A new human cell line, GIST-T1, was established from a metastatic plural tumor from a gastrointestinal stromal tumor (GIST) of the stomach in a Japanese woman, and was characterized by immunohistochemistry, conventional banding methods, comparative genomic hybridization (CGH), and fluorescence in situ hybridization (FISH). Immunohistochemically, GIST-T1 cells were strongly positive for CD34 and c-KIT, but not for desmin, S-100 protein, or a-smooth muscle actin. These findings indicated that the GIST-T1 cell line fully expressed the characteristics of GIST. Conventional banding analysis revealed that GIST-T1 displayed a hypodiploid karyotype with a ring chromosome, several unbalanced translocations, and marker chromosomes. CGH studies showed chromosomal gains and losses on several regions. FISH using painting probes revealed that the ring chromosome was derived from chromosome 1 and some marker chromosomes consisted of more than two different chromosomes. Our study showed that GIST-T1 has a complex karyotype and high-level amplifications involving chromosome bands 3q26. 1–27, 5p12–15.1, and 7q21. 3–36, where amplification of oncogenes may arise. Combined analysis of classical and molecular cytogenetic techniques provides an accurate cytogenetic assessment, including change in the DNA copy number of GIST-T1. This newly established cell line, GIaST-T1, will be a particularly useful model for studying molecular pathogenesis of GIST.

CGH studies of GIST have shown some genetic alterations (El-Rifai et al, 2000; Knuutila et al, 2000), and molecular studies of the c-kit gene of GIST revealed the mutation of the gene in GIST (Hirota et al, 1998; Taniguchi et al, 1999). However, the precise molecular and genetic basis of carcinogenesis in GIST still remains unknown. One approach to studying this tumor is to establish well-characterized human tumor cell lines, which are important research resources for studying tumor cell biology, as well as for developing new strategies against tumor cell growth and progression. To our knowledge, no GIST cell line has yet been reported. The GIST-T1 cell line was established from a metastatic pleural tumor, from a primary gastric GIST in a 47-year-old Japanese woman. The tumor tissue obtained at surgery was minced with knives into small pieces, which were placed in culture flasks and cultured in Dulbecco’s minimum essential medium (Sigma-Aldorich, Tokyo, Japan) supplemented with 10% FBS (Gibco BRL, Grand Island, New York) in a humidified incubator containing 5% CO2 at 37 C. For the pathologic study, GIST-T1 cells growing on the coverslips were fixed with 95% ethanol, and tissue from a xenotransplanted nude mouse tumor was fixed with 20% buffered formalin solution. The coverslips and dewaxed tumor tissue sections were stained with hematoxylin-eosin (Fig. 1A) and examined with antibodies against vimentin (V9, 100, Dako, Dakopatts; Kyoto, Japan), desmin (D33, 30; Dakopatts), α-smooth muscle actin (α-SMA; 1A4, 200; Dakopatts), S-100 protein (S-100; polyclonal, 1000; Dakopatts), CD34 (HPCA-1, 10, Becton Dickinson, Franklin Lakes, New Jersey)(Fig. 1B), c-KIT (polyclonal, 50, Dakopatts)(Fig. 1C), using the streptavidinbiotin immunoperoxidase method (Histofine SAB-PO kit, Nichirei, Tokyo, Japan). Population doubling time was determined by seeding the cells at the initial density of 105 in 24-well plates, and counting was performed for up to 10 days, in triplicate. For the cytogenetic study, subconfluent