The expression of human EP4 receptors was previously reported to decrease in a cellular density‐dependent manner in HCA‐7 human colon cancer cells, and inversely correlated with HIF‐1α expression levels.9, 16 One major HIF‐1α‐binding sequence is GCGTG,24 namely HRE, which is located between −230 and −226 bp of the human EP4 receptor promoter region (Figures 1A and E). Here, HIF1A is linked to malignant colon neoplasm.