1,25(OH)₂D₃ inhibits the growth of MCF-7 cells. MCF-7 cells seeded at 1 × 10⁴ cells/mL in 96-well plates were treated with 1,25(OH)₂D₃ (1 × 10⁻⁷ mol/L) for 0 to 72 hours. The absorbance at 490 nm was measured 2 hours after the addition of 20 μL MTS/PMS. Cells were assayed in triplicate and data were expressed as the percentage of inhibition relative to untreated controls for each individual timepoint. The percentage of dead cells was less than 5% at each time point measured.