Figure 4.

The cytotoxicity of complex 1 in CDK9 overexpressed breast cancer cells. (A) The CDK9 protein level was evaluated in different breast cancer cell lines (MCF7, 4T1, MDA-MB-231) and human normal breast cell lines (MCF 10A, HS578). CDK9, cyclin T1, and β-actin were blotted to control for total protein levels. (B–C) Inhibition effects of 1 or 20 on the c-Myc and Mcl-1 mRNA level in MDA-MB-231 cells were determined by qPCR. (D–E) Inhibition effect of 1 or 20 on the binding ability of CDK9 to c-Myc and Mcl-1 promoter in MDA-MB-231 cells by ChIP-qPCR. Indicated concentrations of 1 or 20 treated with cells for 4 h. Then cells were collected to perform ChIP-qPCR. (F) CDK9 plasmid treatment led to efficient overprotein level in MDA-MB-231 cells. CDK9, c-Myc, Mcl-1, and β-actin were blotted to control for total protein levels. (G–I) Relative densitometry analysis of CDK9 (G), c-Myc (H), and Mcl-1 (I). (J) The cytotoxicity effect of 1 on control, CDK9 knockdown, and CDK9 overexpressing MDA-MB-231 cells. 1 inhibited the growth of on control, CDK9 knockdown, overexpression-treatment MDA-MB-231 cells with an IC₅₀ value of 0.3, 1.5 and 0.09 μmol/L, respectively. Data are presented as the mean ± SD. ∗P < 0.05, ∗∗P < 0.01 vs DMSO group, ^##P < 0.01 compared to DMSO group by the t-test.