CDK1 and breast cancer: In control T24‐derived tumors, we detected fluorescent signals in the nucleus when p‐TFCP2L1 and CDK1 antibodies were used together, indicating an interaction between p‐TFCP2L1 and CDK1 (Fig 7G), whereas few signals were detected when only one of the antibodies was used (negative control; Appendix Fig S9A) or in xenograft tumor samples from T177A TFCP2L1 and shTFCP2L1 xenografts (Appendix Fig S9B and C), confirming that p‐TFCP2L1 interacts with CDK1 in the nuclei of BC cells.