Desmosome not only participates in the connections of epithelial cell and cardiomyocyte to enhance the cell adhesion when subjected to mechanical stress,it also regulates signal pathways of cell behavior.Since the discovery of Pinin(PNN),a desmosome-associated protein,its position and function are controversial.Current results indicate that PNN has two types:a desmosome-like PNN co-localized with desmosomes on the cell membrane,and a karyotype PNN located in the nucleus.The former participates in epithelial cell adhesion,the latter is related to the alternative splicing function of genes.Recent studies have found that PNN is closely related to tumorigenesis via different molecular mechanism.This article reviews the biological function of PNN and its relationship with tumorigenesis.