For example, promoter hypomethylation could cause the upregulation of matrix metalloproteinase‐1 (MMP1) in breast cancer55; promoter hypomethylation is related to upregulation of Syncytin‐1 in non‐small cell lung cancer56; hypomethylation could activate protein lin‐28 homolog B (LIN28B) to induce gastric cancer cell proliferation and metastasis.57 The gene discussed is PROS1; the disease is gastric cancer.