Expression of Transfected Mutant β-actin Genes: Transitions Toward the Stable Tumorigenic State
| Autor: | L Kedes, S Burbeck, John Leavitt, Sun-Yu Ng, M Varma, G Latter, Peter W. Gunning |
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| Rok vydání: | 1987 |
| Předmět: |
Cell
Mutant Mice Nude Tropomyosin macromolecular substances Biology Transfection Cell Line Mice Gene expression medicine Animals Homeostasis Humans Beta-actin Molecular Biology Genetics Genetic transfer Neoplasms Experimental Oncogenes Cell Biology Molecular biology Actins Cell Transformation Neoplastic Phenotype medicine.anatomical_structure Gene Expression Regulation Cell culture Mutation Research Article |
| Zdroj: | Molecular and Cellular Biology. 7:2467-2476 |
| ISSN: | 1098-5549 |
| DOI: | 10.1128/mcb.7.7.2467-2476.1987 |
| Popis: | Mutant human beta-actin genes were introduced into normal human (KD) fibroblasts and the derivative cell line HuT-12, which is immortalized but nontumorigenic, to test their ability to promote conversion to the tumorigenic state. Transfected substrains of HuT-12 fibroblasts that expressed abundant levels of mutant beta-actin (Gly-244----Asp-244) produced subcutaneous tumors in athymic mice after long latent periods (1.5 to 3 months). However, transfected substrains of KD fibroblasts retained their normal finite life span in culture and consequently were incapable of producing tumors. Substrains of HuT-12 cells transfected with the wild-type beta-actin gene and some transfected strains that expressed low or undetectable levels of mutant beta-actin did not produce tumors. Cell lines derived from transfectant cell tumors always exhibited elevated synthesis of the mutant beta-actin, ranging from 145 to 476% of the level expressed by the transfected cells that were inoculated to form the tumor. In general, primary transfectant cells that expressed the highest levels of mutant beta-actin were more tumorigenic than strains that expressed lower levels. The tumor-derived strains were stable in tumorigenicity and produced tumors with shortened latent periods of only 2 to 4 weeks. These findings imply that the primary transfectant strains develop subpopulations of cells that are selected to form tumors because of their elevated rate of exogenous mutant beta-actin synthesis. Actin synthesis and accumulation of gamma-actin mRNA from the endogenous beta- and gamma-actin genes were diminished in tumor-derived strains, apparently to compensate for elevated mutant beta-actin synthesis and maintain the normal cellular concentration of actin. Synthesis of the transformation-sensitive tropomyosin isoforms was decreased along with mutant beta-actin expression. Such modulations in tropomyosin synthesis are characteristically seen in transformation of avian, rodent, and human fibroblasts. Our results suggest that this mutant beta-actin contributes to the neoplastic phenotype of immortalized human fibroblasts by imposing a cytoarchitectural defect and inducing abnormal expression of cytoskeletal tropomyosins. |
| Databáze: | OpenAIRE |
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