ERBB2 and breast cancer: Transfection of breast cancer cells with the PPRHs against ERBB2 prior to engraftment led to a significant decrease in tumor growth, which correlated with the reduction of HER-2 protein levels in those tumors, suggesting that the PPRHs silencing effect is enough to reduce the extra signaling of proliferation caused by the overexpression of HER-2 in breast cancer cells.