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Mutation of the human neu protein facilitates down-modulation by monoclonal antibodies
F van Leeuwen1, M J van de Vijver, J Lomans
1Division of Molecular Biology, Netherlands Cancer Institute, Amsterdam.
Abstract:
Amplification and overexpression of the neu gene have been found in several human adenocarcinomas. We have obtained monoclonal antibodies to the human neu protein by immunizing a Balb/c mouse with a Balb/c cell line expressing the human neu gene by transfection. The monoclonal antibodies reacted with neu protein on intact cells by immunofluorescence and immunoprecipitated neu in metabolically labeled cells, also in the presence of tunicamycin. We tested possible down-modulating effects of these monoclonal antibodies on SKBR-3 mammary tumor cells, which express high levels of wild-type human neu protein. We also used NIH3T3 cells transfected with either a normal or a mutated human neu gene, encoding a protein with a valine to glutamic acid substitution in the transmembrane domain. Down-modulation of the normal cell-surface neu protein was inefficient. In contrast, the antibodies induced 50-65% down-modulation in NIH3T3 cells expressing the mutated human neu protein and could inhibit these cells to form colonies in soft agar. We propose that these differences are due to changed aggregation properties of the point-mutated protein.
Insights
Monoclonal antibodies targeting the neu protein show differential effects on cancer cells. They effectively down-modulate mutated neu protein, inhibiting tumor cell growth, unlike normal neu protein.
Area of Science:
- Oncology
- Molecular Biology
- Immunology
Background:
- The neu gene (also known as ERBB2) is amplified and overexpressed in various human adenocarcinomas.
- The neu protein is a receptor tyrosine kinase implicated in cancer cell proliferation and survival.
Purpose of the Study:
- To develop and characterize monoclonal antibodies against the human neu protein.
- To investigate the down-modulating effects of these antibodies on cancer cells expressing normal or mutated neu protein.
Main Methods:
- Generation of monoclonal antibodies using hybridoma technology.
- Immunofluorescence and immunoprecipitation assays to confirm antibody binding and specificity.
- Assessment of antibody-induced down-modulation of neu protein on cell surfaces.
- Soft agar colony formation assays to evaluate the functional impact on cell proliferation.
Main Results:
- Monoclonal antibodies were successfully generated and recognized the human neu protein.
- Antibodies showed inefficient down-modulation of normal cell-surface neu protein.
- Antibodies induced significant down-modulation (50-65%) of mutated neu protein in NIH3T3 cells.
- Down-modulation of mutated neu protein correlated with inhibition of soft agar colony formation.
Conclusions:
- Monoclonal antibodies against the neu protein can effectively target and down-modulate mutated forms.
- The differential effect is likely due to altered aggregation properties of the point-mutated neu protein.
- Targeting mutated neu protein with antibodies presents a potential therapeutic strategy for specific adenocarcinomas.