Here, we describe the preliminary results of our investigations aimed at understanding the cell biological effects of CDK8 inhibitor 4 on triple-negative breast cancer (TNBC) cell line MDA-MB-468 compared to both APC mutant and β–catenin mutant colon cancer cell lines Colo205 and HCT116. The gene discussed is CDK8; the disease is malignant colon neoplasm.