Expression of Plectin-1 and Trichohyalin in Human Tongue Cancer Cells

In basal squamous cells, plectin-1 interacts with intermediate filaments, whereas trichohyalin, which is distributed primarily in the medulla and inner root sheath cells of human hair follicles, plays a role in strengthening cells during keratinization. Although both cytoskeletal proteins occur in trace amounts in human tongue epithelial cells, there are minimal data on their expression in human tongue primary cancer cells. We therefore investigated the expression of plectin-1 and trichohyalin in human tongue epithelial cell line (DOK) and tongue cancer cell line (BICR31) using western blotting and FITC-labeled immunocytochemistry techniques. DOK and BICR31 cells were cultivated to subconfluence in Dulbecco’s Modified Eagle’s Medium containing 0.4 μg/ml of hydrocortisone and 10% fetal bovine serum, and the levels of trichohyalin and plectin-1 were determined by western blot analysis and immunocytochemical staining. Trichohyalin expression was clearly observed, with no differences between DOK and BICR31 cells. Although DOK cells expressed trace levels of plectin-1, obvious plectin-1 bands were detected in western blot analyses of BICR31 cells. Immunocytochemical staining revealed that trichohyalin and plectin-1 localize in the cytoplasm. Trichohyalin was diffusely distributed in both cell lines, and colocalization of trichohyalin and cytokeratin 1/10 was observed in almost all BICR31 cells. There were no correlations between western blot and immunocytochemical data for trichohyalin. Conversely, correlations in immunochemical reactions for plectin-1 were observed. Most DOK cells showed no localization of plectin-1, but strong reactions were detected in the cytoplasm of BICR31 cells. These results indicate that trichohyalin is expressed by cancerous tongue epithelial cells during various stages of malignancy and that plectin-1 provides an index of malignancy.