Cell proliferation assay

The cell proliferation assay was performed using Cell Counting Kit-8 (CCK-8) method. MCF-7 and MDA-MB-231 cells were first transfected with siRNA-negative control (si-NC), si-DANCR, 216a-inhibitor, or si-DANCR+ 216a-inhibitor. Then the cells were seeded into 96-well plates and cultured in an incubator at 37°C with 5% CO₂. After transfection 24, 48, 72, and 96 h, 10 μl of CCK-8 reagent (Dojindo, Japan) was added to each well and continued incubating for 2 h at 37°C. Finally, the absorbance values of all wells at 450 nm were measured by an enzyme immunoassay analyzer (Bio-Rad, Hercules, CA, U.S.A.).