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Characterization of cisplatin-resistant COLO 316 human ovarian carcinoma cells
P A Andrews1, M P Murphy, S B Howell
1Cancer Center, University of California, San Diego, La Jolla 92093.
Abstract:
The biochemical changes responsible for acquired resistance to cisplatin (DDP) are not fully understood. We have developed DDP-resistant sublines of COLO 316 human ovarian carcinoma cells in vitro and characterized a number of biochemical features of these cells. Following selection with either continuous 50 nM DDP (COLO/DDP50 cells) or intermittent 1 microM DDP (COLO/B, COLO/C, or COLO/D cells) the onset of resistance was rapid. The resistance of the COLO/B cells gradually fell from 14-fold to 5-fold over 6 months in drug-free media. Both selection procedures produced cells exhibiting broad cross-resistance to other platinum analogs, natural products and alkylating agents. There was no significant change in the growth rate (doubling time = 36 h, cloning efficiency (28%), protein content (0.55 mg/10(6) cells), or morphology of these cells. Cell cycle distributions of log-phase cells were similar (60% G0/G1, 35% S, 5% G2/M) as determined by flow cytometry. Glutathione (GSH) levels, while not elevated in COLO-B cells at low levels of resistance (2-3-fold), were 30% elevated at higher levels of resistance (9-fold). However, GSH levels in COLO/DDP50 cells with 13-fold resistance were 2.3-fold elevated. The resistance of both cell types could be partially reversed by extended depletion of GSH with D,L-buthionine-S,R-sulfoximine. COLO/D cells had a 48% decrease in DDP accumulation at 1 h while COLO/DDP50 cells had no change in DDP accumulation. The cross-resistance profiles, GSH biochemistry and DDP accumulation data indicate that acquired DDP-resistance is a complex, multifactorial response in these cells. The specific combination of mechanisms expressed in these cells appears to depend upon the selection procedure.
Insights
Acquired resistance to cisplatin (DDP) in ovarian cancer cells involves complex biochemical changes. Glutathione levels and drug accumulation vary, indicating multifactorial resistance mechanisms dependent on selection methods.
Area of Science:
- Biochemistry
- Molecular Biology
- Oncology
Background:
- Cisplatin (DDP) is a key chemotherapy drug for ovarian cancer.
- Mechanisms of acquired DDP resistance are not fully understood.
- Developing DDP-resistant cell lines is crucial for studying resistance.
Purpose of the Study:
- To develop and characterize DDP-resistant human ovarian carcinoma cell lines.
- To investigate the biochemical features associated with acquired DDP resistance.
- To explore the role of glutathione and DDP accumulation in resistance.
Main Methods:
- Development of DDP-resistant COLO 316 cell sublines using continuous and intermittent DDP selection.
- Characterization of biochemical features including growth rate, cell cycle, glutathione levels, and DDP accumulation.
- Assessment of resistance reversal using D,L-buthionine-S,R-sulfoximine.
Main Results:
- Rapid onset of broad cross-resistance to platinum analogs and other chemotherapeutics.
- Variable changes in glutathione (GSH) levels and DDP accumulation depending on the selection method.
- Partial reversal of resistance observed with GSH depletion.
- No significant changes in cell growth rate, cloning efficiency, or cell cycle distribution.
Conclusions:
- Acquired DDP resistance in ovarian cancer cells is a complex, multifactorial process.
- The specific resistance mechanisms are influenced by the DDP selection procedure.
- Glutathione and altered DDP accumulation are key contributing factors to resistance.