EGFR and cancer: Specifically, for tumor cell targeting we used the CL4 2′Fluoro-pyrimidines (2′F-Py) RNA aptamer (Kd, 10 nM; 39 nt) [19], capable of binding at high efficacy to the extracellular domain of epidermal growth factor receptor (EGFR), one of the most potent oncoprotein of human cancer.