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Gefitinib induces epidermal growth factor receptor dimers which alters the interaction characteristics with ¹²⁵I-EGF
Hanna Björkelund1, Lars Gedda, Pavel Barta
1Biomedical Radiation Sciences, Department of Radiology, Oncology and Radiation Science, Uppsala University, Uppsala, Sweden. hanna@ridgeviewinstruments.com
Abstract:
The tyrosine kinase inhibitor gefitinib inhibits growth in some tumor types by targeting the epidermal growth factor receptor (EGFR). Previous studies show that the affinity of the EGF-EGFR interaction varies between hosting cell line, and that gefitinib increases the affinity for some cell lines. In this paper, we investigate possible mechanisms behind these observations. Real-time interaction analysis in LigandTracer® Grey revealed that the HER2 dimerization preventing antibody pertuzumab clearly modified the binding of ¹²⁵I-EGF to EGFR on HER2 overexpressing SKOV3 cells in the presence of gefitinib. Pertuzumab did not affect the binding on A431 cells, which express low levels of HER2. Cross-linking measurements showed that gefitinib increased the amount of EGFR dimers 3.0-3.8 times in A431 cells in the absence of EGF. In EGF stimulated SKOV3 cells the amount of EGFR dimers increased 1.8-2.2 times by gefitinib, but this effect was cancelled by pertuzumab. Gefitinib treatment did not alter the number of EGFR or HER2 expressed in tumor cell lines A431, U343, SKOV3 and SKBR3. Real-time binding traces were further analyzed in a novel tool, Interaction Map, which deciphered the different components of the measured interaction and supports EGF binding to multiple binding sites. EGFR and HER2 expression affect the levels of EGFR monomers, homodimers and heterodimers and EGF binds to the various monomeric/dimeric forms of EGFR with unique binding properties. Taken together, we conclude that dimerization explains the varying affinity of EGF-EGFR in different cells, and we propose that gefitinib induces EGFR dimmers, which alters the interaction characteristics with ¹²⁵I-EGF.
Insights
Gefitinib, an epidermal growth factor receptor (EGFR) inhibitor, alters EGF-EGFR binding affinity by increasing EGFR dimerization. This dimerization mechanism explains varying affinities observed in different cell lines and impacts drug response.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Gefitinib targets the epidermal growth factor receptor (EGFR) and inhibits tumor growth.
- The affinity of epidermal growth factor (EGF)-EGFR interaction varies across cell lines, with gefitinib influencing this affinity.
- Understanding the molecular mechanisms behind these variations is crucial for optimizing targeted therapies.
Purpose of the Study:
- To investigate the mechanisms underlying variable EGF-EGFR interaction affinity in the presence of gefitinib.
- To explore the role of EGFR dimerization and HER2 co-expression in modulating EGF-EGFR binding characteristics.
- To elucidate how gefitinib affects EGFR dimerization and its impact on EGF binding.
Main Methods:
- Real-time interaction analysis using LigandTracer® Grey to measure ¹²⁵I-EGF binding to EGFR.
- Utilized pertuzumab, a HER2 dimerization-preventing antibody, to assess HER2's role.
- Employed cross-linking measurements to quantify EGFR dimerization levels.
- Analyzed binding data with a novel tool, Interaction Map, for detailed interaction component deciphering.
Main Results:
- Pertuzumab modulated ¹²⁵I-EGF binding to EGFR on HER2-overexpressing SKOV3 cells with gefitinib, but not on A431 cells with low HER2 expression.
- Gefitinib significantly increased EGFR dimerization in A431 cells (3.0-3.8 fold) and in EGF-stimulated SKOV3 cells (1.8-2.2 fold).
- Pertuzumab reversed the gefitinib-induced EGFR dimerization in SKOV3 cells. Gefitinib did not alter EGFR or HER2 expression levels.
Conclusions:
- EGFR and HER2 expression influence EGFR monomer, homodimer, and heterodimer levels, with distinct binding properties for EGF to these forms.
- EGFR dimerization is a key mechanism explaining the variable affinity of EGF-EGFR interactions across different cell lines.
- Gefitinib induces EGFR dimerization, thereby altering EGF-EGFR interaction characteristics and potentially influencing therapeutic efficacy.
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