Claudin 

Claudins are a family of transmembrane proteins, are the most important components of the tight junctions (zonulae occludentes). They have four transmembrane domains, with the N-terminus and the C-terminus in the cytoplasm. Claudin expression and functions are regulated at multiple levels and by diverse mechanisms. Delocalization of claudins from membrane appears to be common among the transformed cells. Constitutive activation of Ras or Ras-mediated signaling pathway/s is one of the initial steps during tumorigenesis that is causatively associated with neoplastic transformation. Importantly, claudins are expressed in the epithelial cells and in a tissue-specific manner and changes among claudin family members in cancer follow tissue-specific and sometimes contrasting pattern. Thus, claudin family of proteins may hold the potential cue to the heterogeneity among the tumors of epithelial origin and beyond being useful markers may also help provide therapeutic opportunities suited for specific cancer type^[1].

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