WNT5A and melanoma: Melanoma-derived Wnt5a promotes the transcriptional expression of IDO1 in nearby DCs by Wnt5a-β-catenin signaling and activates peroxisome proliferator-activated receptor-γ (PPAR-γ) signaling pathway, culminating in enhanced IDO1 activity to establish an immunosuppressive microenvironment (44).