MUC5AC and colorectal carcinoma: Numerous studies have indicated that MUC2 mucin production was reduced in patients with CRC (Bu et al., 2010; Al-Khayal et al., 2016), and higher MUC2 expression was negatively correlated with TNM stage, lymphatic metastasis, and prognosis of CRC (Elzagheid et al., 2013; Li et al., 2018).