PET imaging of hepatocellular carcinoma with [¹²⁴I]IV-14

Currently, positron emission tomography (PET) plays no clear role in clinical imaging and management of hepatocellular carcinoma (HCC). New radiotracers for new target(s) are needed for PET imaging of HCC. Uridine-cytidine kinase 2 (UCK2) is a rate-limiting enzyme of the pyrimidine salvage synthesis pathway to phosphorylate uridine and cytidine. Studies have demonstrated that UCK2 is overexpressed in many types of solid cancers including HCC and is associated with the poor prognosis and proliferation of HCC. This study reported PET imaging using a UCK2-specific radiotracer with a clinically relevant anima model of spontaneously occurring HCC in the woodchucks.

This study used 3'-(E)-(2-iodovinyl) uridine (IV-14), which is derived from a UCK2-selective antitumor agent 3'-(Ethynyl)uridine (EUrd), a cytotoxic ribonucleoside analogs of uridine. By radiolabeling IV-14 with Iodine-124 (¹²⁴I), a UCK2-specific radiotracer [¹²⁴I]IV-14 was obtained for PET imaging of UCK2. A naturally occurring woodchuck model of HCC following chronic viral hepatitis infection was used for PET imaging. Potassium iodide (KI) was tested in one of the three animals to block possible uptake of free ¹²⁴I from de-iodination of [¹²⁴I]IV-14.

We confirmed that UCK2 expression is higher in the woodchuck model of HCC than in the surrounding hepatic tissue, similar to human UCK2 that is highly expressed in human HCC. PET imaging with [¹²⁴I]IV-14 showed a strong uptake in woodchuck HCC with low background uptake at one-hour post-injection. De-iodination did not seem to be an issue for PET imaging.

Our results demonstrate that UCK2 is a viable target for imaging HCC and has the potential for targeted endoradiotherapy of HCC.