To test the binding affinity of the antibodies, we tested four of them in cell lysates of human U2OS osteosarcoma cells and U2OS cells stably expressing TUBG1 single guide (sg) RNA (green fluorescence protein [GFP]-tagged Cas9-CRISPR, knocks out TUBG1 gene; TUBG1-sgRNA-U2OS)11,38 and co-expressing either a sg-resistant TUBG1 (TUBG1-sgRNA-U2OS-TUBG1) or a sg-resistant TUBG2 (TUBG1-sgRNA-U2OS-TUBG2; Fig. 1a). Here, TUBG1 is linked to osteosarcoma.