Abstract
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.
Highlights
Cancer cells are characterized by phenotypic and biological heterogeneity
We investigated the expression of plectin-1 and trichohyalin in DOK human tongue epithelial cells [12] and BICR31 tongue cancer cells [13] using western blotting and FITC-labeled immunocytochemistry techniques
Plectin-1 is expressed in muscle and nerve cells, and it is hypothesized that the protein is involved in complex functions [4] [17] because of its distribution in crosslinks of microtubules and actin filaments
Summary
Cancer cells are characterized by phenotypic and biological heterogeneity. Similar to epithelial-to-mesenchymal transition (EMT), the ability of cancer cells to infiltrate tissues and metastasize during carcinogenesis is associated with changes in the expression of cell structural and adhesion molecules as well as matrix metalloproteases [1] [2] [3]. Plectin-1, which is 500-kDa cross-linker protein, belongs to the plakin family of cytoskeletal proteins and interacts with intermediate filaments, being localized into cells in some tissues. Trichohyalin is a protein of approximately 200 kDa that is distributed primarily in the medulla and inner root sheath cells of human hair follicles, and it is believed to play a role in maintaining cell strength during keratinization [8] [9]. As plectin-1 and trichohyalin interact with intermediate filaments or actin filaments, it is reasonable to hypothesize that they play roles in the formation of invadopodia and/or filopodia. We investigated the expression of plectin-1 and trichohyalin in DOK human tongue epithelial cells [12] and BICR31 tongue cancer cells [13] using western blotting and FITC-labeled immunocytochemistry techniques
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