Differential Expression of Cytokeratin after Orthotopic Implantation of Newly Established Human Tongue Cancer Cell Lines of Defined Metastatic Ability

Abstract

Tongue cancer has a high metastatic ability. The survival of cancer patients often depends primarily on whether or not the tumor metastasizes; therefore, it is important to characterize the phenotype of metastatic tumors and to elucidate both the responsible molecules and their functions.Cytokeratins represent important structural components of the epithelial cytoskeleton and thus constitute major protein markers for cellular differentiation.1 They have been widely used as molecular markers in the diagnosis of a variety of carcinomas as well as in the study of many nonmalignant lesions.2 The CK19 fragment, referred to as CYFRA 21-1, has been reported to be useful as an independent prognostic marker of squamous cell carcinoma.3,4 Alterations in the expression patterns of cytokeratins have been reported in carcinoma or carcinoma cell lines using immunohistochemistry, 5,6 Western blot analysis, 5,7 two-dimensional gel electrophoresis, 1,8 and in situ hybridization. 9 However, few reports have analyzed them using metastatic models. It is necessary to analyze cancer cells that have differences in invasive and metastatic abilities to understand the cytokeratin gene regulation as well as the role of cytokeratin in the progression of carcinoma. An orthotopic implantation enabled us to establish the metastatic models. 10,11 In the present study, we examined the relationship between the malignancy and the cytokeratin expression by using two established squamous cell carcinoma cell lines, SQUU-A and SQUU-B, derived from the same human tongue cancer, which demonstrated different invasive and metastatic potentials in the orthotopic implantation system. Materials and Methods Establishment of Cell LinesSQUU-A and SQUU-B cell lines were established from local recurrences of the tongue cancer obtained from a 66-year-old Japanese woman. This tumor had been diagnosed to be a well differentiated squamous cell carcinoma. Surgical specimens were minced with a scalpel into small cubes measuring from 1 to 3 mm in size. These

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