UPK1B and gastric cancer: Tspan20, also known as uroplakin 1B (UPK1B), promotes the invasion and metastasis of bladder cancer via regulation of the Wnt/β-catenin pathway (Wang et al., 2018; Zhang Z. Y. et al., 2020), while the reduced expression of Tspan21 (UPK1A) might play a role in the progression of gastric cancer (Zheng et al., 2014).