Establishment of HCT116RF10, a 5-FU-resistant derivative of the human colorectal cancer cell line HCT116. (a) Scheme for the establishment of the 5-FU-resistant HCT116 cells (HCT116RF10). (b) HCT116RF10 and parental HCT116 cells were tested for cell viability after a 72 h treatment with 5-FU. Results represent the averages of three independent experiments with error bars showing ±SE from triplicates. (c) Drug sensitivities of HCT116RF10 and HCT116 using the colony formation assay. HCT116RF10 and HCT116 cells were treated with the indicated concentration of 5-FU and incubated for 10 days. (d) HCT116 cells: Colony formation (%) represents the average of two independent experiments, each performed in duplicate, with error bars showing ±SE of four measurement values. HCT116RF3 and RF10 cells: Colony formation (%) represents the average of three independent experiments, each performed in triplicate, with error bars showing ±SE of nine measurement values. White circle, HCT116 cells; black triangle, HCT116RF3 cells; black circle, HCT116RF10 cells. (e) Morphological features were analyzed using a Leica DMi1 microscope with LAS V4.12 at 200× magnification. Scale bar = 100 μm.