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Mr 85,000 membrane protein specifically expressed in adriamycin-resistant human tumor cells
H Hamada1, E Okochi, M Watanabe
1Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, Tokyo.
Abstract:
For the characterization of membrane changes related to Adriamycin resistance in tumor cells, we have developed monoclonal antibodies against Adriamycin-resistant human myelogenous leukemia K562 (K562/ADM). In addition to the monoclonal antibodies which recognize P-glycoprotein, we have obtained two monoclonal antibodies (designated MRK4 and MRK20) which recognize an Mr 85,000 membrane protein. Using MRK20 as a probe, we have studied the expression of the Mr 85,000 protein in various human multidrug-resistant and -sensitive cell lines. The Mr 85,000 protein was overexpressed in K562/ADM and in a human ovarian cancer cell line resistant to Adriamycin, 2780AD. The protein, if any, was not detected in other drug-resistant human cell lines such as colchicine-resistant KB cells (KB-C4), vinblastine-resistant CEM cells (CEM/VLB100), and vincristine-resistant K562 cells (K562/VCR). We have isolated subclones of K562/ADM cells which express different amounts of the Mr 85,000 protein. The expression of the Mr 85,000 protein diminished when the cells were not kept in Adriamycin, and increased when the clones were kept in the presence of Adriamycin. In contrast, the expression of P-glycoprotein remained constant whether in the presence or absence of Adriamycin during these experiments. These findings suggest that the Mr 85,000 membrane protein is closely related to the resistant mechanism specific to Adriamycin resistance, which is different from that of the pleiotropic drug resistance.
Insights
Researchers identified a novel Mr 85,000 membrane protein linked to Adriamycin resistance in cancer cells. This protein
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Biology
Background:
- Adriamycin resistance is a significant challenge in cancer chemotherapy.
- Multidrug resistance (MDR) in cancer cells often involves altered membrane proteins.
- P-glycoprotein is a known mediator of MDR, but other mechanisms may exist.
Purpose of the Study:
- To characterize novel membrane changes associated with Adriamycin resistance in human tumor cells.
- To identify and investigate proteins distinct from P-glycoprotein involved in Adriamycin resistance.
- To explore the specific role of a newly identified Mr 85,000 membrane protein in Adriamycin resistance.
Main Methods:
- Development of monoclonal antibodies against Adriamycin-resistant K562 (K562/ADM) cells.
- Characterization of monoclonal antibodies recognizing P-glycoprotein and a novel Mr 85,000 membrane protein (MRK4, MRK20).
- Analysis of Mr 85,000 protein expression in various multidrug-resistant and sensitive human cell lines using MRK20.
Main Results:
- Two monoclonal antibodies, MRK4 and MRK20, were generated, recognizing an Mr 85,000 membrane protein.
- The Mr 85,000 protein was overexpressed in Adriamycin-resistant K562/ADM cells and a resistant ovarian cancer cell line (2780AD).
- Expression of the Mr 85,000 protein varied with Adriamycin exposure, increasing in its presence and decreasing in its absence, unlike P-glycoprotein.
Conclusions:
- The Mr 85,000 membrane protein is specifically associated with Adriamycin resistance.
- This protein's expression is modulated by Adriamycin, suggesting a direct role in Adriamycin-specific resistance.
- The findings indicate a resistance mechanism distinct from the pleiotropic drug resistance mediated by P-glycoprotein.