CLDN1 and ovarian cancer: The high expression level of CLDN1 in ovarian cancer is related to tumor invasion and recurrence, and CLDN1 methylation can inhibit its expression level (Visco et al., 2021), which means that CLDN1 may be a poor prognosis factor in many cancer types, and methylation is a protective ingredient, which is completely opposite to the five genes that we have screened associated to a positive prognosis.