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Bio-imaging of colorectal cancer models using near infrared labeled epidermal growth factor
Gadi Cohen1, Shimon Lecht, Hadar Arien-Zakay
1School of Pharmacy Institute for Drug Research, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel.
Abstract:
Novel strategies that target the epidermal growth factor receptor (EGFR) have led to the clinical development of monoclonal antibodies, which treat metastatic colorectal cancer (mCRC) but only subgroups of patients with increased wild type KRAS and EGFR gene copy, respond to these agents. Furthermore, resistance to EGFR blockade inevitably occurred, making future therapy difficult. Novel bio-imaging (BOI) methods may assist in quantization of EGFR in mCRC tissue thus complementing the immunohistochemistry methodology, in guiding the future treatment of these patients. The aim of the present study was to explore the usefulness of near infrared-labeled EGF (EGF-NIR) for bio-imaging of CRC using in vitro and in vivo orthotopic tumor CRC models and ex vivo human CRC tissues. We describe the preparation and characterization of EGF-NIR and investigate binding, using BOI of a panel of CRC cell culture models resembling heterogeneity of human CRC tissues. EGF-NIR was specifically and selectively bound by EGFR expressing CRC cells, the intensity of EGF-NIR signal to background ratio (SBR) reflected EGFR levels, dose-response and time course imaging experiments provided optimal conditions for quantization of EGFR levels by BOI. EGF-NIR imaging of mice with HT-29 orthotopic CRC tumor indicated that EGF-NIR is more slowly cleared from the tumor and the highest SBR between tumor and normal adjacent tissue was achieved two days post-injection. Furthermore, images of dissected tissues demonstrated accumulation of EGF-NIR in the tumor and liver. EGF-NIR specifically and strongly labeled EGFR positive human CRC tissues while adjacent CRC tissue and EGFR negative tissues expressed weak NIR signals. This study emphasizes the use of EGF-NIR for preclinical studies. Combined with other methods, EGF-NIR could provide an additional bio-imaging specific tool in the standardization of measurements of EGFR expression in CRC tissues.
Insights
Near-infrared labeled epidermal growth factor (EGF-NIR) enables precise bio-imaging of EGFR in colorectal cancer (CRC) tissues. This novel method aids in quantifying EGFR expression, potentially guiding targeted therapies for metastatic CRC (mCRC).
Area of Science:
- Oncology
- Biomedical Imaging
- Molecular Biology
Background:
- Metastatic colorectal cancer (mCRC) treatment with EGFR-targeting monoclonal antibodies is limited to specific patient subgroups with wild-type KRAS and increased EGFR gene copy.
- Tumor resistance to EGFR blockade is a significant challenge, complicating future therapeutic strategies.
- Current immunohistochemistry methods for EGFR quantification in mCRC may require complementary approaches for improved accuracy.
Purpose of the Study:
- To evaluate the utility of near-infrared labeled EGF (EGF-NIR) for bio-imaging epidermal growth factor receptor (EGFR) in colorectal cancer (CRC).
- To assess EGF-NIR's effectiveness in vitro, in vivo using orthotopic tumor models, and ex vivo using human CRC tissues.
- To explore EGF-NIR as a tool for quantifying EGFR expression in CRC for potential clinical guidance.
Main Methods:
- Preparation and characterization of EGF-NIR conjugate.
- In vitro binding assays using CRC cell lines with varying EGFR expression.
- In vivo bio-imaging of orthotopic HT-29 CRC tumors in mice and ex vivo analysis of human CRC tissues.
- Optimization of imaging conditions including dose-response and time-course studies.
Main Results:
- EGF-NIR specifically bound to EGFR-expressing CRC cells, with signal intensity correlating to EGFR levels.
- Optimal conditions for EGFR quantification via bio-imaging were established through dose-response and time-course experiments.
- In vivo imaging showed sustained tumor accumulation of EGF-NIR in mice, with peak signal-to-background ratio (SBR) at two days post-injection.
- Ex vivo analysis confirmed strong EGF-NIR labeling of EGFR-positive human CRC tissues, with minimal signal in adjacent or EGFR-negative tissues.
Conclusions:
- EGF-NIR serves as a valuable tool for preclinical bio-imaging of EGFR in CRC models.
- The signal-to-background ratio (SBR) effectively quantifies EGFR levels, reflecting tumor heterogeneity.
- EGF-NIR holds promise as an adjunct imaging modality for standardizing EGFR expression measurements in CRC, potentially aiding treatment decisions.
