Materials and Methods: Total RNA NVP-HSP990 clinical trial was isolated from cultures of HS68 and BSCs. Affymetrix HU133 Plus 2 GeneChip® arrays were used to analyze gene exprssion. Six isolates of BSCs were compared with three isolates of HS68 cells. Results: There were 471 differentially expressed genes using stringent criteria. Bioinformatics analysis indicated these genes were significantly more likely to cluster into developmental process pathways

P = 1.4E–10. Several messages coding for secreted molecules were also identified including Hepatocyte growth factor. Conclusions: The bone derived stromal co-culture system coupled with gene expression profile analysis is a powerful method to study the microenvironmental interactions leading to breast metastasis to bone. Poster No. 158 Mural Cell Connexin 43 is Required for Inhibition of Endothelial Proliferation and is Inactivated by Tumor Cells Mayur Choudhary1, Thiazovivin manufacturer Wenhong Chen1, Keith Barlow1,

Christine McMahan1, Linda Metheny-Barlow 1 1 Department of Radiation Oncology, Wake Forest University Health Sciences, Winston-Salem, NC, USA The tight contact between mural cells (vascular smooth muscle cells and pericytes) and the underlying endothelium stabilizes a mature blood vessel and renders the endothelium quiescent. In tumors, contact between mural cells and endothelial cells is decreased and abnormal, which allows tumor vessels to be leaky and proliferative. However, the mechanism by which tumors prevent proper association

MAPK inhibitor between mural cells and the endothelium is unknown. Since gap junction communication between mural cells and endothelial cells plays an important role BCKDHB in vessel communication and mural cell differentiation, we sought to determine the effects of tumors on the gap junction protein Connexin 43 (Cx43) on vascular cells. Here we demonstrate that short term treatment of mural cells with media conditioned by breast tumor cells stimulates a rapid and sustained inactivating phosphorylation of Cx43 at the protein kinase C (PKC) site Ser368, and that Cx43 is phosphorylated at this site on the vasculature of xenograft tumors. We found that longer term (24 hours) treatment of mural cells with media conditioned by breast or brain tumor cells leads to downregulation of Cx43 protein levels in mural cells, while media conditioned by actively proliferating monocytes lacks this activity. The decrease in Cx43 protein results both from decreased mRNA expression and proteasomal degradation of the protein. We have further demonstrated that functional Cx43 is required for mural cell-induced endothelial quiescence, as control siRNA transfected mural cells can reduce proliferation of co-cultured endothelial cells, while mural cells in which Cx43 has been knocked down by siRNA lack this activity.