Astrocytes influence medulloblastoma phenotypes and CD133 surface expression.

The medulloblastoma (MB) microenvironment is diverse, and cell-cell interactions within this milieu is of prime importance. Astrocytes, a major component of the microenvironment, have been shown to impact primary tumor cell phenotypes and metastasis. Based on proximity of MB cells and astrocytes in the brain microenvironment, we investigated whether astrocytes may influence MB cell phenotypes directly. Astrocyte conditioned media (ACM) increased Daoy MB cell invasion, adhesion, and in vivo cellular protrusion formation. ACM conditioning of MB cells also increased CD133 surface expression, a key cancer stem cell marker of MB. Additional neural stem cell markers, Nestin and Oct-4A, were also increased by ACM conditioning, as well as neurosphere formation. By knocking down CD133 using short interfering RNA (siRNA), we showed that ACM upregulated CD133 expression in MB plays an important role in invasion, adhesion and neurosphere formation. Collectively, our data suggests that astrocytes influence MB cell phenotypes by regulating CD133 expression, a key protein with defined roles in MB tumorgenicity and survival.

Hepatic Vein Blood Increases Lung Microvascular Angiogenesis and Endothelial Cell Survival-Toward an Understanding of Univentricular Circulation.

To improve our understanding of pulmonary arteriovenous malformations in univentricular congenital heart disease, our objective was to identify the effects of hepatic vein and superior vena cava constituents on lung microvascular endothelial cells independent of blood flow. Paired blood samples were collected from the hepatic vein and superior vena cava in children 0-10 years old undergoing cardiac catheterization. Isolated serum was subsequently used for in vitro endothelial cell assays. Angiogenic activity was assessed using tube formation and scratch migration. Endothelial cell survival was assessed using proliferation (BrdU incorporation, cell cycle analysis) and apoptosis (caspase 3/7 activity, Annexin-V labeling). Data were analyzed using Wilcoxon signed-rank test and repeated measures analysis. Upon incubating lung microvascular endothelial cells with 10% patient serum, hepatic vein serum increases angiogenic activity (tube formation, P = 0.04, n = 24; migration, P< 0.001, n = 18), increases proliferation (BrdU, P < 0.001, n = 32; S-phase, P = 0.04, n = 13), and decreases apoptosis (caspase 3/7, P < 0.001, n = 32; Annexin-V, P = 0.04, n = 12) compared to superior vena cava serum. Hepatic vein serum regulates lung microvascular endothelial cells by increasing angiogenesis and survival in vitro. Loss of hepatic vein serum signaling in the lung microvasculature may promote maladaptive lung microvascular remodeling and pulmonary arteriovenous malformations.

Interaction of tumor cells and astrocytes promotes breast cancer brain metastases through TGF-ß2/ANGPTL4 axes.

Metastatic outcomes depend on the interactions of metastatic cells with a specific organ microenvironment. Our previous studies have shown that triple-negative breast cancer (TNBC) MDA-MB-231 cells passaged in astrocyte-conditioned medium (ACM) show proclivity to form brain metastases, but the underlying mechanism is unknown. The combination of microarray analysis, qPCR, and ELISA assay were carried out to demonstrate the ACM-induced expression of angiopoietin-like 4 (ANGPTL4) in TNBC cells. A stable ANGPTL4-knockdown MDA-MB-231 cell line was generated by ANGPTL4 short-hairpin RNA (shRNA) and inoculated into mice via left ventricular injection to evaluate the role of ANGPTL4 in brain metastasis formation. The approaches of siRNA, neutralizing antibodies, inhibitors, and immunoprecipitation were used to demonstrate the involved signaling molecules. We first found that ACM-conditioned TNBC cells upregulated the expression of ANGPTL4, a secreted glycoprotein whose effect on tumor progression is known to be tumor microenvironment- and tumor-type dependent. Knockdown of ANGPTL4 in TNBC MDA-MB-231 cells with shRNA decreased ACM-induced tumor cell metastatic growth in the brain and attributed to survival in a mouse model. Furthermore, we identified that astrocytes produced transforming growth factor-beta 2 (TGF-ß2), which in part is responsible for upregulation of ANGPTL4 expression in TNBC through induction of SMAD signaling. Moreover, we identified that tumor cells communicate with astrocytes, where tumor cell-derived interleukin-1 beta (IL-1ß) and tumor necrosis factor alpha (TNF-α) increased the expression of TGF-ß2 in astrocytes. Collectively, these findings indicate that the invading TNBC cells interact with astrocytes in the brain microenvironment that facilitates brain metastases of TNBC cells through a TGF-ß2/ANGPTL4 axis. This provides groundwork to target ANGPTL4 as a treatment for breast cancer brain metastases.