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Increased epidermal growth factor receptor in multidrug-resistant human neuroblastoma cells
M B Meyers1, W P Shen, B A Spengler
1Laboratory of Cellular and Biochemical Genetics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
Abstract:
Multidrug-resistant human neuroblastoma cell lines obtained by selection with vincristine or actinomycin D from two independent clonal lines, SH-SY5Y and MC-IXC, have 3- to 30-fold more cell surface epidermal growth factor (EGF) receptors than the drug-sensitive parental cells as indicated by EGF binding assays and immunoprecipitation, affinity-labeling, and phosphorylation studies. Reversion to drug sensitivity in one line was accompanied by a return to the parental level of EGF receptor. SH-EP cells, a clone derived from the same neuroblastoma cell line as SH-SY5Y but which displays melanocyte rather than neuronal lineage markers, also express significantly more EGF receptor than SH-SY5Y cells. By nucleic acid hybridization analysis with a molecularly cloned probe, increased receptor level in multidrug-resistant cells was shown to be the result of higher levels of EGF receptor mRNA in drug-resistant than in drug-sensitive cells. The increased steady state amount of specific RNA did not result from amplification of receptor-encoding genes. A small difference was observed in the electrophoretic mobility under denaturing conditions of EGF receptor immunoprecipitated from drug-resistant and drug-sensitive cells. Quantitative and qualitative modulation of the EGF receptor might reflect alterations in the transformation and/or differentiation phenotype of the resistant cells or might result from unknown selective pressures associated with the development of multidrug resistance.
Insights
Multidrug-resistant neuroblastoma cells exhibit significantly higher levels of epidermal growth factor (EGF) receptors. This increase is linked to elevated EGF receptor mRNA, not gene amplification, impacting cell phenotype.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- Multidrug resistance (MDR) is a significant challenge in cancer therapy.
- Neuroblastoma is a pediatric cancer with variable outcomes.
- Epidermal Growth Factor (EGF) receptor plays a role in cell growth and differentiation.
Purpose of the Study:
- To investigate the expression and regulation of EGF receptors in multidrug-resistant neuroblastoma cell lines.
- To determine if increased EGF receptor levels are associated with genetic alterations or transcriptional changes.
- To explore the potential implications of altered EGF receptor expression on cell phenotype.
Main Methods:
- Development of multidrug-resistant neuroblastoma cell lines (SH-SY5Y, MC-IXC) via drug selection.
- Quantification of EGF receptors using EGF binding assays, immunoprecipitation, affinity-labeling, and phosphorylation studies.
- Analysis of EGF receptor mRNA levels via nucleic acid hybridization.
- Investigation of gene copy number using nucleic acid hybridization.
- Assessment of receptor protein characteristics using electrophoresis.
Main Results:
- Multidrug-resistant neuroblastoma cells displayed a 3- to 30-fold increase in cell surface EGF receptors compared to drug-sensitive parental cells.
- Reversion to drug sensitivity correlated with a return to parental EGF receptor levels.
- Elevated EGF receptor levels were also observed in a related cell line (SH-EP) with different lineage markers.
- Increased EGF receptor mRNA levels, not gene amplification, accounted for the higher receptor expression in resistant cells.
- Minor differences in EGF receptor protein electrophoretic mobility were detected between sensitive and resistant cells.
Conclusions:
- Multidrug resistance in neuroblastoma is associated with a significant upregulation of epidermal growth factor receptors.
- This upregulation is primarily mediated by increased EGF receptor mRNA, suggesting post-transcriptional or translational regulation.
- The observed modulation of EGF receptors may influence the transformation and differentiation phenotypes of resistant neuroblastoma cells.