Interactions of cancer cells with the vasculature are essential for tumor growth and likely promote metastatic progression. Endothelial cell content and lympho-vascular invasion are generally associated with tumor aggressiveness, however, these features are generally not employed in the clinic. We aimed to determine if endothelial cell gene expression signatures could be utilized to better characterize breast tumor biology, and to establish if vascular cell-derived signatures could provide information to predict tumors likely to metastasize. Here we report on the identification of a gene signature for vascular endothelial cells, and a second for cancer-activated vasculature. Both signatures independently identify subsets of aggressive breast cancers. Interestingly, the vascular content signature and a previously identified hypoxia signature both provide prognostic information beyond currently utilized clinical parameters and intrinsic subtype classifications. In these studies, we also examined the relationship that the breast cancer subtypes have with vascular gene expression profiles, and found that claudin-low tumors and cell lines express vascular gene expression profiles and displayed endothelial-like tube formation when grown in three-dimensions. These findings are directly applicable to clinical care and therapeutic treatment design as they identify highly aggressive subsets of tumors with genetic and morphologic vascular properties.
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