Inhibition of CDK9 suppressed ovarian cancer cell spheroid growth, and clonogenicity formation. A) Representative images of ovarian cancer cells after treatment with the CDK9 inhibitor LDC067 at different time points (5, 10, and 15 d). B) The relative diameters of spheroids in ovarian cancer cell lines. **P < 0.01 compared with the cell only group. C) Representative images of ovarian cancer cell colony formation after incubation with different concentrations of LDC067 (0, 5, and 10 µM) for 14 d. Original magnification value, ×1. D) Quantification of clonogenicity formation of SKOV3 and OVCAR8 cells after LDC067 treatment. **P < 0.01 compared with the cell only group.