ERBB2 and breast cancer: Mechanistically, lethal-7f downregulates β2-adrenergic receptor (β2-AR) levels by interacting with the 3′-UTR (untranslated region) of the gene coding β2-AR levels in human epidermal growth factor receptor 2 (HER2)-positive breast cancer patients, as demonstrated in MCF-7, SKBR3 and BT474 cell lines.