REG4 and colorectal carcinoma: Accordingly, multiplex immunofluorescence (IF) analysis of our CRC tissues confirmed low to absent expression of REG4 and mucins (MUC1 and MUC5AC) genes in the MSI CRC1 and MSS type II CRC3, while MSS type I CRC2 exhibited positive staining consistent with transcriptomic analysis on PDO models (Supplementary Fig. S3A).