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Expression of bone formation-related molecules in a newly established protein-independent osteosarcoma

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Protein-independent cells are useful for analysis of proteins that are produced by the cells themselves without any consideration of exogenous proteins. This experimental protein-independent tumor system provides new biology of the autonomous nature of neoplastic cells during their evolution. We established a Dunn protein-free osteosarcoma (DPF) cell line, which was derived from parental fetal calf serum (FCS)-dependent murine Dunn osteosarcoma (DOS) cells. The DPF cells grew in a chemically defined protein-free medium at the high seeding density of 1x104 cells/well of a 96-well-plate with a similar doubling time to that of cells growing in the presence of FCS, while the cells did not grow at a density lower than 1x103/well. Furthermore, addition of conditioned medium stimulated the growth in a dose-dependent manner. In contrast, DOS did not grow in the protein-free condition at all. Morphological examination revealed that DPF cells exhibited a more round shape than DOS cells. RT-PCR analysis exhibited the augmentation of the RNA message of bone morphogenetic protein-4 (BMP-4) and osteocalcin in DPF cells. Enhanced expression of BMP-4 protein was also demonstrated by immunoblot analysis. Furthermore, alkaline phosphatase (ALP) activity was higher in DPF cells, indicating that bone-formation related molecules may be overexpressed in protein-independent osteosarcoma cells. These results suggest that putative growth factors may play a role in the DPF cell growth in an autocrine fashion, and the acquisition of autonomous growth independent of exogenous proteins may be coupled to the osteogenic differentiation.
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Document Type: Research Article

Affiliations: Department of Orthopedic Surgery, Gunma University Faculty of Medicine, Gunma 371-8511, Japan

Publication date: June 1, 2001

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  • The International Journal of Oncology provides an international forum for the publication of the latest, cutting-edge research in the broad area of oncology and cancer treatment. The journal accepts original high quality works and reviews on all aspects of oncology research including carcinogenesis, metastasis, epidemiology, chemotherapy and viral oncology. Through fair and efficient peer review, the journal is dedicated to publishing top tier research in the field, offering authors rapid publication as well as high standards of copy-editing and production. The International Journal of Oncology is published on a monthly basis in both print and early online.
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