CCR4 and ovarian carcinoma: In malignant ascites from epithelial ovarian cancer, effector-type Tregs are increased, positively associate with CD8+ PD-1, and frequently express CCR4—supporting a Treg-enriched, checkpoint-high suppressive milieu and pointing to the CCL22/CCL17–CCR4 axis as a recruitable, and potentially targetable, node (73).These observations support the immune-low phenotype of HGSOC and help explain the modest activity of PD-1/PD-L1 monotherapy.