The present disclosure relates to the use of one or more biomarkers to evaluate the likelihood that a CDK4 inhibitor would produce an anti-cancer effect in a subject. Accordingly, in certain non-limiting embodiments, the present disclosure provides for methods, compositions and kits for a companion diagnostic for CDK4 inhibitors, and in particular, for the use of the colocalization of Enigma and CDH18 biomarkers to foci within the cancer for determining whether the cancer can be successfully treated by CDK4 inhibition.