Just as the MCPyV LT antigen inactivates RB1 to phenocopy RB1 mutations commonly seen in other cancers (14), we suspected that MCPyV viral antigens also suppress class I antigen presentation through derangement of regulatory mechanisms that might be phenocopied in other cancers, including MCPyV– MCC tumors. Here, RB1 is linked to Merkel cell skin cancer.