PTP4A2 and breast cancer: Considering that breast cancer is a highly heterogeneous disease, to evaluate the role of PRL2 on miR-21 in breast cancer cell lines with different molecular subtypes, we chose triple-negative breast cancer model MDA-MB-231 (M231) and ER-positive breast cancer model MCF7 cell lines and established M231 and MCF7 cells to stably express PRL2.