More recent studies on the biological function of CK isozymes revealed that CKα may play a more prominent role in cancer development as compared to CKβ, as only CKα was upregulated in breast cancer cell lines [14], and specific depletion of the CKα isoform by shRNA selectively induced apoptosis in several tumor-derived cell lines without affecting the viability of normal primary cells [15]. This evidence concerns the gene CHKB and breast cancer.