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[Drug resistance of malignant melanoma. Mechanisms and possible modulation]
D Schadendorf1, B M Czarnetzki
1Universitätsklinik Rudolf Virchow, Hautklinik, FU Berlin.
Abstract:
Response rates of metastatic malignant melanoma to cytostatic treatment are disappointingly low. Although immunomodulators such as interferons are more commonly being used in combination with cytostatics, no major breakthrough has been achieved. The mechanisms underlying the high chemoresistance of melanoma cells are so far ill-defined, and investigations are only just being initiated. Several mechanisms of chemoresistance have, however, been studied with other tumours and might be relevant for human melanoma: (1) "Classical" multidrug resistance, determined by the expression of the p-glycoprotein which resembles a membrane pump that eliminates natural and synthetic agents from the cell interior. Different drugs, including calcium antagonists, interfere with its function and can thus modulate chemoresistance. Preliminary data from investigations of these mechanisms indicate that p-glycoprotein is not, however, involved in the multidrug resistance of malignant melanoma. (2) Detoxification, involving glutathione-S-transferases (GST). GST are a multigene family of enzymes which inactivate alkylating agents by conjugation to glutathione. Their relevance for chemoresistance in melanoma has not yet been clarified. (3) Topoisomerase II, which is involved in DNA recombination and DNA transcription events and represents the target of several inhibitory cytotoxic agents. Low levels of the enzyme render cells resistant to the action of specific drugs. Again nothing is yet known regarding the relevance of this mechanism in human melanoma. Further studies of these potentially important resistance mechanisms are thus urgently needed in order to develop more effective therapies for advanced malignant melanoma.
Insights
Melanoma cells show high chemoresistance, limiting treatment effectiveness. Further research into mechanisms like glutathione-S-transferases and topoisomerase II is crucial for developing better therapies for advanced malignant melanoma.
Area of Science:
- Oncology
- Cancer Biology
- Pharmacology
Background:
- Metastatic malignant melanoma exhibits poor response rates to cytostatic treatments.
- Current combination therapies with immunomodulators like interferons have not yielded significant breakthroughs.
- The precise mechanisms driving melanoma cell chemoresistance remain largely undefined.
Purpose of the Study:
- To investigate potential mechanisms of chemoresistance in malignant melanoma.
- To explore the relevance of known chemoresistance pathways in other tumors for melanoma.
- To identify targets for improving therapeutic efficacy in advanced melanoma.
Main Methods:
- Review of established chemoresistance mechanisms in other cancers.
- Analysis of preliminary data on p-glycoprotein involvement in melanoma multidrug resistance.
- Discussion of the potential roles of glutathione-S-transferases and topoisomerase II.
Main Results:
- Preliminary findings suggest p-glycoprotein is not a primary factor in melanoma multidrug resistance.
- The involvement of glutathione-S-transferases (GST) in melanoma chemoresistance requires further clarification.
- The role of topoisomerase II in melanoma chemoresistance is currently unknown.
Conclusions:
- Understanding melanoma chemoresistance mechanisms is critical for advancing treatment strategies.
- Further investigation into GST and topoisomerase II is urgently needed.
- Developing more effective therapies for advanced malignant melanoma necessitates a deeper understanding of cellular resistance pathways.