CD274 and melanoma: In turn, several studies have shown that the activation of PD-L1 signaling is also crucial for maintaining the characteristic manifestation of malignant tumors with aggressive clinical features, in particular EMT programming,311,313,314 immune escape,307,308 and stem cell properties.315,316 Consequently, higher expression of PD-L1 has been connected to worse prognoses in multiple types of carcinomas, including esophageal cancer,317 renal cell carcinoma,318 gastric carcinoma,319 ovarian cancer,320 and melanoma.321