MiR-34a modulates ErbB2 in breast cancer.

Breast cancer is the second highest cause of carcinoma-related death caused by distant metastasis in women. Estrogen receptor (ER), human epidermal growth factor receptor 2, (HER2) and progesterone receptor (PR) are three classified makers of breast cancer, which are defined as ER+, HER2+, and the most serious ER-PR-HER2- (triple-negative). It is well known that ErbB2 (V-Erb-B2 avian erythroblastic leukemia viral oncogene homolog 2) plays an important part in breast cancer. However, the molecular mechanisms underlying ErbB2 action needs to be well studied. In this report, we discovered that the decreased expression levels of miR-34a were inversely correlated with the increased ErbB2 levels in breast cancer. A luciferase reporter assay was done to understand the potential correlation between ErbB2 and miR-34a. Over-expression of miR-34a reduces ErbB2 expression and suppresses breast cancer cell invasion and growth in vitro. What's more, reduced expression of ErbB2 inhibits breast Cancer cell proliferation and re-expression of ErbB2 reversed miR-34a-dependent tumor suppression. Meanwhile, miR-34a levels were correlated inversely with breast cancer malignancy. Our study demonstrates that miR-34a, like ErbB2, might be a diagnostic target in breast cancer.