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Updated: May 1, 2026
Validated Immunochemical Assay for Comprehensive Determination of the Human Epidermal Growth Factor Receptor 2 Released from and Bound to Cells
Published on: May 9, 2025
Molecular imaging reveals trastuzumab-induced epidermal growth factor receptor downregulation in vivo
Teng Ma1, Xianlei Sun1, Liyang Cui1
1Medical Isotopes Research Center, Peking University, Beijing, China Department of Radiation Medicine, School of Basic Medical Sciences, Peking University, Beijing, China; and.
Unlabelled:
Previous in vitro studies demonstrated that treating tumors expressing both epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 with trastuzumab resulted in increased EGFR homodimerization and subsequent rapid downregulation of EGFR. We investigated whether molecular imaging using near-infrared fluorescence (NIRF) imaging and PET probes could sensitively detect trastuzumab-induced EGFR downregulation in vivo.
Methods:
The F(ab')2 antibody fragment PaniF(ab')2 was generated by digesting the anti-EGFR monoclonal antibody panitumumab. PaniF(ab')2 was labeled with either a NIRF dye or (68)Ga, and optical imaging and small-animal PET imaging of Dye-PaniF(ab')2 and (68)Ga-PaniF(ab')2, respectively, were performed in HT-29 tumor-bearing nude mice treated with trastuzumab or untreated control.
Results:
Longitudinal NIRF imaging studies revealed significantly reduced tumor uptake of Dye-PaniF(ab')2 on days 5 and 7 in trastuzumab-treated HT-29 tumors, compared with control. Western blotting confirmed the downregulation of EGFR after treatment with trastuzumab. Small-animal PET on day 5 after trastuzumab treatment also demonstrated decreased (68)Ga-PaniF(ab')2 uptake in trastuzumab-treated HT-29 tumors. The tumor uptake value of (68)Ga-PaniF(ab')2 obtained from PET imaging had an excellent linear correlation with the uptake value measured using biodistribution.
Conclusion:
The downregulation of EGFR induced by trastuzumab treatment could be detected noninvasively using optical and PET imaging. This molecular imaging strategy could provide a dynamic readout of changes in the tumor signaling and may facilitate the noninvasive monitoring of the early tumor response to drug treatment.
Insights
Molecular imaging detects trastuzumab-induced epidermal growth factor receptor (EGFR) downregulation in vivo. Near-infrared fluorescence (NIRF) and PET imaging show reduced EGFR signaling, enabling early tumor response monitoring.
Area of Science:
- Oncology
- Molecular Imaging
- Pharmacodynamics
Background:
- Trastuzumab treatment of tumors expressing EGFR and HER2 leads to EGFR downregulation.
- Noninvasive methods are needed to monitor this EGFR modulation in vivo.
Purpose of the Study:
- To investigate molecular imaging techniques for detecting trastuzumab-induced EGFR downregulation.
- To assess the utility of near-infrared fluorescence (NIRF) and PET imaging for this purpose.
Main Methods:
- Generated F(ab')2 antibody fragments of panitumumab (PaniF(ab')2) and labeled them with NIRF dye or 68Ga.
- Performed longitudinal NIRF and small-animal PET imaging in HT-29 tumor-bearing mice treated with trastuzumab or control.
- Validated imaging results with Western blotting and biodistribution studies.
Main Results:
- NIRF imaging showed significantly reduced Dye-PaniF(ab')2 uptake in tumors of trastuzumab-treated mice.
- Small-animal PET revealed decreased 68Ga-PaniF(ab')2 uptake in treated tumors.
- Western blotting confirmed EGFR downregulation post-trastuzumab treatment.
- PET imaging uptake values strongly correlated with biodistribution measurements.
Conclusions:
- Trastuzumab-induced EGFR downregulation can be detected noninvasively using optical and PET imaging.
- This molecular imaging strategy offers a dynamic readout of tumor signaling changes.
- It may facilitate early, noninvasive monitoring of drug treatment response.
