Karyotype evolution of the clonal rat liver cell line CL 52 during progression in vitro and in vivo

Defining the sister rat mammary tumor cell lines HH-16 cl.2/1 and HH-16.cl.4 as an in vitro cell model for Erbb2

Cancer cell lines have been shown to be reliable tools in genetic studies of breast cancer, and the characterization of these lines indicates that they are good models for studying the biological mechanisms underlying this disease. Here, we describe the molecular cytogenetic/genetic characterization of two sister rat mammary tumor cell lines, HH-16 cl.2/1 and HH-16.cl.4, for the first time. Molecular cytogenetic analysis using rat and mouse chromosome paint probes and BAC/PAC clones allowed the characterization of clonal chromosome rearrangements; moreover, this strategy assisted in revealing detected breakpoint regions and complex chromosome rearrangements. This comprehensive cytogenetic analysis revealed an increase in the number of copies of the Mycn and Erbb2 genes in the investigated cell lines. To analyze its possible correlation with expression changes, relative RNA expression was assessed by real-time reverse transcription quantitative PCR and RNA FISH. Erbb2 was found to be overexpressed in HH-16.cl.4, but not in the sister cell line HH-16 cl.2/1, even though these lines share the same initial genetic environment. Moreover, the relative expression of Erbb2 decreased after global genome demethylation in the HH-16.cl.4 cell line. As these cell lines are commercially available and have been used in previous studies, the present detailed characterization improves their value as an in vitro cell model. We believe that the development of appropriate in vitro cell models for breast cancer is of crucial importance for revealing the genetic and cellular pathways underlying this neoplasy and for employing them as experimental tools to assist in the generation of new biotherapies.

Establishment and Molecular Cytogenetic Characterization of a Cell Culture Model of Head and Neck Squamous Cell Carcinoma (HNSCC)

Cytogenetic analysis of head and neck squamous cell carcinoma (HNSCC) established several biomarkers that have been correlated to clinical parameters during the past years. Adequate cell culture model systems are required for functional studies investigating those potential prognostic markers in HNSCC. We have used a cell line, CAL 33, for the establishment of a cell culture model in order to perform functional analyses of interesting candidate genes and proteins. The cell line was cytogenetically characterized using array CGH, spectral karyotyping (SKY) and fluorescence in situ hybridization (FISH). As a starting point for the investigation of genetic markers predicting radiosensitivity in tumor cells, irradiation experiments were carried out and radiation responses of CAL 33 have been determined. Radiosensitivity of CAL 33 cells was intermediate when compared to published data on tumor cell lines.

Phenotypic instability of Saos-2 cells in long-term culture

The human osteosarcoma cell line Saos-2 is widely used as a model system for human osteoblastic cells, though its phenotypic stability has not been ascertained. We therefore propagated these cells over 100 passages and compared relevant phenotypic properties. In general, higher passage cells exhibited higher proliferation rates and lower specific alkaline phosphatase activities, though mineralization was significantly more pronounced in cultures of late passage cells. Whereas expression of most genes investigated did not vary profoundly, some genes exhibited remarkable differences. Decorin, for instance, that has been discussed as a regulator of proliferation and mineralization, is strongly expressed only in early passage cells, and two receptors for pleiotrophin and midkine exhibited an almost mutually exclusive expression pattern in early and late passage cells, respectively. Our observations indicate that special care is required when results obtained with Saos-2 cells with different culture history are to be compared.

Further characterization of a rat hepatoma-derived aldose-reductase-like protein--organ distribution and modulation in vitro

A protein detected in N-methyl-N-nitrosourea-initiated rat hepatomas by two-dimensional electrophoresis at 35 kDa/pI 7.4 was identified in a previous study by internal amino acid micro sequencing as an aldose-reductase-like protein [Zeindl-Eberhart, E., Jungblut, P. R., Otto, A. & Rabes, H. M. (1994) Identification of tumor-associated protein variants during rat hepatocarcinogenesis, J. Biol. Chem. 269, 14589-14594]. Two-dimensional electrophoresis of rat lens proteins revealed a spot at 37 kDa/pI 6.8 that showed a high degree of identity (98.5%) with rat lens aldose reductase after amino acid sequencing and 80% sequence identity to the rat-hepatoma-derived aldose-reductase-like protein. This suggests that hepatoma-derived aldose-reductase-like protein and rat lens aldose reductase are related proteins encoded by different genes. A different expression profile of these proteins was found in various rat organs. Rat lens aldose reductase is present, in addition to in lens, in heart, brain, muscle, lung, duodenum, kidney, spleen and bone marrow, while the hepatoma-derived aldose-reductase-like protein is found preferentially in hepatomas and in embryonic liver. Though different in organ expression, an identical response was found for both proteins after stimulation with fibroblast growth factor-1 and after exposure to increased glucose concentrations. Since rat hepatoma-derived aldose-reductase-like protein is expressed in embryonic, but not in adult liver, it is assumed that it is expressed in hepatomas as a functionally active embryonal type of aldose reductase during hepatocarcinogenesis. Immunohistochemistry revealed that the hepatoma-derived aldose-reductase-like protein is expressed already in the preneoplastic stage of hepatocarcinogenesis and might potentially serve as a marker enzyme in early hepatic neoplasia.