Development of a novel DNA aptamer ligand targeting to primary cultured tumor endothelial cells by a cell-based SELEX method.

The present study used a spontaneous cell-based SELEX method (Systemic Evolution of Ligands by EXponential Enrichment) to produce DNA aptamers that specifically bind to cell surface proteins or biomarkers produced by primary cultured mouse tumor endothelial cells (mTECs). In solid tumors, new blood vessels are formed through an angiogenesis process, and this plays a critical role in cancer development as well as metastasis. To combat angiogenesis, an appropriate diagnosis and a molecular-level understanding of the different cancer types are now a high priority. The novel DNA aptamer AraHH001, developed in this study, binds specifically to mTECs with high affinity in the nano-molar range, but does not bind to normal skin endothelial cells (skin-ECs). The selected DNA aptamer was also found to bind to cultured human tumor endothelial cells (hTECs), isolated from a clinical patient with a renal carcinoma. The aptamer AraHH001 showed significant anti-angiogenesis activity by inhibiting tube formation by mTECs on matrigel. Interestingly, a confocal laser scanning microscopy examination of in vitro cellular uptake revealed that AraHH001 was assimilated by mTECs, and became co-localized in acidic compartments, as detected by labeling with Lysotracker Red. Therefore, the development of a specific DNA aptamer that binds to mTECs, as reported here for the first time, holds great promise not only as a therapeutic aptamer but also as a targeted molecular probe that appears to play a major role in angiogenesis, and for the development of a targeted new drug delivery system.