title: Establishment and characterization of pleomorphic adenoma cell systems: an in-vitro demonstration of carcinomas arising secondarily from adenomas in the salivary gland.
abstract: BACKGROUND
  Among the salivary gland carcinomas, carcinoma in pleomorphic adenoma has been regarded as a representative carcinoma type which arises secondarily in the background of a pre-existent benign pleomorphic adenoma. It is still poorly understood how and which benign pleomorphic adenoma cells transform into its malignant form, carcinoma ex pleomorphic adenoma.
  
  
  METHODS
  We have established five cell systems from a benign pleomorphic adenoma of the parotid gland of a 61-year-old woman. They were characterized by immunofluorescence, classical cytogenetics, p53 gene mutational analysis, fluorescence in-situ hybridization, and histopathological and immunohistochemical examinations of their xenografts, to demonstrate their potency of secondary transformation.
  
  
  RESULTS
  We established and characterized five cell systems (designated as SM-AP1 to SM-AP5) from a benign pleomorphic adenoma of the parotid gland. SM-AP1 to SM-AP3 showed polygonal cell shapes while SM-AP4 and SM-AP5 were spindle-shaped. SM-AP1-3 cells were immunopositive for keratin only, indicating their duct-epithelial or squamous cell differentiation, while SM-AP4/5 cells were positive for both keratin and S-100 protein, indicating their myoepithelial cell differentiation. Chromosome analyses showed numeral abnormalities such as 5n ploidies and various kinds of structural abnormalities, such as deletions, translocations, derivatives and isodicentric chromosomes. Among them, der(9)t(9;13)(p13.3;q12.3) was shared by all five of the cell systems. In addition, they all had a common deletion of the last base G of codon 249 (AGG to AG_) of the p53 gene, which resulted in generation of its nonsense gene product. Transplanted cells in nude mice formed subcutaneous tumors, which had histological features of squamous cell carcinoma with apparent keratinizing tendencies. In addition, they had ductal arrangements or plasmacytoid appearances of tumor cells and myxoid or hyaline stromata, indicating some characteristics of pleomorphic adenoma.
  
  
  CONCLUSIONS
  This study demonstrates in vitro that certain cell types from pleomorphic adenoma are able to clone and survive over a long term and develop subcutaneous tumors in nude mice. The histological features of squamous cell carcinoma from the transplanted cell systems in nude mice might suggest a secondary onset of malignancy from a pre-existing benign adenoma.
authors.affiliation: Division of Oral Pathology, Department of Tissue Regeneration and Reconstruction, Niigata University, Graduate School of Medical and Dental Sciences, 2-5274 Gakkoucho-dori, Chuo-ku, Niigata 951-8514, Japan. maru@dent.niigata-u.ac.jp
authors.forename: Satoshi
authors.initials: S
authors.lastname: Maruyama
authors.forename: Jun
authors.initials: J
authors.lastname: Cheng
authors.forename: Susumu
authors.initials: S
authors.lastname: Shingaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Tamura
authors.forename: Shuichi
authors.initials: S
authors.lastname: Asakawa
authors.forename: Shinsei
authors.initials: S
authors.lastname: Minoshima
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Shimizu
authors.forename: Nobuyoshi
authors.initials: N
authors.lastname: Shimizu
authors.forename: Takashi
authors.initials: T
authors.lastname: Saku
mesh_terms: D000236:Adenoma / Q000378:metabolism* / Q000473:pathology*; D000818:Animals; D002277:Carcinoma / Q000378:metabolism* / Q000556:secondary*; D022202:Chromosomes, Artificial, Bacterial; D004252:DNA Mutational Analysis; D005260:Female; D016158:Genes, p53; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D017404:In Situ Hybridization, Fluorescence; D051379:Mice; D008819:Mice, Nude; D008856:Microscopy, Fluorescence / Q000379:methods; D008875:Middle Aged; D009368:Neoplasm Transplantation; D012468:Salivary Gland Neoplasms / Q000378:metabolism* / Q000556:secondary*; D014407:Tumor Cells, Cultured