Tumor angiogenesis

The growth of solid tumors, including head and neck squamous cell carcinomas, depends on the establishment of a blood supply within the tumor (neovascularization or angiogenesis). For this process to take place, tumors produce growth factors which stimulate the proliferation, migration, and differentiation of endothelial cells. These growth factors are polypeptides that preferentially bind heparan sulfate. In several tumor systems, the degree of angiogenesis can be correlated with tumor aggressiveness and clinical outcome.

Head and neck squamous cell carcinomas produce an angiogenic response in the chick embryo chorioallantoic membrane assay. Additionally, supernatants from head and neck squamous cell carcinoma lines enhance endothelial cell proliferation and stimulate adhesion of endothelial cells to elements of the connective tissue matrix.

Experimental evidence appears to demonstrate the angiogenic capacity of head and neck squamous cell carcinomas in vivo. Additionally, data from several laboratories have demonstrated that head and neck carcinomas produce several endothelial cell mitogens and chemotactic factors. Clinical pathologic studies correlating angiogenesis of head and neck carcinomas with node metastasis, survival, and recurrence rate are conflicting. Current studies are underway to more clearly define the mechanism(s) of angiogenesis induced by head and neck cancers.