We noticed that the ERBB2 (HER2)-enriched subtype-like [ER-, ERBB2 (HER2)+/high] SK-BR-3 breast cancer cells express a large amount of the nucleic NUPR1 protein endogenously, as compared to MCF7 and MCF7-TamC3 cells, and the si-NUPR1 treatment also decreased the expression of HDAC5 in SK-BR-3 cells (Fig. 3C and 3D). Here, ESR1 is linked to breast cancer.