Intratumoral administering of a mixture of different IFNα subtypes and IFNβ resulted in a regression of MCPyV-positive, but not MCPyV-negative xenografts of MCC cells, while IFNα-2b, IFNβ-1b, and IFNγ-1b challenge resulted in an increased cell-surface expression of MHC-I on MCC cell lines [96,202]. Here, IFNA1 is linked to Merkel cell skin cancer.