PTEN and cancer: In contrast to the anti-cancer effects resulting from miRNA-induced suppression of autophagy in fulvestrant-resistant cells, a report using parental MCF-7 cells found that miR-21 knockdown increased autophagic cell death via activation of its direct target PTEN and subsequent inhibition of the PI3K/Akt/mTOR pathway to enhance sensitivity to tamoxifen and fulvestrant [46].