Radiolabeled CGRRAGGSC For Nuclear Imaging Of IL-11R? In Nude Mice Bearing Breast Cancer And Its Anti-tumor Effect In Vitro

Background:Breast cancer is the most common malignancy and 65%-75%of breast cancer patients suffer from bone metastases.The study found that the IL-11/IL-11R?signaling pathway play a role in the occurrence and development of breast cancer bone metastases,IL-1 1R? can be used as a potential target for receptor imaging of breast cancer and osteosarcoma and its application in the imaging and therapy of breast cancer worth exploration.Objective:To evaluate the binding property of the IL-11 analogues ring nonapeptide CGRRAGGSC to IL-11R?.On this basis,to establish the radiolabeled CGRRAGGSC probe and to investigate the efficacy of targeting imaging in nude mice bearing breast cancer and anti-tumor effects on breast cancer cells in vitro.Methods:Western blot was done to confirm the IL-11R? expression of breast cancer cells(MCF-7,BT549 and MDA-MB-231)and normal breast cell(MCF-10A).Immunofluorescence staining in vitro was conducted to detect the binding status of CGRRAGGSC,control peptide CGSPGWVRC and Tyrosine(Tyr)or chelating agent(DTPA)modified CGRRAGGSC to breast cancer cells with or without cold CGRRAGGSC and anti IL-11R? antibody.Near infrared fluorescence imaging was performed to evaluate the specific binding of CGRRAGGSC to IL-11R? in mice bearing MCF-7 breast cancer.The peptide CGRRAGGSC was radiolabeled with radionuclide 99mTc to obtain labeled products 99mTc-DTPA-CGRRAGGSC by stannous chloride.The paper chromatography method was used to detect the labeling rate and stability.SPECT imaging was conducted on nude mice bearing breast cancer.The chloramines-T method was used to obtain labeleled products 131I-CGRRAGGSC.Thin Layer Chromatography(TLC)was performed to detect the labeling rate and stability.Methyl thiazol tetrazolium(MTT),Transwell,Wound-healing assay and Western blot were used to detect the anti-tumor effect of radiolabeled CGRRAGGSC on breast cancer cells and detect the protein expression changes of IL-11R?,p-STAT3 and STAT3 before and after treatment.Results:The expression of IL-11R? was higher in this studied breast cancer cells than in the normal breast cell(MCF-10A).The CGRRAGGSC,Tyr-CGRRAGGSC and DTPA-CGRRAGGSC all bound to breast cancer cells,but the control peptide CGSPGWVRC hardly bound.The binding abilities of CGRRAGGSC weakened after the cold CGRRAGGSC or antiIL-11R? antibody treatment.Near infrared fluorescence imaging suggested that the fluorescence signals of tumor were significantly higher than those of other organs or tissues after intravenous injection of Cy7-CGRRAGGSC,but the fluorescence signals of tumor were similar to those of organs and tisuues in Cy7 group.99mTc-DTPA-CGRRAGGSC and 131I-CGRRAGGSC were radiolabeled successfully,the labeling rate both were over 95%and the radiochemical purity both were over 90%after placing for 12 h at 37?.The SPECT imaging demonstrated that the 99mTc-DTPA-CGRRAGGSC was detained in tumor at a high radioactivity with long time after intratumoral injection.The proliferation and migration of breast cancer cells weakened after 131I-CGRRAGGSC treatment,and the mechanism might be down-regulating the IL-11R? to inhibit STAT3 activation.Conclusions:Radiolabeled CGRRAGGSC not only has a simple synthesis and high labeling rate,but also has IL-11R? targeted specifically.Therefore,it may be a promise radiotracer for imaging and therapy of tumors with over IL-11R? expression.