CDK4 and cancer: Clinical inhibitors targeting some of these synthetic lethal partners, such as the anti-apoptotic protein B cell lymphoma-extra large (BCL-XL), cyclin-dependent kinase 4 (CDK4), and serine/threonine-protein kinase TBK1, have already been tested in clinical settings in a combinatorial strategy with a mitogen-activated protein kinase (MEK) inhibitor to treat KRAS-mutant cancers [5].