Send to

Choose Destination
See comment in PubMed Commons below

[123I]-2-Iodo-2-amino-3-phenylpropanoic acid.


Chopra A1.


Molecular Imaging and Contrast Agent Database (MICAD) [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2004-2013.
2008 Jun 03 [updated 2008 Jul 03].

Author information

National Center for Biotechnology Information, NLM, NIH, Bethesda, MD 20894, Email:


Although [18F]fluoro-deoxyglucose ([18F]FDG) is often used for the detection of malignant tumors, it has limitations because the radiochemical is also nonselectively taken up by inflamed or infected tissue (1-3). Compared with [18F]FDG, labeled amino acids (aa) such as ¹¹C-methionine, 18F-tyrosine, and their derivatives have been shown to be superior at distinguishing tumors from infection or inflammation in humans because these radiochemicals are taken up by the cells through a specialized transport system that has an upregulated expression in proliferating cells (4). The upregulation was observed primarily in cells of the tumor tissue, and normal tissue shows little change in expression of the aa transporters (because the cells divide slowly and only when necessary). This phenomenon is believed to be necessary for tumor cell survival because it supports the increased aa demand for protein synthesis in the rapidly dividing cells (5). One of the transporters, described as the major vehicle of large, neutral aa such as phenylalanine, leucine, and tyrosine, is known as the L system (L-type aa transporter 1; LAT1) and is independent of sodium for the transport of these aa (5). Different compounds, including aa, labeled with radioactive fluorine (18F) or carbon (11C) have been used to study tumors and to predict survival after radiotherapy with positron emission tomography (PET) (6-8). However, PET is not widely available, and investigators have developed aa probes that can be used with single-photon emission computed tomography (SPECT) to study tumors because this method is more available than PET (9). Labeled with radioactive iodine (as 123I or 125I), aa derivatives such as 2-iodo-L-tyrosine, 4-iodo-L-phenylalanine, and 2-iodo-L-phenylalanine (2I-L-PA) were developed and observed to accumulate in rhabdomyosarcoma (R1M) tumor cells without incorporation into proteins. These derivatives could be used with SPECT to detect malignant tissue (10-12). Several studies, including in vitro studies, that used 2-[123I]I-L-PA to investigate the detection of tumors and biodistribution in rats, mice, dogs, and humans are available (13-17).

PubMed Commons home

PubMed Commons

How to join PubMed Commons
    Support Center