PDCD4 and breast carcinoma: It has also been shown that the overexpression of ErbB-2/neu, a member of the ErbB family of membrane receptor tyrosine kinases with a major role in breast cancer, causes an increase in the oncogenic miRNA miR-21, which confers an aggressive breast cancer phenotype via the downregulation of the metastasis suppressor protein PDCD-4 [32].