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Updated: May 23, 2026
In vivo Quantification of G Protein Coupled Receptor Interactions using Spectrally Resolved Two-photon Microscopy
Published on: January 19, 2011
Optical fiber-based in vivo quantification of growth factor receptors
Thommey P Thomas1, Yu-Chung Chang, Jing Yong Ye
1Michigan Nanotechnology Institute for Medicine and Biological Sciences, Ann Arbor, Michigan, USA. thommey@umich.edu
Background:
Growth factor receptors such as epidermal growth factor receptor 1 and human epidermal growth receptor 2 (HER2) are overexpressed in certain cancer cells. Antibodies against these receptors (eg. cetuximab and transtuzumab [Herceptin]) have shown therapeutic value in cancer treatment. The existing methods for the quantification of these receptors in tumors involve immunohistochemistry or DNA quantification, both in extracted tissue samples. The goal of the study was to evaluate whether an optical fiber-based technique can be used to quantify the expression of multiple growth factor receptors simultaneously.
Methods:
The authors examined HER2 expression using the monoclonal antibody trastuzumab as a targeting ligand to test their system. They conjugated trastuzumab to 2 different Alexa Fluor dyes with different excitation and emission wavelengths. Two of the dye conjugates were subsequently injected intravenously into mice bearing HER2-expressing subcutaneous tumors. An optical fiber was then inserted into the tumor through a 30-gauge needle, and using a single laser beam as the excitation source, the fluorescence emitted by the 2 conjugates was identified and quantified by 2-photon optical fiber fluorescence.
Results:
The 2 conjugates bound to the HER2-expressing tumor competitively in a receptor-specific fashion, but they failed to bind to a similar cell tumor that did not express HER2. The concentration of the conjugate present in the tumor as determined by 2-photon optical fiber fluorescence was shown to serve as an index of the HER2 expression levels.
Conclusions:
These studies offer a minimally invasive technique for the quantification of tumor receptors simultaneously.
Insights
This study introduces a novel optical fiber technique to quantify multiple tumor growth factor receptors, like HER2, simultaneously. This minimally invasive method accurately measures receptor expression levels in vivo.
Area of Science:
- Biomedical Optics
- Molecular Imaging
- Cancer Diagnostics
Background:
- Growth factor receptors, including epidermal growth factor receptor 1 and human epidermal growth receptor 2 (HER2), are frequently overexpressed in cancer cells.
- Antibody-based therapies targeting these receptors, such as cetuximab and trastuzumab, have demonstrated clinical efficacy.
- Current methods for receptor quantification, like immunohistochemistry and DNA quantification, require invasive tissue sampling.
Purpose of the Study:
- To evaluate the feasibility of an optical fiber-based technique for simultaneous quantification of multiple growth factor receptors.
- To develop a minimally invasive method for assessing tumor receptor expression levels.
Main Methods:
- Human epidermal growth receptor 2 (HER2) expression was assessed using the monoclonal antibody trastuzumab.
- Trastuzumab was conjugated to two distinct Alexa Fluor dyes with different spectral properties.
- The dye conjugates were administered intravenously to mice with HER2-expressing tumors, and fluorescence was measured using 2-photon optical fiber fluorescence via an inserted optical fiber.
Main Results:
- The dye conjugates demonstrated competitive, receptor-specific binding to HER2-expressing tumors.
- No significant binding was observed in tumors lacking HER2 expression.
- Quantification of conjugate concentration via 2-photon optical fiber fluorescence correlated with HER2 expression levels.
Conclusions:
- An optical fiber-based technique enables minimally invasive, simultaneous quantification of tumor receptors.
- This method holds potential for improved cancer diagnostics and treatment monitoring.
