ABSTRACT
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.
