In recent years, two different methods have been developed to image cell proliferation with the functional imaging
technique, Positron emission Tomography (PET), proliferation rate and proliferative status. Proliferation rate is a
measure of the tumor doubling time and uses radiolabeled analogs of the DNA precursor thymidine. This approach measures
the activity of the enzyme thymidine kinase 1 (TK1) and provides a pulse label of the S phase fraction of a tumor.
Proliferative status provides a measure of the ratio of proliferating (P) and quiescent (Q) cells in a tumor. This imaging
approach for measuring proliferative status involves measuring the sigma-2 (σ2) receptor status of a tumor, the only protein
which has been validated for making this measurement in vivo with PET. This article provides an overview of the
biological information obtained from these different imaging strategies, and the development of radiotracers for imaging
proliferation rate and proliferative status.
Keywords: Cell proliferation, DNA synthesis, positron emission tomography, radiotracer, sigma-2 receptors.
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