title: [Binding characteristics of interleukin 11 analogue-cyclic nonapeptide c(CGRRAGGSC) to human prostate cancer PC-3 cells: an in vitro study].
abstract: OBJECTIVE
  To investigate the binding characteristics of interleukin 11 (IL-11) analogue-cyclic nonapeptide c(Cys-Gly-Arg-Arg-Ala-Gly-Gly-Ser-Cys) NH2 C30H54N16O10S2, c(CGRRAGGSC), and human prostate cancer PC-3 cells.
  
  
  METHODS
  c(CGRRAGGSC) was labeled with fluorescent dye LSS670, and the location of LSS670-cyclic nonapeptide in the PC-3 cells was investigated by fluorescent microscopy. Flow cytometry was used to detect the fluorescence intensity of the in vitro binding of LSS670-c (CGRRAGGSC) to PC-3 cells and calculate its IC50 and Ki in competitive inhibition experiments. 99Tcm-DTPA-c(CGRRAGGSC) was synthesized by the reaction of 99mTcO4- with c(CGRRAGGSC). The binding characteristics of 99mTc-DTPA-c(CGRRAGGSC) and IL11R in the PC-3 cells were analyzed by radioreceptor assay. Bmax and Kd were calculated in saturability and reversibility experiments.
  
  
  RESULTS
  The binding of LSS670-c(CGRRAGGSC) to the PC-3 cells showed the characteristics of saturability and concentration-time dependence. Unlabeled c(CGRRAGGSC) and LSS670-c(CGRRAGGSC) exhibited a competitive inhibition on the PC-3 cells (IC50 = [6.31 +/- 0.12] nmol/L, Ki = [2.11 +/- 0.14] nmol/L). Fluorescence was mainly distributed in the cell membrane (Kd = [0.32 +/- 0.02] nmol/L, Bmax = [754 +/- 34] fmol/mg pro).
  
  
  CONCLUSIONS
  c (CGRRAGGSC) could bind PC-3 cells through a receptor-mediated pathway.
authors.affiliation: Center of Medical Imaging, The Fourth Hospital of Wuxi, Wuxi, Jiangsu 214062, China. hyjsusan@126.com
authors.forename: Yu-Jie
authors.initials: YJ
authors.lastname: He
authors.forename: Qing-Hua
authors.initials: QH
authors.lastname: Wu
authors.forename: Chen
authors.initials: C
authors.lastname: Gu
authors.forename: Jian-Wei
authors.initials: JW
authors.lastname: Jiang
mesh_terms: D045744:Cell Line, Tumor; D006801:Humans; D017370:Interleukin-11 / Q000378:metabolism*; D008297:Male; D010455:Peptides / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000378:metabolism*; D011485:Protein Binding
chemical_list: C508611:IL11 protein, human; D017370:Interleukin-11; D010455:Peptides