Related Experiment Video
Updated: May 7, 2026
A Bright NIR-II Fluorescence Probe for Vascular and Tumor Imaging
Published on: March 17, 2023
In vivo type 2 cannabinoid receptor-targeted tumor optical imaging using a near infrared fluorescent probe
Shaojuan Zhang1, Pin Shao, Mingfeng Bai
1Molecular Imaging Laboratory, Department of Radiology, University of Pittsburgh , Pittsburgh, Pennsylvania 15219, United States.
Abstract:
The type 2 cannabinoid receptor (CB2R) plays a vital role in carcinogenesis and progression and is emerging as a therapeutic target for cancers. However, the exact role of CB2R in cancer progression and therapy remains unclear. This has driven the increasing efforts to study CB2R and cancers using molecular imaging tools. In addition, many types of cancers overexpress CB2R, and the expression levels of CB2R appear to be associated with tumor aggressiveness. Such upregulation of the receptor in cancer cells provides opportunities for CB2R-targeted imaging with high contrast and for therapy with low side effects. In the present study, we report the first in vivo tumor-targeted optical imaging using a novel CB2R-targeted near-infrared probe. In vitro cell fluorescent imaging and a competitive binding assay indicated specific binding of NIR760-mbc94 to CB2R in CB2-mid delayed brain tumor (DBT) cells. NIR760-mbc94 also preferentially labeled CB2-mid DBT tumors in vivo, with a 3.7-fold tumor-to-normal contrast enhancement at 72 h postinjection, whereas the fluorescence signal from the tumors of the mice treated with NIR760 free dye was nearly at the background level at the same time point. SR144528, a CB2R competitor, significantly inhibited tumor uptake of NIR760-mbc94, indicating that NIR760-mbc94 binds to CB2R specifically. In summary, NIR760-mbc94 specifically binds to CB2R in vitro and in vivo and appears to be a promising molecular tool that may have great potential for use in diagnostic imaging of CB2R-positive cancers and therapeutic monitoring as well as in elucidating the role of CB2R in cancer progression and therapy.
Insights
Researchers developed a novel near-infrared probe, NIR760-mbc94, for in vivo optical imaging of the type 2 cannabinoid receptor (CB2R) in tumors. This probe shows specific binding to CB2R-positive cancers, offering potential for improved cancer diagnostics and therapy monitoring.
Area of Science:
- Oncology
- Molecular Imaging
- Pharmacology
Background:
- The type 2 cannabinoid receptor (CB2R) is implicated in cancer development and progression.
- CB2R is increasingly recognized as a potential therapeutic target for various cancers.
- Understanding CB2R's role in cancer necessitates advanced molecular imaging tools.
Purpose of the Study:
- To develop and evaluate a novel near-infrared (NIR) fluorescent probe for in vivo imaging of CB2R.
- To assess the specificity and efficacy of the probe for targeting CB2R-overexpressing tumors.
- To explore the potential of CB2R-targeted imaging in cancer diagnostics and therapy.
Main Methods:
- Synthesis and characterization of a novel CB2R-targeted NIR probe (NIR760-mbc94).
- In vitro studies including cell fluorescent imaging and competitive binding assays using CB2-mid delayed brain tumor (DBT) cells.
- In vivo optical imaging in tumor-bearing mice to evaluate tumor targeting, contrast enhancement, and specificity using a CB2R antagonist (SR144528).
Main Results:
- NIR760-mbc94 demonstrated specific binding to CB2R in vitro.
- The probe preferentially accumulated in CB2-mid DBT tumors in vivo, achieving a 3.7-fold tumor-to-normal contrast enhancement at 72 hours post-injection.
- Tumor uptake of NIR760-mbc94 was significantly inhibited by SR144528, confirming CB2R-specific targeting.
- Control groups (NIR760 free dye) showed minimal tumor signal.
Conclusions:
- NIR760-mbc94 is a specific and effective molecular tool for in vivo CB2R-targeted optical imaging.
- This probe holds significant potential for diagnostic imaging of CB2R-positive cancers.
- The probe may also be valuable for monitoring cancer therapy and further elucidating CB2R's role in cancer progression.
