Boris knockout eliminates AOM/DSS‐induced in situ colorectal cancer by suppressing DNA damage repair and inflammation

The Brother of Regulator of Imprinted Sites (BORIS, gene symbol CTCFL) has previously been shown to promote colorectal cancer cell proliferation, inhibit cancer cell apoptosis, and resist chemotherapy. However, it is unknown whether Boris plays a role in the progression of in situ colorectal cancer. Here Boris knockout (KO) mice were constructed. The function loss of the cloned Boris mutation that was retained in KO mice was verified by testing its activities in colorectal cell lines compared with the Boris wild‐type gene. Boris knockout reduced the incidence and severity of azoxymethane/dextran sulfate‐sodium (AOM/DSS)‐induced colon cancer. The importance of Boris is emphasized in the progression of in situ colorectal cancer. Boris knockout significantly promoted the phosphorylation of γH2AX and the DNA damage in colorectal cancer tissues and suppressed Wnt and MAPK pathways that are responsible for the callback of DNA damage repair. This indicates the strong inhibition of colorectal cancer in Boris KO mice. By considering that the DSS‐promoted inflammation contributes to tumorigenesis, Boris KO mice were also studied in DSS‐induced colitis. Our data showed that Boris knockout alleviated DSS‐induced colitis and that Boris knockdown inhibited the NF‐κB signaling pathway in RAW264.7 cells. Therefore Boris knockout eliminates colorectal cancer generation by inhibiting DNA damage repair in cancer cells and relieving inflammation in macrophages. Our findings demonstrate the importance of Boris in the development of in situ colorectal cancer and provide evidence for the feasibility of colorectal cancer therapy on Boris.