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Genetic characterization of human KB cell lines resistant to epidermal growth factor: Pseudomonas exotoxin conjugates
F Amano1, I Pastan, M M Gottesman
1Division of Cancer Biology and Diagnosis, National Cancer Institute, Bethesda, Maryland 20892.
Abstract:
Pleiotropic human KB cell mutants, selected for resistance to a conjugate of epidermal growth factor with Pseudomonas exotoxin (PE-EGF), were characterized genetically. These mutants have a pleiotropic phenotype, which includes reduced number of EGF receptors and reduced growth rate. Hybrid cells between HeLa D98 and four out of five of these resistant cell lines were more resistant to PE-EGF than hybrids formed between HeLa D98 and parental KB cells. This result indicates that the phenotype of PE-EGF resistance is incompletely dominant in four out of five cases and recessive in one out of five variants. In three separate experiments, transfection of DNA from two of the dominant resistant cell lines resulted in transformation of wild-type KB cells to PE-EGF resistance, confirming the dominant nature of these mutations, which affect levels of EGF receptor in KB cells.
Insights
Human cell mutants resistant to epidermal growth factor-Pseudomonas exotoxin (EGF-PE) conjugates were studied. Most mutants showed dominant resistance, linked to reduced EGF receptors, aiding in understanding toxin resistance mechanisms.
Area of Science:
- Cell Biology
- Molecular Genetics
- Toxicology
Background:
- Human KB cell mutants were selected for resistance to a conjugate of epidermal growth factor with Pseudomonas exotoxin (EGF-PE).
- These mutants exhibit a pleiotropic phenotype, including diminished epidermal growth factor (EGF) receptor numbers and reduced proliferation rates.
Purpose of the Study:
- To genetically characterize human KB cell mutants exhibiting resistance to EGF-PE.
- To determine the inheritance pattern (dominance or recessiveness) of EGF-PE resistance.
- To confirm the genetic basis of dominant resistance through DNA transfection.
Main Methods:
- Genetic characterization of KB cell mutants.
- Construction and analysis of hybrid cells (HeLa D98 x resistant KB mutants).
- DNA-mediated gene transfer (transfection) into wild-type KB cells.
Main Results:
- Four out of five EGF-PE resistant mutants displayed incompletely dominant resistance in hybrid cells.
- One mutant exhibited recessive resistance.
- DNA transfection from two dominant resistant cell lines conferred EGF-PE resistance to wild-type KB cells.
Conclusions:
- The mutations conferring EGF-PE resistance are predominantly dominant.
- These dominant mutations are associated with altered epidermal growth factor receptor levels in KB cells.
- The study confirms the genetic basis of dominant resistance to EGF-PE conjugates.