhancing the PFKFB3‐mediated glycolytic flux. Genetic and pharmacological inhibition of PFKFB3 suppressed the enhanced proliferation and migration of HUVECs. We further identified that LT‐α induced PFKFB3 expression was dependent on the TNFR/NF‐κB signaling pathway. In addition, we proved that PFKFB3 blockade decreased the density of CD31 positive blood vessels in HNSCC xenografts. Finally, the results from the human HNSCC tissue array revealed that the expression of LT‐α in HNSCC samples positively correlated with microvessel density, lymphocytes infiltration and endothelial PFKFB3 expression. In conclusion, infiltrated lymphocyte secreted LT‐α enhances the glycolysis of ECs in a PFKFB3‐dependent manner through the classical NF‐κB pathway and promotes the proliferation and migration of ECs, which may contribute to the aberrant angiogenesis in HNSCCs. Our study suggests that PFKFB3 blockade is a promising therapeutic approach for HNSCCs by targeting tumor angiogenesis.