Related Experiment Videos
Isolation of human KB cell lines resistant to epidermal growth factor-Pseudomonas exotoxin conjugates
Abstract:
Mutants of the human KB carcinoma cell line resistant to a cytotoxic conjugate of epidermal growth factor (EGF) and Pseudomonas exotoxin (PE) were selected. EGF-PE and the drug verapamil, which enhanced EGF-PE cytotoxicity, were used in the selection process. These mutants also showed some cross-resistance to PE. All of the EGF-PE resistant variants displayed lower levels of 125I-EGF binding, 20-50% of parental KB levels, without altered affinity for EGF and grew at a slower rate than the parental cell line KB-3-1. These results indicate that EGF-PE resistant KB cells have a complex phenotype which includes a reduction in the number of EGF receptors and reduced sensitivity to unconjugated PE. Resistance to toxin-conjugates, although pleiotropic, is specific and does not lead to resistance to multiple other anticancer drugs, nor are independently selected multidrug resistant KB lines resistant to PE. These results argue that protocols for cancer treatment could effectively use specifically designed cytotoxic toxin conjugates as an adjunct to conventional chemotherapy.
Insights
Researchers developed cancer cell mutants resistant to epidermal growth factor-Pseudomonas exotoxin (EGF-PE) conjugates. These mutants showed reduced EGF receptors and sensitivity to PE, suggesting targeted toxin conjugates could aid chemotherapy.
Area of Science:
- Oncology
- Cell Biology
- Biochemistry
Background:
- Cytotoxic conjugates, such as epidermal growth factor-Pseudomonas exotoxin (EGF-PE), are investigated for targeted cancer therapy.
- Understanding resistance mechanisms is crucial for optimizing the clinical application of toxin conjugates.
Purpose of the Study:
- To select and characterize human KB carcinoma cell line mutants resistant to EGF-PE conjugates.
- To investigate the phenotype of these resistant mutants, including EGF receptor binding and sensitivity to Pseudomonas exotoxin (PE).
Main Methods:
- Selection of resistant mutants using EGF-PE and verapamil.
- Quantification of 125I-EGF binding to assess EGF receptor levels.
- Evaluation of cross-resistance to unconjugated PE and other anticancer drugs.
Main Results:
- EGF-PE resistant mutants exhibited reduced 125I-EGF binding (20-50% of parental levels) without altered EGF affinity.
- These mutants displayed cross-resistance to unconjugated PE but not to multiple other anticancer drugs.
- Independently selected multidrug-resistant cell lines did not show resistance to PE.
Conclusions:
- EGF-PE resistance in KB cells involves a complex phenotype including decreased EGF receptor expression and reduced sensitivity to PE.
- Resistance to cytotoxic toxin conjugates is specific and not indicative of general multidrug resistance.
- Specifically designed cytotoxic toxin conjugates show potential as adjuncts to conventional chemotherapy for cancer treatment.