Cancer Cell-selective Clathrin-mediated Endocytosis of Aptamer-decorated Nanoparticles

Lung cancer is the leading cause of cancer death worldwide, resulting in 88% deaths of all diagnosed patients. Hence, novel therapeutic modalities are greatly needed. Single-stranded oligonucleotide-based aptamers (APTs) are excellent ligands for tumor cell targeting. However, their internalization mechanisms into living cells have been hardly studied. Towards the application of APTs in active drug targeting to cancer cells, we herein studied the mechanism underlying S15-APT internalization into human non-small cell lung cancer A549 cells. We thus delineated the mode of entry of a nanomedical model system based on quantum dots (QDs) decorated with S15-APTs as a selective targeting moiety for uptake by A549 cells. These APTs-decorated QDs displayed selective binding to target A549 cells, but not to normal human bronchial epithelial BEAS2B, cervical carcinoma (HeLa) and colon adenocarcinoma CaCo-2 cells, hence demonstrating high specificity. Flow cytometric analysis revealed a remarkably low dissociation constant of S15-APTs-decorated QDs to A549 cells (K_d =13.1±1.6 nM). Employing a systematic series of established inhibitors of known mechanisms of endocytosis, we show that the uptake of S15-APTs proceeds via a classical clathrin-dependent receptor-mediated endocytosis. This cancer cell-selective mode of entry could readily evade multidrug efflux pumps, thereby overcoming an important mechanism of cancer chemoresistance.