CDK1 and cancer: To test this hypothesis, we treated DLD-1/BRD4-AID cells expressing Flp-In WT BRD4 or the non-phosphorylated mutant with varying doses of (+)-JQ1 and RO-3306 either individually or in combination, and analyzed the potential synergy of BETis with the CDK1 inhibitor in repressing cancer cell proliferation.