cGAS restricted tumorigenesis in both hematopoietic and nonhematopoietic cells.cGAS deficiency promoted the proliferation of IECs and caused mucin depletion during cancer development. cGAS deficiency enhanced the activation of STAT3, T cells exhaustion, myeloid-derived suppressor cells and Th17 cells accumulation in the colon.Intraperitoneal injection of cGAMP partially reduced the number of tumors. Here, MUC5AC is linked to cancer.