Cancer Vaccine Therapy Using Tumor Endothelial Cells as Antigens Suppresses Solid Tumor Growth and Metastasis

Tumor angiogenesis plays an important role in tumor growth and metastasis, with tumor cells requiring nutrients and oxygen via blood flow for their proliferation. In comparison, angiogenesis also occurs under normal physiological conditions, such as wound healing and in the formation of the corpus luteum. Herein, we report on the development of a novel dendritic cell (DC) vaccine therapy using tumor endothelial cells (TECs) derived from tumor vessels as tumor antigens. After density gradient centrifugation and the detection of angiotensin-converting enzyme activities, a TEC-rich fraction was separated from solid tumor tissues. Prophylactic or therapeutic immunization using DCs pulsed with TECs as vaccine antigens significantly suppressed solid tumor growth in a Colon-26 colorectal adenocarcinoma tumor-bearing mouse model, compared with the use of tumor cells as DC vaccine antigens. Tumor tissues showed reduced angiogenesis. However, vaccination using DCs pulsed with TECs did not inhibit physiological angiogenesis as evidenced by a wound healing assay. Additionally, in a B16/BL6 mouse melanoma lung metastasis model, DC vaccination using TECs derived not only from the same tumor tissue but from a different type of tumor also suppressed metastasis. These results thus show that cancer vaccine therapy targeting TECs is an effective therapy against angiogenesis in several types of cancer, but does not affect normal blood vessel growth.