Growth, Metastasis, Immunogenicity, and Chromosomal Content of a Nickel-Induced Rhabdomyosarcoma and Subsequent Cloned Cell Lines in Rats23

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Abstract
Karyotype patterns, growth, metastasis, and immunogenicity were compared in a rhabdomyosarcoma induced by a single injection of metallic nickel with those in subsequent tumor-cloned cell lines. The primary tumor was induced in a male WAG rat by im injection of 20 mg nickel powder. The parental cell line (9–4/0) and 8 cell subpopulations (J 9–4) isolated from a primary tumor by cloning on agarose were examined. The tumor cell dose inducing tumors in 50% of the animals after sc injection (TD50) and the in vitro growth characteristics showed a marked heterogeneity between parental and cloned tumor cell lines. In vitro doubling times and saturation densities were also heterogeneous without showing a discernible relationship with TD5o. Chromosome patterns of the cell lines exhibited very similar modal numbers, whereas chromosome numbers were somewhat different; neither of these exhibited any correlation with tumorigenicity. Parental cell line 9–4/0 expressed a significant degree of immunogenicity, but it did not protect against pulmonary metastasis in immunized rats. Among 6 clones studied, only clone J 9– 4/2 appeared to be immunogenic and reduced metastatic spread. The relevance of the comparison between the different characteristics is discussed.