Cell proliferation assay
MTT assay was used to evaluate the inhibition of cell proliferation. Cells were collected, adjusted to a cell concentration of 4.1 × 104 cells / ml, and 100 microliters were seeded in a 96-well plate. After 24 hours of incubation, NCTD with final concentrations of 0, 0.160, 0.312, 0.625, 1.25, 2.5, 5, 10, 20, 40, and 80 μM were added to each well. The group without NCTD treatment was the control group. Then continue to incubate for 72 hours, then add MTT solution (15.0 μl / well), and continue incubation for 4 hours in a 5% CO2 incubator. Remove the culture plate and add 150 μl of dimethyl sulfoxide (DMSO) to dissolve the purple precipitate. A 96-well plate was analyzed on an automatic microplate spectrophotometer (Thermo Molecular De-vices Co., United States) at a wavelength of 560 nm. Calculate each cell (A560 control cells-A560 treated cells) / A560 control cells x 100% cytostatic rate. The IC50 value is calculated by the logit equation. Experiments were performed in triplicate.Clone formation assay