CLDN1 and colorectal carcinoma: In line with this hypothesis, strong expression of the MMP7, CLDN1, TACSTD2, CTHRC1, KRT23 and SRPX2 genes has been previously reported at the protein level in CRC tissues, their expression been also associated with tumor progression and an increased angiogenesis [51]; of note most of these proteins (i.e.: MMP7, TACSTD2, CTHRC1 and KRT23) have also been found to be secreted and to be present in both tumor tissues and the plasma from CRC patients [52].