The Application of Estrogen Receptor Aptamer in Immunohistochemical Detection of Breast Cancer

  Objective  To synthesize and select an estrogen receptors aptamer that can be used in immunostaining of breast cancer tissues.

  Methods  ER protein was purified. ER aptamer that showed a high affinity and specificity for ER was synthesized and selected and by SELEX. Ligand –receptor interactions assay was adopted to measure the affinity of the aptamer-ER complex. Both the biotinylated aptamer and the anti-ER monoclonal antibody were tested for immunohistochemical staining of ER status on 105 breast cancer samples. Agreement on the detection of ER expression was determined by kappa statistics.

  Results  The dissociation contant (Kd) of the biotinylated aptamer-ER complex, as calculated by a linear regression analysis, was determined to be (0.34±0.05) nmol/L (n=3, r=0.989). The binding capacity (B_max) was 769.23 fmol/(mg prot·nmol^-1·L^-1). The ER aptamer and the anti-ER antibody both exhibited identical specificity to ER-expressing breast cancer cells. There was a high agreement between the two methods (n=105, kappa value=0.943, 95% confident interval=0.879-1.006, P<0.05 for the ER positive and negtive samples; n=75, kappa value=0.805, 95% confident interval=0.642-0.967, P<0.05 for the ER weak and moderate/strong expression samples). Both the anti-ER antibody and the ER aptamer can also recognized breast cancer cells at the same sites. There was no expression in the negative controls. There were also positive expressions in the 2 endometrial cancer tissues by using biotinylated aptamer.

  Conclusions  Our results indicated that the synthesized ER aptamer has a high affinity to bind ER. ER aptamer and the anti-ER antibody can both be used for immunohistochemical staining of ER status in breast cancer tissue.