The gene encoding claudin-1 (CLDN1) has been mapped to human chromosome 3. The claudin-1 gene (CLDN1) is a member of a family of genes that encodes proteins found in tight junctions and it has been implicated as one of several receptors for late stage binding of hepatitis C virus (HCV). Claudin-1 is a recently discovered co-receptor for hepatitis C virus (HCV) that is required for late-stage binding of the virus. Because variants in the gene that encodes claudin-1 (CLDN1) could play a role in HCV infection, the genetic variants in regulatory regions of CLDN1 may alter susceptibility to HCV infection. Claudin1 (CLDN1) plays an important role not only in the intercellular barrier function of tight junctions (TJs) but also in migration and invasiveness of cancer cells. Previous cDNA microarrays indicated that CLDN1 (claudin-1) is an important gene for ovarian cancer-initiating cell (OCIC) invasion and adhesion. Tight junction protein claudin-1 (CLDN1) is mainly involved in the intercellular barrier function of epithelial cells and is known to be dysregulated in many cancer types, including gastrointestinal cancers. CLDN1 (claudin1) is essential for intercellular junctions and has been reported to be involving in cell migration and metastasis, making it as an oncogene in various cancer types. The miR-29a may regulate tumor growth and migration by targeting CLDN1, providing promising therapeutic targets for HCC.