Detection of Bmi-1 antibody in sera from esophageal cancer patients. (A) Absorbance ratios in anti-Bmi-1 ELISA for sera from healthy control (Normal) and patients with ESCC (Tumor). The cutoff for positive antibody reactivity against Bmi-1 was 0.248, which was defined as an absorbance greater than 2 SDs above the mean value of the control. (B) Reactivity of sera from cancer patients with recombinant Bmi-1 protein in Western blotting. Lanes 1-9, stained with 1:100 diluted sera (1 μg Bmi-1/lane). Lanes 1-5, sera from esophageal cancer patients; Lanes 6-9, sera from healthy volunteers; Lane 10. staining of Bmi-1 by anti-Bmi-1 monoclonal antibody (1 μg Bmi-1/lane); Lane 11, staining of purified recombinant Bmi-1 protein (5 μg Bmi-1/lane)by Coomassie blue staining.