RNA Aptamer Binds Heparin-Binding Epidermal Growth Factor-Like Growth Factor with High Affinity and Specificity and Neutralizes Its Activity

Summary Background Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a member of the EGF family and is involved in various diseases including cancers. Aptamers are synthetic oligonucleotides (RNA or DNA) that fold into unique three-dimensional structures and specifically bind to their targets with high affinity. We aimed to generate an aptamer with high affinity and specificity for HB-EGF. Methods Recombinant human HB-EGF (rhHB-EGF), comprised of the extracellular EGF-like and heparin-binding domains of HB-EGF, was used as the target. The aptamer against HB-EGF (the anti-HB-EGF aptamer) was obtained by systematic evolution of ligands by exponential enrichment (SELEX). Results After the 10th round of SELEX, aptamers were reverse-transcribed and PCR-amplified. Within obtained forty-six clones, twenty-three were identical (the anti-HB-EGF aptamer). The analysis using wireless-electrodeless quartz crystal microbalance revealed that the anti-HB-EGF aptamer had high affinity for rhHB-EGF (KD value: 12.2 ± 1.1 nmol/L). The dot-blot analysis revealed that the anti-HB-EGF aptamer specifically bound to rhHB-EGF. The analysis using confocal microscopy indicated that the anti-HB-EGF aptamer also bound to membrane-bound HB-EGF. Western-blot assay indicated that the anti-HB-EGF aptamer inhibited the phosphorylation of rhHB-EGF-mediated EGF receptor (EGFR). Conclusion We identified a novel RNA aptamer that bound with high affinity and specificity to rhHB-EGF and potently inhibited the rhHB-EGF-mediated phosphorylation of EGFR. The anti-HB-EGF aptamer may be a promising therapeutic agent for specifically neutralizing HB-EGF signaling.