Figure 4.

Comparison of proteolytic activity between vascular and avascular tumor nodules in vitro. By day 6 in culture, significant degradation of the collagen gel surrounding the vascular nodules was apparent (A), in contrast to gels surrounding the avascular nodules that remained intact (B). When 1,10-phenanthroline (5 μM) was added to the media overlaying the collagen gels in which vascular nodules were implanted, collagen gel degradation was completely suppressed (C). This result is representative of two independent assays (n = 7 for each treatment group). (Scale bar: A–C, 400 μm.)