DKK2 and breast cancer: In contrast, while overexpressed GAS5 can strengthen ADR sensitivity in vivo and in vitro, GAS5 acted as a sponge to miR-221-3p and subsequently drove the expression of dickkopf 2 (DKK2), which ultimately inactivated the Wnt/β-catenin pathway to weaken ADR resistance in breast cancer cells [21].