Endoglin as a target of antitumor therapy

Abstract

Blood vascular supply significantly affects progression of tumor growth. Inhibition of endothelial cell proliferation by antiangiogenic drugs should lead to growth arrest of both primary tumors and metastases. During the course of lengthy therapy, endothelial cells may, however, become refractory to the action of antiangiogenic agents. Novel approaches to anticancer treatment should explore the issue of drug resistance shown by endothelial cells. One possible therapeutic solution might be tumor immunotherapy directed against antigens expressed on the surface of endothelial cells which co-form tumor blood vasculature. Such therapy is supposed to break immune tolerance to own antigens and to eliminate tumor blood vessel endothelial cells by activating cytotoxic T lymphocytes. This kind of response can be obtained against endoglin (CD105). Endoglin is overexpressed in proliferating endothelial cells which line tumor blood vessels. Presence of endoglin in solid tumor blood vessels has prognostic value in cancer treatment. CD105 is also expressed by certain cancer cells (prostate, melanoma and Ewing sarcoma). It appears that therapeutic strategies directed against endoglin allow several mechanisms of resistance to antiangiogenic drugs to be omitted. The therapeutic approach that we propose, i.e. a tumor blood vessel-destroying strategy combined with immunotherapy, may become an effective therapeutic tool.