PTGDR and gastric cancer: On the other hand, DP1 was shown to be downregulated in the adenoma-carcinoma sequence of patients with colorectal cancer (Kalmar et al., 2015), in intestinal metaplasia and gastric tumor cells from patients with intestinal-type early gastric cancer (Kim et al., 2018), and in artery smooth muscle cells from patients with idiopathic pulmonary arterial hypertension (He et al., 2020).