MUC4 and colorectal carcinoma: In a study involving both human CRC cell line HT29-MTX and rat cell lines as well as in vivo models, it was observed that leptin stimulates the expressions of MUC2, MUC5AC, and MUC4 in human and of Muc2, Muc3, and Muc4 in rat cell lines via the Protein Kinase C (PKC), Phosphoinositide 3-kinase (PI3K), and MAPK pathways [59].