The Role of the Aggressive Tumor Cell in Generating a Perfusion System: Vasculogenic Mimicry
In vitro, and under appropriate matrix microenvironmental conditions, highly aggressive uveal and cutaneous melanoma cells generate two type of non-vascular structures that may play an important vole in tumor perfusion: tubes and patterned extravascular matrix. Poorly aggressive cell lines do not form either tubes or extravascular matrix patterns, regardless of local matrix conditions. Both tubular structures and extravascular matrix patterns may conduct plasma or blood.
Suggested References:
Maniotis AJ, et al. Vascular channel formation by human melanoma cells in vivo and in vitro: vasculogenic mimicry. Am J Pathol 1999;155:996-1001.
Folberg R, et al. Vasculogenic mimicry and tumor angiogenesis. Am J Pathol 2000;156:361-381.
Maniotis AJ, et al. Control of melanoma morphogenesis, endothelial survival, and perfusion by extracellular matrix. Lab Invest 2002;82:1031-1043.
About the name, vasculogenic mimicry. Both tubes and extravascular matrix patterns are generated de novo, not from pre-existing structures. Neither of the tubes nor the extravascular matrix patterns are vessels. Therefore, the de novo generation of a perfusion system mimics an event that generates a perfusion system - hence the name, vasculogenic mimicry.
The tubular form of vasculgenic mimicry may resemble blood vessels. It has been known for many years that channels lined entirely by tumor cells can be detected in neoplasms. Given the fact that there are no reliable ultrastructural or immunohistochemical markers that consistently and reliably separate endothelial cells from melanoma cells, it may be exceptionally difficult to separate tumor cell-lined channels from blood vessels.
The patterned extravascular matrix should, in no way, be confused with blood vessels. These patterns are rich in laminin. Although these patterns anastomose with blood vessels, they are not vessels either ultrastructurally or topologically. They are not fibrovascular septa, as has been suggested by some investigators: they are formed independent of participation by endothelial cells and fibroblasts and are ultrastructurally collagen-poor and avascular. Extravascular matrix patterns, however, conduct fluid in vitro and in vivo and thus form a "fluid-conducting meshwork" in uveal melanomas, cutaneous melanomas, and other tumors.
Recommended References:
Maniotis AJ, et al. Control of melanoma morphogenesis, endothelial survival, and perfusion by extracellular matrix. Lab Invest 2002;82:1031-1043.
Clarijs R, et al. Presence of a fluid-conducting meshwork in xenografted cutaneous and primary human uveal melanoma. Invest Ophthalmol Vis Sci 2002;43:912-918.
Chen X, et al. Uveal melanoma cell staining for CD34 and assessment of tumor vascularity. Invest Ophthalmol Vis Sci 2002;43:2533-2539.