Toward anti-cancer drugs: selection of anti-VEGF and anti-HER2 aptamer to inhibit cancer biomarkers

Official URL: http://192.168.1.20/record=b1493109 (Table of Contents)

There are ~71 cancer types and most of them exhibit heterogenous phenotypic characteristics. For this reason, studying common physiological alterations in cancer cells can be a successful approach for cancer treatment. Sustaining proliferative signaling and inducing angiogenesis are two of the many acquired characteristics during cancer progression. Both HER2 and VEGF are overexpressed in each of the above conditions, respectively. Therefore, the aim of this study is to develop synthetic ssDNA molecules (aptamers) that can bind to HER2 and VEGF, and inhibit their function, respectively. Even though there are already aptamers for these two targets, we wanted to select our aptamers for which there exist the possibility to bind with higher affinity. These aptamers were developed by using SELEX (Systematic Evolution of Ligands by EXponential Enrichment) technology in which HER2/VEGF immobilized magnetic beads were employed for the selection of specific aptamers. The enriched ssDNA pool was cloned, sequenced and characterized. The chosen anti-VEGF contained a G-quartet, while anti-HER2 contained a two stem-loops in their structure. We speculate that these features may play a role in specific binding to the target protein. Equilibrium binding assays with anti-VEGF aptamer showed a dissociation constant (Kd) of 315 nM and anti-HER2 showed a Kd of 309 nM. Despite the similar binding, anti-HER2 was less selective toward its target protein. In this study we incorporated the counter selection step toward human serum to exclude the serum proteins binders. The anti-VEGF can potentially be used to detect cancer in blood by using biosensing technologies.