ERBB2 and breast cancer: The expression of miR-139-5p in luminal A, luminal B, HER2-enriched, and basal-like breast cancers in the TCGA database was observed; the results showed that compared with normal samples, miR-139-5p expression was reduced in luminal A, luminal B, HER2-enriched, and basal-like breast cancers (Figure 1A).