Phyoe Kyawe Myint

Tissue fibrosis and extracellular matrix (ECM) stiffening promote tumour progression. The mechanisms by which ECM regulates its contacting cells have been extensively studied. However, how stiffness influences intercellular communications in the microenvironment for tumour progression remains unknown. Here we report that stiff ECM stimulates the release of exosomes from cancer cells. We delineate a molecular pathway that links stiff ECM to activation of Akt, which in turn promotes GTP loading to Rab8 that drives exosome secretion. We further show that exosomes generated from cells grown on stiff ECM effectively promote tumour growth. Proteomic analysis revealed that the Notch signalling pathway is activated in cells treated with exosomes derived from tumour cells grown on stiff ECM, consistent with our gene expression analysis of liver tissues from patients. Our study reveals a molecular mechanism that regulates exosome secretion and provides insight into how mechanical properties of the ECM control the tumour microenvironment for tumour growth.

The spike glycoprotein attached to the envelope of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) binds to and exploits angiotensin-converting enzyme 2 (ACE2) as an entry receptor to infect pulmonary epithelial cells. A subset of integrins that recognize the arginyl–glycyl–aspartic acid (RGD) sequence in the cognate ligands has been predicted in silico to bind the spike glycoprotein and, thereby, to be exploited for viral infection. Here, we show experimental evidence that the β1 integrins predominantly expressed on human pulmonary epithelial cell lines and primary mouse alveolar epithelial cells bind to this spike protein. The cellular β1 integrins support adhesive interactions with the spike protein independently of ACE2, suggesting the possibility that the β1 integrins may function as an alternative receptor for SARS-CoV-2, which could be targeted for the prevention of viral infections.

Thrombomodulin is a molecule with anti-coagulant and anti-inflammatory properties. Recently, thrombomodulin was reported to be able to bind extracellular matrix proteins, such as fibronectin and collagen; however, whether thrombomodulin regulates the binding of human breast cancer-derived cell lines to the extracellular matrix remains unknown. To investigate this, we created an extracellular domain of thrombomodulin, TMD123-Fc, or domain deletion TM-Fc proteins (TM domain 12-Fc, TM domain 23-Fc) and examined their bindings to fibronectin in vitro by ELISA. The lectin-like domain of thrombomodulin was found to be essential for the binding of the extracellular domain of thrombomodulin to fibronectin. Using a V-well cell adhesion assay or flow cytometry analysis with fluorescent beads, we found that both TMD123-Fc and TMD12-Fc inhibited the binding between β1 integrin of human breast cancer-derived cell lines and fibronectin. Furthermore, TMD123-Fc and TMD12-Fc inhibited the binding of activated integrins to fibronectin under shear stress in the presence of Ca²⁺ and Mg²⁺ but not under strong integrin-activation conditions in the presence of Mg²⁺ without Ca²⁺. This suggests that thrombomodulin Fc fusion protein administered exogenously at a relatively early stage of inflammation may be applied to the development of new therapies that inhibit the binding of β1 integrin of breast cancer cell lines to fibronectin.

Sepsis is a systemically dysregulated inflammatory syndrome, in which dendritic cells (DCs) play a critical role in coordinating aberrant immunity. The aim of this study is to shed light on the differential roles played by systemic versus mucosal DCs in regulating immune responses in sepsis. We identified a differential impact of the systemic and mucosal DCs on proliferating allogenic CD4 T cells in a mouse model of sepsis. Despite the fact that the frequency of CD4 T cells was reduced in septic mice, septic mesenteric lymph node (MLN) DCs proved superior to septic spleen (SP) DCs in expanding allogeneic CD4 T cells. Moreover, septic MLN DCs markedly augmented the surface expression of MHC class II and CD40, as well as the messaging of interleukin-1β (IL-1β). Interestingly, IL-1β-treated CD4 T cells expanded in a dose-dependent manner, suggesting that this cytokine acts as a key mediator of MLN DCs in promoting septic inflammation. Thus, mucosal and systemic DCs were found to be functionally different in the way CD4 T cells respond during sepsis. Our study provides a molecular basis for DC activity, which can be differential in nature depending on location, whereby it induces septic inflammation or immune-paralysis.