To evaluate optimal transfection conditions for complexes of LPEI-PEG-GE11 and NIS pDNA (LPEI-PEG-GE11/NIS polyplexes) in human CRC cells LS174T, which showed EGFR expression as determined by FACS analysis (Figure 1A), radioiodide uptake activity was evaluated 24 h after polyplex application. The gene discussed is SLC5A5; the disease is colorectal carcinoma.