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Ultrastructural features and P-glycoprotein immunolocalization in Saos-2/DX580 multidrug-resistant human osteosarcoma
N M Maraldi1, N Zini, P Sabatelli
1Institute of Normal and Pathologic Cytomorphology.
Abstract:
The multiple drug type of resistance to anticancer agents (MDR) is mediated by an over-expression of the MDR1 gene product, the P-glycoprotein. This is largely present at the cell surface of MDR cells, mediating the active efflux of cytotoxic molecules, but may be found also intracellularly. In this paper, using Saos-2 human osteosarcoma cells as a model, we provide further evidence of increased presence of P-glycoprotein at the plasma membrane and in the nucleus of MDR cells, where it is closely bound to the nuclear matrix. The structural changes observed in Saos-2 MDR cells, including an increase of the cell surface by the formation of blebs, and a peculiar clustering of chromatin, which are similar to those observed in other MDR cell lines, are likely to be associated with the observed overexpression of the P-glycoprotein at the cell membrane and nuclear level. These findings suggest the existence of more complex, still undetermined, mechanisms underlying the MDR phenomenon.
Insights
Multiple drug resistance (MDR) in cancer cells involves P-glycoprotein. This study shows P-glycoprotein accumulates on the cell surface and in the nucleus of resistant osteosarcoma cells, suggesting complex resistance mechanisms.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Multiple drug resistance (MDR) is a major challenge in cancer chemotherapy.
- Overexpression of the MDR1 gene product, P-glycoprotein, is a key mechanism mediating MDR.
- P-glycoprotein is typically found at the cell surface, actively effluxing cytotoxic drugs.
Purpose of the Study:
- To investigate the localization and role of P-glycoprotein in drug-resistant Saos-2 human osteosarcoma cells.
- To explore potential correlations between P-glycoprotein expression and cellular structural changes in MDR cells.
Main Methods:
- Utilized Saos-2 human osteosarcoma cells as a model system.
- Examined P-glycoprotein presence at the plasma membrane and intracellularly, including nuclear localization.
- Observed and analyzed structural alterations in MDR cells, such as cell surface blebbing and chromatin clustering.
Main Results:
- Confirmed increased P-glycoprotein presence at the plasma membrane of MDR Saos-2 cells.
- Demonstrated significant P-glycoprotein accumulation within the nucleus, closely associated with the nuclear matrix.
- Observed cellular structural changes, including increased cell surface area and chromatin alterations, in MDR cells.
Conclusions:
- P-glycoprotein is present not only on the cell surface but also within the nucleus of drug-resistant osteosarcoma cells.
- Cellular structural changes in MDR cells are likely linked to P-glycoprotein overexpression at both membrane and nuclear levels.
- These findings indicate that MDR involves more complex mechanisms than previously understood, warranting further investigation.