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Inhibition of murine osteosarcoma cell proliferation by glucocorticoid
Takashi Yamamoto1, Miyuki Nishiguchi, Naokazu Inoue
1Department of Clinical Laboratory, Osaka Medical Center for Cancer and Cardiovascular Diseases, Higashinari, Osaka, 537-0025, Japan.
Abstract:
The effects of glucocorticoid (GC) on the proliferation of Dunn Osteosarcoma (OS) cells were examined under in vitro culture conditions. Dexamethasone (Dex) inhibited the proliferation of Dunn OS cells in a dose-dependent manner, while the addition of anti-GC, RU486, to the culture medium in part recovered Dex-induced growth inhibition. The number of maximum binding sites (Bmax) and the dissociation constant (Kd) value of glucocorticoid receptor (GR) in Dunn OS cells were 19,560 sites/cell and 5.2 +/- 0.8 nM, respectively. RU486 competed with labeled Dex against GR at a concentration of 10(-6) M. Western blot analysis of [3H]Dex-mesylate-labeled cell homogenate and immunohistochemical staining against GR further confirmed the presence of GR. Dex treatment of Dunn OS cells resulted in apoptosis with the characteristic internucleosomal DNA cleavage shown by the DNA ladder pattern in agarose gel electrophoresis. These data demonstrate that GC inhibits the proliferation of Dunn OS cells via GR, for which one possible mechanism in vitro is induction of apoptosis.
Insights
Glucocorticoids (GC) inhibit Dunn Osteosarcoma cell proliferation by inducing apoptosis through the glucocorticoid receptor (GR). This effect was dose-dependent and partially reversible with RU486.
Area of Science:
- Oncology
- Endocrinology
- Molecular Biology
Background:
- Osteosarcoma (OS) is a primary bone malignancy.
- Glucocorticoids (GC) are potent regulators of cellular functions.
- The role of GC in OS proliferation requires further elucidation.
Purpose of the Study:
- To investigate the in vitro effects of GC on Dunn Osteosarcoma cell proliferation.
- To characterize the glucocorticoid receptor (GR) in Dunn OS cells.
- To explore the mechanism underlying GC-induced growth inhibition.
Main Methods:
- Dunn OS cells were cultured in vitro.
- Dexamethasone (Dex) and RU486 were used to treat cells.
- Glucocorticoid receptor (GR) binding assays (Bmax, Kd) were performed.
- Western blot and immunohistochemistry confirmed GR presence.
- Apoptosis was assessed via DNA laddering.
Main Results:
- Dexamethasone (Dex) inhibited Dunn OS cell proliferation in a dose-dependent manner.
- RU486 partially reversed Dex-induced growth inhibition.
- Dunn OS cells possess functional GR with Bmax of 19,560 sites/cell and Kd of 5.2 nM.
- Dex treatment induced apoptosis, evidenced by DNA fragmentation.
Conclusions:
- Glucocorticoids inhibit Dunn Osteosarcoma cell proliferation via the glucocorticoid receptor.
- Induction of apoptosis is a key mechanism for GC-mediated growth inhibition in vitro.
- These findings suggest a potential therapeutic role for GC in Osteosarcoma treatment.