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What Is the Significance of Lysosomal-Mediated Resistance to Imatinib?
1Department of Anatomy, Faculty of Medicine and Dentistry, Palacky University Olomouc, Hnevotinska 3, 77515 Olomouc, Czech Republic.
Abstract:
The lysosomal sequestration of hydrophobic weak-base anticancer drugs is one proposed mechanism for the reduced availability of these drugs at target sites, resulting in a marked decrease in cytotoxicity and consequent resistance. While this subject is receiving increasing emphasis, it is so far only in laboratory experiments. Imatinib is a targeted anticancer drug used to treat chronic myeloid leukaemia (CML), gastrointestinal stromal tumours (GISTs), and a number of other malignancies. Its physicochemical properties make it a typical hydrophobic weak-base drug that accumulates in the lysosomes of tumour cells. Further laboratory studies suggest that this might significantly reduce its antitumor efficacy. However, a detailed analysis of published laboratory studies shows that lysosomal accumulation cannot be considered a clearly proven mechanism of resistance to imatinib. Second, more than 20 years of clinical experience with imatinib has revealed a number of resistance mechanisms, none of which is related to its accumulation in lysosomes. This review focuses on the analysis of salient evidence and raises a fundamental question about the significance of lysosomal sequestration of weak-base drugs in general as a possible resistance mechanism both in clinical and laboratory settings.
Insights
Lysosomal sequestration of hydrophobic anticancer drugs like imatinib in tumor cells is debated. Clinical data does not support lysosomal accumulation as a resistance mechanism for imatinib, questioning its general significance.
Area of Science:
- Pharmacology
- Oncology
- Cell Biology
Background:
- Lysosomal sequestration of hydrophobic weak-base anticancer drugs is a proposed mechanism for reduced drug availability and resistance.
- Imatinib, a drug for chronic myeloid leukemia and gastrointestinal stromal tumors, is a hydrophobic weak-base that accumulates in tumor cell lysosomes.
- Laboratory studies suggest this accumulation may reduce imatinib's efficacy.
Purpose of the Study:
- To critically analyze the evidence for lysosomal sequestration as a resistance mechanism for imatinib.
- To evaluate the clinical relevance of lysosomal accumulation of weak-base anticancer drugs.
Main Methods:
- Review and analysis of published laboratory studies on imatinib and lysosomal sequestration.
- Examination of clinical data and reported resistance mechanisms for imatinib over 20 years.
Main Results:
- A detailed analysis indicates that lysosomal accumulation is not a clearly proven mechanism of imatinib resistance.
- Extensive clinical experience with imatinib has identified various resistance mechanisms, none linked to lysosomal accumulation.
Conclusions:
- The significance of lysosomal sequestration as a general resistance mechanism for weak-base drugs in both laboratory and clinical settings requires fundamental re-evaluation.
- Current evidence does not support lysosomal accumulation as a clinical resistance mechanism for imatinib.
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