CLDN1 and gastrointestinal stromal tumor: Additionally, AZIN1 (antizyme inhibitor 1), SFRP1 (soluble frizzled related protein 1), and CHST1 (carbohydrate sulfotransferase 1) were up-regulated in mock-transfected GIST cells when compared to CLDN1-knockdown GIST (Figure 10B).