(E/Z) -GO289

(E/Z) -GO289, which strongly lengthened circadian period, is a potent and selective inhibitor of CK2. (E/Z) -GO289 exhibited cell type-dependent inhibition of cancer cell growth that correlated with cellular clock function. The discovery of (E/Z) -GO289 provides a direct link between the circadian clock and cancer regulation and reveals unique design principles underlying kinase selectivity.