Radionuclide imaging of tumor angiogenesis
Ingrid Dijkgraaf1, Otto C Boerman
1Department of Nuclear Medicine, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands. I.Dijkgraaf@nucmed.umcn.nl
Abstract:
Angiogenesis is a multistep process regulated by pro- and antiangiogenic factors. In order to grow and metastasize, tumors need a constant supply of oxygen and nutrients. For growth beyond 1-2 mm in size, tumors are dependent on angiogenesis. Inhibition of angiogenesis is a new cancer treatment strategy that is now widely investigated clinically. Researchers have begun to search for objective measures that indicate pharmacologic responses to antiangiogenic drugs. Therefore, there is a great interest in techniques to visualize angiogenesis in growing tumors noninvasively. Several markers have been described that are preferentially expressed on newly formed blood vessels in tumors (alpha(v)beta(3) integrin, vascular endothelial growth factor, and its receptor, prostate-specific membrane antigen) and in the extracellular matrix surrounding newly formed blood vessels (extra domain B of fibronectin, Tenascin-C, matrix metalloproteinases, and Robo-4). Several ligands targeting these markers have been tested as a radiotracer for imaging angiogenesis in tumors. The potential of some of these tracers, such as radiolabeled cyclic RGD peptides and radiolabeled anti-PSMA antibodies, has already been tested in cancer patients, while for markers such as Robo-4, the ligand has not yet been identified. In this review, an overview on the currently used nuclear imaging probes for noninvasive visualization of tumor angiogenesis is given.
Insights
Tumor growth relies on angiogenesis, the formation of new blood vessels. Nuclear imaging probes offer a way to visualize this process noninvasively, aiding cancer treatment response assessment.
Area of Science:
- Oncology
- Medical Imaging
- Molecular Biology
Background:
- Tumor growth and metastasis depend on angiogenesis, the formation of new blood vessels.
- Tumors larger than 1-2 mm require angiogenesis for oxygen and nutrient supply.
- Inhibiting angiogenesis is a key strategy in cancer treatment.
Purpose of the Study:
- To review nuclear imaging probes for noninvasive visualization of tumor angiogenesis.
- To highlight the importance of objective measures for assessing antiangiogenic drug responses.
- To discuss markers and ligands used in imaging tumor angiogenesis.
Main Methods:
- Review of literature on nuclear imaging probes for angiogenesis.
- Identification of markers expressed on tumor neovasculature and extracellular matrix.
- Discussion of radiotracers targeting these markers for imaging.
Main Results:
- Several markers (e.g., α(v)β(3) integrin, VEGF, PSMA, Fn-EDA, Tenascin-C, MMPs, Robo-4) are associated with tumor angiogenesis.
- Ligands targeting these markers are developed as radiotracers for imaging.
- Some tracers (e.g., radiolabeled RGD peptides, anti-PSMA antibodies) have been tested in patients.
Conclusions:
- Noninvasive visualization of tumor angiogenesis is crucial for evaluating antiangiogenic therapies.
- Targeted nuclear imaging probes show promise for assessing treatment response.
- Further development of ligands for specific markers like Robo-4 is needed.
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