The Use of Keratins as Lung Cell Differentiation Markers and as a Diagnostic Tool in Lung Cancer

Keratins (>50 genes) are abundant in lung epithelial cells. Evolved from common ancestral genes, keratins form intermediate filaments consisting of polymers of paired Type I and Type II subtypes. Keratin expression is epithelial cell-type-specific, and influenced by developmental stage, cellular differentiation, and pathology. Mutations in keratins, while not causing a profound primary pulmonary phenotype, cause genetic diseases, establishing their role to maintain epithelial structure and integrity. Keratins modulate cell functions including receptor signaling, protein targeting, proliferation, migration, differentiation and inflammatory and immune responses. The predictable cell type specific expression pattern, now strengthened by single cell analyzes, underlies their use for cell identification. Keratin fragments are released in pathological conditions, serving as disease markers, and keratins assist in the differential diagnosis of lung neoplasms.