Synthesis, Radiosynthesis and Metabolism of 131I-Y-c(CGRRAGGSC)

Background: The formation of the complex interleukin-11(IL-11) and IL-11 receptor (IL-11R) is closely related with tumor progression. Binding of IL-11 to the IL-11 receptor α-chain (IL-11Rα) has been suggested as a target for human cancer. The cyclic peptide c(CGRRAGGSC) is a mimic of IL-11. Objective: To explore 131I-Y-c(CGRRAGGSC) synthesis and radiosynthesis, and metabolism in SKOV3 tumorbearing mice. Method: In this study, 131I labeled c(CGRRAGGSC) was designed and characterized. For radiolabeling, tyrosine was used as a linker to connect c(CGRRAGGSC) and 131I. Balb/c nude mice bearing SKOV3 human ovarian carcinoma were used for in vivo studies. Uptake of 131I-cyclic nonapeptide by the tumor was visualized by single photon emission computerized tomography (SPECT). Results: The entire labeling process, which took 15 min by chloramine-T method, resulted in a high labeling yield (93.03±6.78%), and high radiochemical purity (RCP) (>95%). SPECT imaging showed that accumulation of the probe in the tumor was close to background levels. In addition, biodistribution studies showed that the accumulation of 131I-Y-c(CGRRAGGSC) in normal mice was similar to that of Na131I. Conclusion: Tyrosine is a suitable chelating agent for the use of radioiodine labeling, however the bioactivity of the conjugate needs further investigation.