KL-6 mucin, a type of MUC1 mucin, is expressed in many malignant tissues including colorectal adenocarcinoma. Previous studies on colorectal adenocarcinoma tissues showed that subcellular localization of KL-6 mucin was associated with the tumor metastatic potential and the patient prognosis. In the present study, to further investigate the significance of subcellular localization of KL-6 mucin, we examined KL-6 mucin expression in colorectal carcinoma cell lines, COLO 201, LoVo, WiDr, and DLD-1, by means of Western blot, flow cytometric and immunocytochemical analyses in conjunction with xylitol treatment. COLO 201 cells characterized by free cells in culture and high metastatic potential revealed extremely high level expression of KL-6 mucin in the cytoplasm and cell surface. The cell surface mucin of COLO 201 cells could not be removed by xylitol treatment, suggesting that the mucin may tightly bind to the cell membrane. LoVo cells characterized by adhesive cells in culture and high metastatic potential express a low level of KL-6 mucin in their cytoplasm and cell surface. In contrast, WiDr and DLD-1 cells, both of which are characterized by low metastatic potential, express KL-6 mucin around the cell surface. The mucin of WiDr and DLD-1 cells could be removed by xylitol treatment, suggesting that KL-6 mucin of these two cell lines may be weakly attached around the cell surface. These results suggest that expression level and subcellular localization of KL-6 mucin may be related to the cell morphology in culture and metastatic potential in colorectal carcinoma cell lines. In addition, xylitol is an effective tool to remove KL-6 mucin weakly attached around the cell surface and to investigate the role of subcellular localization of KL-6 mucin.

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