Our histological observations are consistent with an epithelial cell of origin of the EPO-GEMM tumors, which was confirmed by generating tumors with comparable latency and presentation in a CK8-CreERT2; LSL-Cas9 host that restricts tumor initiation to the CK8+ epithelial compartment (Extended Data Fig. 4t–w and Extended Data Fig. 5f–j). This evidence concerns the gene EPO and neoplasm.