Tissue Content and Pattern of Expression of Claudin-3 and Occludin in Normal and Neoplastic Tissues in Patients with Colorectal Cancer

Background Metastasis is the worst prognostic variable of patients with colorectal cancer (CRC). For the development of metastases, it is necessary that cancer cells detach from the primary tumor, migrate into the angiolymphatic system, and invade the tissue where they will develop. The breakdown of the tight junctions (TJs) plays an important role in colorectal metastatic tumors. Claudin-3 and occludin are the main component proteins of TJs. Aim To analyze the expression and tissue content of claudin-3 and occludin in normal and neoplastic tissues of patients with metastatic CRC. Methods Fifty-seven consecutive patients with stage III and IV CRC were included. Fragments of neoplastic tissue were collected from the tumor margins, and samples of the normal tissue were collected from the same patient in a standardized distance of 10 cm from the cranial margin of the tumor. Immunohistochemistry technique was used to identify the tissue staining of claudin-3 and occludin. To measure the content of both proteins in cellular membranes of normal and cancer cells, a validated immunoscore was used. Results Claudin-3 and occludin in normal tissues are in the apical and lateral membranes of cells, while in the neoplastic, in cytoplasm. The mean of the tissue content of claudin-3 in the normal tissue was 2.57 ± 0.16, while in the neoplastic tissue was 1.03 ± 0.13. The contents of occludin were 2.77 ± 0.1 in normal tissue, while in the neoplastic were 1.08 ± 0.14. Conclusion There is a reduction in the content of the claudin-3 and occludin in the cell membranes of the neoplastic tissue in patients with CRC.