Abstract-Experimental evidence indicates that shear stress (SS) exerts a morphogenetic function during cardiac development of mouse and zebrafish embryos. However, the molecular basis for this effect is still elusive. Our previous work described that in adult endothelial cells, SS regulates gene expression by inducing epigenetic modification of histones and activation of transcription complexes bearing acetyltransferase activity. In this study, we evaluated whether SS treatment could epigenetically modify histones and influence cell differentiation in mouse embryonic stem (ES) cells. Cells were exposed to a laminar SS of 10 dyne per cm 2 /s Ϫ1 , or kept in static conditions in the presence or absence of the histone deacetylase inhibitor trichostatin A (TSA). These experiments revealed that SS enhanced lysine acetylation of histone H3 at position 14 (K14), as well as serine phosphorylation at position 10 (S10) and lysine methylation at position 79 (K79), and cooperated with TSA, inducing acetylation of histone H4 and phosphoacetylation of S10 and K14 of histone H3. In addition, ES cells exposed to SS strongly activated transcription from the vascular endothelial growth factor (VEGF) receptor 2 promoter. This effect was paralleled by an early induction of cardiovascular markers, including smooth muscle actin, smooth muscle protein 22-␣, platelet-endothelial cell adhesion molecule-1, VEGF receptor 2, myocyte enhancer factor-2C (MEF2C), and ␣-sarcomeric actin. In this condition, transcription factors MEF2C and Sma/MAD homolog protein 4 could be isolated from SS-treated ES cells complexed with the cAMP response element-binding protein acetyltransferase. These results provide molecular basis for the SS-dependent cardiovascular commitment of mouse ES cells and suggest that laminar flow may be successfully applied for the in vitro production of cardiovascular precursors. (Circ Res. 2005;96:501-508.)

Functionally relevant markers of glioblastoma stem-like cells (GSCs) have potential for therapeutic targeting to treat this aggressive disease. Here we used generation and screening of thousands of monoclonal antibodies to search for receptors and signaling pathways preferentially enriched in GSCs. We identified integrin α7 (ITGA7) as a major laminin receptor in GSCs and in primary high-grade glioma specimens. Analyses of mRNA profiles in comprehensive datasets revealed that high ITGA7 expression negatively correlated with survival of patients with both low- and high-grade glioma. In vitro and in vivo analyses showed that ITGA7 plays a key functional role in growth and invasiveness of GSCs. We also found that targeting of ITGA7 by RNAi or blocking mAbs impaired laminin-induced signaling, and it led to a significant delay in tumor engraftment plus a strong reduction in tumor size and invasion. Our data, therefore, highlight ITGA7 as a glioblastoma biomarker and candidate therapeutic target.

Glioblastoma multiforme (GBM) is among the most aggressive tumor types and is essentially an incurable malignancy characterized by resistance to chemo-, radio-, and immunotherapy. GBM is maintained by a hierarchical cell organization that includes stem-like, precursor, and differentiated cells. Recurrence and maintenance of the tumor is attributed to a small population of undifferentiated tumor-initiating cells, defined as glioblastoma stem-like cells (GSLCs). This cellular hierarchy offers a potential treatment to induce differentiation of GSLCs away from tumor initiation to a more benign phenotype or to a cell type more amenable to standard therapies. Bone morphogenetic proteins (BMPs), members of the TGF-b superfamily, have numerous biological activities including control of growth and differentiation. In vitro, a BMP7 variant (BMP7v) decreased primary human GSLC proliferation, endothelial cord formation, and stem cell marker expression while enhancing neuronal and astrocyte differentiation marker expression. In subcutaneous and orthotopic GSLC xenografts, which closely reproduce the human disease, BMP7v decreased tumor growth and stem cell marker expression, while enhancing astrocyte and neuronal differentiation compared with control mice. In addition, BMP7v reduced brain invasion, angiogenesis, and associated mortality in the orthotopic model. Inducing differentiation of GSLCs and inhibiting angiogenesis with BMP7v provides a potentially powerful and novel approach to the treatment of GBM.