Low expression of PCDH17, due to its high DNA methylation in cancer cells, including ovarian cancer, hepatocellular carcinoma, bladder cancer, contributed to malignant progression of tumour [28–30], and PCDH17 expression improves the sensitivity of CRC to 5-FU treatment by inducing apoptosis and JNK-dependent autophagic cell death [10]. The gene discussed is PCDH17; the disease is cancer.