Figure 4.

Extracellular matrix (ECM) interactions provide mechanical cues to infiltrating cells. ECM remodeling is required for tumor proliferation, metastasis, angiogenesis, and leukocyte infiltration. The image on the left shows a region with multidirectional bundles of collagen (arrows). The image on the right shows highly organized bundles of parallel collagen fibers found in body (arrow). Dense collagen networks such as these found in capsular regions of lymphoid tissue can be found within the tumor microenvironment. Collagen induced by transforming growth factor β (TGF-β) and other factors provide structural support to cancer cells and a physical barrier to leukocytes. (Transmission electron microscopy images taken by our group.)