*4.6. Cell Viability Assay*

MDA-MB-231 cells (2 <sup>×</sup> 104 cells/well) were seeded in a 96-well plate for 24 h and treated with various concentrations (0, 5, 10, 20, 40, 60 and 80 μM) of tangeretin for 24 h in a medium with 10% FBS (proliferation assay). Then, we followed the manufacturer's protocol for the EZ-Cytox Kit (DoGenBio, Seoul, Korea). The OD at a wavelength of 460 nm was measured using a GloMax® Explorer microplate reader (Promega, Madison, WI, USA).

#### *4.7. Colony Formation Assay*

MDA-MB-231 and MCF-7 cells (2 <sup>×</sup> 103 cells/well) were seeded in a 6-well plate, treated with different concentrations of tangeretin in DMEM and maintained for 7 days at 37 ◦C in a 5% CO2 incubator. The grown colonies were washed with 1× PBS three times, fixed for 10 min using 3.7% formaldehyde, treated for 20 min and stained for 20 min with 0.05% crystal violet.

#### *4.8. Wound-Healing Assay*

MDA-MB-231 cells were seeded in a 6-well plate at 2 <sup>×</sup> 10<sup>6</sup> cells/well. A scratch was made by using a microtip after the cells had grown into a monolayer. After the cells were washed two times with 1× PBS, the cancer cells were cultured with tangeretin in fresh DMEM for 24 h. Photomicrographs of the wounded areas were acquired using a light microscope [36].
