When epithelial and mesenchymal components of salivary rudiments were separated from one another, infection by polyoma virus failed to produced tumors. The implanted inert material exceeds 1 cm 2 and remained intact for 6 months, sarcomas develop along the noncontiguous surfaces of the connective tissue in the rat. If the inert material is perforated, the incidence of tumors is reduced. If it is inserted in the form of a finely divided powder or a textile mesh, no tumors occur. C. Angiogenesis in Tumorigenesis Angiogenesis might be a prerequisite for tumor development.
Solid tumors are angiogenesis-dependent.
Certain animal tumors will undergo complete regression when treated by anti-angiogenesis alone. Apoptosis is the terminal event in the natural history of cell differentiation. It is a response to environmental growth factors and antibodies. C. Apoptosis in Tumorigenesis Failure of apoptotic removal of abnormal cells is one pathogenetic mechanism closely associated with neoplastic cell transformation and clonal expansion. Overexpression of proliferation promoting genes, BCL-2.