The role of collagen and its receptor, discoidin domain receptor 1 (DDR1) in immune response of colorectal cancer (CRC) remains unclear. We identified DDR1 as a promising target of immunotherapy resistance using a pooled in vivo CRISPR/sgRNA screening in microsatellite stable (MSS) CRC mouse models. Our findings demonstrated that knockdown or inhibition of DDR1 could enhance infiltration of CD8