As demonstrated in Fig. 6, after 20 nM of CDK11p110 siRNA transfection, a significant G1 cell cycle arrest accompanied by reductions in the fraction of cells in S phase was observed in both MCF-7 and MDA-MB-468 cells (both P < 0.01), suggesting that CDK11p110 knockdown was able to induce human breast cancer cell cycle arrest in G1 phase and inhibit DNA synthesis. Here, CDK11B is linked to breast cancer.