Pericytes in experimental MDA-MB231 tumor angiogenesis

Abstract.

The role of pericytes (PCs) during embryonic or tumor angiogenesis is a matter of debate. We studied the expression of cytoskeletal, membrane, and matrix markers in experimental tumors of the human mammary ductal adenoma MDA-MB231 cell line that were grown on avian chorioallantoic membranes (CAMs) from incubation day 10 to 18 (chick) or 8 to 15 (quail). The expression patterns of α-smooth muscle actin (αSMA) and desmin, of adhesion molecules β1 integrin and neurothelin, and of fibronectin and laminin were analyzed with conventional and confocal laser scanning microscopy. The CAM arterial wall showed strong αSMA signal in all smooth muscle cell layers but the innermost layer, which was desmin positive. Ramified αSMA-negative cells with delicate desmin staining accompanied most minor vessels and were also seen basal to the capillary plexus indicating the presence of PCs. In the tumor nodules, a diffuse αSMA signal without definite relationship to vascular structures was detected. Strongly desmin-positive, αSMA-negative cells were frequent in the zone of contact to the CAM in small nodules, and were scattered in larger tumors. In some regions they were associated with microvessels, and in others appeared detaching from endothelial cells (ECs) or as single migrating cells. We conclude that: (a) the CAM tumor angiogenesis assay is useful for studying PC/EC interactions, (b) PCs are recruited from the CAM into experimental tumor nodules, (c) variability of vasculature in MDA-MB231 tumors may be due to variable PC/EC interactions, and (d) αSMA should be used with caution as a general PC marker.