To understand the correlation between CDK5 activation and each subtype of BC, we assessed the mRNA expression levels of CDK5, CDK5R1, and CDK5R2 using online analysis in the cBioPortal database (METABRIC, Nature, 2012 & Nature Communications, 2016).[18] This database is composed of 1699 BC cases including 679 Luminal A, 461 Luminal B, 220 HER2‐positive (HER2+), 299 TNBC, and 140 normal breast tissues. Here, CDK5R1 is linked to breast cancer.