Abstract: AIM : To investigate the specific binding between ⁹⁹Tc^m radiomarked molecular probe and MDA-MB-231 cells of human breast cancer and biodistribution in mice in vivo.METHODS: The different expression of IL-11R in MDA-MB-231 tumor cells and normal mammary epithelial cells(MCF-10A) were examined by Western blot. The specific binding of ⁹⁹Tc^m-DTPA-c(CGRRAGGSC)and binding site with MDA-MB-231 cells were observed by a fluorescence microscope. Eighteen tumor-bearing nude mice were randomly divided into 6 groups(n=3), biodistribution in vivo in the nude mice were observed in different times after intravenous injection 0.74 MBq (0.1 mL) of the molecular probe.RESULTS:The expression of IL-11R in MDA-MB-231 tumor cells group was 6.7 times as MCF-10A cells group. Fluorescent staining confirmed that ⁹⁹Tc^m-DTPA- c(CGRRAGGSC)-FITC was located in the cell membrane and cytoplasm of MDA-MB-231. The combination between molecular probe ang IL-11R in MDA-MB-231 cells possessed saturability.The radioactive molecular probe was rapidly, continually concentrated in the tumor tissue of the mice, and peaked (17.63±1.73)% ID/g 4 h later. But the radioactive molecular probe was not obviously observed in other vital organs (P<0.05).CONCLUSION: The IL-11R is highly expressed in MDA-MB-231 cells and has high affinity with the cyclic peptide. The ⁹⁹Tc^m labelled cyclic peptide, which is the radioactive molecular probe, has the specific targeted binding ability with MDA-MB-231 cells in vivo and in vitro.

Key words: cyclic peptide, tumor/breast cancer, MDA-MB-231