Although Hep G2 (liver cancer—mesodermal tissue origin) and MDA-MB-231 (mammary epithelial adenocarcinoma—ectodermal tissue origin) are different cancer types, they shared a large number of CKI DE genes with similar expression profiles, presumably, these shared genes include CKI response genes that are essential to the apoptotic response triggered by CKI. The gene discussed is CHKA; the disease is cancer.