ERBB2 and breast cancer: Dramatic downregulated miR-342 expression is associated with tamoxifen resistance in both MCF-7/HER2Δ16 cell and HER2 negative MCF-7 variants, and such association can also be observed in clinical data; that is, reduced miR-342 expression correlates with tamoxifen resistance [21], while over-expressed miR-342-5p could make HER2 positive breast cancer cells more vulnerable to cellular stress [22–24].