The expression levels of K18 are often increased or decreased in tumor cells compared to normal cells, and this change has been demonstrated to play a variety of roles in different tumors, such as promoting invasion and metastasis, anti-apoptosis, and mediating multidrug resistance, which is achieved by the interactions with various related proteins in different signaling pathways (Tables 1, 2, 3, 4). The gene discussed is KRT18; the disease is neoplasm.