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Differential sensitization by orobol in proliferating and quiescent human ovarian carcinoma cells
1Department of Obstetrics/Gynecology, Jikei University School of Medicine, 3-25-8 Nishi-Shimbashi, Minato-ku, Tokyo 105, Japan. fl1444@leo.bekkoame.ne.jp
Abstract:
The object of this study was to determine how phosphatidylinositol (PI) signaling pathway is involved in the regulation of cisplatin (DDP) sensitivity. Clonogenic survival assay was used to determine the effect of orobol, a potent PI4-kinase inhibitor, on DDP sensitivity in human ovarian carcinoma 2008 cells. Orobol enhanced sensitivity to DDP in 2008 cells by a factor of 2.1+/-0.4 (SD)-fold (N=3; P<0.01). Sensitization was specific for proliferating cells. Orobol did not alter DDP sensitivity in quiescent cells. Orobol also produced a 2-fold increase in sensitivity to DDP in proliferating 2008/C13*5.25 DDP-resistant variants. Our studies indicated that orobol-induced sensitization depended on the presence of proliferating cells in G2+M phase of the cell cycle. Orobol did not modulate the cellular accumulation of DDP nor did it alter the CdCl2 sensitivity, suggesting that the amount of platinated-DNA was not changed by orobol treatment. However, orobol rendered 2008 cells resistant to rhodamin 123 by 5.7+/-1.7 (SD)-fold (N=3, P<0.01). Since sensitivity to rhodamin 123 is indicative of mitochondrial membrane potential, these results imply that mitochondrial alterations may be an important component of the orobol sensitization effect in these cells.
Insights
This study shows that orobol, a PI4-kinase inhibitor, enhances cisplatin sensitivity in ovarian cancer cells, particularly those that are proliferating. This effect may involve alterations in mitochondrial membrane potential.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- Cisplatin (DDP) is a key chemotherapy drug for ovarian cancer.
- The phosphatidylinositol (PI) signaling pathway's role in DDP sensitivity is not fully understood.
- Developing strategies to overcome DDP resistance is crucial.
Purpose of the Study:
- To investigate the involvement of the PI signaling pathway in regulating DDP sensitivity.
- To determine the effect of orobol, a PI4-kinase inhibitor, on DDP sensitivity in human ovarian carcinoma cells.
- To explore the mechanisms underlying orobol-induced sensitization to DDP.
Main Methods:
- Clonogenic survival assays were performed on human ovarian carcinoma 2008 cells and DDP-resistant variants (2008/C13*5.25).
- The effects of orobol on DDP sensitivity were assessed in proliferating and quiescent cells.
- Cellular accumulation of DDP, CdCl2 sensitivity, and rhodamine 123 retention were measured.
Main Results:
- Orobol significantly enhanced DDP sensitivity in proliferating 2008 cells (2.1-fold) and DDP-resistant variants (2-fold).
- Sensitization was specific to proliferating cells, particularly those in the G2+M phase.
- Orobol did not affect DDP accumulation or CdCl2 sensitivity but increased resistance to rhodamine 123 (5.7-fold), indicating altered mitochondrial membrane potential.
Conclusions:
- The PI signaling pathway, modulated by PI4-kinase inhibition with orobol, plays a significant role in DDP sensitivity.
- Orobol enhances DDP efficacy in ovarian cancer, including resistant cell lines, by affecting proliferating cells.
- Mitochondrial alterations appear to be a key component of orobol's sensitization mechanism.