CTNNB1 and gastric cancer: Emerging evidence has demonstrated that Wnt/β‐catenin is activated after gastric cancer and plays a critical role in promoting invasion and migration through overexpressing or increasing the functions of several components of the Wnt pathway such as Wnt1, Wnt2, Wnt3, Wnt5a, Fzd‐3, CTNNB1 and LRP6.