The KRT19 (K19) gene encodes a type I intermediate filament protein (Keratin 19), expressed in various types of epithelial cells from the embryonic layer to adult cells. It is notably expressed in the lungs, oral cavity, bronchi, bronchioles, stomach, and small intestine, as well as in the ductal cells of the pancreas, kidneys, and liver. This protein is a member of the keratin family and plays a crucial role in maintaining the structural integrity of epithelial cells. Deletion of the Krt19 gene can lead to inducible skeletal muscle disease in mice. Additionally, Keratin 19 can be used as a biomarker for detecting tumor cells in various tissues. Depending on the type of cancer cells, regulating the expression of KRT19 can have different impacts on cell proliferation, survival, invasion, migration, and apoptosis. The Krt19-iCre mouse model is constructed by knocking a high-recombination activity iCre element (codon-optimized Cre) into the endogenous Krt19 gene in mice. This strategy disrupts the expression of the endogenous Krt19 gene in mice. When Krt19-iCre mice are crossed with mice containing loxP sites, Cre recombinase-mediated recombination between loxP sites is expected to occur in KRT19-expressing epithelial cells in the offspring.